Merge tag 'fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/arm...

[linux-2.6.git] / fs / ext4 / namei.c

/*
 *  linux/fs/ext4/namei.c
 *
 * Copyright (C) 1992, 1993, 1994, 1995
 * Remy Card (card@masi.ibp.fr)
 * Laboratoire MASI - Institut Blaise Pascal
 * Universite Pierre et Marie Curie (Paris VI)
 *
 *  from
 *
 *  linux/fs/minix/namei.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *
 *  Big-endian to little-endian byte-swapping/bitmaps by
 *        David S. Miller (davem@caip.rutgers.edu), 1995
 *  Directory entry file type support and forward compatibility hooks
 *      for B-tree directories by Theodore Ts'o (tytso@mit.edu), 1998
 *  Hash Tree Directory indexing (c)
 *      Daniel Phillips, 2001
 *  Hash Tree Directory indexing porting
 *      Christopher Li, 2002
 *  Hash Tree Directory indexing cleanup
 *      Theodore Ts'o, 2002
 */

#include <linux/fs.h>
#include <linux/pagemap.h>
#include <linux/jbd2.h>
#include <linux/time.h>
#include <linux/fcntl.h>
#include <linux/stat.h>
#include <linux/string.h>
#include <linux/quotaops.h>
#include <linux/buffer_head.h>
#include <linux/bio.h>
#include "ext4.h"
#include "ext4_jbd2.h"

#include "xattr.h"
#include "acl.h"

#include <trace/events/ext4.h>
/*
 * define how far ahead to read directories while searching them.
 */
#define NAMEI_RA_CHUNKS  2
#define NAMEI_RA_BLOCKS  4
#define NAMEI_RA_SIZE        (NAMEI_RA_CHUNKS * NAMEI_RA_BLOCKS)

static struct buffer_head *ext4_append(handle_t *handle,
                                        struct inode *inode,
                                        ext4_lblk_t *block)
{
        struct buffer_head *bh;
        int err = 0;

        if (unlikely(EXT4_SB(inode->i_sb)->s_max_dir_size_kb &&
                     ((inode->i_size >> 10) >=
                      EXT4_SB(inode->i_sb)->s_max_dir_size_kb)))
                return ERR_PTR(-ENOSPC);

        *block = inode->i_size >> inode->i_sb->s_blocksize_bits;

        bh = ext4_bread(handle, inode, *block, 1, &err);
        if (!bh)
                return ERR_PTR(err);
        inode->i_size += inode->i_sb->s_blocksize;
        EXT4_I(inode)->i_disksize = inode->i_size;
        err = ext4_journal_get_write_access(handle, bh);
        if (err) {
                brelse(bh);
                ext4_std_error(inode->i_sb, err);
                return ERR_PTR(err);
        }
        return bh;
}

static int ext4_dx_csum_verify(struct inode *inode,
                               struct ext4_dir_entry *dirent);

typedef enum {
        EITHER, INDEX, DIRENT
} dirblock_type_t;

#define ext4_read_dirblock(inode, block, type) \
        __ext4_read_dirblock((inode), (block), (type), __LINE__)

static struct buffer_head *__ext4_read_dirblock(struct inode *inode,
                                              ext4_lblk_t block,
                                              dirblock_type_t type,
                                              unsigned int line)
{
        struct buffer_head *bh;
        struct ext4_dir_entry *dirent;
        int err = 0, is_dx_block = 0;

        bh = ext4_bread(NULL, inode, block, 0, &err);
        if (!bh) {
                if (err == 0) {
                        ext4_error_inode(inode, __func__, line, block,
                                               "Directory hole found");
                        return ERR_PTR(-EIO);
                }
                __ext4_warning(inode->i_sb, __func__, line,
                               "error reading directory block "
                               "(ino %lu, block %lu)", inode->i_ino,
                               (unsigned long) block);
                return ERR_PTR(err);
        }
        dirent = (struct ext4_dir_entry *) bh->b_data;
        /* Determine whether or not we have an index block */
        if (is_dx(inode)) {
                if (block == 0)
                        is_dx_block = 1;
                else if (ext4_rec_len_from_disk(dirent->rec_len,
                                                inode->i_sb->s_blocksize) ==
                         inode->i_sb->s_blocksize)
                        is_dx_block = 1;
        }
        if (!is_dx_block && type == INDEX) {
                ext4_error_inode(inode, __func__, line, block,
                       "directory leaf block found instead of index block");
                return ERR_PTR(-EIO);
        }
        if (!EXT4_HAS_RO_COMPAT_FEATURE(inode->i_sb,
                                        EXT4_FEATURE_RO_COMPAT_METADATA_CSUM) ||
            buffer_verified(bh))
                return bh;

        /*
         * An empty leaf block can get mistaken for a index block; for
         * this reason, we can only check the index checksum when the
         * caller is sure it should be an index block.
         */
        if (is_dx_block && type == INDEX) {
                if (ext4_dx_csum_verify(inode, dirent))
                        set_buffer_verified(bh);
                else {
                        ext4_error_inode(inode, __func__, line, block,
                                "Directory index failed checksum");
                        brelse(bh);
                        return ERR_PTR(-EIO);
                }
        }
        if (!is_dx_block) {
                if (ext4_dirent_csum_verify(inode, dirent))
                        set_buffer_verified(bh);
                else {
                        ext4_error_inode(inode, __func__, line, block,
                                "Directory block failed checksum");
                        brelse(bh);
                        return ERR_PTR(-EIO);
                }
        }
        return bh;
}

#ifndef assert
#define assert(test) J_ASSERT(test)
#endif

#ifdef DX_DEBUG
#define dxtrace(command) command
#else
#define dxtrace(command)
#endif

struct fake_dirent
{
        __le32 inode;
        __le16 rec_len;
        u8 name_len;
        u8 file_type;
};

struct dx_countlimit
{
        __le16 limit;
        __le16 count;
};

struct dx_entry
{
        __le32 hash;
        __le32 block;
};

/*
 * dx_root_info is laid out so that if it should somehow get overlaid by a
 * dirent the two low bits of the hash version will be zero.  Therefore, the
 * hash version mod 4 should never be 0.  Sincerely, the paranoia department.
 */

struct dx_root
{
        struct fake_dirent dot;
        char dot_name[4];
        struct fake_dirent dotdot;
        char dotdot_name[4];
        struct dx_root_info
        {
                __le32 reserved_zero;
                u8 hash_version;
                u8 info_length; /* 8 */
                u8 indirect_levels;
                u8 unused_flags;
        }
        info;
        struct dx_entry entries[0];
};

struct dx_node
{
        struct fake_dirent fake;
        struct dx_entry entries[0];
};


struct dx_frame
{
        struct buffer_head *bh;
        struct dx_entry *entries;
        struct dx_entry *at;
};

struct dx_map_entry
{
        u32 hash;
        u16 offs;
        u16 size;
};

/*
 * This goes at the end of each htree block.
 */
struct dx_tail {
        u32 dt_reserved;
        __le32 dt_checksum;     /* crc32c(uuid+inum+dirblock) */
};

static inline ext4_lblk_t dx_get_block(struct dx_entry *entry);
static void dx_set_block(struct dx_entry *entry, ext4_lblk_t value);
static inline unsigned dx_get_hash(struct dx_entry *entry);
static void dx_set_hash(struct dx_entry *entry, unsigned value);
static unsigned dx_get_count(struct dx_entry *entries);
static unsigned dx_get_limit(struct dx_entry *entries);
static void dx_set_count(struct dx_entry *entries, unsigned value);
static void dx_set_limit(struct dx_entry *entries, unsigned value);
static unsigned dx_root_limit(struct inode *dir, unsigned infosize);
static unsigned dx_node_limit(struct inode *dir);
static struct dx_frame *dx_probe(const struct qstr *d_name,
                                 struct inode *dir,
                                 struct dx_hash_info *hinfo,
                                 struct dx_frame *frame,
                                 int *err);
static void dx_release(struct dx_frame *frames);
static int dx_make_map(struct ext4_dir_entry_2 *de, unsigned blocksize,
                       struct dx_hash_info *hinfo, struct dx_map_entry map[]);
static void dx_sort_map(struct dx_map_entry *map, unsigned count);
static struct ext4_dir_entry_2 *dx_move_dirents(char *from, char *to,
                struct dx_map_entry *offsets, int count, unsigned blocksize);
static struct ext4_dir_entry_2* dx_pack_dirents(char *base, unsigned blocksize);
static void dx_insert_block(struct dx_frame *frame,
                                        u32 hash, ext4_lblk_t block);
static int ext4_htree_next_block(struct inode *dir, __u32 hash,
                                 struct dx_frame *frame,
                                 struct dx_frame *frames,
                                 __u32 *start_hash);
static struct buffer_head * ext4_dx_find_entry(struct inode *dir,
                const struct qstr *d_name,
                struct ext4_dir_entry_2 **res_dir,
                int *err);
static int ext4_dx_add_entry(handle_t *handle, struct dentry *dentry,
                             struct inode *inode);

/* checksumming functions */
void initialize_dirent_tail(struct ext4_dir_entry_tail *t,
                            unsigned int blocksize)
{
        memset(t, 0, sizeof(struct ext4_dir_entry_tail));
        t->det_rec_len = ext4_rec_len_to_disk(
                        sizeof(struct ext4_dir_entry_tail), blocksize);
        t->det_reserved_ft = EXT4_FT_DIR_CSUM;
}

/* Walk through a dirent block to find a checksum "dirent" at the tail */
static struct ext4_dir_entry_tail *get_dirent_tail(struct inode *inode,
                                                   struct ext4_dir_entry *de)
{
        struct ext4_dir_entry_tail *t;

#ifdef PARANOID
        struct ext4_dir_entry *d, *top;

        d = de;
        top = (struct ext4_dir_entry *)(((void *)de) +
                (EXT4_BLOCK_SIZE(inode->i_sb) -
                sizeof(struct ext4_dir_entry_tail)));
        while (d < top && d->rec_len)
                d = (struct ext4_dir_entry *)(((void *)d) +
                    le16_to_cpu(d->rec_len));

        if (d != top)
                return NULL;

        t = (struct ext4_dir_entry_tail *)d;
#else
        t = EXT4_DIRENT_TAIL(de, EXT4_BLOCK_SIZE(inode->i_sb));
#endif

        if (t->det_reserved_zero1 ||
            le16_to_cpu(t->det_rec_len) != sizeof(struct ext4_dir_entry_tail) ||
            t->det_reserved_zero2 ||
            t->det_reserved_ft != EXT4_FT_DIR_CSUM)
                return NULL;

        return t;
}

static __le32 ext4_dirent_csum(struct inode *inode,
                               struct ext4_dir_entry *dirent, int size)
{
        struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
        struct ext4_inode_info *ei = EXT4_I(inode);
        __u32 csum;

        csum = ext4_chksum(sbi, ei->i_csum_seed, (__u8 *)dirent, size);
        return cpu_to_le32(csum);
}

static void warn_no_space_for_csum(struct inode *inode)
{
        ext4_warning(inode->i_sb, "no space in directory inode %lu leaf for "
                     "checksum.  Please run e2fsck -D.", inode->i_ino);
}

int ext4_dirent_csum_verify(struct inode *inode, struct ext4_dir_entry *dirent)
{
        struct ext4_dir_entry_tail *t;

        if (!EXT4_HAS_RO_COMPAT_FEATURE(inode->i_sb,
                                        EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
                return 1;

        t = get_dirent_tail(inode, dirent);
        if (!t) {
                warn_no_space_for_csum(inode);
                return 0;
        }

        if (t->det_checksum != ext4_dirent_csum(inode, dirent,
                                                (void *)t - (void *)dirent))
                return 0;

        return 1;
}

static void ext4_dirent_csum_set(struct inode *inode,
                                 struct ext4_dir_entry *dirent)
{
        struct ext4_dir_entry_tail *t;

        if (!EXT4_HAS_RO_COMPAT_FEATURE(inode->i_sb,
                                        EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
                return;

        t = get_dirent_tail(inode, dirent);
        if (!t) {
                warn_no_space_for_csum(inode);
                return;
        }

        t->det_checksum = ext4_dirent_csum(inode, dirent,
                                           (void *)t - (void *)dirent);
}

int ext4_handle_dirty_dirent_node(handle_t *handle,
                                  struct inode *inode,
                                  struct buffer_head *bh)
{
        ext4_dirent_csum_set(inode, (struct ext4_dir_entry *)bh->b_data);
        return ext4_handle_dirty_metadata(handle, inode, bh);
}

static struct dx_countlimit *get_dx_countlimit(struct inode *inode,
                                               struct ext4_dir_entry *dirent,
                                               int *offset)
{
        struct ext4_dir_entry *dp;
        struct dx_root_info *root;
        int count_offset;

        if (le16_to_cpu(dirent->rec_len) == EXT4_BLOCK_SIZE(inode->i_sb))
                count_offset = 8;
        else if (le16_to_cpu(dirent->rec_len) == 12) {
                dp = (struct ext4_dir_entry *)(((void *)dirent) + 12);
                if (le16_to_cpu(dp->rec_len) !=
                    EXT4_BLOCK_SIZE(inode->i_sb) - 12)
                        return NULL;
                root = (struct dx_root_info *)(((void *)dp + 12));
                if (root->reserved_zero ||
                    root->info_length != sizeof(struct dx_root_info))
                        return NULL;
                count_offset = 32;
        } else
                return NULL;

        if (offset)
                *offset = count_offset;
        return (struct dx_countlimit *)(((void *)dirent) + count_offset);
}

static __le32 ext4_dx_csum(struct inode *inode, struct ext4_dir_entry *dirent,
                           int count_offset, int count, struct dx_tail *t)
{
        struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
        struct ext4_inode_info *ei = EXT4_I(inode);
        __u32 csum;
        __le32 save_csum;
        int size;

        size = count_offset + (count * sizeof(struct dx_entry));
        save_csum = t->dt_checksum;
        t->dt_checksum = 0;
        csum = ext4_chksum(sbi, ei->i_csum_seed, (__u8 *)dirent, size);
        csum = ext4_chksum(sbi, csum, (__u8 *)t, sizeof(struct dx_tail));
        t->dt_checksum = save_csum;

