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Commit dbde19da authored by Darrick J. Wong's avatar Darrick J. Wong
Browse files

xfs: cross-reference the rmapbt data with the refcountbt 



Cross reference the refcount data with the rmap data to check that the
number of rmaps for a given block match the refcount of that block, and
that CoW blocks (which are owned entirely by the refcountbt) are tracked
as well.

Signed-off-by: default avatarDarrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: default avatarDave Chinner <dchinner@redhat.com>
parent d852657c

fs/xfs/scrub/refcount.c

+334 −2
Original line number Diff line number Diff line
@@ -50,6 +50,291 @@ xfs_scrub_setup_ag_refcountbt( 


/* Reference count btree scrubber. */



/*

 * Confirming Reference Counts via Reverse Mappings

 *

 * We want to count the reverse mappings overlapping a refcount record

 * (bno, len, refcount), allowing for the possibility that some of the

 * overlap may come from smaller adjoining reverse mappings, while some

 * comes from single extents which overlap the range entirely.  The

 * outer loop is as follows:

 *

 * 1. For all reverse mappings overlapping the refcount extent,

 *    a. If a given rmap completely overlaps, mark it as seen.

 *    b. Otherwise, record the fragment (in agbno order) for later

 *       processing.

 *

 * Once we've seen all the rmaps, we know that for all blocks in the

 * refcount record we want to find $refcount owners and we've already

 * visited $seen extents that overlap all the blocks.  Therefore, we

 * need to find ($refcount - $seen) owners for every block in the

 * extent; call that quantity $target_nr.  Proceed as follows:

 *

 * 2. Pull the first $target_nr fragments from the list; all of them

 *    should start at or before the start of the extent.

 *    Call this subset of fragments the working set.

 * 3. Until there are no more unprocessed fragments,

 *    a. Find the shortest fragments in the set and remove them.

 *    b. Note the block number of the end of these fragments.

 *    c. Pull the same number of fragments from the list.  All of these

 *       fragments should start at the block number recorded in the

 *       previous step.

 *    d. Put those fragments in the set.

 * 4. Check that there are $target_nr fragments remaining in the list,

 *    and that they all end at or beyond the end of the refcount extent.

 *

 * If the refcount is correct, all the check conditions in the algorithm

 * should always hold true.  If not, the refcount is incorrect.

 */

struct xfs_scrub_refcnt_frag {

	struct list_head		list;

	struct xfs_rmap_irec		rm;

};



struct xfs_scrub_refcnt_check {

	struct xfs_scrub_context	*sc;

	struct list_head		fragments;



	/* refcount extent we're examining */

	xfs_agblock_t			bno;

	xfs_extlen_t			len;

	xfs_nlink_t			refcount;



	/* number of owners seen */

	xfs_nlink_t			seen;

};



/*

 * Decide if the given rmap is large enough that we can redeem it

 * towards refcount verification now, or if it's a fragment, in

 * which case we'll hang onto it in the hopes that we'll later

 * discover that we've collected exactly the correct number of

 * fragments as the refcountbt says we should have.

 */

STATIC int

xfs_scrub_refcountbt_rmap_check(

	struct xfs_btree_cur		*cur,

	struct xfs_rmap_irec		*rec,

	void				*priv)

{

	struct xfs_scrub_refcnt_check	*refchk = priv;

	struct xfs_scrub_refcnt_frag	*frag;

	xfs_agblock_t			rm_last;

	xfs_agblock_t			rc_last;

	int				error = 0;



	if (xfs_scrub_should_terminate(refchk->sc, &error))

		return error;



	rm_last = rec->rm_startblock + rec->rm_blockcount - 1;

	rc_last = refchk->bno + refchk->len - 1;



	/* Confirm that a single-owner refc extent is a CoW stage. */

	if (refchk->refcount == 1 && rec->rm_owner != XFS_RMAP_OWN_COW) {

		xfs_scrub_btree_xref_set_corrupt(refchk->sc, cur, 0);

		return 0;

	}



	if (rec->rm_startblock <= refchk->bno && rm_last >= rc_last) {

		/*

		 * The rmap overlaps the refcount record, so we can confirm

		 * one refcount owner seen.

		 */

		refchk->seen++;

	} else {

		/*

		 * This rmap covers only part of the refcount record, so

		 * save the fragment for later processing.  If the rmapbt

		 * is healthy each rmap_irec we see will be in agbno order

		 * so we don't need insertion sort here.

		 */

		frag = kmem_alloc(sizeof(struct xfs_scrub_refcnt_frag),

				KM_MAYFAIL | KM_NOFS);

		if (!frag)

			return -ENOMEM;

		memcpy(&frag->rm, rec, sizeof(frag->rm));

		list_add_tail(&frag->list, &refchk->fragments);

	}



	return 0;

}



/*

 * Given a bunch of rmap fragments, iterate through them, keeping

 * a running tally of the refcount.  If this ever deviates from

 * what we expect (which is the refcountbt's refcount minus the

 * number of extents that totally covered the refcountbt extent),

 * we have a refcountbt error.

