diff mbox series

[v5,2/4] ublk: mark ublk_queue as const for ublk_commit_and_fetch

Message ID 20250416-ublk_task_per_io-v5-2-9261ad7bff20@purestorage.com (mailing list archive)
State New
Headers show
Series ublk: decouple server threads from hctxs | expand

Commit Message

Uday Shankar April 16, 2025, 7:46 p.m. UTC 
We now allow multiple tasks to operate on I/Os belonging to the same
queue concurrently. This means that any writes to ublk_queue in the I/O
path are potential sources of data races. Try to prevent these by
marking ublk_queue pointers as const when handling COMMIT_AND_FETCH.
Move the logic for this command into its own function
ublk_commit_and_fetch. Also open code ublk_commit_completion in
ublk_commit_and_fetch to reduce the number of parameters/avoid a
redundant lookup.

Suggested-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Uday Shankar <ushankar@purestorage.com>
Reviewed-by: Caleb Sander Mateos <csander@purestorage.com>
---
 drivers/block/ublk_drv.c | 91 +++++++++++++++++++++++-------------------------
 1 file changed, 43 insertions(+), 48 deletions(-)

Comments

Ming Lei April 18, 2025, 1:35 a.m. UTC | #1 
On Wed, Apr 16, 2025 at 01:46:06PM -0600, Uday Shankar wrote:
> We now allow multiple tasks to operate on I/Os belonging to the same
> queue concurrently. This means that any writes to ublk_queue in the I/O
> path are potential sources of data races. Try to prevent these by
> marking ublk_queue pointers as const when handling COMMIT_AND_FETCH.
> Move the logic for this command into its own function
> ublk_commit_and_fetch. Also open code ublk_commit_completion in
> ublk_commit_and_fetch to reduce the number of parameters/avoid a
> redundant lookup.
> 
> Suggested-by: Ming Lei <ming.lei@redhat.com>
> Signed-off-by: Uday Shankar <ushankar@purestorage.com>
> Reviewed-by: Caleb Sander Mateos <csander@purestorage.com>
> ---
>  drivers/block/ublk_drv.c | 91 +++++++++++++++++++++++-------------------------
>  1 file changed, 43 insertions(+), 48 deletions(-)
> 
> diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
> index 4e4863d873e6593ad94c72cbf971f792df5795ae..b44cbcbcc9d1735c398dc9ac7e93f4c8736b9201 100644
> --- a/drivers/block/ublk_drv.c
> +++ b/drivers/block/ublk_drv.c
> @@ -1518,30 +1518,6 @@ static int ublk_ch_mmap(struct file *filp, struct vm_area_struct *vma)
>  	return remap_pfn_range(vma, vma->vm_start, pfn, sz, vma->vm_page_prot);
>  }
>  
> -static void ublk_commit_completion(struct ublk_device *ub,
> -		const struct ublksrv_io_cmd *ub_cmd)
> -{
> -	u32 qid = ub_cmd->q_id, tag = ub_cmd->tag;
> -	struct ublk_queue *ubq = ublk_get_queue(ub, qid);
> -	struct ublk_io *io = &ubq->ios[tag];
> -	struct request *req;
> -
> -	/* now this cmd slot is owned by nbd driver */
> -	io->flags &= ~UBLK_IO_FLAG_OWNED_BY_SRV;
> -	io->res = ub_cmd->result;
> -
> -	/* find the io request and complete */
> -	req = blk_mq_tag_to_rq(ub->tag_set.tags[qid], tag);
> -	if (WARN_ON_ONCE(unlikely(!req)))
> -		return;
> -
> -	if (req_op(req) == REQ_OP_ZONE_APPEND)
> -		req->__sector = ub_cmd->zone_append_lba;
> -
> -	if (likely(!blk_should_fake_timeout(req->q)))
> -		ublk_put_req_ref(ubq, req);
> -}
> -
>  /*
>   * Called from io task context via cancel fn, meantime quiesce ublk
>   * blk-mq queue, so we are called exclusively with blk-mq and io task
> @@ -1918,6 +1894,45 @@ static int ublk_unregister_io_buf(struct io_uring_cmd *cmd,
>  	return io_buffer_unregister_bvec(cmd, index, issue_flags);
>  }
>  
> +static int ublk_commit_and_fetch(const struct ublk_queue *ubq,
> +				 struct ublk_io *io, struct io_uring_cmd *cmd,
> +				 const struct ublksrv_io_cmd *ub_cmd,
> +				 struct request *req)

request argument can be removed by getting it inside this function directly,
and it is helpful to switch to retrieve & store it from 'ublk_io' later.

