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xfs: cross-reference the rmapbt data with the refcountbt

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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@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
This commit is contained in:
Darrick J. Wong 2018-01-16 18:53:08 -08:00
parent d852657ccf
commit dbde19da96
1 changed files with 334 additions and 2 deletions
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336
fs/xfs/scrub/refcount.c
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@ -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;
}