mm: close page_mkwrite races

[linux-2.6/mini2440.git] / fs / ufs / dir.c

/*
 *  linux/fs/ufs/ufs_dir.c
 *
 * Copyright (C) 1996
 * Adrian Rodriguez (adrian@franklins-tower.rutgers.edu)
 * Laboratory for Computer Science Research Computing Facility
 * Rutgers, The State University of New Jersey
 *
 * swab support by Francois-Rene Rideau <fare@tunes.org> 19970406
 *
 * 4.4BSD (FreeBSD) support added on February 1st 1998 by
 * Niels Kristian Bech Jensen <nkbj@image.dk> partially based
 * on code by Martin von Loewis <martin@mira.isdn.cs.tu-berlin.de>.
 *
 * Migration to usage of "page cache" on May 2006 by
 * Evgeniy Dushistov <dushistov@mail.ru> based on ext2 code base.
 */

#include <linux/time.h>
#include <linux/fs.h>
#include <linux/swap.h>

#include "ufs_fs.h"
#include "ufs.h"
#include "swab.h"
#include "util.h"

/*
 * NOTE! unlike strncmp, ufs_match returns 1 for success, 0 for failure.
 *
 * len <= UFS_MAXNAMLEN and de != NULL are guaranteed by caller.
 */
static inline int ufs_match(struct super_block *sb, int len,
                const char * const name, struct ufs_dir_entry * de)
{
        if (len != ufs_get_de_namlen(sb, de))
                return 0;
        if (!de->d_ino)
                return 0;
        return !memcmp(name, de->d_name, len);
}

static int ufs_commit_chunk(struct page *page, loff_t pos, unsigned len)
{
        struct address_space *mapping = page->mapping;
        struct inode *dir = mapping->host;
        int err = 0;

        dir->i_version++;
        block_write_end(NULL, mapping, pos, len, len, page, NULL);
        if (pos+len > dir->i_size) {
                i_size_write(dir, pos+len);
                mark_inode_dirty(dir);
        }
        if (IS_DIRSYNC(dir))
                err = write_one_page(page, 1);
        else
                unlock_page(page);
        return err;
}

static inline void ufs_put_page(struct page *page)
{
        kunmap(page);
        page_cache_release(page);
}

static inline unsigned long ufs_dir_pages(struct inode *inode)
{
        return (inode->i_size+PAGE_CACHE_SIZE-1)>>PAGE_CACHE_SHIFT;
}

ino_t ufs_inode_by_name(struct inode *dir, struct dentry *dentry)
{
        ino_t res = 0;
        struct ufs_dir_entry *de;
        struct page *page;
        
        de = ufs_find_entry(dir, dentry, &page);
        if (de) {
                res = fs32_to_cpu(dir->i_sb, de->d_ino);
                ufs_put_page(page);
        }
        return res;
}


/* Releases the page */
void ufs_set_link(struct inode *dir, struct ufs_dir_entry *de,
                  struct page *page, struct inode *inode)
{
        loff_t pos = page_offset(page) +
                        (char *) de - (char *) page_address(page);
        unsigned len = fs16_to_cpu(dir->i_sb, de->d_reclen);
        int err;

        lock_page(page);
        err = __ufs_write_begin(NULL, page->mapping, pos, len,
                                AOP_FLAG_UNINTERRUPTIBLE, &page, NULL);
        BUG_ON(err);

        de->d_ino = cpu_to_fs32(dir->i_sb, inode->i_ino);
        ufs_set_de_type(dir->i_sb, de, inode->i_mode);

        err = ufs_commit_chunk(page, pos, len);
        ufs_put_page(page);
        dir->i_mtime = dir->i_ctime = CURRENT_TIME_SEC;
        mark_inode_dirty(dir);
}


