UBIFS: use bit-fields to store compression type

Save a 4 bytes of RAM per 'struct inode' by stroring inode
compression type in bit-filed, instead of using 'int'.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>

1 files changed, 8 insertions, 0 deletions

diff --git a/fs/ubifs/super.c b/fs/ubifs/super.c
index d80b2aef42b6..21b4103271ec 100644
--- a/fs/ubifs/super.c
+++ b/fs/ubifs/super.c
@@ -2021,6 +2021,14 @@ static int __init ubifs_init(void)
         BUILD_BUG_ON(UBIFS_REF_NODE_SZ != 64);
 
         /*
+         * We use 2 bit wide bit-fields to store compression type, which should
+         * be amended if more compressors are added. The bit-fields are:
+         * @compr_type in 'struct ubifs_inode' and @default_compr in
+         * 'struct ubifs_info'.
+         */
+        BUILD_BUG_ON(UBIFS_COMPR_TYPES_CNT > 4);
+
+        /*
          * We require that PAGE_CACHE_SIZE is greater-than-or-equal-to
          * UBIFS_BLOCK_SIZE. It is assumed that both are powers of 2.
          */