Btrfs: fix gfp flags masking in the compression code

GFP_FS must be masked out, NOFS can't be or'd in.

Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index a11a320..28b92a7 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -478,7 +478,7 @@
 			goto next;
 		}
 
-		page = alloc_page(mapping_gfp_mask(mapping) | GFP_NOFS);
+		page = alloc_page(mapping_gfp_mask(mapping) & ~__GFP_FS);
 		if (!page)
 			break;