static void ufs_check_page(struct page *page)
{
        struct inode *dir = page->mapping->host;
        struct super_block *sb = dir->i_sb;
        char *kaddr = page_address(page);
        unsigned offs, rec_len;
        unsigned limit = PAGE_CACHE_SIZE;
        const unsigned chunk_mask = UFS_SB(sb)->s_uspi->s_dirblksize - 1;
        struct ufs_dir_entry *p;
        char *error;

        if ((dir->i_size >> PAGE_CACHE_SHIFT) == page->index) {
                limit = dir->i_size & ~PAGE_CACHE_MASK;
                if (limit & chunk_mask)
                        goto Ebadsize;
                if (!limit)
                        goto out;
        }
        for (offs = 0; offs <= limit - UFS_DIR_REC_LEN(1); offs += rec_len) {
                p = (struct ufs_dir_entry *)(kaddr + offs);
                rec_len = fs16_to_cpu(sb, p->d_reclen);

                if (rec_len < UFS_DIR_REC_LEN(1))
                        goto Eshort;
                if (rec_len & 3)
                        goto Ealign;
                if (rec_len < UFS_DIR_REC_LEN(ufs_get_de_namlen(sb, p)))
                        goto Enamelen;
                if (((offs + rec_len - 1) ^ offs) & ~chunk_mask)
                        goto Espan;
                if (fs32_to_cpu(sb, p->d_ino) > (UFS_SB(sb)->s_uspi->s_ipg *
                                                  UFS_SB(sb)->s_uspi->s_ncg))
                        goto Einumber;
        }
        if (offs != limit)
                goto Eend;
out:
        SetPageChecked(page);
        return;

        /* Too bad, we had an error */

Ebadsize:
        ufs_error(sb, "ufs_check_page",
                  "size of directory #%lu is not a multiple of chunk size",
                  dir->i_ino
        );
        goto fail;
Eshort:
        error = "rec_len is smaller than minimal";
        goto bad_entry;
Ealign:
        error = "unaligned directory entry";
        goto bad_entry;
Enamelen:
        error = "rec_len is too small for name_len";
        goto bad_entry;
Espan:
        error = "directory entry across blocks";
        goto bad_entry;
Einumber:
        error = "inode out of bounds";
bad_entry:
        ufs_error (sb, "ufs_check_page", "bad entry in directory #%lu: %s - "
                   "offset=%lu, rec_len=%d, name_len=%d",
                   dir->i_ino, error, (page->index<<PAGE_CACHE_SHIFT)+offs,
                   rec_len, ufs_get_de_namlen(sb, p));
        goto fail;
Eend:
        p = (struct ufs_dir_entry *)(kaddr + offs);
        ufs_error(sb, __func__,
                   "entry in directory #%lu spans the page boundary"
                   "offset=%lu",
                   dir->i_ino, (page->index<<PAGE_CACHE_SHIFT)+offs);
fail:
        SetPageChecked(page);
        SetPageError(page);
}

static struct page *ufs_get_page(struct inode *dir, unsigned long n)
{
        struct address_space *mapping = dir->i_mapping;
        struct page *page = read_mapping_page(mapping, n, NULL);
        if (!IS_ERR(page)) {
                kmap(page);
                if (!PageChecked(page))
                        ufs_check_page(page);
                if (PageError(page))
                        goto fail;
        }
        return page;

fail:
        ufs_put_page(page);
        return ERR_PTR(-EIO);
}

/*
 * Return the offset into page `page_nr' of the last valid
 * byte in that page, plus one.
 */
static unsigned
ufs_last_byte(struct inode *inode, unsigned long page_nr)
{
        unsigned last_byte = inode->i_size;

        last_byte -= page_nr << PAGE_CACHE_SHIFT;
        if (last_byte > PAGE_CACHE_SIZE)
                last_byte = PAGE_CACHE_SIZE;
        return last_byte;
}

static inline struct ufs_dir_entry *
ufs_next_entry(struct super_block *sb, struct ufs_dir_entry *p)
{
        return (struct ufs_dir_entry *)((char *)p +
                                        fs16_to_cpu(sb, p->d_reclen));
}

struct ufs_dir_entry *ufs_dotdot(struct inode *dir, struct page **p)
{
        struct page *page = ufs_get_page(dir, 0);
        struct ufs_dir_entry *de = NULL;

        if (!IS_ERR(page)) {
                de = ufs_next_entry(dir->i_sb,
                                    (struct ufs_dir_entry *)page_address(page));
                *p = page;
        }
        return de;
}

