xfs: bmap scrubber should do rmap xref with bmap for sparse files

When we're scanning an extent mapping inode fork, ensure that every rmap
record for this ifork has a corresponding bmbt record too.  This
(mostly) provides the ability to cross-reference rmap records with bmap
data.  The rmap scrubber cannot do the xref on its own because that
requires taking an ilock with the agf lock held, which violates our
locking order rules (inode, then agf).

Note that we only do this for forks that are in btree format due to the
increased complexity; or forks that should have data but suspiciously
have zero extents because the inode could have just had its iforks
zapped by the inode repair code and now we need to reclaim the old
extents.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>

1 files changed, 169 insertions, 1 deletions

diff --git a/fs/xfs/scrub/bmap.c b/fs/xfs/scrub/bmap.c
index d00282130492..75ea2d63429c 100644
--- a/fs/xfs/scrub/bmap.c
+++ b/fs/xfs/scrub/bmap.c
@@ -37,6 +37,7 @@
 #include "xfs_bmap_util.h"
 #include "xfs_bmap_btree.h"
 #include "xfs_rmap.h"
+#include "xfs_rmap_btree.h"
 #include "xfs_refcount.h"
 #include "scrub/xfs_scrub.h"
 #include "scrub/scrub.h"
@@ -423,6 +424,169 @@ xfs_scrub_bmap_btree(
         return error;
 }
 
