UBIFS: commit on sync_fs

[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / fs / ubifs / super.c

/*
 * This file is part of UBIFS.
 *
 * Copyright (C) 2006-2008 Nokia Corporation.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 as published by
 * the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * this program; if not, write to the Free Software Foundation, Inc., 51
 * Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 *
 * Authors: Artem Bityutskiy (Битюцкий Артём)
 *          Adrian Hunter
 */

/*
 * This file implements UBIFS initialization and VFS superblock operations. Some
 * initialization stuff which is rather large and complex is placed at
 * corresponding subsystems, but most of it is here.
 */

#include <linux/init.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/ctype.h>
#include <linux/kthread.h>
#include <linux/parser.h>
#include <linux/seq_file.h>
#include <linux/mount.h>
#include "ubifs.h"

/* Slab cache for UBIFS inodes */
struct kmem_cache *ubifs_inode_slab;

/* UBIFS TNC shrinker description */
static struct shrinker ubifs_shrinker_info = {
        .shrink = ubifs_shrinker,
        .seeks = DEFAULT_SEEKS,
};

/**
 * validate_inode - validate inode.
 * @c: UBIFS file-system description object
 * @inode: the inode to validate
 *
 * This is a helper function for 'ubifs_iget()' which validates various fields
 * of a newly built inode to make sure they contain sane values and prevent
 * possible vulnerabilities. Returns zero if the inode is all right and
 * a non-zero error code if not.
 */
static int validate_inode(struct ubifs_info *c, const struct inode *inode)
{
        int err;
        const struct ubifs_inode *ui = ubifs_inode(inode);

        if (inode->i_size > c->max_inode_sz) {
                ubifs_err("inode is too large (%lld)",
                          (long long)inode->i_size);
                return 1;
        }

        if (ui->compr_type < 0 || ui->compr_type >= UBIFS_COMPR_TYPES_CNT) {
                ubifs_err("unknown compression type %d", ui->compr_type);
                return 2;
        }

        if (ui->xattr_names + ui->xattr_cnt > XATTR_LIST_MAX)
                return 3;

        if (ui->data_len < 0 || ui->data_len > UBIFS_MAX_INO_DATA)
                return 4;

        if (ui->xattr && (inode->i_mode & S_IFMT) != S_IFREG)
                return 5;

        if (!ubifs_compr_present(ui->compr_type)) {
                ubifs_warn("inode %lu uses '%s' compression, but it was not "
                           "compiled in", inode->i_ino,
                           ubifs_compr_name(ui->compr_type));
        }

        err = dbg_check_dir_size(c, inode);
        return err;
}

struct inode *ubifs_iget(struct super_block *sb, unsigned long inum)
{
        int err;
        union ubifs_key key;
        struct ubifs_ino_node *ino;
        struct ubifs_info *c = sb->s_fs_info;
        struct inode *inode;
        struct ubifs_inode *ui;

        dbg_gen("inode %lu", inum);

        inode = iget_locked(sb, inum);
        if (!inode)
                return ERR_PTR(-ENOMEM);
        if (!(inode->i_state & I_NEW))
                return inode;
        ui = ubifs_inode(inode);

        ino = kmalloc(UBIFS_MAX_INO_NODE_SZ, GFP_NOFS);
        if (!ino) {
                err = -ENOMEM;
                goto out;
        }

        ino_key_init(c, &key, inode->i_ino);

        err = ubifs_tnc_lookup(c, &key, ino);
        if (err)
                goto out_ino;

        inode->i_flags |= (S_NOCMTIME | S_NOATIME);
        inode->i_nlink = le32_to_cpu(ino->nlink);
        inode->i_uid   = le32_to_cpu(ino->uid);
        inode->i_gid   = le32_to_cpu(ino->gid);
        inode->i_atime.tv_sec  = (int64_t)le64_to_cpu(ino->atime_sec);
        inode->i_atime.tv_nsec = le32_to_cpu(ino->atime_nsec);
        inode->i_mtime.tv_sec  = (int64_t)le64_to_cpu(ino->mtime_sec);
        inode->i_mtime.tv_nsec = le32_to_cpu(ino->mtime_nsec);
        inode->i_ctime.tv_sec  = (int64_t)le64_to_cpu(ino->ctime_sec);
        inode->i_ctime.tv_nsec = le32_to_cpu(ino->ctime_nsec);
        inode->i_mode = le32_to_cpu(ino->mode);
        inode->i_size = le64_to_cpu(ino->size);

        ui->data_len    = le32_to_cpu(ino->data_len);
        ui->flags       = le32_to_cpu(ino->flags);
        ui->compr_type  = le16_to_cpu(ino->compr_type);
        ui->creat_sqnum = le64_to_cpu(ino->creat_sqnum);
        ui->xattr_cnt   = le32_to_cpu(ino->xattr_cnt);
        ui->xattr_size  = le32_to_cpu(ino->xattr_size);
        ui->xattr_names = le32_to_cpu(ino->xattr_names);
        ui->synced_i_size = ui->ui_size = inode->i_size;

        ui->xattr = (ui->flags & UBIFS_XATTR_FL) ? 1 : 0;

        err = validate_inode(c, inode);
        if (err)
                goto out_invalid;

        /* Disable read-ahead */
        inode->i_mapping->backing_dev_info = &c->bdi;

        switch (inode->i_mode & S_IFMT) {
        case S_IFREG:
                inode->i_mapping->a_ops = &ubifs_file_address_operations;
                inode->i_op = &ubifs_file_inode_operations;
                inode->i_fop = &ubifs_file_operations;
                if (ui->xattr) {
                        ui->data = kmalloc(ui->data_len + 1, GFP_NOFS);
                        if (!ui->data) {
                                err = -ENOMEM;
                                goto out_ino;
                        }
                        memcpy(ui->data, ino->data, ui->data_len);
                        ((char *)ui->data)[ui->data_len] = '\0';
                } else if (ui->data_len != 0) {
                        err = 10;
                        goto out_invalid;
                }
                break;
        case S_IFDIR:
                inode->i_op  = &ubifs_dir_inode_operations;
                inode->i_fop = &ubifs_dir_operations;
                if (ui->data_len != 0) {
                        err = 11;
                        goto out_invalid;
                }
                break;
        case S_IFLNK:
                inode->i_op = &ubifs_symlink_inode_operations;
                if (ui->data_len <= 0 || ui->data_len > UBIFS_MAX_INO_DATA) {
                        err = 12;
                        goto out_invalid;
                }
                ui->data = kmalloc(ui->data_len + 1, GFP_NOFS);
                if (!ui->data) {
                        err = -ENOMEM;
                        goto out_ino;
                }
                memcpy(ui->data, ino->data, ui->data_len);
                ((char *)ui->data)[ui->data_len] = '\0';
                break;
        case S_IFBLK:
        case S_IFCHR:
        {
                dev_t rdev;
                union ubifs_dev_desc *dev;

                ui->data = kmalloc(sizeof(union ubifs_dev_desc), GFP_NOFS);
                if (!ui->data) {
                        err = -ENOMEM;
                        goto out_ino;
                }

                dev = (union ubifs_dev_desc *)ino->data;
                if (ui->data_len == sizeof(dev->new))
                        rdev = new_decode_dev(le32_to_cpu(dev->new));
                else if (ui->data_len == sizeof(dev->huge))
                        rdev = huge_decode_dev(le64_to_cpu(dev->huge));
                else {
                        err = 13;
                        goto out_invalid;
                }
                memcpy(ui->data, ino->data, ui->data_len);
                inode->i_op = &ubifs_file_inode_operations;
                init_special_inode(inode, inode->i_mode, rdev);
                break;
        }
        case S_IFSOCK:
        case S_IFIFO:
                inode->i_op = &ubifs_file_inode_operations;
                init_special_inode(inode, inode->i_mode, 0);
                if (ui->data_len != 0) {
                        err = 14;
                        goto out_invalid;
                }
                break;
        default:
                err = 15;
                goto out_invalid;
        }

        kfree(ino);
        ubifs_set_inode_flags(inode);
        unlock_new_inode(inode);
        return inode;

out_invalid:
        ubifs_err("inode %lu validation failed, error %d", inode->i_ino, err);
        dbg_dump_node(c, ino);
        dbg_dump_inode(c, inode);
        err = -EINVAL;
out_ino:
        kfree(ino);
out:
        ubifs_err("failed to read inode %lu, error %d", inode->i_ino, err);
        iget_failed(inode);
        return ERR_PTR(err);
}

static struct inode *ubifs_alloc_inode(struct super_block *sb)
{
        struct ubifs_inode *ui;

        ui = kmem_cache_alloc(ubifs_inode_slab, GFP_NOFS);
        if (!ui)
                return NULL;

        memset((void *)ui + sizeof(struct inode), 0,
               sizeof(struct ubifs_inode) - sizeof(struct inode));
        mutex_init(&ui->ui_mutex);
        spin_lock_init(&ui->ui_lock);
        return &ui->vfs_inode;
};

static void ubifs_destroy_inode(struct inode *inode)
{
        struct ubifs_inode *ui = ubifs_inode(inode);

        kfree(ui->data);
        kmem_cache_free(ubifs_inode_slab, inode);
}

/*
 * Note, Linux write-back code calls this without 'i_mutex'.
 */
static int ubifs_write_inode(struct inode *inode, int wait)
{
        int err = 0;
        struct ubifs_info *c = inode->i_sb->s_fs_info;
        struct ubifs_inode *ui = ubifs_inode(inode);

        ubifs_assert(!ui->xattr);
        if (is_bad_inode(inode))
                return 0;

        mutex_lock(&ui->ui_mutex);
        /*
         * Due to races between write-back forced by budgeting
         * (see 'sync_some_inodes()') and pdflush write-back, the inode may
         * have already been synchronized, do not do this again. This might
         * also happen if it was synchronized in an VFS operation, e.g.
         * 'ubifs_link()'.
         */
        if (!ui->dirty) {
                mutex_unlock(&ui->ui_mutex);
                return 0;
        }