        return cpu_to_le32(csum);
}

static int ext4_dx_csum_verify(struct inode *inode,
                               struct ext4_dir_entry *dirent)
{
        struct dx_countlimit *c;
        struct dx_tail *t;
        int count_offset, limit, count;

        if (!EXT4_HAS_RO_COMPAT_FEATURE(inode->i_sb,
                                        EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
                return 1;

        c = get_dx_countlimit(inode, dirent, &count_offset);
        if (!c) {
                EXT4_ERROR_INODE(inode, "dir seems corrupt?  Run e2fsck -D.");
                return 1;
        }
        limit = le16_to_cpu(c->limit);
        count = le16_to_cpu(c->count);
        if (count_offset + (limit * sizeof(struct dx_entry)) >
            EXT4_BLOCK_SIZE(inode->i_sb) - sizeof(struct dx_tail)) {
                warn_no_space_for_csum(inode);
                return 1;
        }
        t = (struct dx_tail *)(((struct dx_entry *)c) + limit);

        if (t->dt_checksum != ext4_dx_csum(inode, dirent, count_offset,
                                            count, t))
                return 0;
        return 1;
}

static void ext4_dx_csum_set(struct inode *inode, struct ext4_dir_entry *dirent)
{
        struct dx_countlimit *c;
        struct dx_tail *t;
        int count_offset, limit, count;

        if (!EXT4_HAS_RO_COMPAT_FEATURE(inode->i_sb,
                                        EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
                return;

        c = get_dx_countlimit(inode, dirent, &count_offset);
        if (!c) {
                EXT4_ERROR_INODE(inode, "dir seems corrupt?  Run e2fsck -D.");
                return;
        }
        limit = le16_to_cpu(c->limit);
        count = le16_to_cpu(c->count);
        if (count_offset + (limit * sizeof(struct dx_entry)) >
            EXT4_BLOCK_SIZE(inode->i_sb) - sizeof(struct dx_tail)) {
                warn_no_space_for_csum(inode);
                return;
        }
        t = (struct dx_tail *)(((struct dx_entry *)c) + limit);

        t->dt_checksum = ext4_dx_csum(inode, dirent, count_offset, count, t);
}

static inline int ext4_handle_dirty_dx_node(handle_t *handle,
                                            struct inode *inode,
                                            struct buffer_head *bh)
{
        ext4_dx_csum_set(inode, (struct ext4_dir_entry *)bh->b_data);
        return ext4_handle_dirty_metadata(handle, inode, bh);
}

/*
 * p is at least 6 bytes before the end of page
 */
static inline struct ext4_dir_entry_2 *
ext4_next_entry(struct ext4_dir_entry_2 *p, unsigned long blocksize)
{
        return (struct ext4_dir_entry_2 *)((char *)p +
                ext4_rec_len_from_disk(p->rec_len, blocksize));
}

/*
 * Future: use high four bits of block for coalesce-on-delete flags
 * Mask them off for now.
 */

static inline ext4_lblk_t dx_get_block(struct dx_entry *entry)
{
        return le32_to_cpu(entry->block) & 0x00ffffff;
}

static inline void dx_set_block(struct dx_entry *entry, ext4_lblk_t value)
{
        entry->block = cpu_to_le32(value);
}

static inline unsigned dx_get_hash(struct dx_entry *entry)
{
        return le32_to_cpu(entry->hash);
}

static inline void dx_set_hash(struct dx_entry *entry, unsigned value)
{
        entry->hash = cpu_to_le32(value);
}

static inline unsigned dx_get_count(struct dx_entry *entries)
{
        return le16_to_cpu(((struct dx_countlimit *) entries)->count);
}

static inline unsigned dx_get_limit(struct dx_entry *entries)
{
        return le16_to_cpu(((struct dx_countlimit *) entries)->limit);
}

static inline void dx_set_count(struct dx_entry *entries, unsigned value)
{
        ((struct dx_countlimit *) entries)->count = cpu_to_le16(value);
}

static inline void dx_set_limit(struct dx_entry *entries, unsigned value)
{
        ((struct dx_countlimit *) entries)->limit = cpu_to_le16(value);
}

static inline unsigned dx_root_limit(struct inode *dir, unsigned infosize)
{
        unsigned entry_space = dir->i_sb->s_blocksize - EXT4_DIR_REC_LEN(1) -
                EXT4_DIR_REC_LEN(2) - infosize;

        if (EXT4_HAS_RO_COMPAT_FEATURE(dir->i_sb,
                                       EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
                entry_space -= sizeof(struct dx_tail);
        return entry_space / sizeof(struct dx_entry);
}

static inline unsigned dx_node_limit(struct inode *dir)
{
        unsigned entry_space = dir->i_sb->s_blocksize - EXT4_DIR_REC_LEN(0);

        if (EXT4_HAS_RO_COMPAT_FEATURE(dir->i_sb,
                                       EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
                entry_space -= sizeof(struct dx_tail);
        return entry_space / sizeof(struct dx_entry);
}

/*
 * Debug
 */
#ifdef DX_DEBUG
static void dx_show_index(char * label, struct dx_entry *entries)
{
        int i, n = dx_get_count (entries);
        printk(KERN_DEBUG "%s index ", label);
        for (i = 0; i < n; i++) {
                printk("%x->%lu ", i ? dx_get_hash(entries + i) :
                                0, (unsigned long)dx_get_block(entries + i));
        }
        printk("\n");
}

struct stats
{
        unsigned names;
        unsigned space;
        unsigned bcount;
};

static struct stats dx_show_leaf(struct dx_hash_info *hinfo, struct ext4_dir_entry_2 *de,
                                 int size, int show_names)
{
        unsigned names = 0, space = 0;
        char *base = (char *) de;
        struct dx_hash_info h = *hinfo;

        printk("names: ");
        while ((char *) de < base + size)
        {
                if (de->inode)
                {
                        if (show_names)
                        {
                                int len = de->name_len;
                                char *name = de->name;
                                while (len--) printk("%c", *name++);
                                ext4fs_dirhash(de->name, de->name_len, &h);
                                printk(":%x.%u ", h.hash,
                                       (unsigned) ((char *) de - base));
                        }
                        space += EXT4_DIR_REC_LEN(de->name_len);
                        names++;
                }
                de = ext4_next_entry(de, size);
        }
        printk("(%i)\n", names);
        return (struct stats) { names, space, 1 };
}

struct stats dx_show_entries(struct dx_hash_info *hinfo, struct inode *dir,
                             struct dx_entry *entries, int levels)
{
        unsigned blocksize = dir->i_sb->s_blocksize;
        unsigned count = dx_get_count(entries), names = 0, space = 0, i;
        unsigned bcount = 0;
        struct buffer_head *bh;
        int err;
        printk("%i indexed blocks...\n", count);
        for (i = 0; i < count; i++, entries++)
        {
                ext4_lblk_t block = dx_get_block(entries);
                ext4_lblk_t hash  = i ? dx_get_hash(entries): 0;
                u32 range = i < count - 1? (dx_get_hash(entries + 1) - hash): ~hash;
                struct stats stats;
                printk("%s%3u:%03u hash %8x/%8x ",levels?"":"   ", i, block, hash, range);
                if (!(bh = ext4_bread (NULL,dir, block, 0,&err))) continue;
                stats = levels?
                   dx_show_entries(hinfo, dir, ((struct dx_node *) bh->b_data)->entries, levels - 1):
                   dx_show_leaf(hinfo, (struct ext4_dir_entry_2 *) bh->b_data, blocksize, 0);
                names += stats.names;
                space += stats.space;
                bcount += stats.bcount;
                brelse(bh);
        }
        if (bcount)
                printk(KERN_DEBUG "%snames %u, fullness %u (%u%%)\n",
                       levels ? "" : "   ", names, space/bcount,
                       (space/bcount)*100/blocksize);
        return (struct stats) { names, space, bcount};
}
#endif /* DX_DEBUG */

/*
 * Probe for a directory leaf block to search.
 *
 * dx_probe can return ERR_BAD_DX_DIR, which means there was a format
 * error in the directory index, and the caller should fall back to
 * searching the directory normally.  The callers of dx_probe **MUST**
 * check for this error code, and make sure it never gets reflected
 * back to userspace.
 */
static struct dx_frame *
dx_probe(const struct qstr *d_name, struct inode *dir,
         struct dx_hash_info *hinfo, struct dx_frame *frame_in, int *err)
{
        unsigned count, indirect;
        struct dx_entry *at, *entries, *p, *q, *m;
        struct dx_root *root;
        struct buffer_head *bh;
        struct dx_frame *frame = frame_in;
        u32 hash;

        frame->bh = NULL;
        bh = ext4_read_dirblock(dir, 0, INDEX);
        if (IS_ERR(bh)) {
                *err = PTR_ERR(bh);
                goto fail;
        }
        root = (struct dx_root *) bh->b_data;
        if (root->info.hash_version != DX_HASH_TEA &&
            root->info.hash_version != DX_HASH_HALF_MD4 &&
            root->info.hash_version != DX_HASH_LEGACY) {
                ext4_warning(dir->i_sb, "Unrecognised inode hash code %d",
                             root->info.hash_version);
                brelse(bh);
                *err = ERR_BAD_DX_DIR;
                goto fail;
        }
        hinfo->hash_version = root->info.hash_version;
        if (hinfo->hash_version <= DX_HASH_TEA)
                hinfo->hash_version += EXT4_SB(dir->i_sb)->s_hash_unsigned;
        hinfo->seed = EXT4_SB(dir->i_sb)->s_hash_seed;
        if (d_name)
                ext4fs_dirhash(d_name->name, d_name->len, hinfo);
        hash = hinfo->hash;

        if (root->info.unused_flags & 1) {
                ext4_warning(dir->i_sb, "Unimplemented inode hash flags: %#06x",
                             root->info.unused_flags);
                brelse(bh);
                *err = ERR_BAD_DX_DIR;
                goto fail;
        }

        if ((indirect = root->info.indirect_levels) > 1) {
                ext4_warning(dir->i_sb, "Unimplemented inode hash depth: %#06x",
                             root->info.indirect_levels);
                brelse(bh);
                *err = ERR_BAD_DX_DIR;
                goto fail;
        }

        entries = (struct dx_entry *) (((char *)&root->info) +
                                       root->info.info_length);

        if (dx_get_limit(entries) != dx_root_limit(dir,
                                                   root->info.info_length)) {
                ext4_warning(dir->i_sb, "dx entry: limit != root limit");
                brelse(bh);
                *err = ERR_BAD_DX_DIR;
                goto fail;
        }

        dxtrace(printk("Look up %x", hash));
        while (1)
        {
                count = dx_get_count(entries);
                if (!count || count > dx_get_limit(entries)) {
                        ext4_warning(dir->i_sb,
                                     "dx entry: no count or count > limit");
                        brelse(bh);
                        *err = ERR_BAD_DX_DIR;
                        goto fail2;
                }

                p = entries + 1;
                q = entries + count - 1;
                while (p <= q)
                {
                        m = p + (q - p)/2;
                        dxtrace(printk("."));
                        if (dx_get_hash(m) > hash)
                                q = m - 1;
                        else
                                p = m + 1;
                }

                if (0) // linear search cross check
                {
                        unsigned n = count - 1;
                        at = entries;
                        while (n--)
                        {
                                dxtrace(printk(","));
                                if (dx_get_hash(++at) > hash)
                                {
                                        at--;
                                        break;
                                }
                        }
                        assert (at == p - 1);
                }

                at = p - 1;
                dxtrace(printk(" %x->%u\n", at == entries? 0: dx_get_hash(at), dx_get_block(at)));
                frame->bh = bh;
                frame->entries = entries;
                frame->at = at;
                if (!indirect--) return frame;
                bh = ext4_read_dirblock(dir, dx_get_block(at), INDEX);
                if (IS_ERR(bh)) {
                        *err = PTR_ERR(bh);
                        goto fail2;
                }
                entries = ((struct dx_node *) bh->b_data)->entries;

                if (dx_get_limit(entries) != dx_node_limit (dir)) {
                        ext4_warning(dir->i_sb,
                                     "dx entry: limit != node limit");
                        brelse(bh);
                        *err = ERR_BAD_DX_DIR;
                        goto fail2;
                }
                frame++;
                frame->bh = NULL;
        }
fail2:
        while (frame >= frame_in) {
                brelse(frame->bh);
                frame--;
        }
fail:
        if (*err == ERR_BAD_DX_DIR)
                ext4_warning(dir->i_sb,
                             "Corrupt dir inode %lu, running e2fsck is "
                             "recommended.", dir->i_ino);
        return NULL;
}

static void dx_release (struct dx_frame *frames)
{
        if (frames[0].bh == NULL)
                return;

        if (((struct dx_root *) frames[0].bh->b_data)->info.indirect_levels)
                brelse(frames[1].bh);
        brelse(frames[0].bh);
}

/*
 * This function increments the frame pointer to search the next leaf
 * block, and reads in the necessary intervening nodes if the search
 * should be necessary.  Whether or not the search is necessary is
 * controlled by the hash parameter.  If the hash value is even, then
 * the search is only continued if the next block starts with that
 * hash value.  This is used if we are searching for a specific file.
 *
 * If the hash value is HASH_NB_ALWAYS, then always go to the next block.
 *
 * This function returns 1 if the caller should continue to search,
 * or 0 if it should not.  If there is an error reading one of the
 * index blocks, it will a negative error code.
 *
 * If start_hash is non-null, it will be filled in with the starting
 * hash of the next page.
 */
static int ext4_htree_next_block(struct inode *dir, __u32 hash,
                                 struct dx_frame *frame,
                                 struct dx_frame *frames,
                                 __u32 *start_hash)
{
        struct dx_frame *p;
        struct buffer_head *bh;
        int num_frames = 0;
        __u32 bhash;

        p = frame;
        /*
         * Find the next leaf page by incrementing the frame pointer.
         * If we run out of entries in the interior node, loop around and
         * increment pointer in the parent node.  When we break out of
         * this loop, num_frames indicates the number of interior
         * nodes need to be read.
         */
        while (1) {
                if (++(p->at) < p->entries + dx_get_count(p->entries))
                        break;
                if (p == frames)
                        return 0;
                num_frames++;
                p--;
        }

