[PATCH v2 3/5] io_uring/uring_cmd: support dma-buf registered buffers

[Anuj Gupta <anuj1072538@gmail.com>]

From: Anuj Gupta <anuj20.g@samsung.com>

Let callers of io_uring_cmd_import_fixed() opt in to dma-buf registered
buffers with IO_URING_CMD_IMPORT_DMABUF, and attach the current map on
import.

The map has to be dropped at hardware completion rather than from
task_work. Add io_uring_cmd_hw_done() for drivers to call from end_io,
which drops the map and queues task_work, and warn if task_work is
queued with a map still attached.

Signed-off-by: Anuj Gupta <anuj20.g@samsung.com>
---
 include/linux/io_uring/cmd.h |  9 +++++++++
 io_uring/uring_cmd.c         | 28 ++++++++++++++++++++++++++--
 2 files changed, 35 insertions(+), 2 deletions(-)

diff --git a/include/linux/io_uring/cmd.h b/include/linux/io_uring/cmd.h
index 23fb66a1e2c1..d4e17c2f59fd 100644
--- a/include/linux/io_uring/cmd.h
+++ b/include/linux/io_uring/cmd.h
@@ -12,6 +12,9 @@
 /* io_uring_cmd is being issued again */
 #define IORING_URING_CMD_REISSUE	(1U << 31)
 
+/* io_uring_cmd_import_fixed() flags */
+#define IO_URING_CMD_IMPORT_DMABUF	(1U << 0)
+
 struct io_uring_cmd {
 	struct file	*file;
 	const struct io_uring_sqe *sqe;
@@ -86,6 +89,8 @@ void __io_uring_cmd_done(struct io_uring_cmd *, unsigned issue_flags);
 void __io_uring_cmd_do_in_task(struct io_uring_cmd *ioucmd,
 			    io_req_tw_func_t task_work_cb,
 			    unsigned flags);
+void io_uring_cmd_hw_done(struct io_uring_cmd *ioucmd,
+			  io_req_tw_func_t task_work_cb);
 
 /*
  * Note: the caller should never hard code @issue_flags and only use the
@@ -145,6 +150,10 @@ static inline void __io_uring_cmd_do_in_task(struct io_uring_cmd *ioucmd,
 			    io_req_tw_func_t task_work_cb, unsigned flags)
 {
 }
+static inline void io_uring_cmd_hw_done(struct io_uring_cmd *ioucmd,
+					io_req_tw_func_t task_work_cb)
+{
+}
 static inline void io_uring_cmd_mark_cancelable(struct io_uring_cmd *cmd,
 		unsigned int issue_flags)
 {
diff --git a/io_uring/uring_cmd.c b/io_uring/uring_cmd.c
index c2bc9dd242ec..c89f154190b1 100644
--- a/io_uring/uring_cmd.c
+++ b/io_uring/uring_cmd.c
@@ -10,6 +10,7 @@
 
 #include "io_uring.h"
 #include "alloc_cache.h"
+#include "dma-buf.h"
 #include "rsrc.h"
 #include "kbuf.h"
 #include "uring_cmd.h"
@@ -28,6 +29,7 @@ static void io_req_uring_cleanup(struct io_kiocb *req, unsigned int issue_flags)
 	struct io_uring_cmd *ioucmd = io_kiocb_to_cmd(req, struct io_uring_cmd);
 	struct io_async_cmd *ac = req->async_data;
 
+	io_detach_dmabuf_map(req);
 	if (issue_flags & IO_URING_F_UNLOCKED)
 		return;
 
@@ -132,12 +134,26 @@ void __io_uring_cmd_do_in_task(struct io_uring_cmd *ioucmd,
 
 	if (WARN_ON_ONCE(req->flags & REQ_F_APOLL_MULTISHOT))
 		return;
+	/* the dma-buf map must be dropped first, see io_uring_cmd_hw_done() */
+	WARN_ON_ONCE(req->dmabuf_map);
 
 	req->io_task_work.func = task_work_cb;
 	__io_req_task_work_add(req, flags);
 }
 EXPORT_SYMBOL_GPL(__io_uring_cmd_do_in_task);
 
+/*
+ * Queue completion in task context after dropping references that must be
+ * released at hardware completion rather than from task_work.
+ */
+void io_uring_cmd_hw_done(struct io_uring_cmd *ioucmd,
+			  io_req_tw_func_t task_work_cb)
+{
+	io_detach_dmabuf_map(cmd_to_io_kiocb(ioucmd));
+	__io_uring_cmd_do_in_task(ioucmd, task_work_cb, IOU_F_TWQ_LAZY_WAKE);
+}
+EXPORT_SYMBOL_GPL(io_uring_cmd_hw_done);
+
 /*
  * Called by consumers of io_uring_cmd, if they originally returned
  * -EIOCBQUEUED upon receiving the command.
@@ -257,6 +273,7 @@ int io_uring_cmd(struct io_kiocb *req, unsigned int issue_flags)
 
 	ret = file->f_op->uring_cmd(ioucmd, issue_flags);
 	if (ret == -EAGAIN) {
+		io_detach_dmabuf_map(req);
 		ioucmd->flags |= IORING_URING_CMD_REISSUE;
 		return ret;
 	}
@@ -276,13 +293,20 @@ int io_uring_cmd_import_fixed(u64 ubuf, unsigned long len, int rw,
 			      unsigned int import_flags)
 {
 	struct io_kiocb *req = cmd_to_io_kiocb(ioucmd);
+	unsigned int flags = 0;
+	int ret;
 
 	if (WARN_ON_ONCE(!(ioucmd->flags & IORING_URING_CMD_FIXED)))
 		return -EINVAL;
-	if (WARN_ON_ONCE(import_flags))
+	if (WARN_ON_ONCE(import_flags & ~IO_URING_CMD_IMPORT_DMABUF))
 		return -EINVAL;
+	if (import_flags & IO_URING_CMD_IMPORT_DMABUF)
+		flags |= IO_REGBUF_IMPORT_ALLOW_DMABUF;
 
-	return io_import_reg_buf(req, iter, ubuf, len, rw, issue_flags, 0);
+	ret = io_import_reg_buf(req, iter, ubuf, len, rw, issue_flags, flags);
+	if (ret)
+		return ret;
+	return io_attach_dmabuf_map(req, iter, issue_flags);
 }
 EXPORT_SYMBOL_GPL(io_uring_cmd_import_fixed);
 
-- 
2.43.0