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

[Dave Chinner <david@fromorbit.com>]

On Mon, Oct 16, 2017 at 03:37:08PM -0700, Darrick J. Wong wrote:
> On Mon, Oct 16, 2017 at 03:49:21PM +1100, Dave Chinner wrote:
> > 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.
> > 
> > ....
> > 
> > > +/* 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 ?
> 
> This should already be done by xfs_dir3_leaf_read ->
> xfs_dir3_leaf1_read_verify -> __read_verify -> xfs_dir3_leaf_verify ->
> xfs_dir3_leaf_check_int, right?

True. However, it's simple to do and we're already iterating over
all the structures necessary and detecting the case necessary to
check it, so it doesn't hurt and might catch in-core corruptions
before they hit the write verifier?

And it makes it do the same checks as the free_bestfree checks
below....

> > > +		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?
> 
> Aha, yes, that needs to be checked.
> 
> Also that for loop needs to be terminated on i < freehdr.nused.

Good catch - I missed that, too :P

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com