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ext4: check s_chksum_driver when looking for bg csum presence

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commit 813d32f913 upstream.

Convert the ext4_has_group_desc_csum predicate to look for a checksum
driver instead of the metadata_csum flag and change the bg checksum
calculation function to look for GDT_CSUM before taking the crc16
path.

Without this patch, if we mount with ^uninit_bg,^metadata_csum and
later metadata_csum gets turned on by accident, the block group
checksum functions will incorrectly assume that checksumming is
enabled (metadata_csum) but that crc16 should be used
(!s_chksum_driver).  This is totally wrong, so fix the predicate
and the checksum formula selection.

(Granted, if the metadata_csum feature bit gets enabled on a live FS
then something underhanded is going on, but we could at least avoid
writing garbage into the on-disk fields.)

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Dmitry Monakhov <dmonakhov@openvz.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Darrick J. Wong
2014-10-14 02:35:49 -04:00
committed by Greg Kroah-Hartman
parent 1f1ccdde66
commit 209f5484ef
2 changed files with 6 additions and 2 deletions
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4
fs/ext4/ext4.h
View File

@@ -2261,8 +2261,8 @@ extern int ext4_register_li_request(struct super_block *sb,
static inline int ext4_has_group_desc_csum(struct super_block *sb)
{
return EXT4_HAS_RO_COMPAT_FEATURE(sb,
EXT4_FEATURE_RO_COMPAT_GDT_CSUM |
EXT4_FEATURE_RO_COMPAT_METADATA_CSUM);
EXT4_FEATURE_RO_COMPAT_GDT_CSUM) ||
(EXT4_SB(sb)->s_chksum_driver != NULL);
}
static inline ext4_fsblk_t ext4_blocks_count(struct ext4_super_block *es)

4
fs/ext4/super.c
View File

@@ -1950,6 +1950,10 @@ static __le16 ext4_group_desc_csum(struct ext4_sb_info *sbi, __u32 block_group,
}
/* old crc16 code */
if (!(sbi->s_es->s_feature_ro_compat &
cpu_to_le32(EXT4_FEATURE_RO_COMPAT_GDT_CSUM)))
return 0;
offset = offsetof(struct ext4_group_desc, bg_checksum);
crc = crc16(~0, sbi->s_es->s_uuid, sizeof(sbi->s_es->s_uuid));