On Mon, Apr 14, 2025 at 02:39:33PM -0600, Jens Axboe wrote:
> On 4/14/25 1:58 PM, Uday Shankar wrote:
> > +static int ublk_fetch(struct io_uring_cmd *cmd, struct ublk_device *ub,
> > + struct ublk_queue *ubq, struct ublk_io *io,
> > + const struct ublksrv_io_cmd *ub_cmd,
> > + unsigned int issue_flags)
> > +{
> > + int ret = 0;
> > +
> > + if (issue_flags & IO_URING_F_NONBLOCK)
> > + return -EAGAIN;
> > +
> > + mutex_lock(&ub->mutex);
>
> This looks like overkill, if we can trylock the mutex that should surely
> be fine? And I would imagine succeed most of the time, hence making the
> inline/fastpath fine with F_NONBLOCK?
Yeah, makes sense. How about this?
diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
index cdb1543fa4a9..bf4a88cb1413 100644
--- a/drivers/block/ublk_drv.c
+++ b/drivers/block/ublk_drv.c
@@ -1832,8 +1832,8 @@ static void ublk_nosrv_work(struct work_struct *work)
/* device can only be started after all IOs are ready */
static void ublk_mark_io_ready(struct ublk_device *ub, struct ublk_queue *ubq)
+ __must_hold(&ub->mutex)
{
- mutex_lock(&ub->mutex);
ubq->nr_io_ready++;
if (ublk_queue_ready(ubq)) {
ubq->ubq_daemon = current;
@@ -1845,7 +1845,6 @@ static void ublk_mark_io_ready(struct ublk_device *ub, struct ublk_queue *ubq)
}
if (ub->nr_queues_ready == ub->dev_info.nr_hw_queues)
complete_all(&ub->completion);
- mutex_unlock(&ub->mutex);
}
static void ublk_handle_need_get_data(struct ublk_device *ub, int q_id,
@@ -1929,6 +1928,55 @@ static int ublk_unregister_io_buf(struct io_uring_cmd *cmd,
return io_buffer_unregister_bvec(cmd, index, issue_flags);
}
+static int ublk_fetch(struct io_uring_cmd *cmd, struct ublk_device *ub,
+ struct ublk_queue *ubq, struct ublk_io *io,
+ const struct ublksrv_io_cmd *ub_cmd,
+ unsigned int issue_flags)
+{
+ int ret = 0;
+
+ if (!mutex_trylock(&ub->mutex)) {
+ if (issue_flags & IO_URING_F_NONBLOCK)
+ return -EAGAIN;
+ else
+ mutex_lock(&ub->mutex);
+ }
+
+ /* UBLK_IO_FETCH_REQ is only allowed before queue is setup */
+ if (ublk_queue_ready(ubq)) {
+ ret = -EBUSY;
+ goto out;
+ }
+
+ /* allow each command to be FETCHed at most once */
+ if (io->flags & UBLK_IO_FLAG_ACTIVE) {
+ ret = -EINVAL;
+ goto out;
+ }
+
+ WARN_ON_ONCE(io->flags & UBLK_IO_FLAG_OWNED_BY_SRV);
+
+ if (ublk_need_map_io(ubq)) {
+ /*
+ * FETCH_RQ has to provide IO buffer if NEED GET
+ * DATA is not enabled
+ */
+ if (!ub_cmd->addr && !ublk_need_get_data(ubq))
+ goto out;
+ } else if (ub_cmd->addr) {
+ /* User copy requires addr to be unset */
+ ret = -EINVAL;
+ goto out;
+ }
+
+ ublk_fill_io_cmd(io, cmd, ub_cmd->addr);
+ ublk_mark_io_ready(ub, ubq);
+
+out:
+ mutex_unlock(&ub->mutex);
+ return ret;
+}
+
static int __ublk_ch_uring_cmd(struct io_uring_cmd *cmd,
unsigned int issue_flags,
const struct ublksrv_io_cmd *ub_cmd)
@@ -1985,34 +2033,7 @@ static int __ublk_ch_uring_cmd(struct io_uring_cmd *cmd,
case UBLK_IO_UNREGISTER_IO_BUF:
return ublk_unregister_io_buf(cmd, ub_cmd->addr, issue_flags);
case UBLK_IO_FETCH_REQ:
- /* UBLK_IO_FETCH_REQ is only allowed before queue is setup */
- if (ublk_queue_ready(ubq)) {
- ret = -EBUSY;
- goto out;
- }
- /*
- * The io is being handled by server, so COMMIT_RQ is expected
- * instead of FETCH_REQ
- */
- if (io->flags & UBLK_IO_FLAG_OWNED_BY_SRV)
- goto out;
-
- if (ublk_need_map_io(ubq)) {
- /*
- * FETCH_RQ has to provide IO buffer if NEED GET
- * DATA is not enabled
- */
- if (!ub_cmd->addr && !ublk_need_get_data(ubq))
- goto out;
- } else if (ub_cmd->addr) {
- /* User copy requires addr to be unset */
- ret = -EINVAL;
- goto out;
- }
-
- ublk_fill_io_cmd(io, cmd, ub_cmd->addr);
- ublk_mark_io_ready(ub, ubq);
- break;
+ return ublk_fetch(cmd, ub, ubq, io, ub_cmd, issue_flags);
case UBLK_IO_COMMIT_AND_FETCH_REQ:
req = blk_mq_tag_to_rq(ub->tag_set.tags[ub_cmd->q_id], tag);
