io_uring: don't store bgid in req->buf_index

Pass buffer group id into the rest of helpers via struct buf_sel_arg
and remove all reassignments of req->buf_index back to bgid. Now, it
only stores buffer indexes, and the group is provided by callers.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/3ea9fa08113ecb4d9224b943e7806e80a324bdf9.1743437358.git.asml.silence@gmail.com
Link: https://lore.kernel.org/io-uring/0c01d76ff12986c2f48614db8610caff8f78c869.1743500909.git.asml.silence@gmail.com/
[axboe: fold in patch from second link]
Signed-off-by: Jens Axboe <axboe@kernel.dk>

4 files changed, 8 insertions, 11 deletions

diff --git a/include/linux/io_uring_types.h b/include/linux/io_uring_types.h
index b44d201520d8..3b467879bca8 100644
--- a/include/linux/io_uring_types.h
+++ b/include/linux/io_uring_types.h
@@ -653,8 +653,7 @@ struct io_kiocb {
 	u8				iopoll_completed;
 	/*
 	 * Can be either a fixed buffer index, or used with provided buffers.
-	 * For the latter, before issue it points to the buffer group ID,
-	 * and after selection it points to the buffer ID itself.
+	 * For the latter, it points to the selected buffer ID.
 	 */
 	u16				buf_index;
 
diff --git a/io_uring/kbuf.c b/io_uring/kbuf.c
index f195876732be..1cf0d2c01287 100644
--- a/io_uring/kbuf.c
+++ b/io_uring/kbuf.c
@@ -92,7 +92,6 @@ void io_kbuf_drop_legacy(struct io_kiocb *req)
 {
 	if (WARN_ON_ONCE(!(req->flags & REQ_F_BUFFER_SELECTED)))
 		return;
-	req->buf_index = req->kbuf->bgid;
 	req->flags &= ~REQ_F_BUFFER_SELECTED;
 	kfree(req->kbuf);
 	req->kbuf = NULL;
@@ -110,7 +109,6 @@ bool io_kbuf_recycle_legacy(struct io_kiocb *req, unsigned issue_flags)
 	bl = io_buffer_get_list(ctx, buf->bgid);
 	list_add(&buf->list, &bl->buf_list);
 	req->flags &= ~REQ_F_BUFFER_SELECTED;
-	req->buf_index = buf->bgid;
 
 	io_ring_submit_unlock(ctx, issue_flags);
 	return true;
@@ -302,7 +300,7 @@ int io_buffers_select(struct io_kiocb *req, struct buf_sel_arg *arg,
 	int ret = -ENOENT;
 
 	io_ring_submit_lock(ctx, issue_flags);
-	bl = io_buffer_get_list(ctx, req->buf_index);
+	bl = io_buffer_get_list(ctx, arg->buf_group);
 	if (unlikely(!bl))
 		goto out_unlock;
 
@@ -335,7 +333,7 @@ int io_buffers_peek(struct io_kiocb *req, struct buf_sel_arg *arg)
 
 	lockdep_assert_held(&ctx->uring_lock);
 
-	bl = io_buffer_get_list(ctx, req->buf_index);
+	bl = io_buffer_get_list(ctx, arg->buf_group);
 	if (unlikely(!bl))
 		return -ENOENT;
 
@@ -355,10 +353,9 @@ static inline bool __io_put_kbuf_ring(struct io_kiocb *req, int len, int nr)
 	struct io_buffer_list *bl = req->buf_list;
 	bool ret = true;
 
-	if (bl) {
+	if (bl)
 		ret = io_kbuf_commit(req, bl, len, nr);
-		req->buf_index = bl->bgid;
-	}
+
 	req->flags &= ~REQ_F_BUFFER_RING;
 	return ret;
 }
diff --git a/io_uring/kbuf.h b/io_uring/kbuf.h
index 09129115f3ef..0798a732e6cb 100644
--- a/io_uring/kbuf.h
+++ b/io_uring/kbuf.h
@@ -55,6 +55,7 @@ struct buf_sel_arg {
 	size_t max_len;
 	unsigned short nr_iovs;
 	unsigned short mode;
+	unsigned buf_group;
 };
 
 void __user *io_buffer_select(struct io_kiocb *req, size_t *len,
@@ -94,7 +95,6 @@ static inline bool io_kbuf_recycle_ring(struct io_kiocb *req)
 	 * to monopolize the buffer.
 	 */
 	if (req->buf_list) {
-		req->buf_index = req->buf_list->bgid;
 		req->flags &= ~(REQ_F_BUFFER_RING|REQ_F_BUFFERS_COMMIT);
 		return true;
 	}
diff --git a/io_uring/net.c b/io_uring/net.c
index 6314b1583c8c..5f1a519d1fc6 100644
--- a/io_uring/net.c
+++ b/io_uring/net.c
@@ -190,7 +190,6 @@ static inline void io_mshot_prep_retry(struct io_kiocb *req,
 	sr->done_io = 0;
 	sr->retry = false;
 	sr->len = 0; /* get from the provided buffer */
-	req->buf_index = sr->buf_group;
 }
 
 static int io_net_import_vec(struct io_kiocb *req, struct io_async_msghdr *iomsg,
@@ -568,6 +567,7 @@ static int io_send_select_buffer(struct io_kiocb *req, unsigned int issue_flags,
 		.iovs = &kmsg->fast_iov,
 		.max_len = min_not_zero(sr->len, INT_MAX),
 		.nr_iovs = 1,
+		.buf_group = sr->buf_group,
 	};
 
 	if (kmsg->vec.iovec) {
@@ -1056,6 +1056,7 @@ static int io_recv_buf_select(struct io_kiocb *req, struct io_async_msghdr *kmsg
 			.iovs = &kmsg->fast_iov,
 			.nr_iovs = 1,
 			.mode = KBUF_MODE_EXPAND,
+			.buf_group = sr->buf_group,
 		};
 
 		if (kmsg->vec.iovec) {