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btrfs: enhance superblock checks

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The superblock checksum is not verified upon mount. <awkward silence>

Add that check and also reorder existing checks to a more logical
order.

Current mkfs.btrfs does not calculate the correct checksum of
super_block and thus a freshly created filesytem will fail to mount when
this patch is applied.

First transaction commit calculates correct superblock checksum and
saves it to disk.

Reproducer:
$ mfks.btrfs /dev/sda
$ mount /dev/sda /mnt
$ btrfs scrub start /mnt
$ sleep 5
$ btrfs scrub status /mnt
... super:2 ...

Signed-off-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>
This commit is contained in:
David Sterba 2013-03-06 15:57:46 +01:00 committed by Chris Mason
parent b6919a58f0
commit 1104a88551
2 changed files with 71 additions and 17 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
fs/btrfs/ctree.h
View File

@ -2793,8 +2793,10 @@ BTRFS_SETGET_STACK_FUNCS(super_cache_generation, struct btrfs_super_block,
static inline int btrfs_super_csum_size(struct btrfs_super_block *s)
{
int t = btrfs_super_csum_type(s);
BUG_ON(t >= ARRAY_SIZE(btrfs_csum_sizes));
u16 t = btrfs_super_csum_type(s);
/*
* csum type is validated at mount time
*/
return btrfs_csum_sizes[t];
}

82
fs/btrfs/disk-io.c
View File

@ -356,6 +356,44 @@ out:
return ret;
}
/*
* Return 0 if the superblock checksum type matches the checksum value of that
* algorithm. Pass the raw disk superblock data.
*/
static int btrfs_check_super_csum(char *raw_disk_sb)
{
struct btrfs_super_block *disk_sb =
(struct btrfs_super_block *)raw_disk_sb;
u16 csum_type = btrfs_super_csum_type(disk_sb);
int ret = 0;
if (csum_type == BTRFS_CSUM_TYPE_CRC32) {
u32 crc = ~(u32)0;
const int csum_size = sizeof(crc);
char result[csum_size];
/*
* The super_block structure does not span the whole
* BTRFS_SUPER_INFO_SIZE range, we expect that the unused space
* is filled with zeros and is included in the checkum.
*/
crc = btrfs_csum_data(raw_disk_sb + BTRFS_CSUM_SIZE,
crc, BTRFS_SUPER_INFO_SIZE - BTRFS_CSUM_SIZE);
btrfs_csum_final(crc, result);
if (memcmp(raw_disk_sb, result, csum_size))
ret = 1;
}
if (csum_type >= ARRAY_SIZE(btrfs_csum_sizes)) {
printk(KERN_ERR "btrfs: unsupported checksum algorithm %u\n",
csum_type);
ret = 1;
}
return ret;
}
/*
* helper to read a given tree block, doing retries as required when
* the checksums don't match and we have alternate mirrors to try.
@ -2249,12 +2287,31 @@ int open_ctree(struct super_block *sb,
fs_info, BTRFS_ROOT_TREE_OBJECTID);
invalidate_bdev(fs_devices->latest_bdev);
/*
* Read super block and check the signature bytes only
*/
bh = btrfs_read_dev_super(fs_devices->latest_bdev);
if (!bh) {
err = -EINVAL;
goto fail_alloc;
}
/*
* We want to check superblock checksum, the type is stored inside.
* Pass the whole disk block of size BTRFS_SUPER_INFO_SIZE (4k).
*/
if (btrfs_check_super_csum(bh->b_data)) {
printk(KERN_ERR "btrfs: superblock checksum mismatch\n");
err = -EINVAL;
goto fail_alloc;
}
/*
* super_copy is zeroed at allocation time and we never touch the
* following bytes up to INFO_SIZE, the checksum is calculated from
* the whole block of INFO_SIZE
*/
memcpy(fs_info->super_copy, bh->b_data, sizeof(*fs_info->super_copy));
memcpy(fs_info->super_for_commit, fs_info->super_copy,
sizeof(*fs_info->super_for_commit));
@ -2262,6 +2319,13 @@ int open_ctree(struct super_block *sb,
memcpy(fs_info->fsid, fs_info->super_copy->fsid, BTRFS_FSID_SIZE);
ret = btrfs_check_super_valid(fs_info, sb->s_flags & MS_RDONLY);
if (ret) {
printk(KERN_ERR "btrfs: superblock contains fatal errors\n");
err = -EINVAL;
goto fail_alloc;
}
disk_super = fs_info->super_copy;
if (!btrfs_super_root(disk_super))
goto fail_alloc;
@ -2270,13 +2334,6 @@ int open_ctree(struct super_block *sb,
if (btrfs_super_flags(disk_super) & BTRFS_SUPER_FLAG_ERROR)
set_bit(BTRFS_FS_STATE_ERROR, &fs_info->fs_state);
ret = btrfs_check_super_valid(fs_info, sb->s_flags & MS_RDONLY);
if (ret) {
printk(KERN_ERR "btrfs: superblock contains fatal errors\n");
err = ret;
goto fail_alloc;
}
/*
* run through our array of backup supers and setup
* our ring pointer to the oldest one
@ -3561,14 +3618,9 @@ int btrfs_read_buffer(struct extent_buffer *buf, u64 parent_transid)
static int btrfs_check_super_valid(struct btrfs_fs_info *fs_info,
int read_only)
{
if (btrfs_super_csum_type(fs_info->super_copy) >= ARRAY_SIZE(btrfs_csum_sizes)) {
printk(KERN_ERR "btrfs: unsupported checksum algorithm\n");
return -EINVAL;
}
if (read_only)
return 0;
/*
* Placeholder for checks
*/
return 0;
}