From: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
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: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
---
fs/xfs/scrub/refcount.c | 315 +++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 313 insertions(+), 2 deletions(-)
diff --git a/fs/xfs/scrub/refcount.c b/fs/xfs/scrub/refcount.c
index 8add281..6efae58 100644
--- a/fs/xfs/scrub/refcount.c
+++ b/fs/xfs/scrub/refcount.c
@@ -50,6 +50,274 @@ 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 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.
+ */
+ 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;
+
+ /* Find all the rmaps that start at or before the refc extent. */
+ 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 (rbno > bno)
+ rbno = bno;
+ list_del(&frag->list);
+ list_add_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. */
+ 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 (next_rbno > bno)
+ next_rbno = bno;
+ continue;
+ }
+ list_del(&frag->list);
+ kmem_free(frag);
+ nr++;
+ }
+
+ /* Empty list? We're done. */
+ if (list_empty(&refchk->fragments))
+ break;
+
+ /* 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_del(&frag->list);
+ list_add_tail(&frag->list, &worklist);
+ if (next_rbno > bno)
+ next_rbno = bno;
+ nr--;
+ if (nr == 0)
+ break;
+ }
+
+ 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_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(
@@ -61,6 +329,7 @@ xfs_scrub_refcountbt_xref(
xfs_scrub_xref_not_free(sc, &sc->sa.bno_cur, bno, len);
xfs_scrub_xref_not_inodes(sc, &sc->sa.ino_cur, bno, len);
xfs_scrub_xref_not_inodes(sc, &sc->sa.fino_cur, bno, len);
+ xfs_scrub_refcountbt_xref_rmap(sc, bno, len, refcount);
}
/* Scrub a refcountbt record. */
@@ -70,6 +339,7 @@ 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;
@@ -85,6 +355,8 @@ 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;
@@ -104,14 +376,53 @@ 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;
+
+ /* 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_xref(sc, &error, &sc->sa.rmap_cur) &&
+ 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_xref(sc, &error, &sc->sa.rmap_cur) &&
+ 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;
+
+ if (sc->sa.rmap_cur)
+ xfs_scrub_refcount_xref_rmap(sc, &oinfo, cow_blocks);
+
+ return error;
}
--
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