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>

2 files changed, 11 insertions, 3 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.
          */
diff --git a/fs/ubifs/ubifs.h b/fs/ubifs/ubifs.h
index 46b172560a06..4d76aba57ee1 100644
--- 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);