[PATCH 2/2] btrfs: Use blkdev_issue_flush_no_wait()

[Anand Jain <anand.jain@oracle.com>]

Signed-off-by: Anand Jain <anand.jain@oracle.com>
---
 fs/btrfs/disk-io.c | 108 ++++++++++++++++-------------------------------------
 fs/btrfs/volumes.h |   2 +-
 2 files changed, 33 insertions(+), 77 deletions(-)

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 8685d67185d0..f059f9bdbbd7 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -3478,121 +3478,77 @@ static int write_dev_supers(struct btrfs_device *device,
 }
 
 /*
- * endio for the write_dev_flush, this will wake anyone waiting
+ * endio for blkdev_issues_flush_no_wait, this will wake anyone waiting
  * for the barrier when it is done
  */
 static void btrfs_end_empty_barrier(struct bio *bio)
 {
-	if (bio->bi_private)
-		complete(bio->bi_private);
+	struct btrfs_device *device;
+
+	device = container_of(bio->bi_private, struct btrfs_device,
+						flush_wait);
+
+	device->last_flush_error = bio->bi_error;
+	complete(&device->flush_wait);
+
 	bio_put(bio);
 }
 
-/*
- * trigger flushes for one the devices.  If you pass wait == 0, the flushes are
- * sent down.  With wait == 1, it waits for the previous flush.
- *
- * any device where the flush fails with eopnotsupp are flagged as not-barrier
- * capable
- */
-static int write_dev_flush(struct btrfs_device *device, int wait)
+static void write_dev_flush(struct btrfs_device *device)
 {
+	int ret;
 	struct request_queue *q = bdev_get_queue(device->bdev);
-	struct bio *bio;
-	int ret = 0;
 
 	if (!test_bit(QUEUE_FLAG_WC, &q->queue_flags))
-		return 0;
-
-	if (wait) {
-		bio = device->flush_bio;
-		if (!bio)
-			return 0;
-
-		wait_for_completion(&device->flush_wait);
-
-		if (bio->bi_error) {
-			ret = bio->bi_error;
-			btrfs_dev_stat_inc_and_print(device,
-				BTRFS_DEV_STAT_FLUSH_ERRS);
-		}
-
-		/* drop the reference from the wait == 0 run */
-		bio_put(bio);
-		device->flush_bio = NULL;
-
-		return ret;
-	}
-
-	/*
-	 * one reference for us, and we leave it for the
-	 * caller
-	 */
-	device->flush_bio = NULL;
-	bio = btrfs_io_bio_alloc(GFP_NOFS, 0);
-	if (!bio)
-		return -ENOMEM;
-
-	bio->bi_end_io = btrfs_end_empty_barrier;
-	bio->bi_bdev = device->bdev;
-	bio->bi_opf = REQ_OP_WRITE | REQ_PREFLUSH;
-	init_completion(&device->flush_wait);
-	bio->bi_private = &device->flush_wait;
-	device->flush_bio = bio;
-
-	bio_get(bio);
-	btrfsic_submit_bio(bio);
+		return;
 
-	return 0;
+	ret = blkdev_issue_flush_no_wait(device->bdev, GFP_NOFS,
+		btrfs_end_empty_barrier, &device->flush_wait);
+	if (ret)
+		device->last_flush_error = ret;
+	else
+		device->last_flush_error = -1;
 }
 
 /*
- * send an empty flush down to each device in parallel,
- * then wait for them
+ * send flush down to each device in parallel, then wait for them.
  */
 static int barrier_all_devices(struct btrfs_fs_info *info)
 {
 	struct list_head *head;
 	struct btrfs_device *dev;
-	int errors_send = 0;
 	int errors_wait = 0;
-	int ret;
 
 	/* send down all the barriers */
 	head = &info->fs_devices->devices;
 	list_for_each_entry_rcu(dev, head, dev_list) {
+		dev->last_flush_error = 0;
 		if (dev->missing)
 			continue;
+
+		if (!dev->in_fs_metadata || !dev->writeable)
+			continue;
+
 		if (!dev->bdev) {
-			errors_send++;
+			dev->last_flush_error = -ENXIO;
 			continue;
 		}
-		if (!dev->in_fs_metadata || !dev->writeable)
-			continue;
 
-		ret = write_dev_flush(dev, 0);
-		if (ret)
-			errors_send++;
+		write_dev_flush(dev);
 	}
 
 	/* wait for all the barriers */
 	list_for_each_entry_rcu(dev, head, dev_list) {
-		if (dev->missing)
-			continue;
-		if (!dev->bdev) {
-			errors_wait++;
-			continue;
-		}
-		if (!dev->in_fs_metadata || !dev->writeable)
-			continue;
+		if (dev->last_flush_error == -1)
+			wait_for_completion(&dev->flush_wait);
 
-		ret = write_dev_flush(dev, 1);
-		if (ret)
+		if (dev->last_flush_error)
 			errors_wait++;
 	}
-	if (errors_send > info->num_tolerated_disk_barrier_failures ||
-	    errors_wait > info->num_tolerated_disk_barrier_failures)
+
+	if (errors_wait > info->num_tolerated_disk_barrier_failures)
 		return -EIO;
+
 	return 0;
 }
 
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index c7d0fbc915ca..27af3a227bfb 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -123,8 +123,8 @@ struct btrfs_device {
 	struct list_head resized_list;
 
 	/* for sending down flush barriers */
-	struct bio *flush_bio;
 	struct completion flush_wait;
+	int last_flush_error;
 
 	/* per-device scrub information */
 	struct scrub_ctx *scrub_device;
-- 
2.10.0