/*
 *      ufs_find_entry()
 *
 * finds an entry in the specified directory with the wanted name. It
 * returns the page in which the entry was found, and the entry itself
 * (as a parameter - res_dir). Page is returned mapped and unlocked.
 * Entry is guaranteed to be valid.
 */
struct ufs_dir_entry *ufs_find_entry(struct inode *dir, struct dentry *dentry,
                                     struct page **res_page)
{
        struct super_block *sb = dir->i_sb;
        const char *name = dentry->d_name.name;
        int namelen = dentry->d_name.len;
        unsigned reclen = UFS_DIR_REC_LEN(namelen);
        unsigned long start, n;
        unsigned long npages = ufs_dir_pages(dir);
        struct page *page = NULL;
        struct ufs_inode_info *ui = UFS_I(dir);
        struct ufs_dir_entry *de;

        UFSD("ENTER, dir_ino %lu, name %s, namlen %u\n", dir->i_ino, name, namelen);

        if (npages == 0 || namelen > UFS_MAXNAMLEN)
                goto out;

        /* OFFSET_CACHE */
        *res_page = NULL;

        start = ui->i_dir_start_lookup;

        if (start >= npages)
                start = 0;
        n = start;
        do {
                char *kaddr;
                page = ufs_get_page(dir, n);
                if (!IS_ERR(page)) {
                        kaddr = page_address(page);
                        de = (struct ufs_dir_entry *) kaddr;
                        kaddr += ufs_last_byte(dir, n) - reclen;
                        while ((char *) de <= kaddr) {
                                if (de->d_reclen == 0) {
                                        ufs_error(dir->i_sb, __func__,
                                                  "zero-length directory entry");
                                        ufs_put_page(page);
                                        goto out;
                                }
                                if (ufs_match(sb, namelen, name, de))
                                        goto found;
                                de = ufs_next_entry(sb, de);
                        }
                        ufs_put_page(page);
                }
                if (++n >= npages)
                        n = 0;
        } while (n != start);
out:
        return NULL;

found:
        *res_page = page;
        ui->i_dir_start_lookup = n;
        return de;
}

/*
 *      Parent is locked.
 */
int ufs_add_link(struct dentry *dentry, struct inode *inode)
{
        struct inode *dir = dentry->d_parent->d_inode;
        const char *name = dentry->d_name.name;
        int namelen = dentry->d_name.len;
        struct super_block *sb = dir->i_sb;
        unsigned reclen = UFS_DIR_REC_LEN(namelen);
        const unsigned int chunk_size = UFS_SB(sb)->s_uspi->s_dirblksize;
        unsigned short rec_len, name_len;
        struct page *page = NULL;
        struct ufs_dir_entry *de;
        unsigned long npages = ufs_dir_pages(dir);
        unsigned long n;
        char *kaddr;
        loff_t pos;
        int err;

        UFSD("ENTER, name %s, namelen %u\n", name, namelen);

