btrfs: drop gfp mask tweaking in try_release_extent_state

try_release_extent_state reduces the gfp mask to GFP_NOFS if it is
compatible. This is true for GFP_KERNEL as well. There is no real
reason to do that though. There is no new lock taken down the
the only consumer of the gfp mask which is
try_release_extent_state
  clear_extent_bit
    __clear_extent_bit
      alloc_extent_state

So this seems just unnecessary and confusing.
Signed-off-by: NMichal Hocko <mhocko@suse.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

fs/btrfs/extent_io.c

@@ -4269,8 +4269,6 @@ static int try_release_extent_state(struct extent_map_tree *map,
 			   EXTENT_IOBITS, 0, NULL))
 		ret = 0;
 	else {
-		if ((mask & GFP_NOFS) == GFP_NOFS)
-			mask = GFP_NOFS;
 		/*
 		 * at this point we can safely clear everything except the
 		 * locked bit and the nodatasum bit