Re: [PATCH 25/30] xfs: scrub directory freespace

[Dave Chinner <david@fromorbit.com>]

On Wed, Oct 11, 2017 at 06:43:26PM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@oracle.com>
> 
> Check the free space information in a directory.

....

> diff --git a/fs/xfs/scrub/dir.c b/fs/xfs/scrub/dir.c
> index e2a8f90..a41310f 100644
> --- a/fs/xfs/scrub/dir.c
> +++ b/fs/xfs/scrub/dir.c
> @@ -250,6 +250,426 @@ xfs_scrub_dir_rec(
>  	return error;
>  }
>  
> +/*
> + * Is this unused entry either in the bestfree or smaller than all of them?
> + * We assume the bestfrees are sorted longest to shortest, and that there
> + * aren't any bogus entries.

s/We assume/We've already checked/

> + */
> +static inline void
> +xfs_scrub_directory_check_free_entry(
> +	struct xfs_scrub_context	*sc,
> +	xfs_dablk_t			lblk,
> +	struct xfs_dir2_data_free	*bf,
> +	struct xfs_dir2_data_unused	*dup)

....

> +	while (ptr < endptr) {
> +		dup = (struct xfs_dir2_data_unused *)ptr;
> +		/* Skip real entries */
> +		if (dup->freetag != cpu_to_be16(XFS_DIR2_DATA_FREE_TAG)) {
> +			struct xfs_dir2_data_entry	*dep;
> +
> +			dep = (struct xfs_dir2_data_entry *)ptr;
> +			newlen = d_ops->data_entsize(dep->namelen);
> +			if (newlen <= 0) {
> +				xfs_scrub_fblock_set_corrupt(sc, XFS_DATA_FORK,
> +						lblk);
> +				goto out_buf;
> +			}
> +			ptr += newlen;
> +			if (endptr < ptr)
> +				xfs_scrub_fblock_set_corrupt(sc, XFS_DATA_FORK,
> +					      lblk);
> +			continue;
> +		}
> +
> +		/* Spot check this free entry */
> +		tag = be16_to_cpu(*xfs_dir2_data_unused_tag_p(dup));
> +		if (tag != ((char *)dup - (char *)bp->b_addr))
> +			xfs_scrub_fblock_set_corrupt(sc, XFS_DATA_FORK, lblk);
> +
> +		/*
> +		 * Either this entry is a bestfree or it's smaller than
> +		 * any of the bestfrees.
> +		 */
> +		xfs_scrub_directory_check_free_entry(sc, lblk, bf, dup);
> +
> +		/* Move on. */
> +		newlen = be16_to_cpu(dup->length);
> +		if (newlen <= 0) {
> +			xfs_scrub_fblock_set_corrupt(sc, XFS_DATA_FORK, lblk);
> +			goto out_buf;
> +		}
> +		ptr += newlen;
> +		if (endptr < ptr)
> +			xfs_scrub_fblock_set_corrupt(sc, XFS_DATA_FORK, lblk);

I'd prefer this matches the loop logic order. ie.

		if (ptr >= endptr)

> +		else
> +			nr_frees++;
> +	}
> +
> +	/* Did we see at least as many free slots as there are bestfrees? */
> +	if (nr_frees < nr_bestfrees)
> +		xfs_scrub_fblock_set_corrupt(sc, XFS_DATA_FORK, lblk);
> +out_buf:
> +	xfs_trans_brelse(sc->tp, bp);
> +out:
> +	return error;
> +}
> +
> +/*
> + * Does the free space length in the free space index block ($len) match
> + * the longest length in the directory data block's bestfree array?
> + * Assume that we've already checked that the data block's bestfree
> + * array is in order.
> + */
> +static inline void
> +xfs_scrub_directory_check_freesp(

No need for inline here, the compiler will do that automatically if
appropriate.