        /*
         * We take care of directory expansion in the same loop.
         * This code plays outside i_size, so it locks the page
         * to protect that region.
         */
        for (n = 0; n <= npages; n++) {
                char *dir_end;

                page = ufs_get_page(dir, n);
                err = PTR_ERR(page);
                if (IS_ERR(page))
                        goto out;
                lock_page(page);
                kaddr = page_address(page);
                dir_end = kaddr + ufs_last_byte(dir, n);
                de = (struct ufs_dir_entry *)kaddr;
                kaddr += PAGE_CACHE_SIZE - reclen;
                while ((char *)de <= kaddr) {
                        if ((char *)de == dir_end) {
                                /* We hit i_size */
                                name_len = 0;
                                rec_len = chunk_size;
                                de->d_reclen = cpu_to_fs16(sb, chunk_size);
                                de->d_ino = 0;
                                goto got_it;
                        }
                        if (de->d_reclen == 0) {
                                ufs_error(dir->i_sb, __func__,
                                          "zero-length directory entry");
                                err = -EIO;
                                goto out_unlock;
                        }
                        err = -EEXIST;
                        if (ufs_match(sb, namelen, name, de))
                                goto out_unlock;
                        name_len = UFS_DIR_REC_LEN(ufs_get_de_namlen(sb, de));
                        rec_len = fs16_to_cpu(sb, de->d_reclen);
                        if (!de->d_ino && rec_len >= reclen)
                                goto got_it;
                        if (rec_len >= name_len + reclen)
                                goto got_it;
                        de = (struct ufs_dir_entry *) ((char *) de + rec_len);
                }
                unlock_page(page);
                ufs_put_page(page);
        }
        BUG();
        return -EINVAL;

got_it:
        pos = page_offset(page) +
                        (char*)de - (char*)page_address(page);
        err = __ufs_write_begin(NULL, page->mapping, pos, rec_len,
                                AOP_FLAG_UNINTERRUPTIBLE, &page, NULL);
        if (err)
                goto out_unlock;
        if (de->d_ino) {
                struct ufs_dir_entry *de1 =
                        (struct ufs_dir_entry *) ((char *) de + name_len);
                de1->d_reclen = cpu_to_fs16(sb, rec_len - name_len);
                de->d_reclen = cpu_to_fs16(sb, name_len);

                de = de1;
        }

        ufs_set_de_namlen(sb, de, namelen);
        memcpy(de->d_name, name, namelen + 1);
        de->d_ino = cpu_to_fs32(sb, inode->i_ino);
        ufs_set_de_type(sb, de, inode->i_mode);

        err = ufs_commit_chunk(page, pos, rec_len);
        dir->i_mtime = dir->i_ctime = CURRENT_TIME_SEC;

        mark_inode_dirty(dir);
        /* OFFSET_CACHE */
out_put:
        ufs_put_page(page);
out:
        return err;
out_unlock:
        unlock_page(page);
        goto out_put;
}

static inline unsigned
ufs_validate_entry(struct super_block *sb, char *base,
                   unsigned offset, unsigned mask)
{
        struct ufs_dir_entry *de = (struct ufs_dir_entry*)(base + offset);
        struct ufs_dir_entry *p = (struct ufs_dir_entry*)(base + (offset&mask));
        while ((char*)p < (char*)de) {
                if (p->d_reclen == 0)
                        break;
                p = ufs_next_entry(sb, p);
        }
        return (char *)p - base;
}


/*
 * This is blatantly stolen from ext2fs
 */
static int
ufs_readdir(struct file *filp, void *dirent, filldir_t filldir)
{
        loff_t pos = filp->f_pos;
        struct inode *inode = filp->f_path.dentry->d_inode;
        struct super_block *sb = inode->i_sb;
        unsigned int offset = pos & ~PAGE_CACHE_MASK;
        unsigned long n = pos >> PAGE_CACHE_SHIFT;
        unsigned long npages = ufs_dir_pages(inode);
        unsigned chunk_mask = ~(UFS_SB(sb)->s_uspi->s_dirblksize - 1);
        int need_revalidate = filp->f_version != inode->i_version;
        unsigned flags = UFS_SB(sb)->s_flags;

