bcache: simplify the calculation of the total amount of flash dirty data

Currently we calculate the total amount of flash only devices dirty data
by adding the dirty data of each flash only device under registering
locker. It is very inefficient.

In this patch, we add a member flash_dev_dirty_sectors in struct cache_set
to record the total amount of flash only devices dirty data in real time,
so we didn't need to calculate the total amount of dirty data any more.
Signed-off-by: Tang Junhui <tang.junhui@zte.com.cn>
Signed-off-by: Coly Li <colyli@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/md/bcache/bcache.h

@@ -525,6 +525,7 @@ struct cache_set {
 	unsigned		devices_max_used;
 	struct list_head	cached_devs;
 	uint64_t		cached_dev_sectors;
+	atomic_long_t		flash_dev_dirty_sectors;
 	struct closure		caching;
 
 	struct closure		sb_write;

drivers/md/bcache/super.c

@@ -1311,6 +1311,8 @@ static void flash_dev_free(struct closure *cl)
 {
 	struct bcache_device *d = container_of(cl, struct bcache_device, cl);
 	mutex_lock(&bch_register_lock);
+	atomic_long_sub(bcache_dev_sectors_dirty(d),
+			&d->c->flash_dev_dirty_sectors);
 	bcache_device_free(d);
 	mutex_unlock(&bch_register_lock);
 	kobject_put(&d->kobj);

drivers/md/bcache/writeback.c

@@ -27,7 +27,7 @@ static uint64_t __calc_target_rate(struct cached_dev *dc)
 	 * flash-only devices
 	 */
 	uint64_t cache_sectors = c->nbuckets * c->sb.bucket_size -
-				bcache_flash_devs_sectors_dirty(c);
+				atomic_long_read(&c->flash_dev_dirty_sectors);
 
 	/*
 	 * Unfortunately there is no control of global dirty data.  If the
@@ -476,6 +476,9 @@ void bcache_dev_sectors_dirty_add(struct cache_set *c, unsigned inode,
 	if (!d)
 		return;
 
+	if (UUID_FLASH_ONLY(&c->uuids[inode]))
+		atomic_long_add(nr_sectors, &c->flash_dev_dirty_sectors);
+
 	stripe = offset_to_stripe(d, offset);
 	stripe_offset = offset & (d->stripe_size - 1);
 

drivers/md/bcache/writeback.h

@@ -28,25 +28,6 @@ static inline uint64_t bcache_dev_sectors_dirty(struct bcache_device *d)
 	return ret;
 }
 
-static inline uint64_t  bcache_flash_devs_sectors_dirty(struct cache_set *c)
-{
-	uint64_t i, ret = 0;
-
-	mutex_lock(&bch_register_lock);
-
-	for (i = 0; i < c->devices_max_used; i++) {
-		struct bcache_device *d = c->devices[i];
-
-		if (!d || !UUID_FLASH_ONLY(&c->uuids[i]))
-			continue;
-		ret += bcache_dev_sectors_dirty(d);
-	}
-
-	mutex_unlock(&bch_register_lock);
-
-	return ret;
-}
-
 static inline unsigned offset_to_stripe(struct bcache_device *d,
 					uint64_t offset)
 {