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Commit 5b094d6d authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Darrick J. Wong
Browse files

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: default avatarChristoph Hellwig <hch@lst.de>
Reported-by: default avatarNikolay Borisov <n.borisov.lkml@gmail.com>
Reviewed-by: default avatarDarrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: default avatarDarrick J. Wong <darrick.wong@oracle.com>
parent 6215894e

fs/xfs/libxfs/xfs_bmap.c

+12 −0
Original line number Diff line number Diff line
@@ -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;