        /*
         * As an optimization, do not write orphan inodes to the media just
         * because this is not needed.
         */
        dbg_gen("inode %lu, mode %#x, nlink %u",
                inode->i_ino, (int)inode->i_mode, inode->i_nlink);
        if (inode->i_nlink) {
                err = ubifs_jnl_write_inode(c, inode);
                if (err)
                        ubifs_err("can't write inode %lu, error %d",
                                  inode->i_ino, err);
        }

        ui->dirty = 0;
        mutex_unlock(&ui->ui_mutex);
        ubifs_release_dirty_inode_budget(c, ui);
        return err;
}

static void ubifs_delete_inode(struct inode *inode)
{
        int err;
        struct ubifs_info *c = inode->i_sb->s_fs_info;
        struct ubifs_inode *ui = ubifs_inode(inode);

        if (ui->xattr)
                /*
                 * Extended attribute inode deletions are fully handled in
                 * 'ubifs_removexattr()'. These inodes are special and have
                 * limited usage, so there is nothing to do here.
                 */
                goto out;

        dbg_gen("inode %lu, mode %#x", inode->i_ino, (int)inode->i_mode);
        ubifs_assert(!atomic_read(&inode->i_count));
        ubifs_assert(inode->i_nlink == 0);

        truncate_inode_pages(&inode->i_data, 0);
        if (is_bad_inode(inode))
                goto out;

        ui->ui_size = inode->i_size = 0;
        err = ubifs_jnl_delete_inode(c, inode);
        if (err)
                /*
                 * Worst case we have a lost orphan inode wasting space, so a
                 * simple error message is OK here.
                 */
                ubifs_err("can't delete inode %lu, error %d",
                          inode->i_ino, err);

out:
        if (ui->dirty)
                ubifs_release_dirty_inode_budget(c, ui);
        clear_inode(inode);
}

static void ubifs_dirty_inode(struct inode *inode)
{
        struct ubifs_inode *ui = ubifs_inode(inode);

        ubifs_assert(mutex_is_locked(&ui->ui_mutex));
        if (!ui->dirty) {
                ui->dirty = 1;
                dbg_gen("inode %lu",  inode->i_ino);
        }
}

static int ubifs_statfs(struct dentry *dentry, struct kstatfs *buf)
{
        struct ubifs_info *c = dentry->d_sb->s_fs_info;
        unsigned long long free;
        __le32 *uuid = (__le32 *)c->uuid;

        free = ubifs_get_free_space(c);
        dbg_gen("free space %lld bytes (%lld blocks)",
                free, free >> UBIFS_BLOCK_SHIFT);

        buf->f_type = UBIFS_SUPER_MAGIC;
        buf->f_bsize = UBIFS_BLOCK_SIZE;
        buf->f_blocks = c->block_cnt;
        buf->f_bfree = free >> UBIFS_BLOCK_SHIFT;
        if (free > c->report_rp_size)
                buf->f_bavail = (free - c->report_rp_size) >> UBIFS_BLOCK_SHIFT;
        else
                buf->f_bavail = 0;
        buf->f_files = 0;
        buf->f_ffree = 0;
        buf->f_namelen = UBIFS_MAX_NLEN;
        buf->f_fsid.val[0] = le32_to_cpu(uuid[0]) ^ le32_to_cpu(uuid[2]);
        buf->f_fsid.val[1] = le32_to_cpu(uuid[1]) ^ le32_to_cpu(uuid[3]);
        return 0;
}

static int ubifs_show_options(struct seq_file *s, struct vfsmount *mnt)
{
        struct ubifs_info *c = mnt->mnt_sb->s_fs_info;

        if (c->mount_opts.unmount_mode == 2)
                seq_printf(s, ",fast_unmount");
        else if (c->mount_opts.unmount_mode == 1)
                seq_printf(s, ",norm_unmount");

        if (c->mount_opts.bulk_read == 2)
                seq_printf(s, ",bulk_read");
        else if (c->mount_opts.bulk_read == 1)
                seq_printf(s, ",no_bulk_read");

        if (c->mount_opts.chk_data_crc == 2)
                seq_printf(s, ",chk_data_crc");
        else if (c->mount_opts.chk_data_crc == 1)
                seq_printf(s, ",no_chk_data_crc");

        return 0;
}

static int ubifs_sync_fs(struct super_block *sb, int wait)
{
        struct ubifs_info *c = sb->s_fs_info;
        int i, ret = 0, err;
        long long bud_bytes;

        if (c->jheads)
                for (i = 0; i < c->jhead_cnt; i++) {
                        err = ubifs_wbuf_sync(&c->jheads[i].wbuf);
                        if (err && !ret)
                                ret = err;
                }

        /* Commit the journal unless it has too few data */
        spin_lock(&c->buds_lock);
        bud_bytes = c->bud_bytes;
        spin_unlock(&c->buds_lock);
        if (bud_bytes > c->leb_size) {
                err = ubifs_run_commit(c);
                if (err)
                        return err;
        }

        /*
         * We ought to call sync for c->ubi but it does not have one. If it had
         * it would in turn call mtd->sync, however mtd operations are
         * synchronous anyway, so we don't lose any sleep here.
         */
        return ret;
}

/**
 * init_constants_early - initialize UBIFS constants.
 * @c: UBIFS file-system description object
 *
 * This function initialize UBIFS constants which do not need the superblock to
 * be read. It also checks that the UBI volume satisfies basic UBIFS
 * requirements. Returns zero in case of success and a negative error code in
 * case of failure.
 */
static int init_constants_early(struct ubifs_info *c)
{
        if (c->vi.corrupted) {
                ubifs_warn("UBI volume is corrupted - read-only mode");
                c->ro_media = 1;
        }

        if (c->di.ro_mode) {
                ubifs_msg("read-only UBI device");
                c->ro_media = 1;
        }

        if (c->vi.vol_type == UBI_STATIC_VOLUME) {
                ubifs_msg("static UBI volume - read-only mode");
                c->ro_media = 1;
        }

        c->leb_cnt = c->vi.size;
        c->leb_size = c->vi.usable_leb_size;
        c->half_leb_size = c->leb_size / 2;
        c->min_io_size = c->di.min_io_size;
        c->min_io_shift = fls(c->min_io_size) - 1;

        if (c->leb_size < UBIFS_MIN_LEB_SZ) {
                ubifs_err("too small LEBs (%d bytes), min. is %d bytes",
                          c->leb_size, UBIFS_MIN_LEB_SZ);
                return -EINVAL;
        }

        if (c->leb_cnt < UBIFS_MIN_LEB_CNT) {
                ubifs_err("too few LEBs (%d), min. is %d",
                          c->leb_cnt, UBIFS_MIN_LEB_CNT);
                return -EINVAL;
        }

        if (!is_power_of_2(c->min_io_size)) {
                ubifs_err("bad min. I/O size %d", c->min_io_size);
                return -EINVAL;
        }

        /*
         * UBIFS aligns all node to 8-byte boundary, so to make function in
         * io.c simpler, assume minimum I/O unit size to be 8 bytes if it is
         * less than 8.
         */
        if (c->min_io_size < 8) {
                c->min_io_size = 8;
                c->min_io_shift = 3;
        }

        c->ref_node_alsz = ALIGN(UBIFS_REF_NODE_SZ, c->min_io_size);
        c->mst_node_alsz = ALIGN(UBIFS_MST_NODE_SZ, c->min_io_size);

