On Tue, Apr 06, 2021 at 12:25:19PM +0530, Chandan Babu R wrote:
> xchk_btree_check_minrecs() checks if the contents of the immediate child of a
> bmbt root block can fit within the root block. This check could fail on inodes
> with an attr fork since xfs_bmap_add_attrfork_btree() used to demote the
> current root node of the data fork as the child of a newly allocated root node
> if it found that the size of "struct xfs_btree_block" along with the space
> required for records exceeded that of space available in the data fork.
>
> xfs_bmap_add_attrfork_btree() should have used "struct xfs_bmdr_block" instead
> of "struct xfs_btree_block" for the above mentioned space requirement
> calculation. This commit disables the check for unoptimized (in terms of
> disk space usage) data fork bmbt trees since there could be filesystems
> in use that already have such a layout.
>
> Suggested-by: Darrick J. Wong <djwong@xxxxxxxxxx>
> Signed-off-by: Chandan Babu R <chandanrlinux@xxxxxxxxx>
Looks good!
Reviewed-by: Darrick J. Wong <djwong@xxxxxxxxxx>
--D
> ---
> Changelog:
> V1 -> V2:
> 1. Apply "minimum records check" restriction only to BMBT btrees.
>
> fs/xfs/scrub/btree.c | 30 ++++++++++++++++++++++++++++--
> 1 file changed, 28 insertions(+), 2 deletions(-)
>
> diff --git a/fs/xfs/scrub/btree.c b/fs/xfs/scrub/btree.c
> index debf392e0515..a94bd8122c60 100644
> --- a/fs/xfs/scrub/btree.c
> +++ b/fs/xfs/scrub/btree.c
> @@ -9,6 +9,7 @@
> #include "xfs_format.h"
> #include "xfs_trans_resv.h"
> #include "xfs_mount.h"
> +#include "xfs_inode.h"
> #include "xfs_btree.h"
> #include "scrub/scrub.h"
> #include "scrub/common.h"
> @@ -442,6 +443,30 @@ xchk_btree_check_owner(
> return xchk_btree_check_block_owner(bs, level, XFS_BUF_ADDR(bp));
> }
>
> +/* Decide if we want to check minrecs of a btree block in the inode root. */
> +static inline bool
> +xchk_btree_check_iroot_minrecs(
> + struct xchk_btree *bs)
> +{
> + /*
> + * xfs_bmap_add_attrfork_btree had an implementation bug wherein it
> + * would miscalculate the space required for the data fork bmbt root
> + * when adding an attr fork, and promote the iroot contents to an
> + * external block unnecessarily. This went unnoticed for many years
> + * until scrub found filesystems in this state. Inode rooted btrees are
> + * not supposed to have immediate child blocks that are small enough
> + * that the contents could fit in the inode root, but we can't fail
> + * existing filesystems, so instead we disable the check for data fork
> + * bmap btrees when there's an attr fork.
> + */
> + if (bs->cur->bc_btnum == XFS_BTNUM_BMAP &&
> + bs->cur->bc_ino.whichfork == XFS_DATA_FORK &&
> + XFS_IFORK_Q(bs->sc->ip))
> + return false;
> +
> + return true;
> +}
> +
> /*
> * Check that this btree block has at least minrecs records or is one of the
> * special blocks that don't require that.
> @@ -475,8 +500,9 @@ xchk_btree_check_minrecs(
>
> root_block = xfs_btree_get_block(cur, root_level, &root_bp);
> root_maxrecs = cur->bc_ops->get_dmaxrecs(cur, root_level);
> - if (be16_to_cpu(root_block->bb_numrecs) != 1 ||
> - numrecs <= root_maxrecs)
> + if (xchk_btree_check_iroot_minrecs(bs) &&
> + (be16_to_cpu(root_block->bb_numrecs) != 1 ||
> + numrecs <= root_maxrecs))
> xchk_btree_set_corrupt(bs->sc, cur, level);
> return;
> }
> --
> 2.29.2
>
