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>

diff --git a/fs/ubifs/super.c b/fs/ubifs/super.c
index d80b2aef42b661001b2c87ac645f9a8ac29fbfd7..21b4103271ecf836f1e98a5aaaf23db7ba851058 100644 (file)
--- a/fs/ubifs/super.c
+++ b/fs/ubifs/super.c
@@ -2020,6 +2020,14 @@ static int __init ubifs_init(void)
        BUILD_BUG_ON(UBIFS_INO_NODE_SZ != 160);
        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.

diff --git a/fs/ubifs/ubifs.h b/fs/ubifs/ubifs.h
index 46b172560a064eb7b4d541359aa9b02e7dd39380..4d76aba57ee18c648a8feb74be9b6f2707ab8fef 100644 (file)
--- a/fs/ubifs/ubifs.h
+++ b/fs/ubifs/ubifs.h
@@ -386,12 +386,12 @@ struct ubifs_inode {
        unsigned int dirty:1;
        unsigned int xattr:1;
        unsigned int bulk_read:1;
+       unsigned int compr_type:2;
        struct mutex ui_mutex;
        spinlock_t ui_lock;
        loff_t synced_i_size;
        loff_t ui_size;
        int flags;
-       int compr_type;
        pgoff_t last_page_read;
        pgoff_t read_in_a_row;
        int data_len;
@@ -946,6 +946,7 @@ struct ubifs_mount_opts {
  * @no_chk_data_crc: do not check CRCs when reading data nodes (except during
  *                   recovery)
  * @bulk_read: enable bulk-reads
+ * @default_compr: default compression algorithm (%UBIFS_COMPR_LZO, etc)
  *
  * @tnc_mutex: protects the Tree Node Cache (TNC), @zroot, @cnext, @enext, and
  *             @calc_idx_sz
@@ -986,7 +987,6 @@ struct ubifs_mount_opts {
  * @main_lebs: count of LEBs in the main area
  * @main_first: first LEB of the main area
  * @main_bytes: main area size in bytes
- * @default_compr: default compression algorithm (%UBIFS_COMPR_LZO, etc)
  *
  * @key_hash_type: type of the key hash
  * @key_hash: direntry key hash function
@@ -1196,6 +1196,7 @@ struct ubifs_info {
        unsigned int big_lpt:1;
        unsigned int no_chk_data_crc:1;
        unsigned int bulk_read:1;
+       unsigned int default_compr:2;
 
        struct mutex tnc_mutex;
        struct ubifs_zbranch zroot;
@@ -1237,7 +1238,6 @@ struct ubifs_info {
        int main_lebs;
        int main_first;
        long long main_bytes;
-       int default_compr;
 
        uint8_t key_hash_type;
        uint32_t (*key_hash)(const char *str, int len);