 */

STATIC void

xfs_scrub_refcountbt_process_rmap_fragments(

	struct xfs_scrub_refcnt_check	*refchk)

{

	struct list_head		worklist;

	struct xfs_scrub_refcnt_frag	*frag;

	struct xfs_scrub_refcnt_frag	*n;

	xfs_agblock_t			bno;

	xfs_agblock_t			rbno;

	xfs_agblock_t			next_rbno;

	xfs_nlink_t			nr;

	xfs_nlink_t			target_nr;



	target_nr = refchk->refcount - refchk->seen;

	if (target_nr == 0)

		return;



	/*

	 * There are (refchk->rc.rc_refcount - refchk->nr refcount)

	 * references we haven't found yet.  Pull that many off the

	 * fragment list and figure out where the smallest rmap ends

	 * (and therefore the next rmap should start).  All the rmaps

	 * we pull off should start at or before the beginning of the

	 * refcount record's range.

	 */

	INIT_LIST_HEAD(&worklist);

	rbno = NULLAGBLOCK;

	nr = 1;



	/* Make sure the fragments actually /are/ in agbno order. */

	bno = 0;

	list_for_each_entry(frag, &refchk->fragments, list) {

		if (frag->rm.rm_startblock < bno)

			goto done;

		bno = frag->rm.rm_startblock;

	}



	/*

	 * Find all the rmaps that start at or before the refc extent,

	 * and put them on the worklist.

	 */

	list_for_each_entry_safe(frag, n, &refchk->fragments, list) {

		if (frag->rm.rm_startblock > refchk->bno)

			goto done;

		bno = frag->rm.rm_startblock + frag->rm.rm_blockcount;

		if (bno < rbno)

			rbno = bno;

		list_move_tail(&frag->list, &worklist);

		if (nr == target_nr)

			break;

		nr++;

	}



	/*

	 * We should have found exactly $target_nr rmap fragments starting

	 * at or before the refcount extent.

	 */

	if (nr != target_nr)

		goto done;



	while (!list_empty(&refchk->fragments)) {

		/* Discard any fragments ending at rbno from the worklist. */

		nr = 0;

		next_rbno = NULLAGBLOCK;

		list_for_each_entry_safe(frag, n, &worklist, list) {

			bno = frag->rm.rm_startblock + frag->rm.rm_blockcount;

			if (bno != rbno) {

				if (bno < next_rbno)

					next_rbno = bno;

				continue;

			}

			list_del(&frag->list);

			kmem_free(frag);

			nr++;

		}



		/* Try to add nr rmaps starting at rbno to the worklist. */

		list_for_each_entry_safe(frag, n, &refchk->fragments, list) {

			bno = frag->rm.rm_startblock + frag->rm.rm_blockcount;

			if (frag->rm.rm_startblock != rbno)

				goto done;

			list_move_tail(&frag->list, &worklist);

			if (next_rbno > bno)

				next_rbno = bno;

			nr--;

			if (nr == 0)

				break;

		}



		/*

		 * If we get here and nr > 0, this means that we added fewer

		 * items to the worklist than we discarded because the fragment

		 * list ran out of items.  Therefore, we cannot maintain the

		 * required refcount.  Something is wrong, so we're done.

		 */

		if (nr)

			goto done;



		rbno = next_rbno;

	}



	/*

	 * Make sure the last extent we processed ends at or beyond

	 * the end of the refcount extent.

	 */

	if (rbno < refchk->bno + refchk->len)

		goto done;



	/* Actually record us having seen the remaining refcount. */

	refchk->seen = refchk->refcount;

done:

	/* Delete fragments and work list. */

	list_for_each_entry_safe(frag, n, &worklist, list) {

		list_del(&frag->list);

		kmem_free(frag);

	}

	list_for_each_entry_safe(frag, n, &refchk->fragments, list) {

		list_del(&frag->list);

		kmem_free(frag);

	}

}



/* Use the rmap entries covering this extent to verify the refcount. */

STATIC void

xfs_scrub_refcountbt_xref_rmap(

	struct xfs_scrub_context	*sc,

	xfs_agblock_t			bno,

	xfs_extlen_t			len,

	xfs_nlink_t			refcount)

{

	struct xfs_scrub_refcnt_check	refchk = {

		.sc = sc,

		.bno = bno,

		.len = len,

		.refcount = refcount,

		.seen = 0,

	};

	struct xfs_rmap_irec		low;

	struct xfs_rmap_irec		high;

	struct xfs_scrub_refcnt_frag	*frag;

	struct xfs_scrub_refcnt_frag	*n;

	int				error;



	if (!sc->sa.rmap_cur)

		return;



