btrfs: Fix tail space processing in find_free_dev_extent()

It is another reason for NO_SPACE case.

When we found enough free space in loop and saved them to
max_hole_start/size before, and tail space contains pending extent,
origional innocent max_hole_start/size are reset in retry.

As a result, find_free_dev_extent() returns less space than it can,
and cause NO_SPACE in user program.

Reviewed-by: Liu Bo <bo.li.liu@oracle.com>
Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Signed-off-by: Chris Mason <clm@fb.com>

1 files changed, 13 insertions, 11 deletions

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index a73acf496e10..8bcd2a007517 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1134,11 +1134,11 @@ int find_free_dev_extent(struct btrfs_trans_handle *trans,
         path = btrfs_alloc_path();
         if (!path)
                 return -ENOMEM;
-again:
+
         max_hole_start = search_start;
         max_hole_size = 0;
-        hole_size = 0;
 
+again:
         if (search_start >= search_end || device->is_tgtdev_for_dev_replace) {
                 ret = -ENOSPC;
                 goto out;
@@ -1231,21 +1231,23 @@ next:
          * allocated dev extents, and when shrinking the device,
          * search_end may be smaller than search_start.
          */
-        if (search_end > search_start)
+        if (search_end > search_start) {
                 hole_size = search_end - search_start;
 
-        if (hole_size > max_hole_size) {
-                max_hole_start = search_start;
-                max_hole_size = hole_size;
-        }
+                if (contains_pending_extent(trans, device, &search_start,
+                                            hole_size)) {
+                        btrfs_release_path(path);
+                        goto again;
+                }
 
-        if (contains_pending_extent(trans, device, &search_start, hole_size)) {
-                btrfs_release_path(path);
-                goto again;
+                if (hole_size > max_hole_size) {
+                        max_hole_start = search_start;
+                        max_hole_size = hole_size;
+                }
         }
 
         /* See above. */
-        if (hole_size < num_bytes)
+        if (max_hole_size < num_bytes)
                 ret = -ENOSPC;
         else
                 ret = 0;