xfs: support lowmode allocations in xfs_bmap_exact_minlen_extent_alloc

Currently the debug-only xfs_bmap_exact_minlen_extent_alloc allocation
variant fails to drop into the lowmode last resort 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>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>

diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
index 2873566dea3d3d0e1b0385e50cdc217a423d1b9e..f1c3beb2c435ba30bad3bf1817d6c574d275bd3c 100644 (file)
--- a/fs/xfs/libxfs/xfs_bmap.c
+++ b/fs/xfs/libxfs/xfs_bmap.c
@@ -3492,7 +3492,13 @@ 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);
+       /*
+        * Call xfs_bmap_btalloc_low_space here as it first does a "normal" AG
+        * iteration and then drops args->total to args->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);
 }
 
 /*