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From: Ming Lei <[email protected]>
To: Jens Axboe <[email protected]>,
	[email protected], [email protected]
Cc: [email protected],
	Miklos Szeredi <[email protected]>,
	ZiyangZhang <[email protected]>,
	Xiaoguang Wang <[email protected]>,
	Bernd Schubert <[email protected]>,
	Pavel Begunkov <[email protected]>,
	Stefan Hajnoczi <[email protected]>,
	Dan Williams <[email protected]>,
	Ming Lei <[email protected]>
Subject: [PATCH V5 12/16] block: ublk_drv: grab request reference when the request is handled by userspace
Date: Tue, 28 Mar 2023 23:09:54 +0800	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>

Add one reference counter into request pdu data, and hold this reference
in the request's lifetime. This way is always safe. In theory, the ublk
request won't be completed until fused commands are done. However, it
is userspace, and application can submit fused command at will.

Prepare for supporting zero copy, which needs to retrieve request buffer
by fused command, so we have to guarantee:

- the fused command can't succeed unless the request isn't queued

- when any fused command is successful, this request can't be freed
until all fused commands on this request are done.

Signed-off-by: Ming Lei <[email protected]>
---
 drivers/block/ublk_drv.c | 67 ++++++++++++++++++++++++++++++++++++++--
 1 file changed, 64 insertions(+), 3 deletions(-)

diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
index cca0e95a89d8..0dc8eb04b9a5 100644
--- a/drivers/block/ublk_drv.c
+++ b/drivers/block/ublk_drv.c
@@ -43,6 +43,7 @@
 #include <asm/page.h>
 #include <linux/task_work.h>
 #include <linux/namei.h>
+#include <linux/kref.h>
 #include <uapi/linux/ublk_cmd.h>
 
 #define UBLK_MINORS		(1U << MINORBITS)
@@ -62,6 +63,17 @@
 struct ublk_rq_data {
 	struct llist_node node;
 	struct callback_head work;
+
+	/*
+	 * Only for applying fused command to support zero copy:
+	 *
+	 * - if there is any fused command aiming at this request, not complete
+	 *   request until all fused commands are done
+	 *
+	 * - fused command has to fail unless this reference is grabbed
+	 *   successfully
+	 */
+	struct kref ref;
 };
 
 struct ublk_uring_cmd_pdu {
@@ -180,6 +192,9 @@ struct ublk_params_header {
 	__u32	types;
 };
 
+static inline void __ublk_complete_rq(struct request *req);
+static void ublk_complete_rq(struct kref *ref);
+
 static dev_t ublk_chr_devt;
 static struct class *ublk_chr_class;
 
@@ -288,6 +303,35 @@ static int ublk_apply_params(struct ublk_device *ub)
 	return 0;
 }
 
+static inline bool ublk_support_zc(const struct ublk_queue *ubq)
+{
+	return ubq->flags & UBLK_F_SUPPORT_ZERO_COPY;
+}
+
+static inline bool ublk_get_req_ref(const struct ublk_queue *ubq,
+		struct request *req)
+{
+	if (ublk_support_zc(ubq)) {
+		struct ublk_rq_data *data = blk_mq_rq_to_pdu(req);
+
+		return kref_get_unless_zero(&data->ref);
+	}
+
+	return true;
+}
+
+static inline void ublk_put_req_ref(const struct ublk_queue *ubq,
+		struct request *req)
+{
+	if (ublk_support_zc(ubq)) {
+		struct ublk_rq_data *data = blk_mq_rq_to_pdu(req);
+
+		kref_put(&data->ref, ublk_complete_rq);
+	} else {
+		__ublk_complete_rq(req);
+	}
+}
+
 static inline bool ublk_can_use_task_work(const struct ublk_queue *ubq)
 {
 	if (IS_BUILTIN(CONFIG_BLK_DEV_UBLK) &&
@@ -632,13 +676,19 @@ static inline bool ubq_daemon_is_dying(struct ublk_queue *ubq)
 }
 
 /* todo: handle partial completion */
-static void ublk_complete_rq(struct request *req)
+static inline void __ublk_complete_rq(struct request *req)
 {
 	struct ublk_queue *ubq = req->mq_hctx->driver_data;
 	struct ublk_io *io = &ubq->ios[req->tag];
 	unsigned int unmapped_bytes;
 	blk_status_t res = BLK_STS_OK;
 
+	/* called from ublk_abort_queue() code path */
+	if (io->flags & UBLK_IO_FLAG_ABORTED) {
+		res = BLK_STS_IOERR;
+		goto exit;
+	}
+
 	/* failed read IO if nothing is read */
 	if (!io->res && req_op(req) == REQ_OP_READ)
 		io->res = -EIO;
@@ -678,6 +728,15 @@ static void ublk_complete_rq(struct request *req)
 	blk_mq_end_request(req, res);
 }
 
