From: Ming Lei ming.lei@redhat.com
[ Upstream commit 7678abee0867e6b7fb89aa40f6e9f575f755fb37 ]
Commit 4ce6e2db00de ("virtio-blk: Ensure no requests in virtqueues before deleting vqs.") replaces queue quiesce with queue freeze in virtio-blk's PM callbacks. And the motivation is to drain inflight IOs before suspending.
block layer's queue freeze looks very handy, but it is also easy to cause deadlock, such as, any attempt to call into bio_queue_enter() may run into deadlock if the queue is frozen in current context. There are all kinds of ->suspend() called in suspend context, so keeping queue frozen in the whole suspend context isn't one good idea. And Marek reported lockdep warning[1] caused by virtio-blk's freeze queue in virtblk_freeze().
[1] https://lore.kernel.org/linux-block/ca16370e-d646-4eee-b9cc-87277c89c43c@sam...
Given the motivation is to drain in-flight IOs, it can be done by calling freeze & unfreeze, meantime restore to previous behavior by keeping queue quiesced during suspend.
Cc: Yi Sun yi.sun@unisoc.com Cc: Michael S. Tsirkin mst@redhat.com Cc: Jason Wang jasowang@redhat.com Cc: Stefan Hajnoczi stefanha@redhat.com Cc: virtualization@lists.linux.dev Reported-by: Marek Szyprowski m.szyprowski@samsung.com Signed-off-by: Ming Lei ming.lei@redhat.com Acked-by: Stefan Hajnoczi stefanha@redhat.com Link: https://lore.kernel.org/r/20241112125821.1475793-1-ming.lei@redhat.com Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/block/virtio_blk.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c index 505026f0025c7..f730419d838d3 100644 --- a/drivers/block/virtio_blk.c +++ b/drivers/block/virtio_blk.c @@ -1205,9 +1205,12 @@ static void virtblk_remove(struct virtio_device *vdev) static int virtblk_freeze(struct virtio_device *vdev) { struct virtio_blk *vblk = vdev->priv; + struct request_queue *q = vblk->disk->queue;
/* Ensure no requests in virtqueues before deleting vqs. */ - blk_mq_freeze_queue(vblk->disk->queue); + blk_mq_freeze_queue(q); + blk_mq_quiesce_queue_nowait(q); + blk_mq_unfreeze_queue(q);
/* Ensure we don't receive any more interrupts */ virtio_reset_device(vdev); @@ -1231,8 +1234,8 @@ static int virtblk_restore(struct virtio_device *vdev) return ret;
virtio_device_ready(vdev); + blk_mq_unquiesce_queue(vblk->disk->queue);
- blk_mq_unfreeze_queue(vblk->disk->queue); return 0; } #endif