        /*
         * If the hash is 1, then continue only if the next page has a
         * continuation hash of any value.  This is used for readdir
         * handling.  Otherwise, check to see if the hash matches the
         * desired contiuation hash.  If it doesn't, return since
         * there's no point to read in the successive index pages.
         */
        bhash = dx_get_hash(p->at);
        if (start_hash)
                *start_hash = bhash;
        if ((hash & 1) == 0) {
                if ((bhash & ~1) != hash)
                        return 0;
        }
        /*
         * If the hash is HASH_NB_ALWAYS, we always go to the next
         * block so no check is necessary
         */
        while (num_frames--) {
                bh = ext4_read_dirblock(dir, dx_get_block(p->at), INDEX);
                if (IS_ERR(bh))
                        return PTR_ERR(bh);
                p++;
                brelse(p->bh);
                p->bh = bh;
                p->at = p->entries = ((struct dx_node *) bh->b_data)->entries;
        }
        return 1;
}


/*
 * This function fills a red-black tree with information from a
 * directory block.  It returns the number directory entries loaded
 * into the tree.  If there is an error it is returned in err.
 */
static int htree_dirblock_to_tree(struct file *dir_file,
                                  struct inode *dir, ext4_lblk_t block,
                                  struct dx_hash_info *hinfo,
                                  __u32 start_hash, __u32 start_minor_hash)
{
        struct buffer_head *bh;
        struct ext4_dir_entry_2 *de, *top;
        int err = 0, count = 0;

        dxtrace(printk(KERN_INFO "In htree dirblock_to_tree: block %lu\n",
                                                        (unsigned long)block));
        bh = ext4_read_dirblock(dir, block, DIRENT);
        if (IS_ERR(bh))
                return PTR_ERR(bh);

        de = (struct ext4_dir_entry_2 *) bh->b_data;
        top = (struct ext4_dir_entry_2 *) ((char *) de +
                                           dir->i_sb->s_blocksize -
                                           EXT4_DIR_REC_LEN(0));
        for (; de < top; de = ext4_next_entry(de, dir->i_sb->s_blocksize)) {
                if (ext4_check_dir_entry(dir, NULL, de, bh,
                                bh->b_data, bh->b_size,
                                (block<<EXT4_BLOCK_SIZE_BITS(dir->i_sb))
                                         + ((char *)de - bh->b_data))) {
                        /* silently ignore the rest of the block */
                        break;
                }
                ext4fs_dirhash(de->name, de->name_len, hinfo);
                if ((hinfo->hash < start_hash) ||
                    ((hinfo->hash == start_hash) &&
                     (hinfo->minor_hash < start_minor_hash)))
                        continue;
                if (de->inode == 0)
                        continue;
                if ((err = ext4_htree_store_dirent(dir_file,
                                   hinfo->hash, hinfo->minor_hash, de)) != 0) {
                        brelse(bh);
                        return err;
                }
                count++;
        }
        brelse(bh);
        return count;
}


/*
 * This function fills a red-black tree with information from a
 * directory.  We start scanning the directory in hash order, starting
 * at start_hash and start_minor_hash.
 *
 * This function returns the number of entries inserted into the tree,
 * or a negative error code.
 */
int ext4_htree_fill_tree(struct file *dir_file, __u32 start_hash,
                         __u32 start_minor_hash, __u32 *next_hash)
{
        struct dx_hash_info hinfo;
        struct ext4_dir_entry_2 *de;
        struct dx_frame frames[2], *frame;
        struct inode *dir;
        ext4_lblk_t block;
        int count = 0;
        int ret, err;
        __u32 hashval;

        dxtrace(printk(KERN_DEBUG "In htree_fill_tree, start hash: %x:%x\n",
                       start_hash, start_minor_hash));
        dir = file_inode(dir_file);
        if (!(ext4_test_inode_flag(dir, EXT4_INODE_INDEX))) {
                hinfo.hash_version = EXT4_SB(dir->i_sb)->s_def_hash_version;
                if (hinfo.hash_version <= DX_HASH_TEA)
                        hinfo.hash_version +=
                                EXT4_SB(dir->i_sb)->s_hash_unsigned;
                hinfo.seed = EXT4_SB(dir->i_sb)->s_hash_seed;
                if (ext4_has_inline_data(dir)) {
                        int has_inline_data = 1;
                        count = htree_inlinedir_to_tree(dir_file, dir, 0,
                                                        &hinfo, start_hash,
                                                        start_minor_hash,
                                                        &has_inline_data);
                        if (has_inline_data) {
                                *next_hash = ~0;
                                return count;
                        }
                }
                count = htree_dirblock_to_tree(dir_file, dir, 0, &hinfo,
                                               start_hash, start_minor_hash);
                *next_hash = ~0;
                return count;
        }
        hinfo.hash = start_hash;
        hinfo.minor_hash = 0;
        frame = dx_probe(NULL, dir, &hinfo, frames, &err);
        if (!frame)
                return err;

        /* Add '.' and '..' from the htree header */
        if (!start_hash && !start_minor_hash) {
                de = (struct ext4_dir_entry_2 *) frames[0].bh->b_data;
                if ((err = ext4_htree_store_dirent(dir_file, 0, 0, de)) != 0)
                        goto errout;
                count++;
        }
        if (start_hash < 2 || (start_hash ==2 && start_minor_hash==0)) {
                de = (struct ext4_dir_entry_2 *) frames[0].bh->b_data;
                de = ext4_next_entry(de, dir->i_sb->s_blocksize);
                if ((err = ext4_htree_store_dirent(dir_file, 2, 0, de)) != 0)
                        goto errout;
                count++;
        }

        while (1) {
                block = dx_get_block(frame->at);
                ret = htree_dirblock_to_tree(dir_file, dir, block, &hinfo,
                                             start_hash, start_minor_hash);
                if (ret < 0) {
                        err = ret;
                        goto errout;
                }
                count += ret;
                hashval = ~0;
                ret = ext4_htree_next_block(dir, HASH_NB_ALWAYS,
                                            frame, frames, &hashval);
                *next_hash = hashval;
                if (ret < 0) {
                        err = ret;
                        goto errout;
                }
                /*
                 * Stop if:  (a) there are no more entries, or
                 * (b) we have inserted at least one entry and the
                 * next hash value is not a continuation
                 */
                if ((ret == 0) ||
                    (count && ((hashval & 1) == 0)))
                        break;
        }
        dx_release(frames);
        dxtrace(printk(KERN_DEBUG "Fill tree: returned %d entries, "
                       "next hash: %x\n", count, *next_hash));
        return count;
errout:
        dx_release(frames);
        return (err);
}

static inline int search_dirblock(struct buffer_head *bh,
                                  struct inode *dir,
                                  const struct qstr *d_name,
                                  unsigned int offset,
                                  struct ext4_dir_entry_2 **res_dir)
{
        return search_dir(bh, bh->b_data, dir->i_sb->s_blocksize, dir,
                          d_name, offset, res_dir);
}

/*
 * Directory block splitting, compacting
 */

/*
 * Create map of hash values, offsets, and sizes, stored at end of block.
 * Returns number of entries mapped.
 */
static int dx_make_map(struct ext4_dir_entry_2 *de, unsigned blocksize,
                       struct dx_hash_info *hinfo,
                       struct dx_map_entry *map_tail)
{
        int count = 0;
        char *base = (char *) de;
        struct dx_hash_info h = *hinfo;

        while ((char *) de < base + blocksize) {
                if (de->name_len && de->inode) {
                        ext4fs_dirhash(de->name, de->name_len, &h);
                        map_tail--;
                        map_tail->hash = h.hash;
                        map_tail->offs = ((char *) de - base)>>2;
                        map_tail->size = le16_to_cpu(de->rec_len);
                        count++;
                        cond_resched();
                }
                /* XXX: do we need to check rec_len == 0 case? -Chris */
                de = ext4_next_entry(de, blocksize);
        }
        return count;
}

/* Sort map by hash value */
static void dx_sort_map (struct dx_map_entry *map, unsigned count)
{
        struct dx_map_entry *p, *q, *top = map + count - 1;
        int more;
        /* Combsort until bubble sort doesn't suck */
        while (count > 2) {
                count = count*10/13;
                if (count - 9 < 2) /* 9, 10 -> 11 */
                        count = 11;
                for (p = top, q = p - count; q >= map; p--, q--)
                        if (p->hash < q->hash)
                                swap(*p, *q);
        }
        /* Garden variety bubble sort */
        do {
                more = 0;
                q = top;
                while (q-- > map) {
                        if (q[1].hash >= q[0].hash)
                                continue;
                        swap(*(q+1), *q);
                        more = 1;
                }
        } while(more);
}

static void dx_insert_block(struct dx_frame *frame, u32 hash, ext4_lblk_t block)
{
        struct dx_entry *entries = frame->entries;
        struct dx_entry *old = frame->at, *new = old + 1;
        int count = dx_get_count(entries);

        assert(count < dx_get_limit(entries));
        assert(old < entries + count);
        memmove(new + 1, new, (char *)(entries + count) - (char *)(new));
        dx_set_hash(new, hash);
        dx_set_block(new, block);
        dx_set_count(entries, count + 1);
}

/*
 * NOTE! unlike strncmp, ext4_match returns 1 for success, 0 for failure.
 *
 * `len <= EXT4_NAME_LEN' is guaranteed by caller.
 * `de != NULL' is guaranteed by caller.
 */
static inline int ext4_match (int len, const char * const name,
                              struct ext4_dir_entry_2 * de)
{
        if (len != de->name_len)
                return 0;
        if (!de->inode)
                return 0;
        return !memcmp(name, de->name, len);
}

/*
 * Returns 0 if not found, -1 on failure, and 1 on success
 */
int search_dir(struct buffer_head *bh,
               char *search_buf,
               int buf_size,
               struct inode *dir,
               const struct qstr *d_name,
               unsigned int offset,
               struct ext4_dir_entry_2 **res_dir)
{
        struct ext4_dir_entry_2 * de;
        char * dlimit;
        int de_len;
        const char *name = d_name->name;
        int namelen = d_name->len;

        de = (struct ext4_dir_entry_2 *)search_buf;
        dlimit = search_buf + buf_size;
        while ((char *) de < dlimit) {
                /* this code is executed quadratically often */
                /* do minimal checking `by hand' */

                if ((char *) de + namelen <= dlimit &&
                    ext4_match (namelen, name, de)) {
                        /* found a match - just to be sure, do a full check */
                        if (ext4_check_dir_entry(dir, NULL, de, bh, bh->b_data,
                                                 bh->b_size, offset))
                                return -1;
                        *res_dir = de;
                        return 1;
                }
                /* prevent looping on a bad block */
                de_len = ext4_rec_len_from_disk(de->rec_len,
                                                dir->i_sb->s_blocksize);
                if (de_len <= 0)
                        return -1;
                offset += de_len;
                de = (struct ext4_dir_entry_2 *) ((char *) de + de_len);
        }
        return 0;
}

static int is_dx_internal_node(struct inode *dir, ext4_lblk_t block,
                               struct ext4_dir_entry *de)
{
        struct super_block *sb = dir->i_sb;

        if (!is_dx(dir))
                return 0;
        if (block == 0)
                return 1;
        if (de->inode == 0 &&
            ext4_rec_len_from_disk(de->rec_len, sb->s_blocksize) ==
                        sb->s_blocksize)
                return 1;
        return 0;
}

/*
 *      ext4_find_entry()
 *
 * finds an entry in the specified directory with the wanted name. It
 * returns the cache buffer in which the entry was found, and the entry
 * itself (as a parameter - res_dir). It does NOT read the inode of the
 * entry - you'll have to do that yourself if you want to.
 *
 * The returned buffer_head has ->b_count elevated.  The caller is expected
 * to brelse() it when appropriate.
 */
static struct buffer_head * ext4_find_entry (struct inode *dir,
                                        const struct qstr *d_name,
                                        struct ext4_dir_entry_2 **res_dir,
                                        int *inlined)
{
        struct super_block *sb;
        struct buffer_head *bh_use[NAMEI_RA_SIZE];
        struct buffer_head *bh, *ret = NULL;
        ext4_lblk_t start, block, b;
        const u8 *name = d_name->name;
        int ra_max = 0;         /* Number of bh's in the readahead
                                   buffer, bh_use[] */
        int ra_ptr = 0;         /* Current index into readahead
                                   buffer */
        int num = 0;
        ext4_lblk_t  nblocks;
        int i, err;
        int namelen;

