| Message ID | 1552640264-26101-6-git-send-email-jianchao.w.wang@oracle.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | : blk-mq: use static_rqs to iterate busy tags | expand |
On Fri, 2019-03-15 at 16:57 +0800, Jianchao Wang wrote: > blk_mq_tagset_busy_iter is not safe that it could get stale request > in tags->rqs[]. Use blk_mq_queue_tag_busy_iter here. > > Signed-off-by: Jianchao Wang <jianchao.w.wang@oracle.com> > --- > drivers/block/nbd.c | 2 + > 1 file changed, 1 insertion(), 1 deletion(-) > > diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c > index 7c9a949..9e7e828 100644 > --- a/drivers/block/nbd.c > +++ b/drivers/block/nbd.c > @@ -747,7 +747,7 @@ static bool nbd_clear_req(struct request *req, void *data, bool reserved) > static void nbd_clear_que(struct nbd_device *nbd) > { > blk_mq_quiesce_queue(nbd->disk->queue); > - blk_mq_tagset_busy_iter(&nbd->tag_set, nbd_clear_req, NULL); > + blk_mq_queue_tag_busy_iter(nbd->disk->queue, nbd_clear_req, NULL, true); > blk_mq_unquiesce_queue(nbd->disk->queue); > dev_dbg(disk_to_dev(nbd->disk), "queue cleared\n"); > } Hi Jianchao, The nbd driver calls nbd_clear_que() after having called sock_shutdown(). So what makes you think that it's not safe to call blk_mq_tagset_busy_iter() from nbd_clear_que()? Thanks, Bart.
Hi Bart Thanks for your comment on this. On 3/19/19 1:16 AM, Bart Van Assche wrote: > On Fri, 2019-03-15 at 16:57 +0800, Jianchao Wang wrote: >> blk_mq_tagset_busy_iter is not safe that it could get stale request >> in tags->rqs[]. Use blk_mq_queue_tag_busy_iter here. >> >> Signed-off-by: Jianchao Wang <jianchao.w.wang@oracle.com> >> --- >> drivers/block/nbd.c | 2 + >> 1 file changed, 1 insertion(), 1 deletion(-) >> >> diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c >> index 7c9a949..9e7e828 100644 >> --- a/drivers/block/nbd.c >> +++ b/drivers/block/nbd.c >> @@ -747,7 +747,7 @@ static bool nbd_clear_req(struct request *req, void *data, bool reserved) >> static void nbd_clear_que(struct nbd_device *nbd) >> { >> blk_mq_quiesce_queue(nbd->disk->queue); >> - blk_mq_tagset_busy_iter(&nbd->tag_set, nbd_clear_req, NULL); >> + blk_mq_queue_tag_busy_iter(nbd->disk->queue, nbd_clear_req, NULL, true); >> blk_mq_unquiesce_queue(nbd->disk->queue); >> dev_dbg(disk_to_dev(nbd->disk), "queue cleared\n"); >> } > > Hi Jianchao, > > The nbd driver calls nbd_clear_que() after having called sock_shutdown(). So > what makes you think that it's not safe to call blk_mq_tagset_busy_iter() > from nbd_clear_que()? > The request_queue is not frozen, so there still could be someone enters and get request. If no io scheduler attached, the driver tag could be allocated and tags->rqs[] would be set. During this, blk_mq_tagset_busy_iter could get some stale requests in tags->rqs[] which maybe freed due to switching io scheduler to none. Thanks Jianchao
diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index 7c9a949..9e7e828 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -747,7 +747,7 @@ static bool nbd_clear_req(struct request *req, void *data, bool reserved) static void nbd_clear_que(struct nbd_device *nbd) { blk_mq_quiesce_queue(nbd->disk->queue); - blk_mq_tagset_busy_iter(&nbd->tag_set, nbd_clear_req, NULL); + blk_mq_queue_tag_busy_iter(nbd->disk->queue, nbd_clear_req, NULL, true); blk_mq_unquiesce_queue(nbd->disk->queue); dev_dbg(disk_to_dev(nbd->disk), "queue cleared\n"); }
blk_mq_tagset_busy_iter is not safe that it could get stale request in tags->rqs[]. Use blk_mq_queue_tag_busy_iter here. Signed-off-by: Jianchao Wang <jianchao.w.wang@oracle.com> --- drivers/block/nbd.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)