+struct xfs_scrub_bmap_check_rmap_info {
+        struct xfs_scrub_context        *sc;
+        int                             whichfork;
+        struct xfs_iext_cursor          icur;
+};
+
+/* Can we find bmaps that fit this rmap? */
+STATIC int
+xfs_scrub_bmap_check_rmap(
+        struct xfs_btree_cur            *cur,
+        struct xfs_rmap_irec            *rec,
+        void                            *priv)
+{
+        struct xfs_bmbt_irec            irec;
+        struct xfs_scrub_bmap_check_rmap_info   *sbcri = priv;
+        struct xfs_ifork                *ifp;
+        struct xfs_scrub_context        *sc = sbcri->sc;
+        bool                            have_map;
+
+        /* Is this even the right fork? */
+        if (rec->rm_owner != sc->ip->i_ino)
+                return 0;
+        if ((sbcri->whichfork == XFS_ATTR_FORK) ^
+            !!(rec->rm_flags & XFS_RMAP_ATTR_FORK))
+                return 0;
+        if (rec->rm_flags & XFS_RMAP_BMBT_BLOCK)
+                return 0;
+
+        /* Now look up the bmbt record. */
+        ifp = XFS_IFORK_PTR(sc->ip, sbcri->whichfork);
+        if (!ifp) {
+                xfs_scrub_fblock_set_corrupt(sc, sbcri->whichfork,
+                                rec->rm_offset);
+                goto out;
+        }
+        have_map = xfs_iext_lookup_extent(sc->ip, ifp, rec->rm_offset,
+                        &sbcri->icur, &irec);
+        if (!have_map)
+                xfs_scrub_fblock_set_corrupt(sc, sbcri->whichfork,
+                                rec->rm_offset);
+        /*
+         * bmap extent record lengths are constrained to 2^21 blocks in length
+         * because of space constraints in the on-disk metadata structure.
+         * However, rmap extent record lengths are constrained only by AG
+         * length, so we have to loop through the bmbt to make sure that the
+         * entire rmap is covered by bmbt records.
+         */
+        while (have_map) {
+                if (irec.br_startoff != rec->rm_offset)
+                        xfs_scrub_fblock_set_corrupt(sc, sbcri->whichfork,
+                                        rec->rm_offset);
+                if (irec.br_startblock != XFS_AGB_TO_FSB(sc->mp,
+                                cur->bc_private.a.agno, rec->rm_startblock))
+                        xfs_scrub_fblock_set_corrupt(sc, sbcri->whichfork,
+                                        rec->rm_offset);
+                if (irec.br_blockcount > rec->rm_blockcount)
+                        xfs_scrub_fblock_set_corrupt(sc, sbcri->whichfork,
+                                        rec->rm_offset);
+                if (sc->sm->sm_flags & XFS_SCRUB_OFLAG_CORRUPT)
+                        break;
+                rec->rm_startblock += irec.br_blockcount;
+                rec->rm_offset += irec.br_blockcount;
+                rec->rm_blockcount -= irec.br_blockcount;
+                if (rec->rm_blockcount == 0)
+                        break;
+                have_map = xfs_iext_next_extent(ifp, &sbcri->icur, &irec);
+                if (!have_map)
+                        xfs_scrub_fblock_set_corrupt(sc, sbcri->whichfork,
+                                        rec->rm_offset);
+        }
+
+out:
+        if (sc->sm->sm_flags & XFS_SCRUB_OFLAG_CORRUPT)
+                return XFS_BTREE_QUERY_RANGE_ABORT;
+        return 0;
+}
+
+/* Make sure each rmap has a corresponding bmbt entry. */
+STATIC int
+xfs_scrub_bmap_check_ag_rmaps(
+        struct xfs_scrub_context        *sc,
+        int                             whichfork,
+        xfs_agnumber_t                  agno)
+{
+        struct xfs_scrub_bmap_check_rmap_info   sbcri;
+        struct xfs_btree_cur            *cur;
+        struct xfs_buf                  *agf;
+        int                             error;
+
+        error = xfs_alloc_read_agf(sc->mp, sc->tp, agno, 0, &agf);
+        if (error)
+                return error;
+
+        cur = xfs_rmapbt_init_cursor(sc->mp, sc->tp, agf, agno);
+        if (!cur) {
+                error = -ENOMEM;
+                goto out_agf;
+        }
+
+        sbcri.sc = sc;
+        sbcri.whichfork = whichfork;
+        error = xfs_rmap_query_all(cur, xfs_scrub_bmap_check_rmap, &sbcri);
+        if (error == XFS_BTREE_QUERY_RANGE_ABORT)
+                error = 0;
+
+        xfs_btree_del_cursor(cur, error ? XFS_BTREE_ERROR : XFS_BTREE_NOERROR);
+out_agf:
+        xfs_trans_brelse(sc->tp, agf);
+        return error;
+}
+
+/* Make sure each rmap has a corresponding bmbt entry. */
+STATIC int
+xfs_scrub_bmap_check_rmaps(
+        struct xfs_scrub_context        *sc,
+        int                             whichfork)
+{
+        loff_t                          size;
+        xfs_agnumber_t                  agno;
+        int                             error;
+
+        if (!xfs_sb_version_hasrmapbt(&sc->mp->m_sb) ||
+            whichfork == XFS_COW_FORK ||
+            (sc->sm->sm_flags & XFS_SCRUB_OFLAG_CORRUPT))
+                return 0;
+
+        /* Don't support realtime rmap checks yet. */
+        if (XFS_IS_REALTIME_INODE(sc->ip) && whichfork == XFS_DATA_FORK)
+                return 0;
+
+        /*
+         * Only do this for complex maps that are in btree format, or for
+         * situations where we would seem to have a size but zero extents.
+         * The inode repair code can zap broken iforks, which means we have
+         * to flag this bmap as corrupt if there are rmaps that need to be
+         * reattached.
+         */
+        switch (whichfork) {
+        case XFS_DATA_FORK:
+                size = i_size_read(VFS_I(sc->ip));
+                break;
+        case XFS_ATTR_FORK:
+                size = XFS_IFORK_Q(sc->ip);
+                break;
+        default:
+                size = 0;
+                break;
+        }
+        if (XFS_IFORK_FORMAT(sc->ip, whichfork) != XFS_DINODE_FMT_BTREE &&
+            (size == 0 || XFS_IFORK_NEXTENTS(sc->ip, whichfork) > 0))
+                return 0;
+
+        for (agno = 0; agno < sc->mp->m_sb.sb_agcount; agno++) {
+                error = xfs_scrub_bmap_check_ag_rmaps(sc, whichfork, agno);
+                if (error)
+                        return error;
+                if (sc->sm->sm_flags & XFS_SCRUB_OFLAG_CORRUPT)
+                        break;
+        }
+
+        return 0;
+}
+
 /*
  * Scrub an inode fork's block mappings.
  *
@@ -463,7 +627,7 @@ xfs_scrub_bmap(
                 break;
         case XFS_ATTR_FORK:
                 if (!ifp)
-                        goto out;
+                        goto out_check_rmap;
                 if (!xfs_sb_version_hasattr(&mp->m_sb) &&
                     !xfs_sb_version_hasattr2(&mp->m_sb))
                         xfs_scrub_ino_set_corrupt(sc, sc->ip->i_ino, NULL);
@@ -534,6 +698,10 @@ xfs_scrub_bmap(
                         goto out;
         }
 
+out_check_rmap:
+        error = xfs_scrub_bmap_check_rmaps(sc, whichfork);
+        if (!xfs_scrub_fblock_xref_process_error(sc, whichfork, 0, &error))
+                goto out;
 out:
         return error;
 }