> +	struct xfs_scrub_context	*sc,
> +	xfs_dablk_t			lblk,
> +	struct xfs_buf			*dbp,
> +	unsigned int			len)
> +{
> +	struct xfs_dir2_data_free	*bf;
> +	struct xfs_dir2_data_free	*dfp;
> +	int				offset;
> +
> +	if (len == 0)
> +		return;
> +
> +	bf = sc->ip->d_ops->data_bestfree_p(dbp->b_addr);
> +	for (dfp = &bf[0]; dfp < &bf[XFS_DIR2_DATA_FD_COUNT]; dfp++) {
> +		offset = be16_to_cpu(dfp->offset);
> +		if (offset == 0)
> +			break;
> +		if (len == be16_to_cpu(dfp->length))
> +			return;
> +		/* Didn't find the best length in the bestfree data */
> +		break;
> +	}
> +
> +	xfs_scrub_fblock_set_corrupt(sc, XFS_DATA_FORK, lblk);
> +}
> +
> +/* Check free space info in a directory leaf1 block. */
> +STATIC int
> +xfs_scrub_directory_leaf1_bestfree(
> +	struct xfs_scrub_context	*sc,
> +	struct xfs_da_args		*args,
> +	xfs_dablk_t			lblk)
> +{
> +	struct xfs_dir2_leaf_tail	*ltp;
> +	struct xfs_buf			*dbp;
> +	struct xfs_buf			*bp;
> +	struct xfs_mount		*mp = sc->mp;
> +	__be16				*bestp;
> +	__u16				best;
> +	int				i;
> +	int				error;
> +
> +	/*
> +	 * Read the free space block.  The verifier will check for hash
> +	 * value ordering problems and check the stale entry count.
> +	 */
> +	error = xfs_dir3_leaf_read(sc->tp, sc->ip, lblk, -1, &bp);
> +	if (!xfs_scrub_fblock_process_error(sc, XFS_DATA_FORK, lblk, &error))
> +		goto out;
> +
> +	/* Check all the entries. */
> +	ltp = xfs_dir2_leaf_tail_p(mp->m_dir_geo, bp->b_addr);
> +	bestp = xfs_dir2_leaf_bests_p(ltp);
> +	for (i = 0; i < be32_to_cpu(ltp->bestcount); i++, bestp++) {
> +		best = be16_to_cpu(*bestp);
> +		if (best == NULLDATAOFF)
> +			continue;

Count stale entries, check if matches hdr->stale ?

> +		error = xfs_dir3_data_read(sc->tp, sc->ip,
> +				i * args->geo->fsbcount, -1, &dbp);
> +		if (!xfs_scrub_fblock_process_error(sc, XFS_DATA_FORK, lblk,
> +				&error))
> +			continue;
> +		xfs_scrub_directory_check_freesp(sc, lblk, dbp, best);
> +		xfs_trans_brelse(sc->tp, dbp);
> +	}
> +out:
> +	return error;
> +}
> +
> +/* Check free space info in a directory freespace block. */
> +STATIC int
> +xfs_scrub_directory_free_bestfree(
> +	struct xfs_scrub_context	*sc,
> +	struct xfs_da_args		*args,
> +	xfs_dablk_t			lblk)
> +{
> +	struct xfs_dir3_icfree_hdr	freehdr;
> +	struct xfs_buf			*dbp;
> +	struct xfs_buf			*bp;
> +	__be16				*bestp;
> +	__be16				best;
> +	int				i;
> +	int				error;
> +
> +	/* Read the free space block */
> +	error = xfs_dir2_free_read(sc->tp, sc->ip, lblk, &bp);
> +	if (!xfs_scrub_fblock_process_error(sc, XFS_DATA_FORK, lblk, &error))
> +		goto out;
> +
> +	/* Check all the entries. */
> +	sc->ip->d_ops->free_hdr_from_disk(&freehdr, bp->b_addr);
> +	bestp = sc->ip->d_ops->free_bests_p(bp->b_addr);
> +	for (i = 0; i < freehdr.nvalid; i++, bestp++) {
> +		best = be16_to_cpu(*bestp);
> +		if (best == NULLDATAOFF)
> +			continue;

Count stale entries, check freehdr.nvalid + stale = freehdr.nused?

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com