On Tue, Apr 17, 2018 at 07:40:32PM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
>
> Strengthen the btree block header checks to detect the number of records
> being less than the btree type's minimum record count. Certain blocks
> are allowed to violate this constraint -- specifically any btree block
> at the top of the tree can have fewer than minrecs records.
>
> Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> ---
Reviewed-by: Brian Foster <bfoster@xxxxxxxxxx>
> fs/xfs/scrub/btree.c | 40 ++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 40 insertions(+)
>
>
> diff --git a/fs/xfs/scrub/btree.c b/fs/xfs/scrub/btree.c
> index ea972da..2d29dce 100644
> --- a/fs/xfs/scrub/btree.c
> +++ b/fs/xfs/scrub/btree.c
> @@ -455,6 +455,44 @@ xfs_scrub_btree_check_owner(
> }
>
> /*
> + * Check that this btree block has at least minrecs records or is one of the
> + * special blocks that don't require that.
> + */
> +STATIC void
> +xfs_scrub_btree_check_minrecs(
> + struct xfs_scrub_btree *bs,
> + int level,
> + struct xfs_btree_block *block)
> +{
> + unsigned int numrecs;
> + int ok_level;
> +
> + numrecs = be16_to_cpu(block->bb_numrecs);
> +
> + /* More records than minrecs means the block is ok. */
> + if (numrecs >= bs->cur->bc_ops->get_minrecs(bs->cur, level))
> + return;
> +
> + /*
> + * Certain btree blocks /can/ have fewer than minrecs records. Any
> + * level greater than or equal to the level of the highest dedicated
> + * btree block are allowed to violate this constraint.
> + *
> + * For a btree rooted in a block, the btree root can have fewer than
> + * minrecs records. If the btree is rooted in an inode and does not
> + * store records in the root, the direct children of the root and the
> + * root itself can have fewer than minrecs records.
> + */
> + ok_level = bs->cur->bc_nlevels - 1;
> + if (bs->cur->bc_flags & XFS_BTREE_ROOT_IN_INODE)
> + ok_level--;
> + if (level >= ok_level)
> + return;
> +
> + xfs_scrub_btree_set_corrupt(bs->sc, bs->cur, level);
> +}
> +
> +/*
> * Grab and scrub a btree block given a btree pointer. Returns block
> * and buffer pointers (if applicable) if they're ok to use.
> */
> @@ -491,6 +529,8 @@ xfs_scrub_btree_get_block(
> if (*pbp)
> xfs_scrub_buffer_recheck(bs->sc, *pbp);
>
> + xfs_scrub_btree_check_minrecs(bs, level, *pblock);
> +
> /*
> * Check the block's owner; this function absorbs error codes
> * for us.
>
> --
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