        *res_dir = NULL;
        sb = dir->i_sb;
        namelen = d_name->len;
        if (namelen > EXT4_NAME_LEN)
                return NULL;

        if (ext4_has_inline_data(dir)) {
                int has_inline_data = 1;
                ret = ext4_find_inline_entry(dir, d_name, res_dir,
                                             &has_inline_data);
                if (has_inline_data) {
                        if (inlined)
                                *inlined = 1;
                        return ret;
                }
        }

        if ((namelen <= 2) && (name[0] == '.') &&
            (name[1] == '.' || name[1] == '\0')) {
                /*
                 * "." or ".." will only be in the first block
                 * NFS may look up ".."; "." should be handled by the VFS
                 */
                block = start = 0;
                nblocks = 1;
                goto restart;
        }
        if (is_dx(dir)) {
                bh = ext4_dx_find_entry(dir, d_name, res_dir, &err);
                /*
                 * On success, or if the error was file not found,
                 * return.  Otherwise, fall back to doing a search the
                 * old fashioned way.
                 */
                if (bh || (err != ERR_BAD_DX_DIR))
                        return bh;
                dxtrace(printk(KERN_DEBUG "ext4_find_entry: dx failed, "
                               "falling back\n"));
        }
        nblocks = dir->i_size >> EXT4_BLOCK_SIZE_BITS(sb);
        start = EXT4_I(dir)->i_dir_start_lookup;
        if (start >= nblocks)
                start = 0;
        block = start;
restart:
        do {
                /*
                 * We deal with the read-ahead logic here.
                 */
                if (ra_ptr >= ra_max) {
                        /* Refill the readahead buffer */
                        ra_ptr = 0;
                        b = block;
                        for (ra_max = 0; ra_max < NAMEI_RA_SIZE; ra_max++) {
                                /*
                                 * Terminate if we reach the end of the
                                 * directory and must wrap, or if our
                                 * search has finished at this block.
                                 */
                                if (b >= nblocks || (num && block == start)) {
                                        bh_use[ra_max] = NULL;
                                        break;
                                }
                                num++;
                                bh = ext4_getblk(NULL, dir, b++, 0, &err);
                                bh_use[ra_max] = bh;
                                if (bh)
                                        ll_rw_block(READ | REQ_META | REQ_PRIO,
                                                    1, &bh);
                        }
                }
                if ((bh = bh_use[ra_ptr++]) == NULL)
                        goto next;
                wait_on_buffer(bh);
                if (!buffer_uptodate(bh)) {
                        /* read error, skip block & hope for the best */
                        EXT4_ERROR_INODE(dir, "reading directory lblock %lu",
                                         (unsigned long) block);
                        brelse(bh);
                        goto next;
                }
                if (!buffer_verified(bh) &&
                    !is_dx_internal_node(dir, block,
                                         (struct ext4_dir_entry *)bh->b_data) &&
                    !ext4_dirent_csum_verify(dir,
                                (struct ext4_dir_entry *)bh->b_data)) {
                        EXT4_ERROR_INODE(dir, "checksumming directory "
                                         "block %lu", (unsigned long)block);
                        brelse(bh);
                        goto next;
                }
                set_buffer_verified(bh);
                i = search_dirblock(bh, dir, d_name,
                            block << EXT4_BLOCK_SIZE_BITS(sb), res_dir);
                if (i == 1) {
                        EXT4_I(dir)->i_dir_start_lookup = block;
                        ret = bh;
                        goto cleanup_and_exit;
                } else {
                        brelse(bh);
                        if (i < 0)
                                goto cleanup_and_exit;
                }
        next:
                if (++block >= nblocks)
                        block = 0;
        } while (block != start);

        /*
         * If the directory has grown while we were searching, then
         * search the last part of the directory before giving up.
         */
        block = nblocks;
        nblocks = dir->i_size >> EXT4_BLOCK_SIZE_BITS(sb);
        if (block < nblocks) {
                start = 0;
                goto restart;
        }

cleanup_and_exit:
        /* Clean up the read-ahead blocks */
        for (; ra_ptr < ra_max; ra_ptr++)
                brelse(bh_use[ra_ptr]);
        return ret;
}

static struct buffer_head * ext4_dx_find_entry(struct inode *dir, const struct qstr *d_name,
                       struct ext4_dir_entry_2 **res_dir, int *err)
{
        struct super_block * sb = dir->i_sb;
        struct dx_hash_info     hinfo;
        struct dx_frame frames[2], *frame;
        struct buffer_head *bh;
        ext4_lblk_t block;
        int retval;

        if (!(frame = dx_probe(d_name, dir, &hinfo, frames, err)))
                return NULL;
        do {
                block = dx_get_block(frame->at);
                bh = ext4_read_dirblock(dir, block, DIRENT);
                if (IS_ERR(bh)) {
                        *err = PTR_ERR(bh);
                        goto errout;
                }
                retval = search_dirblock(bh, dir, d_name,
                                         block << EXT4_BLOCK_SIZE_BITS(sb),
                                         res_dir);
                if (retval == 1) {      /* Success! */
                        dx_release(frames);
                        return bh;
                }
                brelse(bh);
                if (retval == -1) {
                        *err = ERR_BAD_DX_DIR;
                        goto errout;
                }

                /* Check to see if we should continue to search */
                retval = ext4_htree_next_block(dir, hinfo.hash, frame,
                                               frames, NULL);
                if (retval < 0) {
                        ext4_warning(sb,
                             "error reading index page in directory #%lu",
                             dir->i_ino);
                        *err = retval;
                        goto errout;
                }
        } while (retval == 1);

        *err = -ENOENT;
errout:
        dxtrace(printk(KERN_DEBUG "%s not found\n", d_name->name));
        dx_release (frames);
        return NULL;
}

static struct dentry *ext4_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
{
        struct inode *inode;
        struct ext4_dir_entry_2 *de;
        struct buffer_head *bh;

        if (dentry->d_name.len > EXT4_NAME_LEN)
                return ERR_PTR(-ENAMETOOLONG);

        bh = ext4_find_entry(dir, &dentry->d_name, &de, NULL);
        inode = NULL;
        if (bh) {
                __u32 ino = le32_to_cpu(de->inode);
                brelse(bh);
                if (!ext4_valid_inum(dir->i_sb, ino)) {
                        EXT4_ERROR_INODE(dir, "bad inode number: %u", ino);
                        return ERR_PTR(-EIO);
                }
                if (unlikely(ino == dir->i_ino)) {
                        EXT4_ERROR_INODE(dir, "'%.*s' linked to parent dir",
                                         dentry->d_name.len,
                                         dentry->d_name.name);
                        return ERR_PTR(-EIO);
                }
                inode = ext4_iget(dir->i_sb, ino);
                if (inode == ERR_PTR(-ESTALE)) {
                        EXT4_ERROR_INODE(dir,
                                         "deleted inode referenced: %u",
                                         ino);
                        return ERR_PTR(-EIO);
                }
        }
        return d_splice_alias(inode, dentry);
}


struct dentry *ext4_get_parent(struct dentry *child)
{
        __u32 ino;
        static const struct qstr dotdot = QSTR_INIT("..", 2);
        struct ext4_dir_entry_2 * de;
        struct buffer_head *bh;

        bh = ext4_find_entry(child->d_inode, &dotdot, &de, NULL);
        if (!bh)
                return ERR_PTR(-ENOENT);
        ino = le32_to_cpu(de->inode);
        brelse(bh);

        if (!ext4_valid_inum(child->d_inode->i_sb, ino)) {
                EXT4_ERROR_INODE(child->d_inode,
                                 "bad parent inode number: %u", ino);
                return ERR_PTR(-EIO);
        }

        return d_obtain_alias(ext4_iget(child->d_inode->i_sb, ino));
}

/*
 * Move count entries from end of map between two memory locations.
 * Returns pointer to last entry moved.
 */
static struct ext4_dir_entry_2 *
dx_move_dirents(char *from, char *to, struct dx_map_entry *map, int count,
                unsigned blocksize)
{
        unsigned rec_len = 0;

        while (count--) {
                struct ext4_dir_entry_2 *de = (struct ext4_dir_entry_2 *)
                                                (from + (map->offs<<2));
                rec_len = EXT4_DIR_REC_LEN(de->name_len);
                memcpy (to, de, rec_len);
                ((struct ext4_dir_entry_2 *) to)->rec_len =
                                ext4_rec_len_to_disk(rec_len, blocksize);
                de->inode = 0;
                map++;
                to += rec_len;
        }
        return (struct ext4_dir_entry_2 *) (to - rec_len);
}

/*
 * Compact each dir entry in the range to the minimal rec_len.
 * Returns pointer to last entry in range.
 */
static struct ext4_dir_entry_2* dx_pack_dirents(char *base, unsigned blocksize)
{
        struct ext4_dir_entry_2 *next, *to, *prev, *de = (struct ext4_dir_entry_2 *) base;
        unsigned rec_len = 0;

        prev = to = de;
        while ((char*)de < base + blocksize) {
                next = ext4_next_entry(de, blocksize);
                if (de->inode && de->name_len) {
                        rec_len = EXT4_DIR_REC_LEN(de->name_len);
                        if (de > to)
                                memmove(to, de, rec_len);
                        to->rec_len = ext4_rec_len_to_disk(rec_len, blocksize);
                        prev = to;
                        to = (struct ext4_dir_entry_2 *) (((char *) to) + rec_len);
                }
                de = next;
        }
        return prev;
}

/*
 * Split a full leaf block to make room for a new dir entry.
 * Allocate a new block, and move entries so that they are approx. equally full.
 * Returns pointer to de in block into which the new entry will be inserted.
 */
static struct ext4_dir_entry_2 *do_split(handle_t *handle, struct inode *dir,
                        struct buffer_head **bh,struct dx_frame *frame,
                        struct dx_hash_info *hinfo, int *error)
{
        unsigned blocksize = dir->i_sb->s_blocksize;
        unsigned count, continued;
        struct buffer_head *bh2;
        ext4_lblk_t newblock;
        u32 hash2;
        struct dx_map_entry *map;
        char *data1 = (*bh)->b_data, *data2;
        unsigned split, move, size;
        struct ext4_dir_entry_2 *de = NULL, *de2;
        struct ext4_dir_entry_tail *t;
        int     csum_size = 0;
        int     err = 0, i;

        if (EXT4_HAS_RO_COMPAT_FEATURE(dir->i_sb,
                                       EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
                csum_size = sizeof(struct ext4_dir_entry_tail);

        bh2 = ext4_append(handle, dir, &newblock);
        if (IS_ERR(bh2)) {
                brelse(*bh);
                *bh = NULL;
                *error = PTR_ERR(bh2);
                return NULL;
        }

        BUFFER_TRACE(*bh, "get_write_access");
        err = ext4_journal_get_write_access(handle, *bh);
        if (err)
                goto journal_error;

        BUFFER_TRACE(frame->bh, "get_write_access");
        err = ext4_journal_get_write_access(handle, frame->bh);
        if (err)
                goto journal_error;

        data2 = bh2->b_data;

        /* create map in the end of data2 block */
        map = (struct dx_map_entry *) (data2 + blocksize);
        count = dx_make_map((struct ext4_dir_entry_2 *) data1,
                             blocksize, hinfo, map);
        map -= count;
        dx_sort_map(map, count);
        /* Split the existing block in the middle, size-wise */
        size = 0;
        move = 0;
        for (i = count-1; i >= 0; i--) {
                /* is more than half of this entry in 2nd half of the block? */
                if (size + map[i].size/2 > blocksize/2)
                        break;
                size += map[i].size;
                move++;
        }
        /* map index at which we will split */
        split = count - move;
        hash2 = map[split].hash;
        continued = hash2 == map[split - 1].hash;
        dxtrace(printk(KERN_INFO "Split block %lu at %x, %i/%i\n",
                        (unsigned long)dx_get_block(frame->at),
                                        hash2, split, count-split));

        /* Fancy dance to stay within two buffers */
        de2 = dx_move_dirents(data1, data2, map + split, count - split, blocksize);
        de = dx_pack_dirents(data1, blocksize);
        de->rec_len = ext4_rec_len_to_disk(data1 + (blocksize - csum_size) -
                                           (char *) de,
                                           blocksize);
        de2->rec_len = ext4_rec_len_to_disk(data2 + (blocksize - csum_size) -
                                            (char *) de2,
                                            blocksize);
        if (csum_size) {
                t = EXT4_DIRENT_TAIL(data2, blocksize);
                initialize_dirent_tail(t, blocksize);

                t = EXT4_DIRENT_TAIL(data1, blocksize);
                initialize_dirent_tail(t, blocksize);
        }

        dxtrace(dx_show_leaf (hinfo, (struct ext4_dir_entry_2 *) data1, blocksize, 1));
        dxtrace(dx_show_leaf (hinfo, (struct ext4_dir_entry_2 *) data2, blocksize, 1));

        /* Which block gets the new entry? */
        if (hinfo->hash >= hash2)
        {
                swap(*bh, bh2);
                de = de2;
        }
        dx_insert_block(frame, hash2 + continued, newblock);
        err = ext4_handle_dirty_dirent_node(handle, dir, bh2);
        if (err)
                goto journal_error;
        err = ext4_handle_dirty_dx_node(handle, dir, frame->bh);
        if (err)
                goto journal_error;
        brelse(bh2);
        dxtrace(dx_show_index("frame", frame->entries));
        return de;

journal_error:
        brelse(*bh);
        brelse(bh2);
        *bh = NULL;
        ext4_std_error(dir->i_sb, err);
        *error = err;
        return NULL;
}

int ext4_find_dest_de(struct inode *dir, struct inode *inode,
                      struct buffer_head *bh,
                      void *buf, int buf_size,
                      const char *name, int namelen,
                      struct ext4_dir_entry_2 **dest_de)
{
        struct ext4_dir_entry_2 *de;
        unsigned short reclen = EXT4_DIR_REC_LEN(namelen);
        int nlen, rlen;
        unsigned int offset = 0;
        char *top;

        de = (struct ext4_dir_entry_2 *)buf;
        top = buf + buf_size - reclen;
        while ((char *) de <= top) {
                if (ext4_check_dir_entry(dir, NULL, de, bh,
                                         buf, buf_size, offset))
                        return -EIO;
                if (ext4_match(namelen, name, de))
                        return -EEXIST;
                nlen = EXT4_DIR_REC_LEN(de->name_len);
                rlen = ext4_rec_len_from_disk(de->rec_len, buf_size);
                if ((de->inode ? rlen - nlen : rlen) >= reclen)
                        break;
                de = (struct ext4_dir_entry_2 *)((char *)de + rlen);
                offset += rlen;
        }
        if ((char *) de > top)
                return -ENOSPC;

