Btrfs: check unused against how much space we actually want

There is a bug that may lead to early ENOSPC in our reservation code.  We've
been checking against num_bytes which may be above and beyond what we want to
actually reserve, which could give us a false ENOSPC.  Fix this by making sure
the unused space is above how much we want to reserve and not how much we're
trying to flush.  Thanks,

Signed-off-by: Josef Bacik <josef@redhat.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 5498bdacd4c3..fd65f6bc676c 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -3472,7 +3472,7 @@ again:
          */
         if (unused <= space_info->total_bytes) {
                 unused = space_info->total_bytes - unused;
-                if (unused >= num_bytes) {
+                if (unused >= orig_bytes) {
                         space_info->bytes_may_use += orig_bytes;
                         ret = 0;
                 } else {