xfs: fix multi-AG deadlock in xfs_bunmapi
[sfrench/cifs-2.6.git] / fs / xfs / libxfs / xfs_bmap.c
index ee118ceb702fbefd0c34668cee28be587bb1c989..c09c16b1ad3b8b1f883e2ee93b9fcc275c7ed63c 100644 (file)
@@ -5435,6 +5435,7 @@ __xfs_bunmapi(
        xfs_fsblock_t           sum;
        xfs_filblks_t           len = *rlen;    /* length to unmap in file */
        xfs_fileoff_t           max_len;
+       xfs_agnumber_t          prev_agno = NULLAGNUMBER, agno;
 
        trace_xfs_bunmap(ip, bno, len, flags, _RET_IP_);
 
@@ -5534,6 +5535,17 @@ __xfs_bunmapi(
                 */
                del = got;
                wasdel = isnullstartblock(del.br_startblock);
+
+               /*
+                * Make sure we don't touch multiple AGF headers out of order
+                * in a single transaction, as that could cause AB-BA deadlocks.
+                */
+               if (!wasdel) {
+                       agno = XFS_FSB_TO_AGNO(mp, del.br_startblock);
+                       if (prev_agno != NULLAGNUMBER && prev_agno > agno)
+                               break;
+                       prev_agno = agno;
+               }
                if (got.br_startoff < start) {
                        del.br_startoff = start;
                        del.br_blockcount -= start - got.br_startoff;