On Fri 17-06-22 14:25:15, Li Lingfeng wrote:
> When migrating to extents, the checksum seed of temporary inode
> need to be replaced by inode's, otherwise the inode checksums
> will be incorrect when swapping the inodes data.
>
> However, the temporary inode can not match it's checksum to
> itself since it has lost it's own checksum seed.
>
> mkfs.ext4 -F /dev/sdc
> mount /dev/sdc /mnt/sdc
> xfs_io -fc "pwrite 4k 4k" -c "fsync" /mnt/sdc/testfile
> chattr -e /mnt/sdc/testfile
> chattr +e /mnt/sdc/testfile
> umount /dev/sdc
> fsck -fn /dev/sdc
>
> ========
> ...
> Pass 1: Checking inodes, blocks, and sizes
> Inode 13 passes checks, but checksum does not match inode. Fix? no
> ...
> ========
>
> The fix is simple, save the checksum seed of temporary inode, and
> recover it after migrating to extents.
>
> Fixes: e81c9302a6c3 ("ext4: set csum seed in tmp inode while migrating to extents")
> Signed-off-by: Li Lingfeng <lilingfeng3@xxxxxxxxxx>
Yeah, the migration code and checksums never quite worked together. That's
the reason why we'd decided to deprecate this code. But I guess this fix is
simple enough and improves things so feel free to add:
Reviewed-by: Jan Kara <jack@xxxxxxx>
Honza
> ---
> fs/ext4/migrate.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/fs/ext4/migrate.c b/fs/ext4/migrate.c
> index 49912814f3d8..04320715d61f 100644
> --- a/fs/ext4/migrate.c
> +++ b/fs/ext4/migrate.c
> @@ -417,7 +417,7 @@ int ext4_ext_migrate(struct inode *inode)
> struct inode *tmp_inode = NULL;
> struct migrate_struct lb;
> unsigned long max_entries;
> - __u32 goal;
> + __u32 goal, tmp_csum_seed;
> uid_t owner[2];
>
> /*
> @@ -465,6 +465,7 @@ int ext4_ext_migrate(struct inode *inode)
> * the migration.
> */
> ei = EXT4_I(inode);
> + tmp_csum_seed = EXT4_I(tmp_inode)->i_csum_seed;
> EXT4_I(tmp_inode)->i_csum_seed = ei->i_csum_seed;
> i_size_write(tmp_inode, i_size_read(inode));
> /*
> @@ -575,6 +576,7 @@ int ext4_ext_migrate(struct inode *inode)
> * the inode is not visible to user space.
> */
> tmp_inode->i_blocks = 0;
> + EXT4_I(tmp_inode)->i_csum_seed = tmp_csum_seed;
>
> /* Reset the extent details */
> ext4_ext_tree_init(handle, tmp_inode);
> --
> 2.31.1
>
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