        /*
         * Initialize node length ranges which are mostly needed for node
         * length validation.
         */
        c->ranges[UBIFS_PAD_NODE].len  = UBIFS_PAD_NODE_SZ;
        c->ranges[UBIFS_SB_NODE].len   = UBIFS_SB_NODE_SZ;
        c->ranges[UBIFS_MST_NODE].len  = UBIFS_MST_NODE_SZ;
        c->ranges[UBIFS_REF_NODE].len  = UBIFS_REF_NODE_SZ;
        c->ranges[UBIFS_TRUN_NODE].len = UBIFS_TRUN_NODE_SZ;
        c->ranges[UBIFS_CS_NODE].len   = UBIFS_CS_NODE_SZ;

        c->ranges[UBIFS_INO_NODE].min_len  = UBIFS_INO_NODE_SZ;
        c->ranges[UBIFS_INO_NODE].max_len  = UBIFS_MAX_INO_NODE_SZ;
        c->ranges[UBIFS_ORPH_NODE].min_len =
                                UBIFS_ORPH_NODE_SZ + sizeof(__le64);
        c->ranges[UBIFS_ORPH_NODE].max_len = c->leb_size;
        c->ranges[UBIFS_DENT_NODE].min_len = UBIFS_DENT_NODE_SZ;
        c->ranges[UBIFS_DENT_NODE].max_len = UBIFS_MAX_DENT_NODE_SZ;
        c->ranges[UBIFS_XENT_NODE].min_len = UBIFS_XENT_NODE_SZ;
        c->ranges[UBIFS_XENT_NODE].max_len = UBIFS_MAX_XENT_NODE_SZ;
        c->ranges[UBIFS_DATA_NODE].min_len = UBIFS_DATA_NODE_SZ;
        c->ranges[UBIFS_DATA_NODE].max_len = UBIFS_MAX_DATA_NODE_SZ;
        /*
         * Minimum indexing node size is amended later when superblock is
         * read and the key length is known.
         */
        c->ranges[UBIFS_IDX_NODE].min_len = UBIFS_IDX_NODE_SZ + UBIFS_BRANCH_SZ;
        /*
         * Maximum indexing node size is amended later when superblock is
         * read and the fanout is known.
         */
        c->ranges[UBIFS_IDX_NODE].max_len = INT_MAX;

        /*
         * Initialize dead and dark LEB space watermarks.
         *
         * Dead space is the space which cannot be used. Its watermark is
         * equivalent to min. I/O unit or minimum node size if it is greater
         * then min. I/O unit.
         *
         * Dark space is the space which might be used, or might not, depending
         * on which node should be written to the LEB. Its watermark is
         * equivalent to maximum UBIFS node size.
         */
        c->dead_wm = ALIGN(MIN_WRITE_SZ, c->min_io_size);
        c->dark_wm = ALIGN(UBIFS_MAX_NODE_SZ, c->min_io_size);

        /*
         * Calculate how many bytes would be wasted at the end of LEB if it was
         * fully filled with data nodes of maximum size. This is used in
         * calculations when reporting free space.
         */
        c->leb_overhead = c->leb_size % UBIFS_MAX_DATA_NODE_SZ;
        /* Buffer size for bulk-reads */
        c->bulk_read_buf_size = UBIFS_MAX_BULK_READ * UBIFS_MAX_DATA_NODE_SZ;
        if (c->bulk_read_buf_size > c->leb_size)
                c->bulk_read_buf_size = c->leb_size;
        if (c->bulk_read_buf_size > 128 * 1024) {
                /* Check if we can kmalloc more than 128KiB */
                void *try = kmalloc(c->bulk_read_buf_size, GFP_KERNEL);

                kfree(try);
                if (!try)
                        c->bulk_read_buf_size = 128 * 1024;
        }
        return 0;
}

/**
 * bud_wbuf_callback - bud LEB write-buffer synchronization call-back.
 * @c: UBIFS file-system description object
 * @lnum: LEB the write-buffer was synchronized to
 * @free: how many free bytes left in this LEB
 * @pad: how many bytes were padded
 *
 * This is a callback function which is called by the I/O unit when the
 * write-buffer is synchronized. We need this to correctly maintain space
 * accounting in bud logical eraseblocks. This function returns zero in case of
 * success and a negative error code in case of failure.
 *
 * This function actually belongs to the journal, but we keep it here because
 * we want to keep it static.
 */
static int bud_wbuf_callback(struct ubifs_info *c, int lnum, int free, int pad)
{
        return ubifs_update_one_lp(c, lnum, free, pad, 0, 0);
}

/*
 * init_constants_late - initialize UBIFS constants.
 * @c: UBIFS file-system description object
 *
 * This is a helper function which initializes various UBIFS constants after
 * the superblock has been read. It also checks various UBIFS parameters and
 * makes sure they are all right. Returns zero in case of success and a
 * negative error code in case of failure.
 */
static int init_constants_late(struct ubifs_info *c)
{
        int tmp, err;
        uint64_t tmp64;

        c->main_bytes = (long long)c->main_lebs * c->leb_size;
        c->max_znode_sz = sizeof(struct ubifs_znode) +
                                c->fanout * sizeof(struct ubifs_zbranch);

        tmp = ubifs_idx_node_sz(c, 1);
        c->ranges[UBIFS_IDX_NODE].min_len = tmp;
        c->min_idx_node_sz = ALIGN(tmp, 8);

        tmp = ubifs_idx_node_sz(c, c->fanout);
        c->ranges[UBIFS_IDX_NODE].max_len = tmp;
        c->max_idx_node_sz = ALIGN(tmp, 8);

        /* Make sure LEB size is large enough to fit full commit */
        tmp = UBIFS_CS_NODE_SZ + UBIFS_REF_NODE_SZ * c->jhead_cnt;
        tmp = ALIGN(tmp, c->min_io_size);
        if (tmp > c->leb_size) {
                dbg_err("too small LEB size %d, at least %d needed",
                        c->leb_size, tmp);
                return -EINVAL;
        }

        /*
         * Make sure that the log is large enough to fit reference nodes for
         * all buds plus one reserved LEB.
         */
        tmp64 = c->max_bud_bytes;
        tmp = do_div(tmp64, c->leb_size);
        c->max_bud_cnt = tmp64 + !!tmp;
        tmp = (c->ref_node_alsz * c->max_bud_cnt + c->leb_size - 1);
        tmp /= c->leb_size;
        tmp += 1;
        if (c->log_lebs < tmp) {
                dbg_err("too small log %d LEBs, required min. %d LEBs",
                        c->log_lebs, tmp);
                return -EINVAL;
        }

        /*
         * When budgeting we assume worst-case scenarios when the pages are not
         * be compressed and direntries are of the maximum size.
         *
         * Note, data, which may be stored in inodes is budgeted separately, so
         * it is not included into 'c->inode_budget'.
         */
        c->page_budget = UBIFS_MAX_DATA_NODE_SZ * UBIFS_BLOCKS_PER_PAGE;
        c->inode_budget = UBIFS_INO_NODE_SZ;
        c->dent_budget = UBIFS_MAX_DENT_NODE_SZ;

        /*
         * When the amount of flash space used by buds becomes
         * 'c->max_bud_bytes', UBIFS just blocks all writers and starts commit.
         * The writers are unblocked when the commit is finished. To avoid
         * writers to be blocked UBIFS initiates background commit in advance,
         * when number of bud bytes becomes above the limit defined below.
         */
        c->bg_bud_bytes = (c->max_bud_bytes * 13) >> 4;

        /*
         * Ensure minimum journal size. All the bytes in the journal heads are
         * considered to be used, when calculating the current journal usage.
         * Consequently, if the journal is too small, UBIFS will treat it as
         * always full.
         */
        tmp64 = (uint64_t)(c->jhead_cnt + 1) * c->leb_size + 1;
        if (c->bg_bud_bytes < tmp64)
                c->bg_bud_bytes = tmp64;
        if (c->max_bud_bytes < tmp64 + c->leb_size)
                c->max_bud_bytes = tmp64 + c->leb_size;

        err = ubifs_calc_lpt_geom(c);
        if (err)
                return err;

        c->min_idx_lebs = ubifs_calc_min_idx_lebs(c);

        /*
         * Calculate total amount of FS blocks. This number is not used
         * internally because it does not make much sense for UBIFS, but it is
         * necessary to report something for the 'statfs()' call.
         *
         * Subtract the LEB reserved for GC, the LEB which is reserved for
         * deletions, and assume only one journal head is available.
         */
        tmp64 = c->main_lebs - 2 - c->jhead_cnt + 1;
        tmp64 *= (uint64_t)c->leb_size - c->leb_overhead;
        tmp64 = ubifs_reported_space(c, tmp64);
        c->block_cnt = tmp64 >> UBIFS_BLOCK_SHIFT;

        return 0;
}

/**
 * take_gc_lnum - reserve GC LEB.
 * @c: UBIFS file-system description object
 *
 * This function ensures that the LEB reserved for garbage collection is
 * unmapped and is marked as "taken" in lprops. We also have to set free space
 * to LEB size and dirty space to zero, because lprops may contain out-of-date
 * information if the file-system was un-mounted before it has been committed.
 * This function returns zero in case of success and a negative error code in
 * case of failure.
 */
static int take_gc_lnum(struct ubifs_info *c)
{
        int err;

        if (c->gc_lnum == -1) {
                ubifs_err("no LEB for GC");
                return -EINVAL;
        }

        err = ubifs_leb_unmap(c, c->gc_lnum);
        if (err)
                return err;

        /* And we have to tell lprops that this LEB is taken */
        err = ubifs_change_one_lp(c, c->gc_lnum, c->leb_size, 0,
                                  LPROPS_TAKEN, 0, 0);
        return err;
}

