[XFS] Allow xfs_bmbt_split() to fallback to the lowspace allocator

algorithm

If xfs_bmbt_split() cannot find an AG with sufficient free space to
satisfy a full extent btree split then fall back to the lowspace allocator
algorithm.

SGI-PV: 983338

SGI-Modid: xfs-linux-melb:xfs-kern:31359a

Signed-off-by: Lachlan McIlroy <lachlan@sgi.com>
Signed-off-by: David Chinner <dgc@sgi.com>

1 files changed, 15 insertions, 0 deletions

diff --git a/fs/xfs/xfs_bmap_btree.c b/fs/xfs/xfs_bmap_btree.c
index 1140cef4ba99..23efad29a5cd 100644
--- a/fs/xfs/xfs_bmap_btree.c
+++ b/fs/xfs/xfs_bmap_btree.c
@@ -1525,6 +1525,21 @@ xfs_bmbt_split(
                 XFS_BMBT_TRACE_CURSOR(cur, ERROR);
                 return error;
         }
+        if (args.fsbno == NULLFSBLOCK && args.minleft) {
+                /*
+                 * Could not find an AG with enough free space to satisfy
+                 * a full btree split.  Try again without minleft and if
+                 * successful activate the lowspace algorithm.
+                 */
+                args.fsbno = 0;
+                args.type = XFS_ALLOCTYPE_FIRST_AG;
+                args.minleft = 0;
+                if ((error = xfs_alloc_vextent(&args))) {
+                        XFS_BMBT_TRACE_CURSOR(cur, ERROR);
+                        return error;
+                }
+                cur->bc_private.b.flist->xbf_low = 1;
+        }
         if (args.fsbno == NULLFSBLOCK) {
                 XFS_BMBT_TRACE_CURSOR(cur, EXIT);
                 *stat = 0;