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author | Asias He <asias@redhat.com> | 2012-05-25 16:03:27 +0800 |
---|---|---|
committer | Ben Hutchings <ben@decadent.org.uk> | 2012-08-10 00:24:58 +0100 |
commit | e551857183b52b1af787e35b25a4e556fa0c0c75 (patch) | |
tree | 9c30de1138b56cdbd307dcb4aec8e57a02006bb8 | |
parent | 785781699d5534735e59edc74886fc59752dcabd (diff) | |
download | lwn-e551857183b52b1af787e35b25a4e556fa0c0c75.tar.gz lwn-e551857183b52b1af787e35b25a4e556fa0c0c75.zip |
virtio-blk: Use block layer provided spinlock
commit 2c95a3290919541b846bee3e0fbaa75860929f53 upstream.
Block layer will allocate a spinlock for the queue if the driver does
not provide one in blk_init_queue().
The reason to use the internal spinlock is that blk_cleanup_queue() will
switch to use the internal spinlock in the cleanup code path.
if (q->queue_lock != &q->__queue_lock)
q->queue_lock = &q->__queue_lock;
However, processes which are in D state might have taken the driver
provided spinlock, when the processes wake up, they would release the
block provided spinlock.
=====================================
[ BUG: bad unlock balance detected! ]
3.4.0-rc7+ #238 Not tainted
-------------------------------------
fio/3587 is trying to release lock (&(&q->__queue_lock)->rlock) at:
[<ffffffff813274d2>] blk_queue_bio+0x2a2/0x380
but there are no more locks to release!
other info that might help us debug this:
1 lock held by fio/3587:
#0: (&(&vblk->lock)->rlock){......}, at:
[<ffffffff8132661a>] get_request_wait+0x19a/0x250
Other drivers use block layer provided spinlock as well, e.g. SCSI.
Switching to the block layer provided spinlock saves a bit of memory and
does not increase lock contention. Performance test shows no real
difference is observed before and after this patch.
Changes in v2: Improve commit log as Michael suggested.
Cc: virtualization@lists.linux-foundation.org
Cc: kvm@vger.kernel.org
Signed-off-by: Asias He <asias@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
-rw-r--r-- | drivers/block/virtio_blk.c | 9 |
1 files changed, 3 insertions, 6 deletions
diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c index e46f2f7bba1d..650a308e444e 100644 --- a/drivers/block/virtio_blk.c +++ b/drivers/block/virtio_blk.c @@ -20,8 +20,6 @@ struct workqueue_struct *virtblk_wq; struct virtio_blk { - spinlock_t lock; - struct virtio_device *vdev; struct virtqueue *vq; @@ -62,7 +60,7 @@ static void blk_done(struct virtqueue *vq) unsigned int len; unsigned long flags; - spin_lock_irqsave(&vblk->lock, flags); + spin_lock_irqsave(vblk->disk->queue->queue_lock, flags); while ((vbr = virtqueue_get_buf(vblk->vq, &len)) != NULL) { int error; @@ -97,7 +95,7 @@ static void blk_done(struct virtqueue *vq) } /* In case queue is stopped waiting for more buffers. */ blk_start_queue(vblk->disk->queue); - spin_unlock_irqrestore(&vblk->lock, flags); + spin_unlock_irqrestore(vblk->disk->queue->queue_lock, flags); } static bool do_req(struct request_queue *q, struct virtio_blk *vblk, @@ -384,7 +382,6 @@ static int __devinit virtblk_probe(struct virtio_device *vdev) } INIT_LIST_HEAD(&vblk->reqs); - spin_lock_init(&vblk->lock); vblk->vdev = vdev; vblk->sg_elems = sg_elems; sg_init_table(vblk->sg, vblk->sg_elems); @@ -410,7 +407,7 @@ static int __devinit virtblk_probe(struct virtio_device *vdev) goto out_mempool; } - q = vblk->disk->queue = blk_init_queue(do_virtblk_request, &vblk->lock); + q = vblk->disk->queue = blk_init_queue(do_virtblk_request, NULL); if (!q) { err = -ENOMEM; goto out_put_disk; |