super.c

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/*
 * Squashfs - a compressed read only filesystem for Linux
 *
 * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008
 * Phillip Lougher <[email protected]>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2,
 * or (at your option) any later version.
 *
 * 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, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 * super.c
 */

/*
 * This file implements code to read the superblock, read and initialise
 * in-memory structures at mount time, and all the VFS glue code to register
 * the filesystem.
 */

#include <linux/fs.h>
#include <linux/vfs.h>
#include <linux/slab.h>
#include <linux/mutex.h>
#include <linux/pagemap.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/magic.h>
#include <linux/xattr.h>

#include "squashfs_fs.h"
#include "squashfs_fs_sb.h"
#include "squashfs_fs_i.h"
#include "squashfs.h"
#include "decompressor.h"
#include "xattr.h"

static struct file_system_type squashfs_fs_type;
static const struct super_operations squashfs_super_ops;

static const struct squashfs_decompressor *supported_squashfs_filesystem(short
    major, short minor, short id)
{
    const struct squashfs_decompressor *decompressor;

    if (major < SQUASHFS_MAJOR) {
        ERROR("Major/Minor mismatch, older Squashfs %d.%d "
            "filesystems are unsupported\n", major, minor);
        return NULL;
    } else if (major > SQUASHFS_MAJOR || minor > SQUASHFS_MINOR) {
        ERROR("Major/Minor mismatch, trying to mount newer "
            "%d.%d filesystem\n", major, minor);
        ERROR("Please update your kernel\n");
        return NULL;
    }

    decompressor = squashfs_lookup_decompressor(id);
    if (!decompressor->supported) {
        ERROR("Filesystem uses \"%s\" compression. This is not "
            "supported\n", decompressor->name);
        return NULL;
    }

    return decompressor;
}


static int squashfs_fill_super(struct super_block *sb, void *data, int silent)
{
    struct squashfs_sb_info *msblk;
    struct squashfs_super_block *sblk = NULL;
    char b[BDEVNAME_SIZE];
    struct inode *root;
    long long root_inode;
    unsigned short flags;
    unsigned int fragments;
    u64 lookup_table_start, xattr_id_table_start, next_table;
    int err;

    TRACE("Entered squashfs_fill_superblock\n");

    sb->s_fs_info = kzalloc(sizeof(*msblk), GFP_KERNEL);
    if (sb->s_fs_info == NULL) {
        ERROR("Failed to allocate squashfs_sb_info\n");
        return -ENOMEM;
    }
    msblk = sb->s_fs_info;

    msblk->devblksize = sb_min_blocksize(sb, SQUASHFS_DEVBLK_SIZE);
    msblk->devblksize_log2 = ffz(~msblk->devblksize);

    mutex_init(&msblk->read_data_mutex);
    mutex_init(&msblk->meta_index_mutex);

    /*
     * msblk->bytes_used is checked in squashfs_read_table to ensure reads
     * are not beyond filesystem end.  But as we're using
     * squashfs_read_table here to read the superblock (including the value
     * of bytes_used) we need to set it to an initial sensible dummy value
     */
    msblk->bytes_used = sizeof(*sblk);
    sblk = squashfs_read_table(sb, SQUASHFS_START, sizeof(*sblk));

    if (IS_ERR(sblk)) {
        ERROR("unable to read squashfs_super_block\n");
        err = PTR_ERR(sblk);
        sblk = NULL;
        goto failed_mount;
    }

    err = -EINVAL;

    /* Check it is a SQUASHFS superblock */
    sb->s_magic = le32_to_cpu(sblk->s_magic);
    if (sb->s_magic != SQUASHFS_MAGIC) {
        if (!silent)
            ERROR("Can't find a SQUASHFS superblock on %s\n",
                        bdevname(sb->s_bdev, b));
        goto failed_mount;
    }

    /* Check the MAJOR & MINOR versions and lookup compression type */
    msblk->decompressor = supported_squashfs_filesystem(
            le16_to_cpu(sblk->s_major),
            le16_to_cpu(sblk->s_minor),
            le16_to_cpu(sblk->compression));
    if (msblk->decompressor == NULL)
        goto failed_mount;