        *dest_de = de;
        return 0;
}

void ext4_insert_dentry(struct inode *inode,
                        struct ext4_dir_entry_2 *de,
                        int buf_size,
                        const char *name, int namelen)
{

        int nlen, rlen;

        nlen = EXT4_DIR_REC_LEN(de->name_len);
        rlen = ext4_rec_len_from_disk(de->rec_len, buf_size);
        if (de->inode) {
                struct ext4_dir_entry_2 *de1 =
                                (struct ext4_dir_entry_2 *)((char *)de + nlen);
                de1->rec_len = ext4_rec_len_to_disk(rlen - nlen, buf_size);
                de->rec_len = ext4_rec_len_to_disk(nlen, buf_size);
                de = de1;
        }
        de->file_type = EXT4_FT_UNKNOWN;
        de->inode = cpu_to_le32(inode->i_ino);
        ext4_set_de_type(inode->i_sb, de, inode->i_mode);
        de->name_len = namelen;
        memcpy(de->name, name, namelen);
}
/*
 * Add a new entry into a directory (leaf) block.  If de is non-NULL,
 * it points to a directory entry which is guaranteed to be large
 * enough for new directory entry.  If de is NULL, then
 * add_dirent_to_buf will attempt search the directory block for
 * space.  It will return -ENOSPC if no space is available, and -EIO
 * and -EEXIST if directory entry already exists.
 */
static int add_dirent_to_buf(handle_t *handle, struct dentry *dentry,
                             struct inode *inode, struct ext4_dir_entry_2 *de,
                             struct buffer_head *bh)
{
        struct inode    *dir = dentry->d_parent->d_inode;
        const char      *name = dentry->d_name.name;
        int             namelen = dentry->d_name.len;
        unsigned int    blocksize = dir->i_sb->s_blocksize;
        int             csum_size = 0;
        int             err;

        if (EXT4_HAS_RO_COMPAT_FEATURE(inode->i_sb,
                                       EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
                csum_size = sizeof(struct ext4_dir_entry_tail);

        if (!de) {
                err = ext4_find_dest_de(dir, inode,
                                        bh, bh->b_data, blocksize - csum_size,
                                        name, namelen, &de);
                if (err)
                        return err;
        }
        BUFFER_TRACE(bh, "get_write_access");
        err = ext4_journal_get_write_access(handle, bh);
        if (err) {
                ext4_std_error(dir->i_sb, err);
                return err;
        }

        /* By now the buffer is marked for journaling */
        ext4_insert_dentry(inode, de, blocksize, name, namelen);

        /*
         * XXX shouldn't update any times until successful
         * completion of syscall, but too many callers depend
         * on this.
         *
         * XXX similarly, too many callers depend on
         * ext4_new_inode() setting the times, but error
         * recovery deletes the inode, so the worst that can
         * happen is that the times are slightly out of date
         * and/or different from the directory change time.
         */
        dir->i_mtime = dir->i_ctime = ext4_current_time(dir);
        ext4_update_dx_flag(dir);
        dir->i_version++;
        ext4_mark_inode_dirty(handle, dir);
        BUFFER_TRACE(bh, "call ext4_handle_dirty_metadata");
        err = ext4_handle_dirty_dirent_node(handle, dir, bh);
        if (err)
                ext4_std_error(dir->i_sb, err);
        return 0;
}

/*
 * This converts a one block unindexed directory to a 3 block indexed
 * directory, and adds the dentry to the indexed directory.
 */
static int make_indexed_dir(handle_t *handle, struct dentry *dentry,
                            struct inode *inode, struct buffer_head *bh)
{
        struct inode    *dir = dentry->d_parent->d_inode;
        const char      *name = dentry->d_name.name;
        int             namelen = dentry->d_name.len;
        struct buffer_head *bh2;
        struct dx_root  *root;
        struct dx_frame frames[2], *frame;
        struct dx_entry *entries;
        struct ext4_dir_entry_2 *de, *de2;
        struct ext4_dir_entry_tail *t;
        char            *data1, *top;
        unsigned        len;
        int             retval;
        unsigned        blocksize;
        struct dx_hash_info hinfo;
        ext4_lblk_t  block;
        struct fake_dirent *fde;
        int             csum_size = 0;

        if (EXT4_HAS_RO_COMPAT_FEATURE(inode->i_sb,
                                       EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
                csum_size = sizeof(struct ext4_dir_entry_tail);

        blocksize =  dir->i_sb->s_blocksize;
        dxtrace(printk(KERN_DEBUG "Creating index: inode %lu\n", dir->i_ino));
        retval = ext4_journal_get_write_access(handle, bh);
        if (retval) {
                ext4_std_error(dir->i_sb, retval);
                brelse(bh);
                return retval;
        }
        root = (struct dx_root *) bh->b_data;

        /* The 0th block becomes the root, move the dirents out */
        fde = &root->dotdot;
        de = (struct ext4_dir_entry_2 *)((char *)fde +
                ext4_rec_len_from_disk(fde->rec_len, blocksize));
        if ((char *) de >= (((char *) root) + blocksize)) {
                EXT4_ERROR_INODE(dir, "invalid rec_len for '..'");
                brelse(bh);
                return -EIO;
        }
        len = ((char *) root) + (blocksize - csum_size) - (char *) de;

        /* Allocate new block for the 0th block's dirents */
        bh2 = ext4_append(handle, dir, &block);
        if (IS_ERR(bh2)) {
                brelse(bh);
                return PTR_ERR(bh2);
        }
        ext4_set_inode_flag(dir, EXT4_INODE_INDEX);
        data1 = bh2->b_data;

        memcpy (data1, de, len);
        de = (struct ext4_dir_entry_2 *) data1;
        top = data1 + len;
        while ((char *)(de2 = ext4_next_entry(de, blocksize)) < top)
                de = de2;
        de->rec_len = ext4_rec_len_to_disk(data1 + (blocksize - csum_size) -
                                           (char *) de,
                                           blocksize);

        if (csum_size) {
                t = EXT4_DIRENT_TAIL(data1, blocksize);
                initialize_dirent_tail(t, blocksize);
        }

        /* Initialize the root; the dot dirents already exist */
        de = (struct ext4_dir_entry_2 *) (&root->dotdot);
        de->rec_len = ext4_rec_len_to_disk(blocksize - EXT4_DIR_REC_LEN(2),
                                           blocksize);
        memset (&root->info, 0, sizeof(root->info));
        root->info.info_length = sizeof(root->info);
        root->info.hash_version = EXT4_SB(dir->i_sb)->s_def_hash_version;
        entries = root->entries;
        dx_set_block(entries, 1);
        dx_set_count(entries, 1);
        dx_set_limit(entries, dx_root_limit(dir, sizeof(root->info)));

        /* Initialize as for dx_probe */
        hinfo.hash_version = root->info.hash_version;
        if (hinfo.hash_version <= DX_HASH_TEA)
                hinfo.hash_version += EXT4_SB(dir->i_sb)->s_hash_unsigned;
        hinfo.seed = EXT4_SB(dir->i_sb)->s_hash_seed;
        ext4fs_dirhash(name, namelen, &hinfo);
        frame = frames;
        frame->entries = entries;
        frame->at = entries;
        frame->bh = bh;
        bh = bh2;

        ext4_handle_dirty_dx_node(handle, dir, frame->bh);
        ext4_handle_dirty_dirent_node(handle, dir, bh);

        de = do_split(handle,dir, &bh, frame, &hinfo, &retval);
        if (!de) {
                /*
                 * Even if the block split failed, we have to properly write
                 * out all the changes we did so far. Otherwise we can end up
                 * with corrupted filesystem.
                 */
                ext4_mark_inode_dirty(handle, dir);
                dx_release(frames);
                return retval;
        }
        dx_release(frames);

        retval = add_dirent_to_buf(handle, dentry, inode, de, bh);
        brelse(bh);
        return retval;
}

/*
 *      ext4_add_entry()
 *
 * adds a file entry to the specified directory, using the same
 * semantics as ext4_find_entry(). It returns NULL if it failed.
 *
 * NOTE!! The inode part of 'de' is left at 0 - which means you
 * may not sleep between calling this and putting something into
 * the entry, as someone else might have used it while you slept.
 */
static int ext4_add_entry(handle_t *handle, struct dentry *dentry,
                          struct inode *inode)
{
        struct inode *dir = dentry->d_parent->d_inode;
        struct buffer_head *bh;
        struct ext4_dir_entry_2 *de;
        struct ext4_dir_entry_tail *t;
        struct super_block *sb;
        int     retval;
        int     dx_fallback=0;
        unsigned blocksize;
        ext4_lblk_t block, blocks;
        int     csum_size = 0;

        if (EXT4_HAS_RO_COMPAT_FEATURE(inode->i_sb,
                                       EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
                csum_size = sizeof(struct ext4_dir_entry_tail);

        sb = dir->i_sb;
        blocksize = sb->s_blocksize;
        if (!dentry->d_name.len)
                return -EINVAL;

        if (ext4_has_inline_data(dir)) {
                retval = ext4_try_add_inline_entry(handle, dentry, inode);
                if (retval < 0)
                        return retval;
                if (retval == 1) {
                        retval = 0;
                        return retval;
                }
        }

        if (is_dx(dir)) {
                retval = ext4_dx_add_entry(handle, dentry, inode);
                if (!retval || (retval != ERR_BAD_DX_DIR))
                        return retval;
                ext4_clear_inode_flag(dir, EXT4_INODE_INDEX);
                dx_fallback++;
                ext4_mark_inode_dirty(handle, dir);
        }
        blocks = dir->i_size >> sb->s_blocksize_bits;
        for (block = 0; block < blocks; block++) {
                bh = ext4_read_dirblock(dir, block, DIRENT);
                if (IS_ERR(bh))
                        return PTR_ERR(bh);

                retval = add_dirent_to_buf(handle, dentry, inode, NULL, bh);
                if (retval != -ENOSPC) {
                        brelse(bh);
                        return retval;
                }

                if (blocks == 1 && !dx_fallback &&
                    EXT4_HAS_COMPAT_FEATURE(sb, EXT4_FEATURE_COMPAT_DIR_INDEX))
                        return make_indexed_dir(handle, dentry, inode, bh);
                brelse(bh);
        }
        bh = ext4_append(handle, dir, &block);
        if (IS_ERR(bh))
                return PTR_ERR(bh);
        de = (struct ext4_dir_entry_2 *) bh->b_data;
        de->inode = 0;
        de->rec_len = ext4_rec_len_to_disk(blocksize - csum_size, blocksize);

        if (csum_size) {
                t = EXT4_DIRENT_TAIL(bh->b_data, blocksize);
                initialize_dirent_tail(t, blocksize);
        }

        retval = add_dirent_to_buf(handle, dentry, inode, de, bh);
        brelse(bh);
        if (retval == 0)
                ext4_set_inode_state(inode, EXT4_STATE_NEWENTRY);
        return retval;
}

/*
 * Returns 0 for success, or a negative error value
 */
static int ext4_dx_add_entry(handle_t *handle, struct dentry *dentry,
                             struct inode *inode)
{
        struct dx_frame frames[2], *frame;
        struct dx_entry *entries, *at;
        struct dx_hash_info hinfo;
        struct buffer_head *bh;
        struct inode *dir = dentry->d_parent->d_inode;
        struct super_block *sb = dir->i_sb;
        struct ext4_dir_entry_2 *de;
        int err;

        frame = dx_probe(&dentry->d_name, dir, &hinfo, frames, &err);
        if (!frame)
                return err;
        entries = frame->entries;
        at = frame->at;
        bh = ext4_read_dirblock(dir, dx_get_block(frame->at), DIRENT);
        if (IS_ERR(bh)) {
                err = PTR_ERR(bh);
                bh = NULL;
                goto cleanup;
        }

        BUFFER_TRACE(bh, "get_write_access");
        err = ext4_journal_get_write_access(handle, bh);
        if (err)
                goto journal_error;

        err = add_dirent_to_buf(handle, dentry, inode, NULL, bh);
        if (err != -ENOSPC)
                goto cleanup;

        /* Block full, should compress but for now just split */
        dxtrace(printk(KERN_DEBUG "using %u of %u node entries\n",
                       dx_get_count(entries), dx_get_limit(entries)));
        /* Need to split index? */
        if (dx_get_count(entries) == dx_get_limit(entries)) {
                ext4_lblk_t newblock;
                unsigned icount = dx_get_count(entries);
                int levels = frame - frames;
                struct dx_entry *entries2;
                struct dx_node *node2;
                struct buffer_head *bh2;

                if (levels && (dx_get_count(frames->entries) ==
                               dx_get_limit(frames->entries))) {
                        ext4_warning(sb, "Directory index full!");
                        err = -ENOSPC;
                        goto cleanup;
                }
                bh2 = ext4_append(handle, dir, &newblock);
                if (IS_ERR(bh2)) {
                        err = PTR_ERR(bh2);
                        goto cleanup;
                }
                node2 = (struct dx_node *)(bh2->b_data);
                entries2 = node2->entries;
                memset(&node2->fake, 0, sizeof(struct fake_dirent));
                node2->fake.rec_len = ext4_rec_len_to_disk(sb->s_blocksize,
                                                           sb->s_blocksize);
                BUFFER_TRACE(frame->bh, "get_write_access");
                err = ext4_journal_get_write_access(handle, frame->bh);
                if (err)
                        goto journal_error;
                if (levels) {
                        unsigned icount1 = icount/2, icount2 = icount - icount1;
                        unsigned hash2 = dx_get_hash(entries + icount1);
                        dxtrace(printk(KERN_DEBUG "Split index %i/%i\n",
                                       icount1, icount2));

                        BUFFER_TRACE(frame->bh, "get_write_access"); /* index root */
                        err = ext4_journal_get_write_access(handle,
                                                             frames[0].bh);
                        if (err)
                                goto journal_error;

                        memcpy((char *) entries2, (char *) (entries + icount1),
                               icount2 * sizeof(struct dx_entry));
                        dx_set_count(entries, icount1);
                        dx_set_count(entries2, icount2);
                        dx_set_limit(entries2, dx_node_limit(dir));

                        /* Which index block gets the new entry? */
                        if (at - entries >= icount1) {
                                frame->at = at = at - entries - icount1 + entries2;
                                frame->entries = entries = entries2;
                                swap(frame->bh, bh2);
                        }
                        dx_insert_block(frames + 0, hash2, newblock);
                        dxtrace(dx_show_index("node", frames[1].entries));
                        dxtrace(dx_show_index("node",
                               ((struct dx_node *) bh2->b_data)->entries));
                        err = ext4_handle_dirty_dx_node(handle, dir, bh2);
                        if (err)
                                goto journal_error;
                        brelse (bh2);
                } else {
                        dxtrace(printk(KERN_DEBUG
                                       "Creating second level index...\n"));
                        memcpy((char *) entries2, (char *) entries,
                               icount * sizeof(struct dx_entry));
                        dx_set_limit(entries2, dx_node_limit(dir));