/**
 * alloc_wbufs - allocate write-buffers.
 * @c: UBIFS file-system description object
 *
 * This helper function allocates and initializes UBIFS write-buffers. Returns
 * zero in case of success and %-ENOMEM in case of failure.
 */
static int alloc_wbufs(struct ubifs_info *c)
{
        int i, err;

        c->jheads = kzalloc(c->jhead_cnt * sizeof(struct ubifs_jhead),
                           GFP_KERNEL);
        if (!c->jheads)
                return -ENOMEM;

        /* Initialize journal heads */
        for (i = 0; i < c->jhead_cnt; i++) {
                INIT_LIST_HEAD(&c->jheads[i].buds_list);
                err = ubifs_wbuf_init(c, &c->jheads[i].wbuf);
                if (err)
                        return err;

                c->jheads[i].wbuf.sync_callback = &bud_wbuf_callback;
                c->jheads[i].wbuf.jhead = i;
        }

        c->jheads[BASEHD].wbuf.dtype = UBI_SHORTTERM;
        /*
         * Garbage Collector head likely contains long-term data and
         * does not need to be synchronized by timer.
         */
        c->jheads[GCHD].wbuf.dtype = UBI_LONGTERM;
        c->jheads[GCHD].wbuf.timeout = 0;

        return 0;
}

/**
 * free_wbufs - free write-buffers.
 * @c: UBIFS file-system description object
 */
static void free_wbufs(struct ubifs_info *c)
{
        int i;

        if (c->jheads) {
                for (i = 0; i < c->jhead_cnt; i++) {
                        kfree(c->jheads[i].wbuf.buf);
                        kfree(c->jheads[i].wbuf.inodes);
                }
                kfree(c->jheads);
                c->jheads = NULL;
        }
}

/**
 * free_orphans - free orphans.
 * @c: UBIFS file-system description object
 */
static void free_orphans(struct ubifs_info *c)
{
        struct ubifs_orphan *orph;

        while (c->orph_dnext) {
                orph = c->orph_dnext;
                c->orph_dnext = orph->dnext;
                list_del(&orph->list);
                kfree(orph);
        }

        while (!list_empty(&c->orph_list)) {
                orph = list_entry(c->orph_list.next, struct ubifs_orphan, list);
                list_del(&orph->list);
                kfree(orph);
                dbg_err("orphan list not empty at unmount");
        }

        vfree(c->orph_buf);
        c->orph_buf = NULL;
}

/**
 * free_buds - free per-bud objects.
 * @c: UBIFS file-system description object
 */
static void free_buds(struct ubifs_info *c)
{
        struct rb_node *this = c->buds.rb_node;
        struct ubifs_bud *bud;

        while (this) {
                if (this->rb_left)
                        this = this->rb_left;
                else if (this->rb_right)
                        this = this->rb_right;
                else {
                        bud = rb_entry(this, struct ubifs_bud, rb);
                        this = rb_parent(this);
                        if (this) {
                                if (this->rb_left == &bud->rb)
                                        this->rb_left = NULL;
                                else
                                        this->rb_right = NULL;
                        }
                        kfree(bud);
                }
        }
}

/**
 * check_volume_empty - check if the UBI volume is empty.
 * @c: UBIFS file-system description object
 *
 * This function checks if the UBIFS volume is empty by looking if its LEBs are
 * mapped or not. The result of checking is stored in the @c->empty variable.
 * Returns zero in case of success and a negative error code in case of
 * failure.
 */
static int check_volume_empty(struct ubifs_info *c)
{
        int lnum, err;

        c->empty = 1;
        for (lnum = 0; lnum < c->leb_cnt; lnum++) {
                err = ubi_is_mapped(c->ubi, lnum);
                if (unlikely(err < 0))
                        return err;
                if (err == 1) {
                        c->empty = 0;
                        break;
                }

                cond_resched();
        }

        return 0;
}

/*
 * UBIFS mount options.
 *
 * Opt_fast_unmount: do not run a journal commit before un-mounting
 * Opt_norm_unmount: run a journal commit before un-mounting
 * Opt_bulk_read: enable bulk-reads
 * Opt_no_bulk_read: disable bulk-reads
 * Opt_chk_data_crc: check CRCs when reading data nodes
 * Opt_no_chk_data_crc: do not check CRCs when reading data nodes
 * Opt_err: just end of array marker
 */
enum {
        Opt_fast_unmount,
        Opt_norm_unmount,
        Opt_bulk_read,
        Opt_no_bulk_read,
        Opt_chk_data_crc,
        Opt_no_chk_data_crc,
        Opt_err,
};

static match_table_t tokens = {
        {Opt_fast_unmount, "fast_unmount"},
        {Opt_norm_unmount, "norm_unmount"},
        {Opt_bulk_read, "bulk_read"},
        {Opt_no_bulk_read, "no_bulk_read"},
        {Opt_chk_data_crc, "chk_data_crc"},
        {Opt_no_chk_data_crc, "no_chk_data_crc"},
        {Opt_err, NULL},
};

/**
 * ubifs_parse_options - parse mount parameters.
 * @c: UBIFS file-system description object
 * @options: parameters to parse
 * @is_remount: non-zero if this is FS re-mount
 *
 * This function parses UBIFS mount options and returns zero in case success
 * and a negative error code in case of failure.
 */
static int ubifs_parse_options(struct ubifs_info *c, char *options,
                               int is_remount)
{
        char *p;
        substring_t args[MAX_OPT_ARGS];

        if (!options)
                return 0;

        while ((p = strsep(&options, ","))) {
                int token;

                if (!*p)
                        continue;

                token = match_token(p, tokens, args);
                switch (token) {
                case Opt_fast_unmount:
                        c->mount_opts.unmount_mode = 2;
                        c->fast_unmount = 1;
                        break;
                case Opt_norm_unmount:
                        c->mount_opts.unmount_mode = 1;
                        c->fast_unmount = 0;
                        break;
                case Opt_bulk_read:
                        c->mount_opts.bulk_read = 2;
                        c->bulk_read = 1;
                        break;
                case Opt_no_bulk_read:
                        c->mount_opts.bulk_read = 1;
                        c->bulk_read = 0;
                        break;
                case Opt_chk_data_crc:
                        c->mount_opts.chk_data_crc = 2;
                        c->no_chk_data_crc = 0;
                        break;
                case Opt_no_chk_data_crc:
                        c->mount_opts.chk_data_crc = 1;
                        c->no_chk_data_crc = 1;
                        break;
                default:
                        ubifs_err("unrecognized mount option \"%s\" "
                                  "or missing value", p);
                        return -EINVAL;
                }
        }

        return 0;
}

/**
 * destroy_journal - destroy journal data structures.
 * @c: UBIFS file-system description object
 *
 * This function destroys journal data structures including those that may have
 * been created by recovery functions.
 */
static void destroy_journal(struct ubifs_info *c)
{
        while (!list_empty(&c->unclean_leb_list)) {
                struct ubifs_unclean_leb *ucleb;

                ucleb = list_entry(c->unclean_leb_list.next,
                                   struct ubifs_unclean_leb, list);
                list_del(&ucleb->list);
                kfree(ucleb);
        }
        while (!list_empty(&c->old_buds)) {
                struct ubifs_bud *bud;

                bud = list_entry(c->old_buds.next, struct ubifs_bud, list);
                list_del(&bud->list);
                kfree(bud);
        }
        ubifs_destroy_idx_gc(c);
        ubifs_destroy_size_tree(c);
        ubifs_tnc_close(c);
        free_buds(c);
}

/**
 * mount_ubifs - mount UBIFS file-system.
 * @c: UBIFS file-system description object
 *
 * This function mounts UBIFS file system. Returns zero in case of success and
 * a negative error code in case of failure.
 *
 * Note, the function does not de-allocate resources it it fails half way
 * through, and the caller has to do this instead.
 */
static int mount_ubifs(struct ubifs_info *c)
{
        struct super_block *sb = c->vfs_sb;
        int err, mounted_read_only = (sb->s_flags & MS_RDONLY);
        long long x;
        size_t sz;

        err = init_constants_early(c);
        if (err)
                return err;

#ifdef CONFIG_UBIFS_FS_DEBUG
        c->dbg_buf = vmalloc(c->leb_size);
        if (!c->dbg_buf)
                return -ENOMEM;
#endif

        err = check_volume_empty(c);
        if (err)
                goto out_free;

        if (c->empty && (mounted_read_only || c->ro_media)) {
                /*
                 * This UBI volume is empty, and read-only, or the file system
                 * is mounted read-only - we cannot format it.
                 */
                ubifs_err("can't format empty UBI volume: read-only %s",
                          c->ro_media ? "UBI volume" : "mount");
                err = -EROFS;
                goto out_free;
        }

        if (c->ro_media && !mounted_read_only) {
                ubifs_err("cannot mount read-write - read-only media");
                err = -EROFS;
                goto out_free;
        }