        UFSD("BEGIN\n");

        if (pos > inode->i_size - UFS_DIR_REC_LEN(1))
                return 0;

        for ( ; n < npages; n++, offset = 0) {
                char *kaddr, *limit;
                struct ufs_dir_entry *de;

                struct page *page = ufs_get_page(inode, n);

                if (IS_ERR(page)) {
                        ufs_error(sb, __func__,
                                  "bad page in #%lu",
                                  inode->i_ino);
                        filp->f_pos += PAGE_CACHE_SIZE - offset;
                        return -EIO;
                }
                kaddr = page_address(page);
                if (unlikely(need_revalidate)) {
                        if (offset) {
                                offset = ufs_validate_entry(sb, kaddr, offset, chunk_mask);
                                filp->f_pos = (n<<PAGE_CACHE_SHIFT) + offset;
                        }
                        filp->f_version = inode->i_version;
                        need_revalidate = 0;
                }
                de = (struct ufs_dir_entry *)(kaddr+offset);
                limit = kaddr + ufs_last_byte(inode, n) - UFS_DIR_REC_LEN(1);
                for ( ;(char*)de <= limit; de = ufs_next_entry(sb, de)) {
                        if (de->d_reclen == 0) {
                                ufs_error(sb, __func__,
                                        "zero-length directory entry");
                                ufs_put_page(page);
                                return -EIO;
                        }
                        if (de->d_ino) {
                                int over;
                                unsigned char d_type = DT_UNKNOWN;

                                offset = (char *)de - kaddr;

                                UFSD("filldir(%s,%u)\n", de->d_name,
                                      fs32_to_cpu(sb, de->d_ino));
                                UFSD("namlen %u\n", ufs_get_de_namlen(sb, de));

                                if ((flags & UFS_DE_MASK) == UFS_DE_44BSD)
                                        d_type = de->d_u.d_44.d_type;

                                over = filldir(dirent, de->d_name,
                                               ufs_get_de_namlen(sb, de),
                                                (n<<PAGE_CACHE_SHIFT) | offset,
                                               fs32_to_cpu(sb, de->d_ino), d_type);
                                if (over) {
                                        ufs_put_page(page);
                                        return 0;
                                }
                        }
                        filp->f_pos += fs16_to_cpu(sb, de->d_reclen);
                }
                ufs_put_page(page);
        }
        return 0;
}


/*
 * ufs_delete_entry deletes a directory entry by merging it with the
 * previous entry.
 */
int ufs_delete_entry(struct inode *inode, struct ufs_dir_entry *dir,
                     struct page * page)
{
        struct super_block *sb = inode->i_sb;
        struct address_space *mapping = page->mapping;
        char *kaddr = page_address(page);
        unsigned from = ((char*)dir - kaddr) & ~(UFS_SB(sb)->s_uspi->s_dirblksize - 1);
        unsigned to = ((char*)dir - kaddr) + fs16_to_cpu(sb, dir->d_reclen);
        loff_t pos;
        struct ufs_dir_entry *pde = NULL;
        struct ufs_dir_entry *de = (struct ufs_dir_entry *) (kaddr + from);
        int err;

        UFSD("ENTER\n");

        UFSD("ino %u, reclen %u, namlen %u, name %s\n",
              fs32_to_cpu(sb, de->d_ino),
              fs16_to_cpu(sb, de->d_reclen),
              ufs_get_de_namlen(sb, de), de->d_name);

        while ((char*)de < (char*)dir) {
                if (de->d_reclen == 0) {
                        ufs_error(inode->i_sb, __func__,
                                  "zero-length directory entry");
                        err = -EIO;
                        goto out;
                }
                pde = de;
                de = ufs_next_entry(sb, de);
        }
        if (pde)
                from = (char*)pde - (char*)page_address(page);

        pos = page_offset(page) + from;
        lock_page(page);
        err = __ufs_write_begin(NULL, mapping, pos, to - from,
                                AOP_FLAG_UNINTERRUPTIBLE, &page, NULL);
        BUG_ON(err);
        if (pde)
                pde->d_reclen = cpu_to_fs16(sb, to - from);
        dir->d_ino = 0;
        err = ufs_commit_chunk(page, pos, to - from);
        inode->i_ctime = inode->i_mtime = CURRENT_TIME_SEC;
        mark_inode_dirty(inode);
out:
        ufs_put_page(page);
        UFSD("EXIT\n");
        return err;
}

