linux-kernel - [PATCH] ublk: complete command synchronously on error

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Message-ID: <20250225212456.2902549-1-csander@purestorage.com>
Date: Tue, 25 Feb 2025 14:24:55 -0700
From: Caleb Sander Mateos <csander@...estorage.com>
To: Keith Busch <kbusch@...nel.org>,
	Ming Lei <ming.lei@...hat.com>,
	Jens Axboe <axboe@...nel.dk>
Cc: io-uring@...r.kernel.org,
	Caleb Sander Mateos <csander@...estorage.com>,
	linux-block@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] ublk: complete command synchronously on error

In case of an error, ublk's ->uring_cmd() functions currently return
-EIOCBQUEUED and immediately call io_uring_cmd_done(). -EIOCBQUEUED and
io_uring_cmd_done() are intended for asynchronous completions. For
synchronous completions, the ->uring_cmd() function can just return the
negative return code directly. This skips io_uring_cmd_del_cancelable(),
and deferring the completion to task work. So return the error code
directly from __ublk_ch_uring_cmd() and ublk_ctrl_uring_cmd().

Update ublk_ch_uring_cmd_cb(), which currently ignores the return value
from __ublk_ch_uring_cmd(), to call io_uring_cmd_done() for synchronous
completions.

Signed-off-by: Caleb Sander Mateos <csander@...estorage.com>
---
 drivers/block/ublk_drv.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
index 529085181f35..ff648c6839c1 100644
--- a/drivers/block/ublk_drv.c
+++ b/drivers/block/ublk_drv.c
@@ -1864,14 +1864,13 @@ static int __ublk_ch_uring_cmd(struct io_uring_cmd *cmd,
 	}
 	ublk_prep_cancel(cmd, issue_flags, ubq, tag);
 	return -EIOCBQUEUED;
 
  out:
-	io_uring_cmd_done(cmd, ret, 0, issue_flags);
 	pr_devel("%s: complete: cmd op %d, tag %d ret %x io_flags %x\n",
 			__func__, cmd_op, tag, ret, io->flags);
-	return -EIOCBQUEUED;
+	return ret;
 }
 
 static inline struct request *__ublk_check_and_get_req(struct ublk_device *ub,
 		struct ublk_queue *ubq, int tag, size_t offset)
 {
@@ -1923,11 +1922,14 @@ static inline int ublk_ch_uring_cmd_local(struct io_uring_cmd *cmd,
 }
 
 static void ublk_ch_uring_cmd_cb(struct io_uring_cmd *cmd,
 		unsigned int issue_flags)
 {
-	ublk_ch_uring_cmd_local(cmd, issue_flags);
+	int ret = ublk_ch_uring_cmd_local(cmd, issue_flags);
+
+	if (ret != -EIOCBQUEUED)
+		io_uring_cmd_done(cmd, ret, 0, issue_flags);
 }
 
 static int ublk_ch_uring_cmd(struct io_uring_cmd *cmd, unsigned int issue_flags)
 {
 	if (unlikely(issue_flags & IO_URING_F_CANCEL)) {
@@ -3054,14 +3056,13 @@ static int ublk_ctrl_uring_cmd(struct io_uring_cmd *cmd,
 
  put_dev:
 	if (ub)
 		ublk_put_device(ub);
  out:
-	io_uring_cmd_done(cmd, ret, 0, issue_flags);
 	pr_devel("%s: cmd done ret %d cmd_op %x, dev id %d qid %d\n",
 			__func__, ret, cmd->cmd_op, header->dev_id, header->queue_id);
-	return -EIOCBQUEUED;
+	return ret;
 }
 
 static const struct file_operations ublk_ctl_fops = {
 	.open		= nonseekable_open,
 	.uring_cmd      = ublk_ctrl_uring_cmd,
-- 
2.45.2