	/* Cross-reference with the rmapbt to confirm the refcount. */

	memset(&low, 0, sizeof(low));

	low.rm_startblock = bno;

	memset(&high, 0xFF, sizeof(high));

	high.rm_startblock = bno + len - 1;



	INIT_LIST_HEAD(&refchk.fragments);

	error = xfs_rmap_query_range(sc->sa.rmap_cur, &low, &high,

			&xfs_scrub_refcountbt_rmap_check, &refchk);

	if (!xfs_scrub_should_check_xref(sc, &error, &sc->sa.rmap_cur))

		goto out_free;



	xfs_scrub_refcountbt_process_rmap_fragments(&refchk);

	if (refcount != refchk.seen)

		xfs_scrub_btree_xref_set_corrupt(sc, sc->sa.rmap_cur, 0);



out_free:

	list_for_each_entry_safe(frag, n, &refchk.fragments, list) {

		list_del(&frag->list);

		kmem_free(frag);

	}

}



/* Cross-reference with the other btrees. */

STATIC void

xfs_scrub_refcountbt_xref(
@@ -63,6 +348,7 @@ xfs_scrub_refcountbt_xref( 


	xfs_scrub_xref_is_used_space(sc, agbno, len);

	xfs_scrub_xref_is_not_inode_chunk(sc, agbno, len);

	xfs_scrub_refcountbt_xref_rmap(sc, agbno, len, refcount);

}



/* Scrub a refcountbt record. */
@@ -72,6 +358,7 @@ xfs_scrub_refcountbt_rec( 
	union xfs_btree_rec		*rec)

{

	struct xfs_mount		*mp = bs->cur->bc_mp;

	xfs_agblock_t			*cow_blocks = bs->private;

	xfs_agnumber_t			agno = bs->cur->bc_private.a.agno;

	xfs_agblock_t			bno;

	xfs_extlen_t			len;
@@ -87,6 +374,8 @@ xfs_scrub_refcountbt_rec( 
	has_cowflag = (bno & XFS_REFC_COW_START);

	if ((refcount == 1 && !has_cowflag) || (refcount != 1 && has_cowflag))

		xfs_scrub_btree_set_corrupt(bs->sc, bs->cur, 0);

	if (has_cowflag)

		(*cow_blocks) += len;



	/* Check the extent. */

	bno &= ~XFS_REFC_COW_START;
@@ -103,14 +392,57 @@ xfs_scrub_refcountbt_rec( 
	return error;

}



/* Make sure we have as many refc blocks as the rmap says. */

STATIC void

xfs_scrub_refcount_xref_rmap(

	struct xfs_scrub_context	*sc,

	struct xfs_owner_info		*oinfo,

	xfs_filblks_t			cow_blocks)

{

	xfs_extlen_t			refcbt_blocks = 0;

	xfs_filblks_t			blocks;

	int				error;



	if (!sc->sa.rmap_cur)

		return;



	/* Check that we saw as many refcbt blocks as the rmap knows about. */

	error = xfs_btree_count_blocks(sc->sa.refc_cur, &refcbt_blocks);

	if (!xfs_scrub_btree_process_error(sc, sc->sa.refc_cur, 0, &error))

		return;

	error = xfs_scrub_count_rmap_ownedby_ag(sc, sc->sa.rmap_cur, oinfo,

			&blocks);

	if (!xfs_scrub_should_check_xref(sc, &error, &sc->sa.rmap_cur))

		return;

	if (blocks != refcbt_blocks)

		xfs_scrub_btree_xref_set_corrupt(sc, sc->sa.rmap_cur, 0);



	/* Check that we saw as many cow blocks as the rmap knows about. */

	xfs_rmap_ag_owner(oinfo, XFS_RMAP_OWN_COW);

	error = xfs_scrub_count_rmap_ownedby_ag(sc, sc->sa.rmap_cur, oinfo,

			&blocks);

	if (!xfs_scrub_should_check_xref(sc, &error, &sc->sa.rmap_cur))

		return;

	if (blocks != cow_blocks)

		xfs_scrub_btree_xref_set_corrupt(sc, sc->sa.rmap_cur, 0);

}



/* Scrub the refcount btree for some AG. */

int

xfs_scrub_refcountbt(

	struct xfs_scrub_context	*sc)

{

	struct xfs_owner_info		oinfo;

	xfs_agblock_t			cow_blocks = 0;

	int				error;



	xfs_rmap_ag_owner(&oinfo, XFS_RMAP_OWN_REFC);

	return xfs_scrub_btree(sc, sc->sa.refc_cur, xfs_scrub_refcountbt_rec,

			&oinfo, NULL);

	error = xfs_scrub_btree(sc, sc->sa.refc_cur, xfs_scrub_refcountbt_rec,

			&oinfo, &cow_blocks);

	if (error)

		return error;



	xfs_scrub_refcount_xref_rmap(sc, &oinfo, cow_blocks);



	return 0;

}