    /* Check the filesystem does not extend beyond the end of the
       block device */
    msblk->bytes_used = le64_to_cpu(sblk->bytes_used);
    if (msblk->bytes_used < 0 || msblk->bytes_used >
            i_size_read(sb->s_bdev->bd_inode))
        goto failed_mount;

    /* Check block size for sanity */
    msblk->block_size = le32_to_cpu(sblk->block_size);
    if (msblk->block_size > SQUASHFS_FILE_MAX_SIZE)
        goto failed_mount;

    /*
     * Check the system page size is not larger than the filesystem
     * block size (by default 128K).  This is currently not supported.
     */
    if (PAGE_CACHE_SIZE > msblk->block_size) {
        ERROR("Page size > filesystem block size (%d).  This is "
            "currently not supported!\n", msblk->block_size);
        goto failed_mount;
    }

    /* Check block log for sanity */
    msblk->block_log = le16_to_cpu(sblk->block_log);
    if (msblk->block_log > SQUASHFS_FILE_MAX_LOG)
        goto failed_mount;

    /* Check that block_size and block_log match */
    if (msblk->block_size != (1 << msblk->block_log))
        goto failed_mount;

    /* Check the root inode for sanity */
    root_inode = le64_to_cpu(sblk->root_inode);
    if (SQUASHFS_INODE_OFFSET(root_inode) > SQUASHFS_METADATA_SIZE)
        goto failed_mount;

    msblk->inode_table = le64_to_cpu(sblk->inode_table_start);
    msblk->directory_table = le64_to_cpu(sblk->directory_table_start);
    msblk->inodes = le32_to_cpu(sblk->inodes);
    flags = le16_to_cpu(sblk->flags);

    TRACE("Found valid superblock on %s\n", bdevname(sb->s_bdev, b));
    TRACE("Inodes are %scompressed\n", SQUASHFS_UNCOMPRESSED_INODES(flags)
                ? "un" : "");
    TRACE("Data is %scompressed\n", SQUASHFS_UNCOMPRESSED_DATA(flags)
                ? "un" : "");
    TRACE("Filesystem size %lld bytes\n", msblk->bytes_used);
    TRACE("Block size %d\n", msblk->block_size);
    TRACE("Number of inodes %d\n", msblk->inodes);
    TRACE("Number of fragments %d\n", le32_to_cpu(sblk->fragments));
    TRACE("Number of ids %d\n", le16_to_cpu(sblk->no_ids));
    TRACE("sblk->inode_table_start %llx\n", msblk->inode_table);
    TRACE("sblk->directory_table_start %llx\n", msblk->directory_table);
    TRACE("sblk->fragment_table_start %llx\n",
        (u64) le64_to_cpu(sblk->fragment_table_start));
    TRACE("sblk->id_table_start %llx\n",
        (u64) le64_to_cpu(sblk->id_table_start));

    sb->s_maxbytes = MAX_LFS_FILESIZE;
    sb->s_flags |= MS_RDONLY;
    sb->s_op = &squashfs_super_ops;

    err = -ENOMEM;

    msblk->block_cache = squashfs_cache_init("metadata",
            SQUASHFS_CACHED_BLKS, SQUASHFS_METADATA_SIZE);
    if (msblk->block_cache == NULL)
        goto failed_mount;

    /* Allocate read_page block */
    msblk->read_page = squashfs_cache_init("data", 1, msblk->block_size);
    if (msblk->read_page == NULL) {
        ERROR("Failed to allocate read_page block\n");
        goto failed_mount;
    }

    msblk->stream = squashfs_decompressor_init(sb, flags);
    if (IS_ERR(msblk->stream)) {
        err = PTR_ERR(msblk->stream);
        msblk->stream = NULL;
        goto failed_mount;
    }

    /* Handle xattrs */
    sb->s_xattr = squashfs_xattr_handlers;
    xattr_id_table_start = le64_to_cpu(sblk->xattr_id_table_start);
    if (xattr_id_table_start == SQUASHFS_INVALID_BLK) {
        next_table = msblk->bytes_used;
        goto allocate_id_index_table;
    }

