[PATCH v3 4/8] io_uring/kbuf: return buffer id in buffer selection

[Joanne Koong <joannelkoong@gmail.com>]

Return the id of the selected buffer in io_buffer_select(). This is
needed for kernel-managed buffer rings to later recycle the selected
buffer.

Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
---
 include/linux/io_uring/cmd.h   | 2 +-
 include/linux/io_uring_types.h | 2 ++
 io_uring/kbuf.c                | 7 +++++--
 3 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/include/linux/io_uring/cmd.h b/include/linux/io_uring/cmd.h
index 7ce36e143285..505a5b13e57c 100644
--- a/include/linux/io_uring/cmd.h
+++ b/include/linux/io_uring/cmd.h
@@ -78,7 +78,7 @@ void io_uring_cmd_issue_blocking(struct io_uring_cmd *ioucmd);
 
 /*
  * Select a buffer from the provided buffer group for multishot uring_cmd.
- * Returns the selected buffer address and size.
+ * Returns the selected buffer address, size, and id.
  */
 struct io_br_sel io_uring_cmd_buffer_select(struct io_uring_cmd *ioucmd,
 					    unsigned buf_group, size_t *len,
diff --git a/include/linux/io_uring_types.h b/include/linux/io_uring_types.h
index 36cc2e0346d9..5a56bb341337 100644
--- a/include/linux/io_uring_types.h
+++ b/include/linux/io_uring_types.h
@@ -100,6 +100,8 @@ struct io_br_sel {
 		void *kaddr;
 	};
 	ssize_t val;
+	/* id of the selected buffer */
+	unsigned buf_id;
 };
 
 
diff --git a/io_uring/kbuf.c b/io_uring/kbuf.c
index cb2d3bbdca67..9a681241c8b3 100644
--- a/io_uring/kbuf.c
+++ b/io_uring/kbuf.c
@@ -206,6 +206,7 @@ static struct io_br_sel io_ring_buffer_select(struct io_kiocb *req, size_t *len,
 	req->flags |= REQ_F_BUFFER_RING | REQ_F_BUFFERS_COMMIT;
 	req->buf_index = READ_ONCE(buf->bid);
 	sel.buf_list = bl;
+	sel.buf_id = req->buf_index;
 	if (bl->flags & IOBL_KERNEL_MANAGED)
 		sel.kaddr = (void *)(uintptr_t)READ_ONCE(buf->addr);
 	else
@@ -229,10 +230,12 @@ struct io_br_sel io_buffer_select(struct io_kiocb *req, size_t *len,
 
 	bl = io_buffer_get_list(ctx, buf_group);
 	if (likely(bl)) {
-		if (bl->flags & IOBL_BUF_RING)
+		if (bl->flags & IOBL_BUF_RING) {
 			sel = io_ring_buffer_select(req, len, bl, issue_flags);
-		else
+		} else {
 			sel.addr = io_provided_buffer_select(req, len, bl);
+			sel.buf_id = req->buf_index;
+		}
 	}
 	io_ring_submit_unlock(req->ctx, issue_flags);
 	return sel;
-- 
2.47.3