        /*
         * The requirement for the buffer is that it should fit indexing B-tree
         * height amount of integers. We assume the height if the TNC tree will
         * never exceed 64.
         */
        err = -ENOMEM;
        c->bottom_up_buf = kmalloc(BOTTOM_UP_HEIGHT * sizeof(int), GFP_KERNEL);
        if (!c->bottom_up_buf)
                goto out_free;

        c->sbuf = vmalloc(c->leb_size);
        if (!c->sbuf)
                goto out_free;

        if (!mounted_read_only) {
                c->ileb_buf = vmalloc(c->leb_size);
                if (!c->ileb_buf)
                        goto out_free;
        }

        c->always_chk_crc = 1;

        err = ubifs_read_superblock(c);
        if (err)
                goto out_free;

        /*
         * Make sure the compressor which is set as the default on in the
         * superblock was actually compiled in.
         */
        if (!ubifs_compr_present(c->default_compr)) {
                ubifs_warn("'%s' compressor is set by superblock, but not "
                           "compiled in", ubifs_compr_name(c->default_compr));
                c->default_compr = UBIFS_COMPR_NONE;
        }

        dbg_failure_mode_registration(c);

        err = init_constants_late(c);
        if (err)
                goto out_dereg;

        sz = ALIGN(c->max_idx_node_sz, c->min_io_size);
        sz = ALIGN(sz + c->max_idx_node_sz, c->min_io_size);
        c->cbuf = kmalloc(sz, GFP_NOFS);
        if (!c->cbuf) {
                err = -ENOMEM;
                goto out_dereg;
        }

        sprintf(c->bgt_name, BGT_NAME_PATTERN, c->vi.ubi_num, c->vi.vol_id);
        if (!mounted_read_only) {
                err = alloc_wbufs(c);
                if (err)
                        goto out_cbuf;

                /* Create background thread */
                c->bgt = kthread_create(ubifs_bg_thread, c, c->bgt_name);
                if (IS_ERR(c->bgt)) {
                        err = PTR_ERR(c->bgt);
                        c->bgt = NULL;
                        ubifs_err("cannot spawn \"%s\", error %d",
                                  c->bgt_name, err);
                        goto out_wbufs;
                }
                wake_up_process(c->bgt);
        }

        err = ubifs_read_master(c);
        if (err)
                goto out_master;

        if ((c->mst_node->flags & cpu_to_le32(UBIFS_MST_DIRTY)) != 0) {
                ubifs_msg("recovery needed");
                c->need_recovery = 1;
                if (!mounted_read_only) {
                        err = ubifs_recover_inl_heads(c, c->sbuf);
                        if (err)
                                goto out_master;
                }
        } else if (!mounted_read_only) {
                /*
                 * Set the "dirty" flag so that if we reboot uncleanly we
                 * will notice this immediately on the next mount.
                 */
                c->mst_node->flags |= cpu_to_le32(UBIFS_MST_DIRTY);
                err = ubifs_write_master(c);
                if (err)
                        goto out_master;
        }

        err = ubifs_lpt_init(c, 1, !mounted_read_only);
        if (err)
                goto out_lpt;

        err = dbg_check_idx_size(c, c->old_idx_sz);
        if (err)
                goto out_lpt;

        err = ubifs_replay_journal(c);
        if (err)
                goto out_journal;

        err = ubifs_mount_orphans(c, c->need_recovery, mounted_read_only);
        if (err)
                goto out_orphans;

        if (!mounted_read_only) {
                int lnum;

                /* Check for enough free space */
                if (ubifs_calc_available(c, c->min_idx_lebs) <= 0) {
                        ubifs_err("insufficient available space");
                        err = -EINVAL;
                        goto out_orphans;
                }

                /* Check for enough log space */
                lnum = c->lhead_lnum + 1;
                if (lnum >= UBIFS_LOG_LNUM + c->log_lebs)
                        lnum = UBIFS_LOG_LNUM;
                if (lnum == c->ltail_lnum) {
                        err = ubifs_consolidate_log(c);
                        if (err)
                                goto out_orphans;
                }

                if (c->need_recovery) {
                        err = ubifs_recover_size(c);
                        if (err)
                                goto out_orphans;
                        err = ubifs_rcvry_gc_commit(c);
                } else
                        err = take_gc_lnum(c);
                if (err)
                        goto out_orphans;

                err = dbg_check_lprops(c);
                if (err)
                        goto out_orphans;
        } else if (c->need_recovery) {
                err = ubifs_recover_size(c);
                if (err)
                        goto out_orphans;
        }

        spin_lock(&ubifs_infos_lock);
        list_add_tail(&c->infos_list, &ubifs_infos);
        spin_unlock(&ubifs_infos_lock);

        if (c->need_recovery) {
                if (mounted_read_only)
                        ubifs_msg("recovery deferred");
                else {
                        c->need_recovery = 0;
                        ubifs_msg("recovery completed");
                }
        }

        err = dbg_check_filesystem(c);
        if (err)
                goto out_infos;

        c->always_chk_crc = 0;

        ubifs_msg("mounted UBI device %d, volume %d, name \"%s\"",
                  c->vi.ubi_num, c->vi.vol_id, c->vi.name);
        if (mounted_read_only)
                ubifs_msg("mounted read-only");
        x = (long long)c->main_lebs * c->leb_size;
        ubifs_msg("file system size:   %lld bytes (%lld KiB, %lld MiB, %d "
                  "LEBs)", x, x >> 10, x >> 20, c->main_lebs);
        x = (long long)c->log_lebs * c->leb_size + c->max_bud_bytes;
        ubifs_msg("journal size:       %lld bytes (%lld KiB, %lld MiB, %d "
                  "LEBs)", x, x >> 10, x >> 20, c->log_lebs + c->max_bud_cnt);
        ubifs_msg("media format:       %d (latest is %d)",
                  c->fmt_version, UBIFS_FORMAT_VERSION);
        ubifs_msg("default compressor: %s", ubifs_compr_name(c->default_compr));
        ubifs_msg("reserved pool size: %llu bytes (%llu KiB)",
                c->report_rp_size, c->report_rp_size >> 10);

        dbg_msg("compiled on:         " __DATE__ " at " __TIME__);
        dbg_msg("min. I/O unit size:  %d bytes", c->min_io_size);
        dbg_msg("LEB size:            %d bytes (%d KiB)",
                c->leb_size, c->leb_size >> 10);
        dbg_msg("data journal heads:  %d",
                c->jhead_cnt - NONDATA_JHEADS_CNT);
        dbg_msg("UUID:                %02X%02X%02X%02X-%02X%02X"
               "-%02X%02X-%02X%02X-%02X%02X%02X%02X%02X%02X",
               c->uuid[0], c->uuid[1], c->uuid[2], c->uuid[3],
               c->uuid[4], c->uuid[5], c->uuid[6], c->uuid[7],
               c->uuid[8], c->uuid[9], c->uuid[10], c->uuid[11],
               c->uuid[12], c->uuid[13], c->uuid[14], c->uuid[15]);
        dbg_msg("fast unmount:        %d", c->fast_unmount);
        dbg_msg("big_lpt              %d", c->big_lpt);
        dbg_msg("log LEBs:            %d (%d - %d)",
                c->log_lebs, UBIFS_LOG_LNUM, c->log_last);
        dbg_msg("LPT area LEBs:       %d (%d - %d)",
                c->lpt_lebs, c->lpt_first, c->lpt_last);
        dbg_msg("orphan area LEBs:    %d (%d - %d)",
                c->orph_lebs, c->orph_first, c->orph_last);
        dbg_msg("main area LEBs:      %d (%d - %d)",
                c->main_lebs, c->main_first, c->leb_cnt - 1);
        dbg_msg("index LEBs:          %d", c->lst.idx_lebs);
        dbg_msg("total index bytes:   %lld (%lld KiB, %lld MiB)",
                c->old_idx_sz, c->old_idx_sz >> 10, c->old_idx_sz >> 20);
        dbg_msg("key hash type:       %d", c->key_hash_type);
        dbg_msg("tree fanout:         %d", c->fanout);
        dbg_msg("reserved GC LEB:     %d", c->gc_lnum);
        dbg_msg("first main LEB:      %d", c->main_first);
        dbg_msg("dead watermark:      %d", c->dead_wm);
        dbg_msg("dark watermark:      %d", c->dark_wm);
        x = (long long)c->main_lebs * c->dark_wm;
        dbg_msg("max. dark space:     %lld (%lld KiB, %lld MiB)",
                x, x >> 10, x >> 20);
        dbg_msg("maximum bud bytes:   %lld (%lld KiB, %lld MiB)",
                c->max_bud_bytes, c->max_bud_bytes >> 10,
                c->max_bud_bytes >> 20);
        dbg_msg("BG commit bud bytes: %lld (%lld KiB, %lld MiB)",
                c->bg_bud_bytes, c->bg_bud_bytes >> 10,
                c->bg_bud_bytes >> 20);
        dbg_msg("current bud bytes    %lld (%lld KiB, %lld MiB)",
                c->bud_bytes, c->bud_bytes >> 10, c->bud_bytes >> 20);
        dbg_msg("max. seq. number:    %llu", c->max_sqnum);
        dbg_msg("commit number:       %llu", c->cmt_no);

        return 0;

out_infos:
        spin_lock(&ubifs_infos_lock);
        list_del(&c->infos_list);
        spin_unlock(&ubifs_infos_lock);
out_orphans:
        free_orphans(c);
out_journal:
        destroy_journal(c);
out_lpt:
        ubifs_lpt_free(c, 0);
out_master:
        kfree(c->mst_node);
        kfree(c->rcvrd_mst_node);
        if (c->bgt)
                kthread_stop(c->bgt);
out_wbufs:
        free_wbufs(c);
out_cbuf:
        kfree(c->cbuf);
out_dereg:
        dbg_failure_mode_deregistration(c);
out_free:
        vfree(c->ileb_buf);
        vfree(c->sbuf);
        kfree(c->bottom_up_buf);
        UBIFS_DBG(vfree(c->dbg_buf));
        return err;
}