                        /* Set up root */
                        dx_set_count(entries, 1);
                        dx_set_block(entries + 0, newblock);
                        ((struct dx_root *) frames[0].bh->b_data)->info.indirect_levels = 1;

                        /* Add new access path frame */
                        frame = frames + 1;
                        frame->at = at = at - entries + entries2;
                        frame->entries = entries = entries2;
                        frame->bh = bh2;
                        err = ext4_journal_get_write_access(handle,
                                                             frame->bh);
                        if (err)
                                goto journal_error;
                }
                err = ext4_handle_dirty_dx_node(handle, dir, frames[0].bh);
                if (err) {
                        ext4_std_error(inode->i_sb, err);
                        goto cleanup;
                }
        }
        de = do_split(handle, dir, &bh, frame, &hinfo, &err);
        if (!de)
                goto cleanup;
        err = add_dirent_to_buf(handle, dentry, inode, de, bh);
        goto cleanup;

journal_error:
        ext4_std_error(dir->i_sb, err);
cleanup:
        brelse(bh);
        dx_release(frames);
        return err;
}

/*
 * ext4_generic_delete_entry deletes a directory entry by merging it
 * with the previous entry
 */
int ext4_generic_delete_entry(handle_t *handle,
                              struct inode *dir,
                              struct ext4_dir_entry_2 *de_del,
                              struct buffer_head *bh,
                              void *entry_buf,
                              int buf_size,
                              int csum_size)
{
        struct ext4_dir_entry_2 *de, *pde;
        unsigned int blocksize = dir->i_sb->s_blocksize;
        int i;

        i = 0;
        pde = NULL;
        de = (struct ext4_dir_entry_2 *)entry_buf;
        while (i < buf_size - csum_size) {
                if (ext4_check_dir_entry(dir, NULL, de, bh,
                                         bh->b_data, bh->b_size, i))
                        return -EIO;
                if (de == de_del)  {
                        if (pde)
                                pde->rec_len = ext4_rec_len_to_disk(
                                        ext4_rec_len_from_disk(pde->rec_len,
                                                               blocksize) +
                                        ext4_rec_len_from_disk(de->rec_len,
                                                               blocksize),
                                        blocksize);
                        else
                                de->inode = 0;
                        dir->i_version++;
                        return 0;
                }
                i += ext4_rec_len_from_disk(de->rec_len, blocksize);
                pde = de;
                de = ext4_next_entry(de, blocksize);
        }
        return -ENOENT;
}

static int ext4_delete_entry(handle_t *handle,
                             struct inode *dir,
                             struct ext4_dir_entry_2 *de_del,
                             struct buffer_head *bh)
{
        int err, csum_size = 0;

        if (ext4_has_inline_data(dir)) {
                int has_inline_data = 1;
                err = ext4_delete_inline_entry(handle, dir, de_del, bh,
                                               &has_inline_data);
                if (has_inline_data)
                        return err;
        }

        if (EXT4_HAS_RO_COMPAT_FEATURE(dir->i_sb,
                                       EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
                csum_size = sizeof(struct ext4_dir_entry_tail);

        BUFFER_TRACE(bh, "get_write_access");
        err = ext4_journal_get_write_access(handle, bh);
        if (unlikely(err))
                goto out;

        err = ext4_generic_delete_entry(handle, dir, de_del,
                                        bh, bh->b_data,
                                        dir->i_sb->s_blocksize, csum_size);
        if (err)
                goto out;

        BUFFER_TRACE(bh, "call ext4_handle_dirty_metadata");
        err = ext4_handle_dirty_dirent_node(handle, dir, bh);
        if (unlikely(err))
                goto out;

        return 0;
out:
        if (err != -ENOENT)
                ext4_std_error(dir->i_sb, err);
        return err;
}

/*
 * DIR_NLINK feature is set if 1) nlinks > EXT4_LINK_MAX or 2) nlinks == 2,
 * since this indicates that nlinks count was previously 1.
 */
static void ext4_inc_count(handle_t *handle, struct inode *inode)
{
        inc_nlink(inode);
        if (is_dx(inode) && inode->i_nlink > 1) {
                /* limit is 16-bit i_links_count */
                if (inode->i_nlink >= EXT4_LINK_MAX || inode->i_nlink == 2) {
                        set_nlink(inode, 1);
                        EXT4_SET_RO_COMPAT_FEATURE(inode->i_sb,
                                              EXT4_FEATURE_RO_COMPAT_DIR_NLINK);
                }
        }
}

/*
 * If a directory had nlink == 1, then we should let it be 1. This indicates
 * directory has >EXT4_LINK_MAX subdirs.
 */
static void ext4_dec_count(handle_t *handle, struct inode *inode)
{
        if (!S_ISDIR(inode->i_mode) || inode->i_nlink > 2)
                drop_nlink(inode);
}


static int ext4_add_nondir(handle_t *handle,
                struct dentry *dentry, struct inode *inode)
{
        int err = ext4_add_entry(handle, dentry, inode);
        if (!err) {
                ext4_mark_inode_dirty(handle, inode);
                unlock_new_inode(inode);
                d_instantiate(dentry, inode);
                return 0;
        }
        drop_nlink(inode);
        unlock_new_inode(inode);
        iput(inode);
        return err;
}

/*
 * By the time this is called, we already have created
 * the directory cache entry for the new file, but it
 * is so far negative - it has no inode.
 *
 * If the create succeeds, we fill in the inode information
 * with d_instantiate().
 */
static int ext4_create(struct inode *dir, struct dentry *dentry, umode_t mode,
                       bool excl)
{
        handle_t *handle;
        struct inode *inode;
        int err, credits, retries = 0;

        dquot_initialize(dir);

        credits = (EXT4_DATA_TRANS_BLOCKS(dir->i_sb) +
                   EXT4_INDEX_EXTRA_TRANS_BLOCKS + 3);
retry:
        inode = ext4_new_inode_start_handle(dir, mode, &dentry->d_name, 0,
                                            NULL, EXT4_HT_DIR, credits);
        handle = ext4_journal_current_handle();
        err = PTR_ERR(inode);
        if (!IS_ERR(inode)) {
                inode->i_op = &ext4_file_inode_operations;
                inode->i_fop = &ext4_file_operations;
                ext4_set_aops(inode);
                err = ext4_add_nondir(handle, dentry, inode);
                if (!err && IS_DIRSYNC(dir))
                        ext4_handle_sync(handle);
        }
        if (handle)
                ext4_journal_stop(handle);
        if (err == -ENOSPC && ext4_should_retry_alloc(dir->i_sb, &retries))
                goto retry;
        return err;
}

static int ext4_mknod(struct inode *dir, struct dentry *dentry,
                      umode_t mode, dev_t rdev)
{
        handle_t *handle;
        struct inode *inode;
        int err, credits, retries = 0;

        if (!new_valid_dev(rdev))
                return -EINVAL;

        dquot_initialize(dir);

        credits = (EXT4_DATA_TRANS_BLOCKS(dir->i_sb) +
                   EXT4_INDEX_EXTRA_TRANS_BLOCKS + 3);
retry:
        inode = ext4_new_inode_start_handle(dir, mode, &dentry->d_name, 0,
                                            NULL, EXT4_HT_DIR, credits);
        handle = ext4_journal_current_handle();
        err = PTR_ERR(inode);
        if (!IS_ERR(inode)) {
                init_special_inode(inode, inode->i_mode, rdev);
                inode->i_op = &ext4_special_inode_operations;
                err = ext4_add_nondir(handle, dentry, inode);
                if (!err && IS_DIRSYNC(dir))
                        ext4_handle_sync(handle);
        }
        if (handle)
                ext4_journal_stop(handle);
        if (err == -ENOSPC && ext4_should_retry_alloc(dir->i_sb, &retries))
                goto retry;
        return err;
}

static int ext4_tmpfile(struct inode *dir, struct dentry *dentry, umode_t mode)
{
        handle_t *handle;
        struct inode *inode;
        int err, retries = 0;

        dquot_initialize(dir);

retry:
        inode = ext4_new_inode_start_handle(dir, mode,
                                            NULL, 0, NULL,
                                            EXT4_HT_DIR,
                        EXT4_MAXQUOTAS_INIT_BLOCKS(dir->i_sb) +
                          4 + EXT4_XATTR_TRANS_BLOCKS);
        handle = ext4_journal_current_handle();
        err = PTR_ERR(inode);
        if (!IS_ERR(inode)) {
                inode->i_op = &ext4_file_inode_operations;
                inode->i_fop = &ext4_file_operations;
                ext4_set_aops(inode);
                d_tmpfile(dentry, inode);
                err = ext4_orphan_add(handle, inode);
                if (err)
                        goto err_unlock_inode;
                mark_inode_dirty(inode);
                unlock_new_inode(inode);
        }
        if (handle)
                ext4_journal_stop(handle);
        if (err == -ENOSPC && ext4_should_retry_alloc(dir->i_sb, &retries))
                goto retry;
        return err;
err_unlock_inode:
        ext4_journal_stop(handle);
        unlock_new_inode(inode);
        return err;
}

struct ext4_dir_entry_2 *ext4_init_dot_dotdot(struct inode *inode,
                          struct ext4_dir_entry_2 *de,
                          int blocksize, int csum_size,
                          unsigned int parent_ino, int dotdot_real_len)
{
        de->inode = cpu_to_le32(inode->i_ino);
        de->name_len = 1;
        de->rec_len = ext4_rec_len_to_disk(EXT4_DIR_REC_LEN(de->name_len),
                                           blocksize);
        strcpy(de->name, ".");
        ext4_set_de_type(inode->i_sb, de, S_IFDIR);

        de = ext4_next_entry(de, blocksize);
        de->inode = cpu_to_le32(parent_ino);
        de->name_len = 2;
        if (!dotdot_real_len)
                de->rec_len = ext4_rec_len_to_disk(blocksize -
                                        (csum_size + EXT4_DIR_REC_LEN(1)),
                                        blocksize);
        else
                de->rec_len = ext4_rec_len_to_disk(
                                EXT4_DIR_REC_LEN(de->name_len), blocksize);
        strcpy(de->name, "..");
        ext4_set_de_type(inode->i_sb, de, S_IFDIR);

        return ext4_next_entry(de, blocksize);
}

static int ext4_init_new_dir(handle_t *handle, struct inode *dir,
                             struct inode *inode)
{
        struct buffer_head *dir_block = NULL;
        struct ext4_dir_entry_2 *de;
        struct ext4_dir_entry_tail *t;
        ext4_lblk_t block = 0;
        unsigned int blocksize = dir->i_sb->s_blocksize;
        int csum_size = 0;
        int err;

        if (EXT4_HAS_RO_COMPAT_FEATURE(dir->i_sb,
                                       EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
                csum_size = sizeof(struct ext4_dir_entry_tail);

        if (ext4_test_inode_state(inode, EXT4_STATE_MAY_INLINE_DATA)) {
                err = ext4_try_create_inline_dir(handle, dir, inode);
                if (err < 0 && err != -ENOSPC)
                        goto out;
                if (!err)
                        goto out;
        }

        inode->i_size = 0;
        dir_block = ext4_append(handle, inode, &block);
        if (IS_ERR(dir_block))
                return PTR_ERR(dir_block);
        BUFFER_TRACE(dir_block, "get_write_access");
        err = ext4_journal_get_write_access(handle, dir_block);
        if (err)
                goto out;
        de = (struct ext4_dir_entry_2 *)dir_block->b_data;
        ext4_init_dot_dotdot(inode, de, blocksize, csum_size, dir->i_ino, 0);
        set_nlink(inode, 2);
        if (csum_size) {
                t = EXT4_DIRENT_TAIL(dir_block->b_data, blocksize);
                initialize_dirent_tail(t, blocksize);
        }

        BUFFER_TRACE(dir_block, "call ext4_handle_dirty_metadata");
        err = ext4_handle_dirty_dirent_node(handle, inode, dir_block);
        if (err)
                goto out;
        set_buffer_verified(dir_block);
out:
        brelse(dir_block);
        return err;
}

static int ext4_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
{
        handle_t *handle;
        struct inode *inode;
        int err, credits, retries = 0;

        if (EXT4_DIR_LINK_MAX(dir))
                return -EMLINK;

        dquot_initialize(dir);

        credits = (EXT4_DATA_TRANS_BLOCKS(dir->i_sb) +
                   EXT4_INDEX_EXTRA_TRANS_BLOCKS + 3);
retry:
        inode = ext4_new_inode_start_handle(dir, S_IFDIR | mode,
                                            &dentry->d_name,
                                            0, NULL, EXT4_HT_DIR, credits);
        handle = ext4_journal_current_handle();
        err = PTR_ERR(inode);
        if (IS_ERR(inode))
                goto out_stop;

        inode->i_op = &ext4_dir_inode_operations;
        inode->i_fop = &ext4_dir_operations;
        err = ext4_init_new_dir(handle, dir, inode);
        if (err)
                goto out_clear_inode;
        err = ext4_mark_inode_dirty(handle, inode);
        if (!err)
                err = ext4_add_entry(handle, dentry, inode);
        if (err) {
out_clear_inode:
                clear_nlink(inode);
                unlock_new_inode(inode);
                ext4_mark_inode_dirty(handle, inode);
                iput(inode);
                goto out_stop;
        }
        ext4_inc_count(handle, dir);
        ext4_update_dx_flag(dir);
        err = ext4_mark_inode_dirty(handle, dir);
        if (err)
                goto out_clear_inode;
        unlock_new_inode(inode);
        d_instantiate(dentry, inode);
        if (IS_DIRSYNC(dir))
                ext4_handle_sync(handle);

out_stop:
        if (handle)
                ext4_journal_stop(handle);
        if (err == -ENOSPC && ext4_should_retry_alloc(dir->i_sb, &retries))
                goto retry;
        return err;
}