+static void ublk_complete_rq(struct kref *ref)
+{
+	struct ublk_rq_data *data = container_of(ref, struct ublk_rq_data,
+			ref);
+	struct request *req = blk_mq_rq_from_pdu(data);
+
+	__ublk_complete_rq(req);
+}
+
 /*
  * Since __ublk_rq_task_work always fails requests immediately during
  * exiting, __ublk_fail_req() is only called from abort context during
@@ -696,7 +755,7 @@ static void __ublk_fail_req(struct ublk_queue *ubq, struct ublk_io *io,
 		if (ublk_queue_can_use_recovery_reissue(ubq))
 			blk_mq_requeue_request(req, false);
 		else
-			blk_mq_end_request(req, BLK_STS_IOERR);
+			ublk_put_req_ref(ubq, req);
 	}
 }
 
@@ -734,6 +793,7 @@ static inline void __ublk_rq_task_work(struct request *req,
 				       unsigned issue_flags)
 {
 	struct ublk_queue *ubq = req->mq_hctx->driver_data;
+	struct ublk_rq_data *data = blk_mq_rq_to_pdu(req);
 	int tag = req->tag;
 	struct ublk_io *io = &ubq->ios[tag];
 	unsigned int mapped_bytes;
@@ -805,6 +865,7 @@ static inline void __ublk_rq_task_work(struct request *req,
 			mapped_bytes >> 9;
 	}
 
+	kref_init(&data->ref);
 	ubq_complete_io_cmd(io, UBLK_IO_RES_OK, issue_flags);
 }
 
@@ -1017,7 +1078,7 @@ static void ublk_commit_completion(struct ublk_device *ub,
 	req = blk_mq_tag_to_rq(ub->tag_set.tags[qid], tag);
 
 	if (req && likely(!blk_should_fake_timeout(req->q)))
-		ublk_complete_rq(req);
+		ublk_put_req_ref(ubq, req);
 }
 
 /*
-- 
2.39.2


  parent reply	other threads:[~2023-03-28 15:14 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-03-28 15:09 [PATCH V5 00/16] io_uring/ublk: add IORING_OP_FUSED_CMD Ming Lei
2023-03-28 15:09 ` [PATCH V5 01/16] io_uring: increase io_kiocb->flags into 64bit Ming Lei
2023-03-28 15:09 ` [PATCH V5 02/16] io_uring: add IORING_OP_FUSED_CMD Ming Lei
2023-03-28 17:33   ` kernel test robot
2023-03-28 15:09 ` [PATCH V5 03/16] io_uring: support normal SQE for fused command Ming Lei
2023-03-28 15:09 ` [PATCH V5 04/16] io_uring: support OP_READ/OP_WRITE for fused secondary request Ming Lei
2023-03-28 15:09 ` [PATCH V5 05/16] io_uring: support OP_SEND_ZC/OP_RECV " Ming Lei
2023-03-28 15:09 ` [PATCH V5 06/16] block: ublk_drv: add common exit handling Ming Lei
2023-03-28 15:09 ` [PATCH V5 07/16] block: ublk_drv: don't consider flush request in map/unmap io Ming Lei
2023-03-28 15:09 ` [PATCH V5 08/16] block: ublk_drv: add two helpers to clean up map/unmap request Ming Lei
2023-03-28 15:09 ` [PATCH V5 09/16] block: ublk_drv: clean up several helpers Ming Lei
2023-03-28 15:09 ` [PATCH V5 10/16] block: ublk_drv: cleanup 'struct ublk_map_data' Ming Lei
2023-03-28 15:09 ` [PATCH V5 11/16] block: ublk_drv: cleanup ublk_copy_user_pages Ming Lei
2023-03-28 15:09 ` Ming Lei [this message]
2023-03-28 15:09 ` [PATCH V5 13/16] block: ublk_drv: support to copy any part of request pages Ming Lei
2023-03-28 15:09 ` [PATCH V5 14/16] block: ublk_drv: add read()/write() support for ublk char device Ming Lei
2023-03-28 15:09 ` [PATCH V5 15/16] block: ublk_drv: don't check buffer in case of zero copy Ming Lei
2023-03-28 15:09 ` [PATCH V5 16/16] block: ublk_drv: apply io_uring FUSED_CMD for supporting " Ming Lei
2023-03-29  2:57   ` Ziyang Zhang
2023-03-29  9:00     ` Ming Lei
2023-03-29 10:01       ` Ziyang Zhang
2023-03-29 10:52         ` Ming Lei
2023-04-03  8:38           ` Ziyang Zhang
2023-04-03  9:22             ` Ming Lei

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