On Fri, 10 Sep 2010 06:30:42 am Mike Snitzer wrote: > On Thu, Sep 09 2010 at 4:30pm -0400, > Ryan Harper <ryanh@xxxxxxxxxx> wrote: > > > * Mike Snitzer <snitzer@xxxxxxxxxx> [2010-09-09 15:15]: > > > On Thu, Sep 09 2010 at 3:43pm -0400, > > > Mike Snitzer <snitzer@xxxxxxxxxx> wrote: > > > # while true ; do cat /sys/block/vda/queue/nr_requests_used && cat /sys/block/vda/serial && date && sleep 1 ; done > > > 10 > > > Thu Sep 9 16:04:40 EDT 2010 > > > 11 ... > > The qemu on the host isn't new enough to handle the request. This > > serial attribute should have had a feature bit with it (it did at one > > point in one of the previous forms of the virtio-blk serial patch > > series, but it isn't present now) so we don't expose the attribute > > unless backend can handle the request type. > > Be that as it may, it doesn't change the fact that the request created > in virtblk_get_id (via blk_make_request) isn't being properly cleaned > up. Thanks for re-sending Mike. This patch confused me at first, but it's correct. Took me a few minutes of checking though. For those not familiar with the block layer, here are the key points: 1) blk_execute_rq waits for the request to finish. 2) blk_execute_rq grabs its own reference to the req. 3) Once qemu finishes with it and sends an interrupt blk_done() releases that reference via __blk_end_request_all() 4) As caller of blk_make_request, it is our responsibility to free it after it's finished, ie. after blk_execute_rq. > This patch fixes the issue for me; Rusty and/or Christoph please > review/advise. Thanks, applied, and CC'd stable@xxxxxxxxxx (it's in 2.6.35 as well). From: Mike Snitzer <snitzer@xxxxxxxxxx> Subject: virtio-blk: fix request leak. Must drop reference taken by blk_make_request(). Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx> Signed-off-by: Rusty Russell <rusty@xxxxxxxxxxxxxxx> Cc: stable@xxxxxxxxxx # .35.x --- drivers/block/virtio_blk.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c index 1260628..831e75c 100644 --- a/drivers/block/virtio_blk.c +++ b/drivers/block/virtio_blk.c @@ -199,6 +199,7 @@ static int virtblk_get_id(struct gendisk *disk, char *id_str) struct virtio_blk *vblk = disk->private_data; struct request *req; struct bio *bio; + int err; bio = bio_map_kern(vblk->disk->queue, id_str, VIRTIO_BLK_ID_BYTES, GFP_KERNEL); @@ -212,7 +213,10 @@ static int virtblk_get_id(struct gendisk *disk, char *id_str) } req->cmd_type = REQ_TYPE_SPECIAL; - return blk_execute_rq(vblk->disk->queue, vblk->disk, req, false); + err = blk_execute_rq(vblk->disk->queue, vblk->disk, req, false); + blk_put_request(req); + + return err; } static int virtblk_locked_ioctl(struct block_device *bdev, fmode_t mode, -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