int ufs_make_empty(struct inode * inode, struct inode *dir)
{
        struct super_block * sb = dir->i_sb;
        struct address_space *mapping = inode->i_mapping;
        struct page *page = grab_cache_page(mapping, 0);
        const unsigned int chunk_size = UFS_SB(sb)->s_uspi->s_dirblksize;
        struct ufs_dir_entry * de;
        char *base;
        int err;

        if (!page)
                return -ENOMEM;

        err = __ufs_write_begin(NULL, mapping, 0, chunk_size,
                                AOP_FLAG_UNINTERRUPTIBLE, &page, NULL);
        if (err) {
                unlock_page(page);
                goto fail;
        }

        kmap(page);
        base = (char*)page_address(page);
        memset(base, 0, PAGE_CACHE_SIZE);

        de = (struct ufs_dir_entry *) base;

        de->d_ino = cpu_to_fs32(sb, inode->i_ino);
        ufs_set_de_type(sb, de, inode->i_mode);
        ufs_set_de_namlen(sb, de, 1);
        de->d_reclen = cpu_to_fs16(sb, UFS_DIR_REC_LEN(1));
        strcpy (de->d_name, ".");
        de = (struct ufs_dir_entry *)
                ((char *)de + fs16_to_cpu(sb, de->d_reclen));
        de->d_ino = cpu_to_fs32(sb, dir->i_ino);
        ufs_set_de_type(sb, de, dir->i_mode);
        de->d_reclen = cpu_to_fs16(sb, chunk_size - UFS_DIR_REC_LEN(1));
        ufs_set_de_namlen(sb, de, 2);
        strcpy (de->d_name, "..");
        kunmap(page);

        err = ufs_commit_chunk(page, 0, chunk_size);
fail:
        page_cache_release(page);
        return err;
}

/*
 * routine to check that the specified directory is empty (for rmdir)
 */
int ufs_empty_dir(struct inode * inode)
{
        struct super_block *sb = inode->i_sb;
        struct page *page = NULL;
        unsigned long i, npages = ufs_dir_pages(inode);

        for (i = 0; i < npages; i++) {
                char *kaddr;
                struct ufs_dir_entry *de;
                page = ufs_get_page(inode, i);

                if (IS_ERR(page))
                        continue;

                kaddr = page_address(page);
                de = (struct ufs_dir_entry *)kaddr;
                kaddr += ufs_last_byte(inode, i) - UFS_DIR_REC_LEN(1);

                while ((char *)de <= kaddr) {
                        if (de->d_reclen == 0) {
                                ufs_error(inode->i_sb, __func__,
                                        "zero-length directory entry: "
                                        "kaddr=%p, de=%p\n", kaddr, de);
                                goto not_empty;
                        }
                        if (de->d_ino) {
                                u16 namelen=ufs_get_de_namlen(sb, de);
                                /* check for . and .. */
                                if (de->d_name[0] != '.')
                                        goto not_empty;
                                if (namelen > 2)
                                        goto not_empty;
                                if (namelen < 2) {
                                        if (inode->i_ino !=
                                            fs32_to_cpu(sb, de->d_ino))
                                                goto not_empty;
                                } else if (de->d_name[1] != '.')
                                        goto not_empty;
                        }
                        de = ufs_next_entry(sb, de);
                }
                ufs_put_page(page);
        }
        return 1;

not_empty:
        ufs_put_page(page);
        return 0;
}

const struct file_operations ufs_dir_operations = {
        .read           = generic_read_dir,
        .readdir        = ufs_readdir,
        .fsync          = file_fsync,
        .llseek         = generic_file_llseek,
};