    /* Allocate and read xattr id lookup table */
    msblk->xattr_id_table = squashfs_read_xattr_id_table(sb,
        xattr_id_table_start, &msblk->xattr_table, &msblk->xattr_ids);
    if (IS_ERR(msblk->xattr_id_table)) {
        ERROR("unable to read xattr id index table\n");
        err = PTR_ERR(msblk->xattr_id_table);
        msblk->xattr_id_table = NULL;
        if (err != -ENOTSUPP)
            goto failed_mount;
    }
    next_table = msblk->xattr_table;

allocate_id_index_table:
    /* Allocate and read id index table */
    msblk->id_table = squashfs_read_id_index_table(sb,
        le64_to_cpu(sblk->id_table_start), next_table,
        le16_to_cpu(sblk->no_ids));
    if (IS_ERR(msblk->id_table)) {
        ERROR("unable to read id index table\n");
        err = PTR_ERR(msblk->id_table);
        msblk->id_table = NULL;
        goto failed_mount;
    }
    next_table = le64_to_cpu(msblk->id_table[0]);

    /* Handle inode lookup table */
    lookup_table_start = le64_to_cpu(sblk->lookup_table_start);
    if (lookup_table_start == SQUASHFS_INVALID_BLK)
        goto handle_fragments;

    /* Allocate and read inode lookup table */
    msblk->inode_lookup_table = squashfs_read_inode_lookup_table(sb,
        lookup_table_start, next_table, msblk->inodes);
    if (IS_ERR(msblk->inode_lookup_table)) {
        ERROR("unable to read inode lookup table\n");
        err = PTR_ERR(msblk->inode_lookup_table);
        msblk->inode_lookup_table = NULL;
        goto failed_mount;
    }
    next_table = le64_to_cpu(msblk->inode_lookup_table[0]);

    sb->s_export_op = &squashfs_export_ops;

handle_fragments:
    fragments = le32_to_cpu(sblk->fragments);
    if (fragments == 0)
        goto check_directory_table;

    msblk->fragment_cache = squashfs_cache_init("fragment",
        SQUASHFS_CACHED_FRAGMENTS, msblk->block_size);
    if (msblk->fragment_cache == NULL) {
        err = -ENOMEM;
        goto failed_mount;
    }

    /* Allocate and read fragment index table */
    msblk->fragment_index = squashfs_read_fragment_index_table(sb,
        le64_to_cpu(sblk->fragment_table_start), next_table, fragments);
    if (IS_ERR(msblk->fragment_index)) {
        ERROR("unable to read fragment index table\n");
        err = PTR_ERR(msblk->fragment_index);
        msblk->fragment_index = NULL;
        goto failed_mount;
    }
    next_table = le64_to_cpu(msblk->fragment_index[0]);

check_directory_table:
    /* Sanity check directory_table */
    if (msblk->directory_table > next_table) {
        err = -EINVAL;
        goto failed_mount;
    }

    /* Sanity check inode_table */
    if (msblk->inode_table >= msblk->directory_table) {
        err = -EINVAL;
        goto failed_mount;
    }

    /* allocate root */
    root = new_inode(sb);
    if (!root) {
        err = -ENOMEM;
        goto failed_mount;
    }

    err = squashfs_read_inode(root, root_inode);
    if (err) {
        make_bad_inode(root);
        iput(root);
        goto failed_mount;
    }
    insert_inode_hash(root);

    sb->s_root = d_make_root(root);
    if (sb->s_root == NULL) {
        ERROR("Root inode create failed\n");
        err = -ENOMEM;
        goto failed_mount;
    }

    TRACE("Leaving squashfs_fill_super\n");
    kfree(sblk);
    return 0;

failed_mount:
    squashfs_cache_delete(msblk->block_cache);
    squashfs_cache_delete(msblk->fragment_cache);
    squashfs_cache_delete(msblk->read_page);
    squashfs_decompressor_free(msblk, msblk->stream);
    kfree(msblk->inode_lookup_table);
    kfree(msblk->fragment_index);
    kfree(msblk->id_table);
    kfree(msblk->xattr_id_table);
    kfree(sb->s_fs_info);
    sb->s_fs_info = NULL;
    kfree(sblk);
    return err;
}


static int squashfs_statfs(struct dentry *dentry, struct kstatfs *buf)
{
    struct squashfs_sb_info *msblk = dentry->d_sb->s_fs_info;
    u64 id = huge_encode_dev(dentry->d_sb->s_bdev->bd_dev);

