xfs: check the reference counts of gaps in the refcount btree

Gaps in the reference count btree are also significant -- for these
regions, there must not be any overlapping reverse mappings.  We don't
currently check this, so make the refcount scrubber more complete.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

diff --git a/fs/xfs/scrub/refcount.c b/fs/xfs/scrub/refcount.c
index ed47c57..771a591 100644 (file)
--- a/fs/xfs/scrub/refcount.c
+++ b/fs/xfs/scrub/refcount.c
@@ -332,6 +332,64 @@ xchk_refcountbt_xref(
        xchk_refcountbt_xref_rmap(sc, irec);
 }
 
+struct xchk_refcbt_records {
+       /* The next AG block where we aren't expecting shared extents. */
+       xfs_agblock_t           next_unshared_agbno;
+
+       /* Number of CoW blocks we expect. */
+       xfs_agblock_t           cow_blocks;
+
+       /* Was the last record a shared or CoW staging extent? */
+       enum xfs_refc_domain    prev_domain;
+};
+
+STATIC int
+xchk_refcountbt_rmap_check_gap(
+       struct xfs_btree_cur            *cur,
+       const struct xfs_rmap_irec      *rec,
+       void                            *priv)
+{
+       xfs_agblock_t                   *next_bno = priv;
+
+       if (*next_bno != NULLAGBLOCK && rec->rm_startblock < *next_bno)
+               return -ECANCELED;
+
+       *next_bno = rec->rm_startblock + rec->rm_blockcount;
+       return 0;
+}
+
+/*
+ * Make sure that a gap in the reference count records does not correspond to
+ * overlapping records (i.e. shared extents) in the reverse mappings.
+ */
+static inline void
+xchk_refcountbt_xref_gaps(
+       struct xfs_scrub        *sc,
+       struct xchk_refcbt_records *rrc,
+       xfs_agblock_t           bno)
+{
+       struct xfs_rmap_irec    low;
+       struct xfs_rmap_irec    high;
+       xfs_agblock_t           next_bno = NULLAGBLOCK;
+       int                     error;
+
+       if (bno <= rrc->next_unshared_agbno || !sc->sa.rmap_cur ||
+            xchk_skip_xref(sc->sm))
+               return;
+
+       memset(&low, 0, sizeof(low));
+       low.rm_startblock = rrc->next_unshared_agbno;
+       memset(&high, 0xFF, sizeof(high));
+       high.rm_startblock = bno - 1;
+
+       error = xfs_rmap_query_range(sc->sa.rmap_cur, &low, &high,
+                       xchk_refcountbt_rmap_check_gap, &next_bno);
+       if (error == -ECANCELED)
+               xchk_btree_xref_set_corrupt(sc, sc->sa.rmap_cur, 0);
+       else
+               xchk_should_check_xref(sc, &error, &sc->sa.rmap_cur);
+}
+
 /* Scrub a refcountbt record. */
 STATIC int
 xchk_refcountbt_rec(
@@ -339,7 +397,7 @@ xchk_refcountbt_rec(
        const union xfs_btree_rec *rec)
 {
        struct xfs_refcount_irec irec;
-       xfs_agblock_t           *cow_blocks = bs->private;
+       struct xchk_refcbt_records *rrc = bs->private;
 
        xfs_refcount_btrec_to_irec(rec, &irec);
        if (xfs_refcount_check_irec(bs->cur, &irec) != NULL) {
@@ -348,10 +406,27 @@ xchk_refcountbt_rec(
        }
 
        if (irec.rc_domain == XFS_REFC_DOMAIN_COW)
-               (*cow_blocks) += irec.rc_blockcount;
+               rrc->cow_blocks += irec.rc_blockcount;
+
+       /* Shared records always come before CoW records. */
+       if (irec.rc_domain == XFS_REFC_DOMAIN_SHARED &&
+           rrc->prev_domain == XFS_REFC_DOMAIN_COW)
+               xchk_btree_set_corrupt(bs->sc, bs->cur, 0);
+       rrc->prev_domain = irec.rc_domain;
 
        xchk_refcountbt_xref(bs->sc, &irec);
 
+       /*
+        * If this is a record for a shared extent, check that all blocks
+        * between the previous record and this one have at most one reverse
+        * mapping.
+        */
+       if (irec.rc_domain == XFS_REFC_DOMAIN_SHARED) {
+               xchk_refcountbt_xref_gaps(bs->sc, rrc, irec.rc_startblock);
+               rrc->next_unshared_agbno = irec.rc_startblock +
+                                          irec.rc_blockcount;
+       }
+
        return 0;
 }
 
@@ -393,15 +468,25 @@ int
 xchk_refcountbt(
        struct xfs_scrub        *sc)
 {
-       xfs_agblock_t           cow_blocks = 0;
+       struct xchk_refcbt_records rrc = {
+               .cow_blocks             = 0,
+               .next_unshared_agbno    = 0,
+               .prev_domain            = XFS_REFC_DOMAIN_SHARED,
+       };
        int                     error;
 
        error = xchk_btree(sc, sc->sa.refc_cur, xchk_refcountbt_rec,
-                       &XFS_RMAP_OINFO_REFC, &cow_blocks);
+                       &XFS_RMAP_OINFO_REFC, &rrc);
        if (error)
                return error;
 
-       xchk_refcount_xref_rmap(sc, cow_blocks);
+       /*
+        * Check that all blocks between the last refcount > 1 record and the
+        * end of the AG have at most one reverse mapping.
+        */
+       xchk_refcountbt_xref_gaps(sc, &rrc, sc->mp->m_sb.sb_agblocks);
+
+       xchk_refcount_xref_rmap(sc, rrc.cow_blocks);
 
        return 0;
 }