dm: reorder 'struct mapped_device' members to fix alignment and holes

Saves 16 bytes by eliminating 4 4byte holes but more importantly:
numerous members that crossed cachelines were fixed.

Signed-off-by: Mike Snitzer <snitzer@redhat.com>

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 3cae8547420a10f454bdcbfcd8f1a19ad2db2945..503988ff66eafc30c4505570e2f57cc068012601 100644 (file)
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -126,8 +126,6 @@ struct dm_rq_clone_bio_info {
 struct mapped_device {
        struct srcu_struct io_barrier;
        struct mutex suspend_lock;
-       atomic_t holders;
-       atomic_t open_count;
 
        /*
         * The current mapping (struct dm_table *).
@@ -148,6 +146,9 @@ struct mapped_device {
        /* Protect queue and type against concurrent access. */
        struct mutex type_lock;
 
+       atomic_t holders;
+       atomic_t open_count;
+
        struct dm_target *immutable_target;
        struct target_type *immutable_target_type;
 
@@ -162,8 +163,20 @@ struct mapped_device {
        atomic_t pending[2];
        wait_queue_head_t wait;
        struct work_struct work;
-       struct bio_list deferred;
        spinlock_t deferred_lock;
+       struct bio_list deferred;
+
+       /*
+        * Event handling.
+        */
+       wait_queue_head_t eventq;
+       atomic_t event_nr;
+       atomic_t uevent_seq;
+       struct list_head uevent_list;
+       spinlock_t uevent_lock; /* Protect access to uevent_list */
+
+       /* the number of internal suspends */
+       unsigned internal_suspend_count;
 
        /*
         * Processing queue (flush)
@@ -178,33 +191,22 @@ struct mapped_device {
 
        struct bio_set *bs;
 
-       /*
-        * Event handling.
-        */
-       atomic_t event_nr;
-       wait_queue_head_t eventq;
-       atomic_t uevent_seq;
-       struct list_head uevent_list;
-       spinlock_t uevent_lock; /* Protect access to uevent_list */
-
        /*
         * freeze/thaw support require holding onto a super block
         */
        struct super_block *frozen_sb;
-       struct block_device *bdev;
 
        /* forced geometry settings */
        struct hd_geometry geometry;
 
+       struct block_device *bdev;
+
        /* kobject and completion */
        struct dm_kobject_holder kobj_holder;
 
        /* zero-length flush that will be cloned and submitted to targets */
        struct bio flush_bio;
 
-       /* the number of internal suspends */
-       unsigned internal_suspend_count;
-
        struct dm_stats stats;
 
        struct kthread_worker kworker;