virtio-blk: put request that was created to retrieve the device id
On Fri, 10 Sep 2010 06:30:42 am Mike Snitzer wrote:
> On Thu, Sep 09 2010 at 4:30pm -0400,
> Ryan Harper <firstname.lastname@example.org> wrote:
> > * Mike Snitzer <email@example.com> [2010-09-09 15:15]:
> > > On Thu, Sep 09 2010 at 3:43pm -0400,
> > > Mike Snitzer <firstname.lastname@example.org> 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
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
Thanks, applied, and CC'd email@example.com (it's in 2.6.35 as well).
From: Mike Snitzer <firstname.lastname@example.org>
Subject: virtio-blk: fix request leak.
Must drop reference taken by blk_make_request().
Signed-off-by: Mike Snitzer <email@example.com>
Signed-off-by: Rusty Russell <firstname.lastname@example.org>
Cc: email@example.com # .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
@@ -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,
@@ -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);
+ return err;
static int virtblk_locked_ioctl(struct block_device *bdev, fmode_t mode,
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