/**
 * ubifs_umount - un-mount UBIFS file-system.
 * @c: UBIFS file-system description object
 *
 * Note, this function is called to free allocated resourced when un-mounting,
 * as well as free resources when an error occurred while we were half way
 * through mounting (error path cleanup function). So it has to make sure the
 * resource was actually allocated before freeing it.
 */
static void ubifs_umount(struct ubifs_info *c)
{
        dbg_gen("un-mounting UBI device %d, volume %d", c->vi.ubi_num,
                c->vi.vol_id);

        spin_lock(&ubifs_infos_lock);
        list_del(&c->infos_list);
        spin_unlock(&ubifs_infos_lock);

        if (c->bgt)
                kthread_stop(c->bgt);

        destroy_journal(c);
        free_wbufs(c);
        free_orphans(c);
        ubifs_lpt_free(c, 0);

        kfree(c->cbuf);
        kfree(c->rcvrd_mst_node);
        kfree(c->mst_node);
        vfree(c->sbuf);
        kfree(c->bottom_up_buf);
        UBIFS_DBG(vfree(c->dbg_buf));
        vfree(c->ileb_buf);
        dbg_failure_mode_deregistration(c);
}

/**
 * ubifs_remount_rw - re-mount in read-write mode.
 * @c: UBIFS file-system description object
 *
 * UBIFS avoids allocating many unnecessary resources when mounted in read-only
 * mode. This function allocates the needed resources and re-mounts UBIFS in
 * read-write mode.
 */
static int ubifs_remount_rw(struct ubifs_info *c)
{
        int err, lnum;

        if (c->ro_media)
                return -EINVAL;

        mutex_lock(&c->umount_mutex);
        c->remounting_rw = 1;
        c->always_chk_crc = 1;

        /* Check for enough free space */
        if (ubifs_calc_available(c, c->min_idx_lebs) <= 0) {
                ubifs_err("insufficient available space");
                err = -EINVAL;
                goto out;
        }

        if (c->old_leb_cnt != c->leb_cnt) {
                struct ubifs_sb_node *sup;

                sup = ubifs_read_sb_node(c);
                if (IS_ERR(sup)) {
                        err = PTR_ERR(sup);
                        goto out;
                }
                sup->leb_cnt = cpu_to_le32(c->leb_cnt);
                err = ubifs_write_sb_node(c, sup);
                if (err)
                        goto out;
        }

        if (c->need_recovery) {
                ubifs_msg("completing deferred recovery");
                err = ubifs_write_rcvrd_mst_node(c);
                if (err)
                        goto out;
                err = ubifs_recover_size(c);
                if (err)
                        goto out;
                err = ubifs_clean_lebs(c, c->sbuf);
                if (err)
                        goto out;
                err = ubifs_recover_inl_heads(c, c->sbuf);
                if (err)
                        goto out;
        }

        if (!(c->mst_node->flags & cpu_to_le32(UBIFS_MST_DIRTY))) {
                c->mst_node->flags |= cpu_to_le32(UBIFS_MST_DIRTY);
                err = ubifs_write_master(c);
                if (err)
                        goto out;
        }

        c->ileb_buf = vmalloc(c->leb_size);
        if (!c->ileb_buf) {
                err = -ENOMEM;
                goto out;
        }

        err = ubifs_lpt_init(c, 0, 1);
        if (err)
                goto out;

        err = alloc_wbufs(c);
        if (err)
                goto out;

        ubifs_create_buds_lists(c);

        /* Create background thread */
        c->bgt = kthread_create(ubifs_bg_thread, c, c->bgt_name);
        if (IS_ERR(c->bgt)) {
                err = PTR_ERR(c->bgt);
                c->bgt = NULL;
                ubifs_err("cannot spawn \"%s\", error %d",
                          c->bgt_name, err);
                goto out;
        }
        wake_up_process(c->bgt);

        c->orph_buf = vmalloc(c->leb_size);
        if (!c->orph_buf) {
                err = -ENOMEM;
                goto out;
        }

        /* Check for enough log space */
        lnum = c->lhead_lnum + 1;
        if (lnum >= UBIFS_LOG_LNUM + c->log_lebs)
                lnum = UBIFS_LOG_LNUM;
        if (lnum == c->ltail_lnum) {
                err = ubifs_consolidate_log(c);
                if (err)
                        goto out;
        }

        if (c->need_recovery)
                err = ubifs_rcvry_gc_commit(c);
        else
                err = take_gc_lnum(c);
        if (err)
                goto out;

        if (c->need_recovery) {
                c->need_recovery = 0;
                ubifs_msg("deferred recovery completed");
        }

        dbg_gen("re-mounted read-write");
        c->vfs_sb->s_flags &= ~MS_RDONLY;
        c->remounting_rw = 0;
        c->always_chk_crc = 0;
        mutex_unlock(&c->umount_mutex);
        return 0;

out:
        vfree(c->orph_buf);
        c->orph_buf = NULL;
        if (c->bgt) {
                kthread_stop(c->bgt);
                c->bgt = NULL;
        }
        free_wbufs(c);
        vfree(c->ileb_buf);
        c->ileb_buf = NULL;
        ubifs_lpt_free(c, 1);
        c->remounting_rw = 0;
        c->always_chk_crc = 0;
        mutex_unlock(&c->umount_mutex);
        return err;
}

/**
 * commit_on_unmount - commit the journal when un-mounting.
 * @c: UBIFS file-system description object
 *
 * This function is called during un-mounting and re-mounting, and it commits
 * the journal unless the "fast unmount" mode is enabled. It also avoids
 * committing the journal if it contains too few data.
 */
static void commit_on_unmount(struct ubifs_info *c)
{
        if (!c->fast_unmount) {
                long long bud_bytes;

                spin_lock(&c->buds_lock);
                bud_bytes = c->bud_bytes;
                spin_unlock(&c->buds_lock);
                if (bud_bytes > c->leb_size)
                        ubifs_run_commit(c);
        }
}

/**
 * ubifs_remount_ro - re-mount in read-only mode.
 * @c: UBIFS file-system description object
 *
 * We rely on VFS to have stopped writing. Possibly the background thread could
 * be running a commit, however kthread_stop will wait in that case.
 */
static void ubifs_remount_ro(struct ubifs_info *c)
{
        int i, err;

        ubifs_assert(!c->need_recovery);
        commit_on_unmount(c);

        mutex_lock(&c->umount_mutex);
        if (c->bgt) {
                kthread_stop(c->bgt);
                c->bgt = NULL;
        }

        for (i = 0; i < c->jhead_cnt; i++) {
                ubifs_wbuf_sync(&c->jheads[i].wbuf);
                del_timer_sync(&c->jheads[i].wbuf.timer);
        }

        if (!c->ro_media) {
                c->mst_node->flags &= ~cpu_to_le32(UBIFS_MST_DIRTY);
                c->mst_node->flags |= cpu_to_le32(UBIFS_MST_NO_ORPHS);
                c->mst_node->gc_lnum = cpu_to_le32(c->gc_lnum);
                err = ubifs_write_master(c);
                if (err)
                        ubifs_ro_mode(c, err);
        }

        ubifs_destroy_idx_gc(c);
        free_wbufs(c);
        vfree(c->orph_buf);
        c->orph_buf = NULL;
        vfree(c->ileb_buf);
        c->ileb_buf = NULL;
        ubifs_lpt_free(c, 1);
        mutex_unlock(&c->umount_mutex);
}

static void ubifs_put_super(struct super_block *sb)
{
        int i;
        struct ubifs_info *c = sb->s_fs_info;

        ubifs_msg("un-mount UBI device %d, volume %d", c->vi.ubi_num,
                  c->vi.vol_id);
        /*
         * The following asserts are only valid if there has not been a failure
         * of the media. For example, there will be dirty inodes if we failed
         * to write them back because of I/O errors.
         */
        ubifs_assert(atomic_long_read(&c->dirty_pg_cnt) == 0);
        ubifs_assert(c->budg_idx_growth == 0);
        ubifs_assert(c->budg_dd_growth == 0);
        ubifs_assert(c->budg_data_growth == 0);

