[PATCH 1/8] ublk: factor out ublk_commit_and_fetch

[Caleb Sander Mateos <csander@purestorage.com>]

From: Uday Shankar <ushankar@purestorage.com>

Move the logic for the UBLK_IO_COMMIT_AND_FETCH_REQ opcode into its own
function. This also allows us to mark ublk_queue pointers as const for
that operation, which can help prevent data races since we may allow
concurrent operation on one ublk_queue in the future. 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>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Caleb Sander Mateos <csander@purestorage.com>
[Restore __ublk_ch_uring_cmd() req variable used in commit d6aa0c178bf8
("ublk: call ublk_dispatch_req() for handling UBLK_U_IO_NEED_GET_DATA")]
---
 drivers/block/ublk_drv.c | 90 +++++++++++++++++++---------------------
 1 file changed, 43 insertions(+), 47 deletions(-)

diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
index a183aa7648c3..7809ed585e1c 100644
--- a/drivers/block/ublk_drv.c
+++ b/drivers/block/ublk_drv.c
@@ -1587,34 +1587,10 @@ static int ublk_ch_mmap(struct file *filp, struct vm_area_struct *vma)
 
 	pfn = virt_to_phys(ublk_queue_cmd_buf(ub, q_id)) >> PAGE_SHIFT;
 	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);
-}
-
 static void __ublk_fail_req(struct ublk_queue *ubq, struct ublk_io *io,
 		struct request *req)
 {
 	WARN_ON_ONCE(io->flags & UBLK_IO_FLAG_ACTIVE);
 
@@ -2019,10 +1995,51 @@ static int ublk_fetch(struct io_uring_cmd *cmd, struct ublk_queue *ubq,
 out:
 	mutex_unlock(&ub->mutex);
 	return ret;
 }
 
+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 blk_mq_tags *tags = ubq->dev->tag_set.tags[ub_cmd->q_id];
+	struct request *req = blk_mq_tag_to_rq(tags, ub_cmd->tag);
+
+	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)
 {
 	struct ublk_device *ub = cmd->file->private_data;
@@ -2077,34 +2094,13 @@ static int __ublk_ch_uring_cmd(struct io_uring_cmd *cmd,
 		ret = ublk_fetch(cmd, ubq, io, ub_cmd->addr);
 		if (ret)
 			goto out;
 		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);
+		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))
 			goto out;
 		ublk_fill_io_cmd(io, cmd, ub_cmd->addr);
-- 
2.45.2