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Commit 51684082 authored by Chris Mason's avatar Chris Mason
Browse files

Btrfs: run the backing dev more often in the submit_bio helper 



The submit_bio helper thread can decide to loop back around to
service more bios.  This commit forces it to unplug first, which helps
reduce the latency seen by submitters.

Signed-off-by: default avatarChris Mason <chris.mason@oracle.com>
parent 4849f01d

fs/btrfs/volumes.c

+10 −10
Original line number Diff line number Diff line
@@ -325,16 +325,6 @@ static noinline int run_scheduled_bios(struct btrfs_device *device) 
		num_sync_run = 0;

		blk_run_backing_dev(bdi, NULL);

	}



	cond_resched();

	if (again)

		goto loop;



	spin_lock(&device->io_lock);

	if (device->pending_bios.head || device->pending_sync_bios.head)

		goto loop_lock;

	spin_unlock(&device->io_lock);



	/*

	 * IO has already been through a long path to get here.  Checksumming,

	 * async helper threads, perhaps compression.  We've done a pretty
@@ -346,6 +336,16 @@ static noinline int run_scheduled_bios(struct btrfs_device *device) 
	 * cared about found its way down here.

	 */

	blk_run_backing_dev(bdi, NULL);



	cond_resched();

	if (again)

		goto loop;



	spin_lock(&device->io_lock);

	if (device->pending_bios.head || device->pending_sync_bios.head)

		goto loop_lock;

	spin_unlock(&device->io_lock);



done:

	return 0;

}