    TRACE("Entered squashfs_statfs\n");

    buf->f_type = SQUASHFS_MAGIC;
    buf->f_bsize = msblk->block_size;
    buf->f_blocks = ((msblk->bytes_used - 1) >> msblk->block_log) + 1;
    buf->f_bfree = buf->f_bavail = 0;
    buf->f_files = msblk->inodes;
    buf->f_ffree = 0;
    buf->f_namelen = SQUASHFS_NAME_LEN;
    buf->f_fsid.val[0] = (u32)id;
    buf->f_fsid.val[1] = (u32)(id >> 32);

    return 0;
}


static int squashfs_remount(struct super_block *sb, int *flags, char *data)
{
    *flags |= MS_RDONLY;
    return 0;
}


static void squashfs_put_super(struct super_block *sb)
{
    if (sb->s_fs_info) {
        struct squashfs_sb_info *sbi = sb->s_fs_info;
        squashfs_cache_delete(sbi->block_cache);
        squashfs_cache_delete(sbi->fragment_cache);
        squashfs_cache_delete(sbi->read_page);
        squashfs_decompressor_free(sbi, sbi->stream);
        kfree(sbi->id_table);
        kfree(sbi->fragment_index);
        kfree(sbi->meta_index);
        kfree(sbi->inode_lookup_table);
        kfree(sbi->xattr_id_table);
        kfree(sb->s_fs_info);
        sb->s_fs_info = NULL;
    }
}


static struct dentry *squashfs_mount(struct file_system_type *fs_type,
                int flags, const char *dev_name, void *data)
{
    return mount_bdev(fs_type, flags, dev_name, data, squashfs_fill_super);
}


static struct kmem_cache *squashfs_inode_cachep;


static void init_once(void *foo)
{
    struct squashfs_inode_info *ei = foo;

    inode_init_once(&ei->vfs_inode);
}


static int __init init_inodecache(void)
{
    squashfs_inode_cachep = kmem_cache_create("squashfs_inode_cache",
        sizeof(struct squashfs_inode_info), 0,
        SLAB_HWCACHE_ALIGN|SLAB_RECLAIM_ACCOUNT, init_once);

    return squashfs_inode_cachep ? 0 : -ENOMEM;
}


static void destroy_inodecache(void)
{
    /*
     * Make sure all delayed rcu free inodes are flushed before we
     * destroy cache.
     */
    rcu_barrier();
    kmem_cache_destroy(squashfs_inode_cachep);
}


static int __init init_squashfs_fs(void)
{
    int err = init_inodecache();

    if (err)
        return err;

    err = register_filesystem(&squashfs_fs_type);
    if (err) {
        destroy_inodecache();
        return err;
    }

    printk(KERN_INFO "squashfs: version 4.0 (2009/01/31) "
        "Phillip Lougher\n");

    return 0;
}


static void __exit exit_squashfs_fs(void)
{
    unregister_filesystem(&squashfs_fs_type);
    destroy_inodecache();
}


static struct inode *squashfs_alloc_inode(struct super_block *sb)
{
    struct squashfs_inode_info *ei =
        kmem_cache_alloc(squashfs_inode_cachep, GFP_KERNEL);

    return ei ? &ei->vfs_inode : NULL;
}


static void squashfs_i_callback(struct rcu_head *head)
{
    struct inode *inode = container_of(head, struct inode, i_rcu);
    kmem_cache_free(squashfs_inode_cachep, squashfs_i(inode));
}

static void squashfs_destroy_inode(struct inode *inode)
{
    call_rcu(&inode->i_rcu, squashfs_i_callback);
}


static struct file_system_type squashfs_fs_type = {
    .owner = THIS_MODULE,
    .name = "squashfs",
    .mount = squashfs_mount,
    .kill_sb = kill_block_super,
    .fs_flags = FS_REQUIRES_DEV
};

static const struct super_operations squashfs_super_ops = {
    .alloc_inode = squashfs_alloc_inode,
    .destroy_inode = squashfs_destroy_inode,
    .statfs = squashfs_statfs,
    .put_super = squashfs_put_super,
    .remount_fs = squashfs_remount
};

module_init(init_squashfs_fs);
module_exit(exit_squashfs_fs);
MODULE_DESCRIPTION("squashfs 4.0, a compressed read-only filesystem");
MODULE_AUTHOR("Phillip Lougher <[email protected]>");
MODULE_LICENSE("GPL");