[PATCH 6/6] xfs: support lowmode allocations in xfs_bmap_exact_minlen_extent_alloc

[Christoph Hellwig <hch@lst.de>]

Currently the debug-only xfs_bmap_exact_minlen_extent_alloc allocation
variant fails to drop into the lowmode last restor allocator, and
thus can sometimes fail allocations for which the caller has a
transaction block reservation.

Fix this by using xfs_bmap_btalloc_low_space to do the actual allocation.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 fs/xfs/libxfs/xfs_bmap.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
index b5eeaea164ee46..784dd5dda2a1a2 100644
--- a/fs/xfs/libxfs/xfs_bmap.c
+++ b/fs/xfs/libxfs/xfs_bmap.c
@@ -3493,7 +3493,13 @@ xfs_bmap_exact_minlen_extent_alloc(
 	 */
 	ap->blkno = XFS_AGB_TO_FSB(ap->ip->i_mount, 0, 0);
 
-	return xfs_alloc_vextent_first_ag(args, ap->blkno);
+	/*
+	 * Use the low space allocator as it first does a "normal" AG iteration
+	 * and then drops the reservation to minlen, which might be required to
+	 * find an allocation for the transaction reservation when the file
+	 * system is very full.
+	 */
+	return xfs_bmap_btalloc_low_space(ap, args);
 }
 #else
 
-- 
2.43.0