/*
 * routine to check that the specified directory is empty (for rmdir)
 */
static int empty_dir(struct inode *inode)
{
        unsigned int offset;
        struct buffer_head *bh;
        struct ext4_dir_entry_2 *de, *de1;
        struct super_block *sb;
        int err = 0;

        if (ext4_has_inline_data(inode)) {
                int has_inline_data = 1;

                err = empty_inline_dir(inode, &has_inline_data);
                if (has_inline_data)
                        return err;
        }

        sb = inode->i_sb;
        if (inode->i_size < EXT4_DIR_REC_LEN(1) + EXT4_DIR_REC_LEN(2)) {
                EXT4_ERROR_INODE(inode, "invalid size");
                return 1;
        }
        bh = ext4_read_dirblock(inode, 0, EITHER);
        if (IS_ERR(bh))
                return 1;

        de = (struct ext4_dir_entry_2 *) bh->b_data;
        de1 = ext4_next_entry(de, sb->s_blocksize);
        if (le32_to_cpu(de->inode) != inode->i_ino ||
                        !le32_to_cpu(de1->inode) ||
                        strcmp(".", de->name) ||
                        strcmp("..", de1->name)) {
                ext4_warning(inode->i_sb,
                             "bad directory (dir #%lu) - no `.' or `..'",
                             inode->i_ino);
                brelse(bh);
                return 1;
        }
        offset = ext4_rec_len_from_disk(de->rec_len, sb->s_blocksize) +
                 ext4_rec_len_from_disk(de1->rec_len, sb->s_blocksize);
        de = ext4_next_entry(de1, sb->s_blocksize);
        while (offset < inode->i_size) {
                if (!bh ||
                    (void *) de >= (void *) (bh->b_data+sb->s_blocksize)) {
                        unsigned int lblock;
                        err = 0;
                        brelse(bh);
                        lblock = offset >> EXT4_BLOCK_SIZE_BITS(sb);
                        bh = ext4_read_dirblock(inode, lblock, EITHER);
                        if (IS_ERR(bh))
                                return 1;
                        de = (struct ext4_dir_entry_2 *) bh->b_data;
                }
                if (ext4_check_dir_entry(inode, NULL, de, bh,
                                         bh->b_data, bh->b_size, offset)) {
                        de = (struct ext4_dir_entry_2 *)(bh->b_data +
                                                         sb->s_blocksize);
                        offset = (offset | (sb->s_blocksize - 1)) + 1;
                        continue;
                }
                if (le32_to_cpu(de->inode)) {
                        brelse(bh);
                        return 0;
                }
                offset += ext4_rec_len_from_disk(de->rec_len, sb->s_blocksize);
                de = ext4_next_entry(de, sb->s_blocksize);
        }
        brelse(bh);
        return 1;
}

/* ext4_orphan_add() links an unlinked or truncated inode into a list of
 * such inodes, starting at the superblock, in case we crash before the
 * file is closed/deleted, or in case the inode truncate spans multiple
 * transactions and the last transaction is not recovered after a crash.
 *
 * At filesystem recovery time, we walk this list deleting unlinked
 * inodes and truncating linked inodes in ext4_orphan_cleanup().
 */
int ext4_orphan_add(handle_t *handle, struct inode *inode)
{
        struct super_block *sb = inode->i_sb;
        struct ext4_iloc iloc;
        int err = 0, rc;

        if (!EXT4_SB(sb)->s_journal)
                return 0;

        mutex_lock(&EXT4_SB(sb)->s_orphan_lock);
        if (!list_empty(&EXT4_I(inode)->i_orphan))
                goto out_unlock;

        /*
         * Orphan handling is only valid for files with data blocks
         * being truncated, or files being unlinked. Note that we either
         * hold i_mutex, or the inode can not be referenced from outside,
         * so i_nlink should not be bumped due to race
         */
        J_ASSERT((S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode) ||
                  S_ISLNK(inode->i_mode)) || inode->i_nlink == 0);

        BUFFER_TRACE(EXT4_SB(sb)->s_sbh, "get_write_access");
        err = ext4_journal_get_write_access(handle, EXT4_SB(sb)->s_sbh);
        if (err)
                goto out_unlock;

        err = ext4_reserve_inode_write(handle, inode, &iloc);
        if (err)
                goto out_unlock;
        /*
         * Due to previous errors inode may be already a part of on-disk
         * orphan list. If so skip on-disk list modification.
         */
        if (NEXT_ORPHAN(inode) && NEXT_ORPHAN(inode) <=
                (le32_to_cpu(EXT4_SB(sb)->s_es->s_inodes_count)))
                        goto mem_insert;

        /* Insert this inode at the head of the on-disk orphan list... */
        NEXT_ORPHAN(inode) = le32_to_cpu(EXT4_SB(sb)->s_es->s_last_orphan);
        EXT4_SB(sb)->s_es->s_last_orphan = cpu_to_le32(inode->i_ino);
        err = ext4_handle_dirty_super(handle, sb);
        rc = ext4_mark_iloc_dirty(handle, inode, &iloc);
        if (!err)
                err = rc;

        /* Only add to the head of the in-memory list if all the
         * previous operations succeeded.  If the orphan_add is going to
         * fail (possibly taking the journal offline), we can't risk
         * leaving the inode on the orphan list: stray orphan-list
         * entries can cause panics at unmount time.
         *
         * This is safe: on error we're going to ignore the orphan list
         * anyway on the next recovery. */
mem_insert:
        if (!err)
                list_add(&EXT4_I(inode)->i_orphan, &EXT4_SB(sb)->s_orphan);

        jbd_debug(4, "superblock will point to %lu\n", inode->i_ino);
        jbd_debug(4, "orphan inode %lu will point to %d\n",
                        inode->i_ino, NEXT_ORPHAN(inode));
out_unlock:
        mutex_unlock(&EXT4_SB(sb)->s_orphan_lock);
        ext4_std_error(inode->i_sb, err);
        return err;
}

/*
 * ext4_orphan_del() removes an unlinked or truncated inode from the list
 * of such inodes stored on disk, because it is finally being cleaned up.
 */
int ext4_orphan_del(handle_t *handle, struct inode *inode)
{
        struct list_head *prev;
        struct ext4_inode_info *ei = EXT4_I(inode);
        struct ext4_sb_info *sbi;
        __u32 ino_next;
        struct ext4_iloc iloc;
        int err = 0;

        if ((!EXT4_SB(inode->i_sb)->s_journal) &&
            !(EXT4_SB(inode->i_sb)->s_mount_state & EXT4_ORPHAN_FS))
                return 0;

        mutex_lock(&EXT4_SB(inode->i_sb)->s_orphan_lock);
        if (list_empty(&ei->i_orphan))
                goto out;

        ino_next = NEXT_ORPHAN(inode);
        prev = ei->i_orphan.prev;
        sbi = EXT4_SB(inode->i_sb);

        jbd_debug(4, "remove inode %lu from orphan list\n", inode->i_ino);

        list_del_init(&ei->i_orphan);

        /* If we're on an error path, we may not have a valid
         * transaction handle with which to update the orphan list on
         * disk, but we still need to remove the inode from the linked
         * list in memory. */
        if (!handle)
                goto out;

        err = ext4_reserve_inode_write(handle, inode, &iloc);
        if (err)
                goto out_err;

        if (prev == &sbi->s_orphan) {
                jbd_debug(4, "superblock will point to %u\n", ino_next);
                BUFFER_TRACE(sbi->s_sbh, "get_write_access");
                err = ext4_journal_get_write_access(handle, sbi->s_sbh);
                if (err)
                        goto out_brelse;
                sbi->s_es->s_last_orphan = cpu_to_le32(ino_next);
                err = ext4_handle_dirty_super(handle, inode->i_sb);
        } else {
                struct ext4_iloc iloc2;
                struct inode *i_prev =
                        &list_entry(prev, struct ext4_inode_info, i_orphan)->vfs_inode;

                jbd_debug(4, "orphan inode %lu will point to %u\n",
                          i_prev->i_ino, ino_next);
                err = ext4_reserve_inode_write(handle, i_prev, &iloc2);
                if (err)
                        goto out_brelse;
                NEXT_ORPHAN(i_prev) = ino_next;
                err = ext4_mark_iloc_dirty(handle, i_prev, &iloc2);
        }
        if (err)
                goto out_brelse;
        NEXT_ORPHAN(inode) = 0;
        err = ext4_mark_iloc_dirty(handle, inode, &iloc);

out_err:
        ext4_std_error(inode->i_sb, err);
out:
        mutex_unlock(&EXT4_SB(inode->i_sb)->s_orphan_lock);
        return err;

out_brelse:
        brelse(iloc.bh);
        goto out_err;
}

static int ext4_rmdir(struct inode *dir, struct dentry *dentry)
{
        int retval;
        struct inode *inode;
        struct buffer_head *bh;
        struct ext4_dir_entry_2 *de;
        handle_t *handle = NULL;

        /* Initialize quotas before so that eventual writes go in
         * separate transaction */
        dquot_initialize(dir);
        dquot_initialize(dentry->d_inode);

        retval = -ENOENT;
        bh = ext4_find_entry(dir, &dentry->d_name, &de, NULL);
        if (!bh)
                goto end_rmdir;

        inode = dentry->d_inode;

        retval = -EIO;
        if (le32_to_cpu(de->inode) != inode->i_ino)
                goto end_rmdir;

        retval = -ENOTEMPTY;
        if (!empty_dir(inode))
                goto end_rmdir;

        handle = ext4_journal_start(dir, EXT4_HT_DIR,
                                    EXT4_DATA_TRANS_BLOCKS(dir->i_sb));
        if (IS_ERR(handle)) {
                retval = PTR_ERR(handle);
                handle = NULL;
                goto end_rmdir;
        }

        if (IS_DIRSYNC(dir))
                ext4_handle_sync(handle);

        retval = ext4_delete_entry(handle, dir, de, bh);
        if (retval)
                goto end_rmdir;
        if (!EXT4_DIR_LINK_EMPTY(inode))
                ext4_warning(inode->i_sb,
                             "empty directory has too many links (%d)",
                             inode->i_nlink);
        inode->i_version++;
        clear_nlink(inode);
        /* There's no need to set i_disksize: the fact that i_nlink is
         * zero will ensure that the right thing happens during any
         * recovery. */
        inode->i_size = 0;
        ext4_orphan_add(handle, inode);
        inode->i_ctime = dir->i_ctime = dir->i_mtime = ext4_current_time(inode);
        ext4_mark_inode_dirty(handle, inode);
        ext4_dec_count(handle, dir);
        ext4_update_dx_flag(dir);
        ext4_mark_inode_dirty(handle, dir);

end_rmdir:
        brelse(bh);
        if (handle)
                ext4_journal_stop(handle);
        return retval;
}

static int ext4_unlink(struct inode *dir, struct dentry *dentry)
{
        int retval;
        struct inode *inode;
        struct buffer_head *bh;
        struct ext4_dir_entry_2 *de;
        handle_t *handle = NULL;

        trace_ext4_unlink_enter(dir, dentry);
        /* Initialize quotas before so that eventual writes go
         * in separate transaction */
        dquot_initialize(dir);
        dquot_initialize(dentry->d_inode);

        retval = -ENOENT;
        bh = ext4_find_entry(dir, &dentry->d_name, &de, NULL);
        if (!bh)
                goto end_unlink;

        inode = dentry->d_inode;

        retval = -EIO;
        if (le32_to_cpu(de->inode) != inode->i_ino)
                goto end_unlink;

        handle = ext4_journal_start(dir, EXT4_HT_DIR,
                                    EXT4_DATA_TRANS_BLOCKS(dir->i_sb));
        if (IS_ERR(handle)) {
                retval = PTR_ERR(handle);
                handle = NULL;
                goto end_unlink;
        }

        if (IS_DIRSYNC(dir))
                ext4_handle_sync(handle);

        if (!inode->i_nlink) {
                ext4_warning(inode->i_sb,
                             "Deleting nonexistent file (%lu), %d",
                             inode->i_ino, inode->i_nlink);
                set_nlink(inode, 1);
        }
        retval = ext4_delete_entry(handle, dir, de, bh);
        if (retval)
                goto end_unlink;
        dir->i_ctime = dir->i_mtime = ext4_current_time(dir);
        ext4_update_dx_flag(dir);
        ext4_mark_inode_dirty(handle, dir);
        drop_nlink(inode);
        if (!inode->i_nlink)
                ext4_orphan_add(handle, inode);
        inode->i_ctime = ext4_current_time(inode);
        ext4_mark_inode_dirty(handle, inode);
        retval = 0;

end_unlink:
        brelse(bh);
        if (handle)
                ext4_journal_stop(handle);
        trace_ext4_unlink_exit(dentry, retval);
        return retval;
}

static int ext4_symlink(struct inode *dir,
                        struct dentry *dentry, const char *symname)
{
        handle_t *handle;
        struct inode *inode;
        int l, err, retries = 0;
        int credits;

        l = strlen(symname)+1;
        if (l > dir->i_sb->s_blocksize)
                return -ENAMETOOLONG;

        dquot_initialize(dir);

        if (l > EXT4_N_BLOCKS * 4) {
                /*
                 * For non-fast symlinks, we just allocate inode and put it on
                 * orphan list in the first transaction => we need bitmap,
                 * group descriptor, sb, inode block, quota blocks, and
                 * possibly selinux xattr blocks.
                 */
                credits = 4 + EXT4_MAXQUOTAS_INIT_BLOCKS(dir->i_sb) +
                          EXT4_XATTR_TRANS_BLOCKS;
        } else {
                /*
                 * Fast symlink. We have to add entry to directory
                 * (EXT4_DATA_TRANS_BLOCKS + EXT4_INDEX_EXTRA_TRANS_BLOCKS),
                 * allocate new inode (bitmap, group descriptor, inode block,
                 * quota blocks, sb is already counted in previous macros).
                 */
                credits = EXT4_DATA_TRANS_BLOCKS(dir->i_sb) +
                          EXT4_INDEX_EXTRA_TRANS_BLOCKS + 3;
        }
retry:
        inode = ext4_new_inode_start_handle(dir, S_IFLNK|S_IRWXUGO,
                                            &dentry->d_name, 0, NULL,
                                            EXT4_HT_DIR, credits);
        handle = ext4_journal_current_handle();
        err = PTR_ERR(inode);
        if (IS_ERR(inode))
                goto out_stop;