Otherwise, looks nice cleanup.


thanks,
Ming
diff mbox series

Patch

diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
index 4e4863d873e6593ad94c72cbf971f792df5795ae..b44cbcbcc9d1735c398dc9ac7e93f4c8736b9201 100644
--- a/drivers/block/ublk_drv.c
+++ b/drivers/block/ublk_drv.c
@@ -1518,30 +1518,6 @@  static int ublk_ch_mmap(struct file *filp, struct vm_area_struct *vma)
 	return remap_pfn_range(vma, vma->vm_start, pfn, sz, vma->vm_page_prot);
 }
 
-static void ublk_commit_completion(struct ublk_device *ub,
-		const struct ublksrv_io_cmd *ub_cmd)
-{
-	u32 qid = ub_cmd->q_id, tag = ub_cmd->tag;
-	struct ublk_queue *ubq = ublk_get_queue(ub, qid);
-	struct ublk_io *io = &ubq->ios[tag];
-	struct request *req;
-
-	/* now this cmd slot is owned by nbd driver */
-	io->flags &= ~UBLK_IO_FLAG_OWNED_BY_SRV;
-	io->res = ub_cmd->result;
-
-	/* find the io request and complete */
-	req = blk_mq_tag_to_rq(ub->tag_set.tags[qid], tag);
-	if (WARN_ON_ONCE(unlikely(!req)))
-		return;
-
-	if (req_op(req) == REQ_OP_ZONE_APPEND)
-		req->__sector = ub_cmd->zone_append_lba;
-
-	if (likely(!blk_should_fake_timeout(req->q)))
-		ublk_put_req_ref(ubq, req);
-}
-
 /*
  * Called from io task context via cancel fn, meantime quiesce ublk
  * blk-mq queue, so we are called exclusively with blk-mq and io task
@@ -1918,6 +1894,45 @@  static int ublk_unregister_io_buf(struct io_uring_cmd *cmd,
 	return io_buffer_unregister_bvec(cmd, index, issue_flags);
 }
 
+static int ublk_commit_and_fetch(const struct ublk_queue *ubq,
+				 struct ublk_io *io, struct io_uring_cmd *cmd,
+				 const struct ublksrv_io_cmd *ub_cmd,
+				 struct request *req)
+{
+	if (!(io->flags & UBLK_IO_FLAG_OWNED_BY_SRV))
+		return -EINVAL;
+
+	if (ublk_need_map_io(ubq)) {
+		/*
+		 * COMMIT_AND_FETCH_REQ has to provide IO buffer if
+		 * NEED GET DATA is not enabled or it is Read IO.
+		 */
+		if (!ub_cmd->addr && (!ublk_need_get_data(ubq) ||
+					req_op(req) == REQ_OP_READ))
+			return -EINVAL;
+	} else if (req_op(req) != REQ_OP_ZONE_APPEND && ub_cmd->addr) {
+		/*
+		 * User copy requires addr to be unset when command is
+		 * not zone append
+		 */
+		return -EINVAL;
+	}
+
+	ublk_fill_io_cmd(io, cmd, ub_cmd->addr);
+
+	/* now this cmd slot is owned by ublk driver */
+	io->flags &= ~UBLK_IO_FLAG_OWNED_BY_SRV;
+	io->res = ub_cmd->result;
+
+	if (req_op(req) == REQ_OP_ZONE_APPEND)
+		req->__sector = ub_cmd->zone_append_lba;
+
+	if (likely(!blk_should_fake_timeout(req->q)))
+		ublk_put_req_ref(ubq, req);
+
+	return 0;
+}
+
 static int __ublk_ch_uring_cmd(struct io_uring_cmd *cmd,
 			       unsigned int issue_flags,
 			       const struct ublksrv_io_cmd *ub_cmd)
@@ -1929,7 +1944,6 @@  static int __ublk_ch_uring_cmd(struct io_uring_cmd *cmd,
 	u32 cmd_op = cmd->cmd_op;
 	unsigned tag = ub_cmd->tag;
 	int ret = -EINVAL;
-	struct request *req;
 
 	pr_devel("%s: received: cmd op %d queue %d tag %d result %d\n",
 			__func__, cmd->cmd_op, ub_cmd->q_id, tag,
@@ -2005,30 +2019,11 @@  static int __ublk_ch_uring_cmd(struct io_uring_cmd *cmd,
 		ublk_mark_io_ready(ub, ubq);
 		break;
 	case UBLK_IO_COMMIT_AND_FETCH_REQ:
-		req = blk_mq_tag_to_rq(ub->tag_set.tags[ub_cmd->q_id], tag);
-
-		if (!(io->flags & UBLK_IO_FLAG_OWNED_BY_SRV))
-			goto out;
-
-		if (ublk_need_map_io(ubq)) {
-			/*
-			 * COMMIT_AND_FETCH_REQ has to provide IO buffer if
-			 * NEED GET DATA is not enabled or it is Read IO.
-			 */
-			if (!ub_cmd->addr && (!ublk_need_get_data(ubq) ||
-						req_op(req) == REQ_OP_READ))
-				goto out;
-		} else if (req_op(req) != REQ_OP_ZONE_APPEND && ub_cmd->addr) {
-			/*
-			 * User copy requires addr to be unset when command is
-			 * not zone append
-			 */
-			ret = -EINVAL;
+		ret = ublk_commit_and_fetch(
+			ubq, io, cmd, ub_cmd,
+			blk_mq_tag_to_rq(ub->tag_set.tags[ub_cmd->q_id], tag));
+		if (ret)
 			goto out;
-		}
-
-		ublk_fill_io_cmd(io, cmd, ub_cmd->addr);
-		ublk_commit_completion(ub, ub_cmd);
 		break;
 	case UBLK_IO_NEED_GET_DATA:
 		if (!(io->flags & UBLK_IO_FLAG_OWNED_BY_SRV))