This is a note to let you know that I've just added the patch titled
virtio-blk: Use block layer provided spinlock
to the 3.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
virtio-blk-use-block-layer-provided-spinlock.patch
and it can be found in the queue-3.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From e551857183b52b1af787e35b25a4e556fa0c0c75 Mon Sep 17 00:00:00 2001
From: Asias He <asias@xxxxxxxxxx>
Date: Fri, 25 May 2012 16:03:27 +0800
Subject: virtio-blk: Use block layer provided spinlock
From: Asias He <asias@xxxxxxxxxx>
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@xxxxxxxxxxxxxxxxxxxxxxxxxx
Cc: kvm@xxxxxxxxxxxxxxx
Signed-off-by: Asias He <asias@xxxxxxxxxx>
Acked-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
Signed-off-by: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
Cc: Li Zefan <lizefan@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/block/virtio_blk.c | 9 +++------
1 file changed, 3 insertions(+), 6 deletions(-)
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -21,8 +21,6 @@ struct workqueue_struct *virtblk_wq;
struct virtio_blk
{
- spinlock_t lock;
-
struct virtio_device *vdev;
struct virtqueue *vq;
@@ -69,7 +67,7 @@ static void blk_done(struct virtqueue *v
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;
@@ -104,7 +102,7 @@ static void blk_done(struct virtqueue *v
}
/* 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,
@@ -438,7 +436,6 @@ static int __devinit virtblk_probe(struc
}
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);
@@ -463,7 +460,7 @@ static int __devinit virtblk_probe(struc
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;
Patches currently in stable-queue which might be from asias@xxxxxxxxxx are
queue-3.4/virtio-blk-use-block-layer-provided-spinlock.patch
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