        if (l > EXT4_N_BLOCKS * 4) {
                inode->i_op = &ext4_symlink_inode_operations;
                ext4_set_aops(inode);
                /*
                 * We cannot call page_symlink() with transaction started
                 * because it calls into ext4_write_begin() which can wait
                 * for transaction commit if we are running out of space
                 * and thus we deadlock. So we have to stop transaction now
                 * and restart it when symlink contents is written.
                 * 
                 * To keep fs consistent in case of crash, we have to put inode
                 * to orphan list in the mean time.
                 */
                drop_nlink(inode);
                err = ext4_orphan_add(handle, inode);
                ext4_journal_stop(handle);
                if (err)
                        goto err_drop_inode;
                err = __page_symlink(inode, symname, l, 1);
                if (err)
                        goto err_drop_inode;
                /*
                 * Now inode is being linked into dir (EXT4_DATA_TRANS_BLOCKS
                 * + EXT4_INDEX_EXTRA_TRANS_BLOCKS), inode is also modified
                 */
                handle = ext4_journal_start(dir, EXT4_HT_DIR,
                                EXT4_DATA_TRANS_BLOCKS(dir->i_sb) +
                                EXT4_INDEX_EXTRA_TRANS_BLOCKS + 1);
                if (IS_ERR(handle)) {
                        err = PTR_ERR(handle);
                        goto err_drop_inode;
                }
                set_nlink(inode, 1);
                err = ext4_orphan_del(handle, inode);
                if (err) {
                        ext4_journal_stop(handle);
                        clear_nlink(inode);
                        goto err_drop_inode;
                }
        } else {
                /* clear the extent format for fast symlink */
                ext4_clear_inode_flag(inode, EXT4_INODE_EXTENTS);
                inode->i_op = &ext4_fast_symlink_inode_operations;
                memcpy((char *)&EXT4_I(inode)->i_data, symname, l);
                inode->i_size = l-1;
        }
        EXT4_I(inode)->i_disksize = inode->i_size;
        err = ext4_add_nondir(handle, dentry, inode);
        if (!err && IS_DIRSYNC(dir))
                ext4_handle_sync(handle);

out_stop:
        if (handle)
                ext4_journal_stop(handle);
        if (err == -ENOSPC && ext4_should_retry_alloc(dir->i_sb, &retries))
                goto retry;
        return err;
err_drop_inode:
        unlock_new_inode(inode);
        iput(inode);
        return err;
}

static int ext4_link(struct dentry *old_dentry,
                     struct inode *dir, struct dentry *dentry)
{
        handle_t *handle;
        struct inode *inode = old_dentry->d_inode;
        int err, retries = 0;

        if (inode->i_nlink >= EXT4_LINK_MAX)
                return -EMLINK;

        dquot_initialize(dir);

retry:
        handle = ext4_journal_start(dir, EXT4_HT_DIR,
                (EXT4_DATA_TRANS_BLOCKS(dir->i_sb) +
                 EXT4_INDEX_EXTRA_TRANS_BLOCKS) + 1);
        if (IS_ERR(handle))
                return PTR_ERR(handle);

        if (IS_DIRSYNC(dir))
                ext4_handle_sync(handle);

        inode->i_ctime = ext4_current_time(inode);
        ext4_inc_count(handle, inode);
        ihold(inode);

        err = ext4_add_entry(handle, dentry, inode);
        if (!err) {
                ext4_mark_inode_dirty(handle, inode);
                /* this can happen only for tmpfile being
                 * linked the first time
                 */
                if (inode->i_nlink == 1)
                        ext4_orphan_del(handle, inode);
                d_instantiate(dentry, inode);
        } else {
                drop_nlink(inode);
                iput(inode);
        }
        ext4_journal_stop(handle);
        if (err == -ENOSPC && ext4_should_retry_alloc(dir->i_sb, &retries))
                goto retry;
        return err;
}


/*
 * Try to find buffer head where contains the parent block.
 * It should be the inode block if it is inlined or the 1st block
 * if it is a normal dir.
 */
static struct buffer_head *ext4_get_first_dir_block(handle_t *handle,
                                        struct inode *inode,
                                        int *retval,
                                        struct ext4_dir_entry_2 **parent_de,
                                        int *inlined)
{
        struct buffer_head *bh;

        if (!ext4_has_inline_data(inode)) {
                bh = ext4_read_dirblock(inode, 0, EITHER);
                if (IS_ERR(bh)) {
                        *retval = PTR_ERR(bh);
                        return NULL;
                }
                *parent_de = ext4_next_entry(
                                        (struct ext4_dir_entry_2 *)bh->b_data,
                                        inode->i_sb->s_blocksize);
                return bh;
        }

        *inlined = 1;
        return ext4_get_first_inline_block(inode, parent_de, retval);
}

/*
 * Anybody can rename anything with this: the permission checks are left to the
 * higher-level routines.
 *
 * n.b.  old_{dentry,inode) refers to the source dentry/inode
 * while new_{dentry,inode) refers to the destination dentry/inode
 * This comes from rename(const char *oldpath, const char *newpath)
 */
static int ext4_rename(struct inode *old_dir, struct dentry *old_dentry,
                       struct inode *new_dir, struct dentry *new_dentry)
{
        handle_t *handle = NULL;
        struct inode *old_inode, *new_inode;
        struct buffer_head *old_bh, *new_bh, *dir_bh;
        struct ext4_dir_entry_2 *old_de, *new_de;
        int retval;
        int inlined = 0, new_inlined = 0;
        struct ext4_dir_entry_2 *parent_de;

        dquot_initialize(old_dir);
        dquot_initialize(new_dir);

        old_bh = new_bh = dir_bh = NULL;

        /* Initialize quotas before so that eventual writes go
         * in separate transaction */
        if (new_dentry->d_inode)
                dquot_initialize(new_dentry->d_inode);

        old_bh = ext4_find_entry(old_dir, &old_dentry->d_name, &old_de, NULL);
        /*
         *  Check for inode number is _not_ due to possible IO errors.
         *  We might rmdir the source, keep it as pwd of some process
         *  and merrily kill the link to whatever was created under the
         *  same name. Goodbye sticky bit ;-<
         */
        old_inode = old_dentry->d_inode;
        retval = -ENOENT;
        if (!old_bh || le32_to_cpu(old_de->inode) != old_inode->i_ino)
                goto end_rename;

        new_inode = new_dentry->d_inode;
        new_bh = ext4_find_entry(new_dir, &new_dentry->d_name,
                                 &new_de, &new_inlined);
        if (new_bh) {
                if (!new_inode) {
                        brelse(new_bh);
                        new_bh = NULL;
                }
        }
        if (new_inode && !test_opt(new_dir->i_sb, NO_AUTO_DA_ALLOC))
                ext4_alloc_da_blocks(old_inode);

        handle = ext4_journal_start(old_dir, EXT4_HT_DIR,
                (2 * EXT4_DATA_TRANS_BLOCKS(old_dir->i_sb) +
                 EXT4_INDEX_EXTRA_TRANS_BLOCKS + 2));
        if (IS_ERR(handle))
                return PTR_ERR(handle);

        if (IS_DIRSYNC(old_dir) || IS_DIRSYNC(new_dir))
                ext4_handle_sync(handle);

        if (S_ISDIR(old_inode->i_mode)) {
                if (new_inode) {
                        retval = -ENOTEMPTY;
                        if (!empty_dir(new_inode))
                                goto end_rename;
                }
                retval = -EIO;
                dir_bh = ext4_get_first_dir_block(handle, old_inode,
                                                  &retval, &parent_de,
                                                  &inlined);
                if (!dir_bh)
                        goto end_rename;
                if (le32_to_cpu(parent_de->inode) != old_dir->i_ino)
                        goto end_rename;
                retval = -EMLINK;
                if (!new_inode && new_dir != old_dir &&
                    EXT4_DIR_LINK_MAX(new_dir))
                        goto end_rename;
                BUFFER_TRACE(dir_bh, "get_write_access");
                retval = ext4_journal_get_write_access(handle, dir_bh);
                if (retval)
                        goto end_rename;
        }
        if (!new_bh) {
                retval = ext4_add_entry(handle, new_dentry, old_inode);
                if (retval)
                        goto end_rename;
        } else {
                BUFFER_TRACE(new_bh, "get write access");
                retval = ext4_journal_get_write_access(handle, new_bh);
                if (retval)
                        goto end_rename;
                new_de->inode = cpu_to_le32(old_inode->i_ino);
                if (EXT4_HAS_INCOMPAT_FEATURE(new_dir->i_sb,
                                              EXT4_FEATURE_INCOMPAT_FILETYPE))
                        new_de->file_type = old_de->file_type;
                new_dir->i_version++;
                new_dir->i_ctime = new_dir->i_mtime =
                                        ext4_current_time(new_dir);
                ext4_mark_inode_dirty(handle, new_dir);
                BUFFER_TRACE(new_bh, "call ext4_handle_dirty_metadata");
                if (!new_inlined) {
                        retval = ext4_handle_dirty_dirent_node(handle,
                                                               new_dir, new_bh);
                        if (unlikely(retval)) {
                                ext4_std_error(new_dir->i_sb, retval);
                                goto end_rename;
                        }
                }
                brelse(new_bh);
                new_bh = NULL;
        }

        /*
         * Like most other Unix systems, set the ctime for inodes on a
         * rename.
         */
        old_inode->i_ctime = ext4_current_time(old_inode);
        ext4_mark_inode_dirty(handle, old_inode);

        /*
         * ok, that's it
         */
        if (le32_to_cpu(old_de->inode) != old_inode->i_ino ||
            old_de->name_len != old_dentry->d_name.len ||
            strncmp(old_de->name, old_dentry->d_name.name, old_de->name_len) ||
            (retval = ext4_delete_entry(handle, old_dir,
                                        old_de, old_bh)) == -ENOENT) {
                /* old_de could have moved from under us during htree split, so
                 * make sure that we are deleting the right entry.  We might
                 * also be pointing to a stale entry in the unused part of
                 * old_bh so just checking inum and the name isn't enough. */
                struct buffer_head *old_bh2;
                struct ext4_dir_entry_2 *old_de2;

                old_bh2 = ext4_find_entry(old_dir, &old_dentry->d_name,
                                          &old_de2, NULL);
                if (old_bh2) {
                        retval = ext4_delete_entry(handle, old_dir,
                                                   old_de2, old_bh2);
                        brelse(old_bh2);
                }
        }
        if (retval) {
                ext4_warning(old_dir->i_sb,
                                "Deleting old file (%lu), %d, error=%d",
                                old_dir->i_ino, old_dir->i_nlink, retval);
        }

        if (new_inode) {
                ext4_dec_count(handle, new_inode);
                new_inode->i_ctime = ext4_current_time(new_inode);
        }
        old_dir->i_ctime = old_dir->i_mtime = ext4_current_time(old_dir);
        ext4_update_dx_flag(old_dir);
        if (dir_bh) {
                parent_de->inode = cpu_to_le32(new_dir->i_ino);
                BUFFER_TRACE(dir_bh, "call ext4_handle_dirty_metadata");
                if (!inlined) {
                        if (is_dx(old_inode)) {
                                retval = ext4_handle_dirty_dx_node(handle,
                                                                   old_inode,
                                                                   dir_bh);
                        } else {
                                retval = ext4_handle_dirty_dirent_node(handle,
                                                        old_inode, dir_bh);
                        }
                } else {
                        retval = ext4_mark_inode_dirty(handle, old_inode);
                }
                if (retval) {
                        ext4_std_error(old_dir->i_sb, retval);
                        goto end_rename;
                }
                ext4_dec_count(handle, old_dir);
                if (new_inode) {
                        /* checked empty_dir above, can't have another parent,
                         * ext4_dec_count() won't work for many-linked dirs */
                        clear_nlink(new_inode);
                } else {
                        ext4_inc_count(handle, new_dir);
                        ext4_update_dx_flag(new_dir);
                        ext4_mark_inode_dirty(handle, new_dir);
                }
        }
        ext4_mark_inode_dirty(handle, old_dir);
        if (new_inode) {
                ext4_mark_inode_dirty(handle, new_inode);
                if (!new_inode->i_nlink)
                        ext4_orphan_add(handle, new_inode);
        }
        retval = 0;

end_rename:
        brelse(dir_bh);
        brelse(old_bh);
        brelse(new_bh);
        if (handle)
                ext4_journal_stop(handle);
        return retval;
}

/*
 * directories can handle most operations...
 */
const struct inode_operations ext4_dir_inode_operations = {
        .create         = ext4_create,
        .lookup         = ext4_lookup,
        .link           = ext4_link,
        .unlink         = ext4_unlink,
        .symlink        = ext4_symlink,
        .mkdir          = ext4_mkdir,
        .rmdir          = ext4_rmdir,
        .mknod          = ext4_mknod,
        .tmpfile        = ext4_tmpfile,
        .rename         = ext4_rename,
        .setattr        = ext4_setattr,
        .setxattr       = generic_setxattr,
        .getxattr       = generic_getxattr,
        .listxattr      = ext4_listxattr,
        .removexattr    = generic_removexattr,
        .get_acl        = ext4_get_acl,
        .fiemap         = ext4_fiemap,
};

const struct inode_operations ext4_special_inode_operations = {
        .setattr        = ext4_setattr,
        .setxattr       = generic_setxattr,
        .getxattr       = generic_getxattr,
        .listxattr      = ext4_listxattr,
        .removexattr    = generic_removexattr,
        .get_acl        = ext4_get_acl,
};