xfs: fix multi-AG deadlock in xfs_bunmapi
Just like in the allocator we must avoid touching multiple AGs out of
order when freeing blocks, as freeing still locks the AGF and can cause
the same AB-BA deadlocks as in the allocation path.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reported-by: Nikolay Borisov <n.borisov.lkml@gmail.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
index ee118ce..c09c16b 100644
--- a/fs/xfs/libxfs/xfs_bmap.c
+++ b/fs/xfs/libxfs/xfs_bmap.c
@@ -5435,6 +5435,7 @@
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 @@
*/
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;