From dbde19da96370670cfc4379ab2bfa8db6be42c2b Mon Sep 17 00:00:00 2001 From: "Darrick J. Wong" Date: Tue, 16 Jan 2018 18:53:08 -0800 Subject: 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: Darrick J. Wong Reviewed-by: Dave Chinner --- fs/xfs/scrub/refcount.c | 336 +++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 334 insertions(+), 2 deletions(-) (limited to 'fs/xfs') diff --git a/fs/xfs/scrub/refcount.c b/fs/xfs/scrub/refcount.c index af54590f331b..0c02f2fba394 100644 --- a/fs/xfs/scrub/refcount.c +++ b/fs/xfs/scrub/refcount.c @@ -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; } -- cgit v1.2.3