Btrfs: make the device lock and its protected data in the same cacheline

The lock in btrfs_device structure was far away from its protected data, it would
make CPU load the cache line twice when we accessed them, move them together.

Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Chris Mason <clm@fb.com>

1 files changed, 12 insertions, 13 deletions

diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index 2aaa00c47816..6fcc8eae7834 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -36,30 +36,31 @@ struct btrfs_device {
         struct list_head dev_list;
         struct list_head dev_alloc_list;
         struct btrfs_fs_devices *fs_devices;
+
         struct btrfs_root *dev_root;
 
+        struct rcu_string *name;
+
+        u64 generation;
+
+        spinlock_t io_lock ____cacheline_aligned;
+        int running_pending;
         /* regular prio bios */
         struct btrfs_pending_bios pending_bios;
         /* WRITE_SYNC bios */
         struct btrfs_pending_bios pending_sync_bios;
 
-        u64 generation;
-        int running_pending;
+        struct block_device *bdev;
+
+        /* the mode sent to blkdev_get */
+        fmode_t mode;
+
         int writeable;
         int in_fs_metadata;
         int missing;
         int can_discard;
         int is_tgtdev_for_dev_replace;
 
-        spinlock_t io_lock;
-        /* the mode sent to blkdev_get */
-        fmode_t mode;
-
-        struct block_device *bdev;
-
-
-        struct rcu_string *name;
-
         /* the internal btrfs device id */
         u64 devid;
 
@@ -83,7 +84,6 @@ struct btrfs_device {
         /* minimal io size for this device */
         u32 sector_size;
 
-
         /* physical drive uuid (or lvm uuid) */
         u8 uuid[BTRFS_UUID_SIZE];
 
@@ -107,7 +107,6 @@ struct btrfs_device {
         struct radix_tree_root reada_zones;
         struct radix_tree_root reada_extents;
 
-
         /* disk I/O failure stats. For detailed description refer to
          * enum btrfs_dev_stat_values in ioctl.h */
         int dev_stats_valid;