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: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 41ecbb2..ace2e8d 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -325,16 +325,6 @@
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 @@
* 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;
}