xfs: sanity check ag header values in xrep_calc_ag_resblks

Check the values we read in from the AG headers when calculating the
block reservations for a repair transaction.  If they're obviously
wrong, substitute worst case assumptions (rather than ENOSPC on a bogus
reservation request).

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com>

1 files changed, 27 insertions, 19 deletions

diff --git a/fs/xfs/scrub/repair.c b/fs/xfs/scrub/repair.c
index 17cf48564390..9f08dd9bf1d5 100644
--- a/fs/xfs/scrub/repair.c
+++ b/fs/xfs/scrub/repair.c
@@ -195,8 +195,8 @@ xrep_calc_ag_resblks(
         struct xfs_scrub_metadata       *sm = sc->sm;
         struct xfs_perag                *pag;
         struct xfs_buf                  *bp;
-        xfs_agino_t                     icount = 0;
-        xfs_extlen_t                    aglen = 0;
+        xfs_agino_t                     icount = NULLAGINO;
+        xfs_extlen_t                    aglen = NULLAGBLOCK;
         xfs_extlen_t                    usedlen;
         xfs_extlen_t                    freelen;
         xfs_extlen_t                    bnobt_sz;
@@ -208,20 +208,14 @@ xrep_calc_ag_resblks(
         if (!(sm->sm_flags & XFS_SCRUB_IFLAG_REPAIR))
                 return 0;
 
-        /* Use in-core counters if possible. */
         pag = xfs_perag_get(mp, sm->sm_agno);
-        if (pag->pagi_init)
+        if (pag->pagi_init) {
+                /* Use in-core icount if possible. */
                 icount = pag->pagi_count;
-
-        /*
-         * Otherwise try to get the actual counters from disk; if not, make
-         * some worst case assumptions.
-         */
-        if (icount == 0) {
+        } else {
+                /* Try to get the actual counters from disk. */
                 error = xfs_ialloc_read_agi(mp, NULL, sm->sm_agno, &bp);
-                if (error) {
-                        icount = mp->m_sb.sb_agblocks / mp->m_sb.sb_inopblock;
-                } else {
+                if (!error) {
                         icount = pag->pagi_count;
                         xfs_buf_relse(bp);
                 }
@@ -229,18 +223,32 @@ xrep_calc_ag_resblks(
 
         /* Now grab the block counters from the AGF. */
         error = xfs_alloc_read_agf(mp, NULL, sm->sm_agno, 0, &bp);
-        if (error) {
-                aglen = mp->m_sb.sb_agblocks;
-                freelen = aglen;
-                usedlen = aglen;
-        } else {
+        if (!error) {
                 aglen = be32_to_cpu(XFS_BUF_TO_AGF(bp)->agf_length);
-                freelen = pag->pagf_freeblks;
+                freelen = be32_to_cpu(XFS_BUF_TO_AGF(bp)->agf_freeblks);
                 usedlen = aglen - freelen;
                 xfs_buf_relse(bp);
         }
         xfs_perag_put(pag);
 
+        /* If the icount is impossible, make some worst-case assumptions. */
+        if (icount == NULLAGINO ||
+            !xfs_verify_agino(mp, sm->sm_agno, icount)) {
+                xfs_agino_t     first, last;
+
+                xfs_agino_range(mp, sm->sm_agno, &first, &last);
+                icount = last - first + 1;
+        }
+
+        /* If the block counts are impossible, make worst-case assumptions. */
+        if (aglen == NULLAGBLOCK ||
+            aglen != xfs_ag_block_count(mp, sm->sm_agno) ||
+            freelen >= aglen) {
+                aglen = xfs_ag_block_count(mp, sm->sm_agno);
+                freelen = aglen;
+                usedlen = aglen;
+        }
+
         trace_xrep_calc_ag_resblks(mp, sm->sm_agno, icount, aglen,
                         freelen, usedlen);