        /*
         * The 'c->umount_lock' prevents races between UBIFS memory shrinker
         * and file system un-mount. Namely, it prevents the shrinker from
         * picking this superblock for shrinking - it will be just skipped if
         * the mutex is locked.
         */
        mutex_lock(&c->umount_mutex);
        if (!(c->vfs_sb->s_flags & MS_RDONLY)) {
                /*
                 * First of all kill the background thread to make sure it does
                 * not interfere with un-mounting and freeing resources.
                 */
                if (c->bgt) {
                        kthread_stop(c->bgt);
                        c->bgt = NULL;
                }

                /* Synchronize write-buffers */
                if (c->jheads)
                        for (i = 0; i < c->jhead_cnt; i++) {
                                ubifs_wbuf_sync(&c->jheads[i].wbuf);
                                del_timer_sync(&c->jheads[i].wbuf.timer);
                        }

                /*
                 * On fatal errors c->ro_media is set to 1, in which case we do
                 * not write the master node.
                 */
                if (!c->ro_media) {
                        /*
                         * We are being cleanly unmounted which means the
                         * orphans were killed - indicate this in the master
                         * node. Also save the reserved GC LEB number.
                         */
                        int err;

                        c->mst_node->flags &= ~cpu_to_le32(UBIFS_MST_DIRTY);
                        c->mst_node->flags |= cpu_to_le32(UBIFS_MST_NO_ORPHS);
                        c->mst_node->gc_lnum = cpu_to_le32(c->gc_lnum);
                        err = ubifs_write_master(c);
                        if (err)
                                /*
                                 * Recovery will attempt to fix the master area
                                 * next mount, so we just print a message and
                                 * continue to unmount normally.
                                 */
                                ubifs_err("failed to write master node, "
                                          "error %d", err);
                }
        }

        ubifs_umount(c);
        bdi_destroy(&c->bdi);
        ubi_close_volume(c->ubi);
        mutex_unlock(&c->umount_mutex);
        kfree(c);
}

static int ubifs_remount_fs(struct super_block *sb, int *flags, char *data)
{
        int err;
        struct ubifs_info *c = sb->s_fs_info;

        dbg_gen("old flags %#lx, new flags %#x", sb->s_flags, *flags);

        err = ubifs_parse_options(c, data, 1);
        if (err) {
                ubifs_err("invalid or unknown remount parameter");
                return err;
        }
        if ((sb->s_flags & MS_RDONLY) && !(*flags & MS_RDONLY)) {
                err = ubifs_remount_rw(c);
                if (err)
                        return err;
        } else if (!(sb->s_flags & MS_RDONLY) && (*flags & MS_RDONLY))
                ubifs_remount_ro(c);

        return 0;
}

struct super_operations ubifs_super_operations = {
        .alloc_inode   = ubifs_alloc_inode,
        .destroy_inode = ubifs_destroy_inode,
        .put_super     = ubifs_put_super,
        .write_inode   = ubifs_write_inode,
        .delete_inode  = ubifs_delete_inode,
        .statfs        = ubifs_statfs,
        .dirty_inode   = ubifs_dirty_inode,
        .remount_fs    = ubifs_remount_fs,
        .show_options  = ubifs_show_options,
        .sync_fs       = ubifs_sync_fs,
};

/**
 * open_ubi - parse UBI device name string and open the UBI device.
 * @name: UBI volume name
 * @mode: UBI volume open mode
 *
 * There are several ways to specify UBI volumes when mounting UBIFS:
 * o ubiX_Y    - UBI device number X, volume Y;
 * o ubiY      - UBI device number 0, volume Y;
 * o ubiX:NAME - mount UBI device X, volume with name NAME;
 * o ubi:NAME  - mount UBI device 0, volume with name NAME.
 *
 * Alternative '!' separator may be used instead of ':' (because some shells
 * like busybox may interpret ':' as an NFS host name separator). This function
 * returns ubi volume object in case of success and a negative error code in
 * case of failure.
 */
static struct ubi_volume_desc *open_ubi(const char *name, int mode)
{
        int dev, vol;
        char *endptr;

        if (name[0] != 'u' || name[1] != 'b' || name[2] != 'i')
                return ERR_PTR(-EINVAL);

        /* ubi:NAME method */
        if ((name[3] == ':' || name[3] == '!') && name[4] != '\0')
                return ubi_open_volume_nm(0, name + 4, mode);

        if (!isdigit(name[3]))
                return ERR_PTR(-EINVAL);

        dev = simple_strtoul(name + 3, &endptr, 0);

        /* ubiY method */
        if (*endptr == '\0')
                return ubi_open_volume(0, dev, mode);

        /* ubiX_Y method */
        if (*endptr == '_' && isdigit(endptr[1])) {
                vol = simple_strtoul(endptr + 1, &endptr, 0);
                if (*endptr != '\0')
                        return ERR_PTR(-EINVAL);
                return ubi_open_volume(dev, vol, mode);
        }

        /* ubiX:NAME method */
        if ((*endptr == ':' || *endptr == '!') && endptr[1] != '\0')
                return ubi_open_volume_nm(dev, ++endptr, mode);

        return ERR_PTR(-EINVAL);
}

static int ubifs_fill_super(struct super_block *sb, void *data, int silent)
{
        struct ubi_volume_desc *ubi = sb->s_fs_info;
        struct ubifs_info *c;
        struct inode *root;
        int err;

        c = kzalloc(sizeof(struct ubifs_info), GFP_KERNEL);
        if (!c)
                return -ENOMEM;

        spin_lock_init(&c->cnt_lock);
        spin_lock_init(&c->cs_lock);
        spin_lock_init(&c->buds_lock);
        spin_lock_init(&c->space_lock);
        spin_lock_init(&c->orphan_lock);
        init_rwsem(&c->commit_sem);
        mutex_init(&c->lp_mutex);
        mutex_init(&c->tnc_mutex);
        mutex_init(&c->log_mutex);
        mutex_init(&c->mst_mutex);
        mutex_init(&c->umount_mutex);
        init_waitqueue_head(&c->cmt_wq);
        c->buds = RB_ROOT;
        c->old_idx = RB_ROOT;
        c->size_tree = RB_ROOT;
        c->orph_tree = RB_ROOT;
        INIT_LIST_HEAD(&c->infos_list);
        INIT_LIST_HEAD(&c->idx_gc);
        INIT_LIST_HEAD(&c->replay_list);
        INIT_LIST_HEAD(&c->replay_buds);
        INIT_LIST_HEAD(&c->uncat_list);
        INIT_LIST_HEAD(&c->empty_list);
        INIT_LIST_HEAD(&c->freeable_list);
        INIT_LIST_HEAD(&c->frdi_idx_list);
        INIT_LIST_HEAD(&c->unclean_leb_list);
        INIT_LIST_HEAD(&c->old_buds);
        INIT_LIST_HEAD(&c->orph_list);
        INIT_LIST_HEAD(&c->orph_new);

        c->highest_inum = UBIFS_FIRST_INO;
        c->lhead_lnum = c->ltail_lnum = UBIFS_LOG_LNUM;

        ubi_get_volume_info(ubi, &c->vi);
        ubi_get_device_info(c->vi.ubi_num, &c->di);

        /* Re-open the UBI device in read-write mode */
        c->ubi = ubi_open_volume(c->vi.ubi_num, c->vi.vol_id, UBI_READWRITE);
        if (IS_ERR(c->ubi)) {
                err = PTR_ERR(c->ubi);
                goto out_free;
        }

        /*
         * UBIFS provides 'backing_dev_info' in order to disable read-ahead. For
         * UBIFS, I/O is not deferred, it is done immediately in readpage,
         * which means the user would have to wait not just for their own I/O
         * but the read-ahead I/O as well i.e. completely pointless.
         *
         * Read-ahead will be disabled because @c->bdi.ra_pages is 0.
         */
        c->bdi.capabilities = BDI_CAP_MAP_COPY;
        c->bdi.unplug_io_fn = default_unplug_io_fn;
        err  = bdi_init(&c->bdi);
        if (err)
                goto out_close;

        err = ubifs_parse_options(c, data, 0);
        if (err)
                goto out_bdi;

        c->vfs_sb = sb;

        sb->s_fs_info = c;
        sb->s_magic = UBIFS_SUPER_MAGIC;
        sb->s_blocksize = UBIFS_BLOCK_SIZE;
        sb->s_blocksize_bits = UBIFS_BLOCK_SHIFT;
        sb->s_dev = c->vi.cdev;
        sb->s_maxbytes = c->max_inode_sz = key_max_inode_size(c);
        if (c->max_inode_sz > MAX_LFS_FILESIZE)
                sb->s_maxbytes = c->max_inode_sz = MAX_LFS_FILESIZE;
        sb->s_op = &ubifs_super_operations;

        mutex_lock(&c->umount_mutex);
        err = mount_ubifs(c);
        if (err) {
                ubifs_assert(err < 0);
                goto out_unlock;
        }

