"Darrick J. Wong" <darrick.wong@xxxxxxxxxx> writes:
> 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.)
>
Agree. feel free to add
Ack-by: Dmitry Monakhov <dmonakhov@xxxxxxxxxx>
> Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> Cc: Dmitry Monakhov <dmonakhov@xxxxxxxxxx>
> ---
> fs/ext4/ext4.h | 4 ++--
> fs/ext4/super.c | 4 ++++
> 2 files changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index fb6aadf..db38ca0f 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -2367,8 +2367,8 @@ 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 int ext4_has_metadata_csum(struct super_block *sb)
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index 6ae47d4..de38a96 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -2032,6 +2032,10 @@ 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));
Attachment:
pgpWUYPnIOeNG.pgp
Description: PGP signature
