linux-kernel - [PATCH 2/4] io_uring/cmd: introduce IORING_URING_CMD

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Message-ID: <20250619192748.3602122-3-csander@purestorage.com>
Date: Thu, 19 Jun 2025 13:27:46 -0600
From: Caleb Sander Mateos <csander@...estorage.com>
To: Chris Mason <clm@...com>,
	Josef Bacik <josef@...icpanda.com>,
	David Sterba <dsterba@...e.com>,
	Jens Axboe <axboe@...nel.dk>
Cc: Mark Harmstone <maharmstone@...com>,
	linux-btrfs@...r.kernel.org,
	io-uring@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Caleb Sander Mateos <csander@...estorage.com>
Subject: [PATCH 2/4] io_uring/cmd: introduce IORING_URING_CMD_REISSUE flag

Add a flag IORING_URING_CMD_REISSUE that ->uring_cmd() implementations
can use to tell whether this is the first or subsequent issue of the
uring_cmd. This will allow ->uring_cmd() implementations to store
information in the io_uring_cmd's pdu across issues.

Signed-off-by: Caleb Sander Mateos <csander@...estorage.com>
---
 include/linux/io_uring/cmd.h | 2 ++
 io_uring/uring_cmd.c         | 2 ++
 2 files changed, 4 insertions(+)

diff --git a/include/linux/io_uring/cmd.h b/include/linux/io_uring/cmd.h
index 53408124c1e5..29892f54e0ac 100644
--- a/include/linux/io_uring/cmd.h
+++ b/include/linux/io_uring/cmd.h
@@ -6,10 +6,12 @@
 #include <linux/io_uring_types.h>
 #include <linux/blk-mq.h>
 
 /* only top 8 bits of sqe->uring_cmd_flags for kernel internal use */
 #define IORING_URING_CMD_CANCELABLE	(1U << 30)
+/* io_uring_cmd is being issued again */
+#define IORING_URING_CMD_REISSUE	(1U << 31)
 
 struct io_uring_cmd {
 	struct file	*file;
 	const struct io_uring_sqe *sqe;
 	/* callback to defer completions to task context */
diff --git a/io_uring/uring_cmd.c b/io_uring/uring_cmd.c
index 929cad6ee326..7cddc4c1c554 100644
--- a/io_uring/uring_cmd.c
+++ b/io_uring/uring_cmd.c
@@ -257,10 +257,12 @@ int io_uring_cmd(struct io_kiocb *req, unsigned int issue_flags)
 			req->iopoll_start = ktime_get_ns();
 		}
 	}
 
 	ret = file->f_op->uring_cmd(ioucmd, issue_flags);
+	if (ret == -EAGAIN)
+		ioucmd->flags |= IORING_URING_CMD_REISSUE;
 	if (ret == -EAGAIN || ret == -EIOCBQUEUED)
 		return ret;
 	if (ret < 0)
 		req_set_fail(req);
 	io_req_uring_cleanup(req, issue_flags);
-- 
2.45.2