        /* Read the root inode */
        root = ubifs_iget(sb, UBIFS_ROOT_INO);
        if (IS_ERR(root)) {
                err = PTR_ERR(root);
                goto out_umount;
        }

        sb->s_root = d_alloc_root(root);
        if (!sb->s_root)
                goto out_iput;

        mutex_unlock(&c->umount_mutex);

        return 0;

out_iput:
        iput(root);
out_umount:
        ubifs_umount(c);
out_unlock:
        mutex_unlock(&c->umount_mutex);
out_bdi:
        bdi_destroy(&c->bdi);
out_close:
        ubi_close_volume(c->ubi);
out_free:
        kfree(c);
        return err;
}

static int sb_test(struct super_block *sb, void *data)
{
        dev_t *dev = data;

        return sb->s_dev == *dev;
}

static int sb_set(struct super_block *sb, void *data)
{
        dev_t *dev = data;

        sb->s_dev = *dev;
        return 0;
}

static int ubifs_get_sb(struct file_system_type *fs_type, int flags,
                        const char *name, void *data, struct vfsmount *mnt)
{
        struct ubi_volume_desc *ubi;
        struct ubi_volume_info vi;
        struct super_block *sb;
        int err;

        dbg_gen("name %s, flags %#x", name, flags);

        /*
         * Get UBI device number and volume ID. Mount it read-only so far
         * because this might be a new mount point, and UBI allows only one
         * read-write user at a time.
         */
        ubi = open_ubi(name, UBI_READONLY);
        if (IS_ERR(ubi)) {
                ubifs_err("cannot open \"%s\", error %d",
                          name, (int)PTR_ERR(ubi));
                return PTR_ERR(ubi);
        }
        ubi_get_volume_info(ubi, &vi);

        dbg_gen("opened ubi%d_%d", vi.ubi_num, vi.vol_id);

        sb = sget(fs_type, &sb_test, &sb_set, &vi.cdev);
        if (IS_ERR(sb)) {
                err = PTR_ERR(sb);
                goto out_close;
        }

        if (sb->s_root) {
                /* A new mount point for already mounted UBIFS */
                dbg_gen("this ubi volume is already mounted");
                if ((flags ^ sb->s_flags) & MS_RDONLY) {
                        err = -EBUSY;
                        goto out_deact;
                }
        } else {
                sb->s_flags = flags;
                /*
                 * Pass 'ubi' to 'fill_super()' in sb->s_fs_info where it is
                 * replaced by 'c'.
                 */
                sb->s_fs_info = ubi;
                err = ubifs_fill_super(sb, data, flags & MS_SILENT ? 1 : 0);
                if (err)
                        goto out_deact;
                /* We do not support atime */
                sb->s_flags |= MS_ACTIVE | MS_NOATIME;
        }

        /* 'fill_super()' opens ubi again so we must close it here */
        ubi_close_volume(ubi);

        return simple_set_mnt(mnt, sb);

out_deact:
        up_write(&sb->s_umount);
        deactivate_super(sb);
out_close:
        ubi_close_volume(ubi);
        return err;
}

static void ubifs_kill_sb(struct super_block *sb)
{
        struct ubifs_info *c = sb->s_fs_info;

        /*
         * We do 'commit_on_unmount()' here instead of 'ubifs_put_super()'
         * in order to be outside BKL.
         */
        if (sb->s_root && !(sb->s_flags & MS_RDONLY))
                commit_on_unmount(c);
        /* The un-mount routine is actually done in put_super() */
        generic_shutdown_super(sb);
}

static struct file_system_type ubifs_fs_type = {
        .name    = "ubifs",
        .owner   = THIS_MODULE,
        .get_sb  = ubifs_get_sb,
        .kill_sb = ubifs_kill_sb
};

/*
 * Inode slab cache constructor.
 */
static void inode_slab_ctor(void *obj)
{
        struct ubifs_inode *ui = obj;
        inode_init_once(&ui->vfs_inode);
}

static int __init ubifs_init(void)
{
        int err;

        BUILD_BUG_ON(sizeof(struct ubifs_ch) != 24);

        /* Make sure node sizes are 8-byte aligned */
        BUILD_BUG_ON(UBIFS_CH_SZ        & 7);
        BUILD_BUG_ON(UBIFS_INO_NODE_SZ  & 7);
        BUILD_BUG_ON(UBIFS_DENT_NODE_SZ & 7);
        BUILD_BUG_ON(UBIFS_XENT_NODE_SZ & 7);
        BUILD_BUG_ON(UBIFS_DATA_NODE_SZ & 7);
        BUILD_BUG_ON(UBIFS_TRUN_NODE_SZ & 7);
        BUILD_BUG_ON(UBIFS_SB_NODE_SZ   & 7);
        BUILD_BUG_ON(UBIFS_MST_NODE_SZ  & 7);
        BUILD_BUG_ON(UBIFS_REF_NODE_SZ  & 7);
        BUILD_BUG_ON(UBIFS_CS_NODE_SZ   & 7);
        BUILD_BUG_ON(UBIFS_ORPH_NODE_SZ & 7);

        BUILD_BUG_ON(UBIFS_MAX_DENT_NODE_SZ & 7);
        BUILD_BUG_ON(UBIFS_MAX_XENT_NODE_SZ & 7);
        BUILD_BUG_ON(UBIFS_MAX_DATA_NODE_SZ & 7);
        BUILD_BUG_ON(UBIFS_MAX_INO_NODE_SZ  & 7);
        BUILD_BUG_ON(UBIFS_MAX_NODE_SZ      & 7);
        BUILD_BUG_ON(MIN_WRITE_SZ           & 7);

        /* Check min. node size */
        BUILD_BUG_ON(UBIFS_INO_NODE_SZ  < MIN_WRITE_SZ);
        BUILD_BUG_ON(UBIFS_DENT_NODE_SZ < MIN_WRITE_SZ);
        BUILD_BUG_ON(UBIFS_XENT_NODE_SZ < MIN_WRITE_SZ);
        BUILD_BUG_ON(UBIFS_TRUN_NODE_SZ < MIN_WRITE_SZ);

        BUILD_BUG_ON(UBIFS_MAX_DENT_NODE_SZ > UBIFS_MAX_NODE_SZ);
        BUILD_BUG_ON(UBIFS_MAX_XENT_NODE_SZ > UBIFS_MAX_NODE_SZ);
        BUILD_BUG_ON(UBIFS_MAX_DATA_NODE_SZ > UBIFS_MAX_NODE_SZ);
        BUILD_BUG_ON(UBIFS_MAX_INO_NODE_SZ  > UBIFS_MAX_NODE_SZ);

        /* Defined node sizes */
        BUILD_BUG_ON(UBIFS_SB_NODE_SZ  != 4096);
        BUILD_BUG_ON(UBIFS_MST_NODE_SZ != 512);
        BUILD_BUG_ON(UBIFS_INO_NODE_SZ != 160);
        BUILD_BUG_ON(UBIFS_REF_NODE_SZ != 64);

        /*
         * We require that PAGE_CACHE_SIZE is greater-than-or-equal-to
         * UBIFS_BLOCK_SIZE. It is assumed that both are powers of 2.
         */
        if (PAGE_CACHE_SIZE < UBIFS_BLOCK_SIZE) {
                ubifs_err("VFS page cache size is %u bytes, but UBIFS requires"
                          " at least 4096 bytes",
                          (unsigned int)PAGE_CACHE_SIZE);
                return -EINVAL;
        }

        err = register_filesystem(&ubifs_fs_type);
        if (err) {
                ubifs_err("cannot register file system, error %d", err);
                return err;
        }

        err = -ENOMEM;
        ubifs_inode_slab = kmem_cache_create("ubifs_inode_slab",
                                sizeof(struct ubifs_inode), 0,
                                SLAB_MEM_SPREAD | SLAB_RECLAIM_ACCOUNT,
                                &inode_slab_ctor);
        if (!ubifs_inode_slab)
                goto out_reg;

        register_shrinker(&ubifs_shrinker_info);

        err = ubifs_compressors_init();
        if (err)
                goto out_compr;

        return 0;

out_compr:
        unregister_shrinker(&ubifs_shrinker_info);
        kmem_cache_destroy(ubifs_inode_slab);
out_reg:
        unregister_filesystem(&ubifs_fs_type);
        return err;
}
/* late_initcall to let compressors initialize first */
late_initcall(ubifs_init);

static void __exit ubifs_exit(void)
{
        ubifs_assert(list_empty(&ubifs_infos));
        ubifs_assert(atomic_long_read(&ubifs_clean_zn_cnt) == 0);

        ubifs_compressors_exit();
        unregister_shrinker(&ubifs_shrinker_info);
        kmem_cache_destroy(ubifs_inode_slab);
        unregister_filesystem(&ubifs_fs_type);
}
module_exit(ubifs_exit);

MODULE_LICENSE("GPL");
MODULE_VERSION(__stringify(UBIFS_VERSION));
MODULE_AUTHOR("Artem Bityutskiy, Adrian Hunter");
MODULE_DESCRIPTION("UBIFS - UBI File System");