io_uring: indicate if io_kbuf_recycle did recycle anything

It can be useful to know if io_kbuf_recycle did actually recycle the
buffer on the request, or if it left the request alone.

Signed-off-by: Dylan Yudaken <dyudaken@gmail.com>
Link: https://lore.kernel.org/r/20231106203909.197089-2-dyudaken@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: DylanZA

io_uring/kbuf.c

@@ -52,7 +52,7 @@ static int io_buffer_add_list(struct io_ring_ctx *ctx,
 	return xa_err(xa_store(&ctx->io_bl_xa, bgid, bl, GFP_KERNEL));
 }
 
-void io_kbuf_recycle_legacy(struct io_kiocb *req, unsigned issue_flags)
+bool io_kbuf_recycle_legacy(struct io_kiocb *req, unsigned issue_flags)
 {
 	struct io_ring_ctx *ctx = req->ctx;
 	struct io_buffer_list *bl;
@@ -65,7 +65,7 @@ void io_kbuf_recycle_legacy(struct io_kiocb *req, unsigned issue_flags)
 	 * multiple use.
 	 */
 	if (req->flags & REQ_F_PARTIAL_IO)
-		return;
+		return false;
 
 	io_ring_submit_lock(ctx, issue_flags);
 
@@ -76,7 +76,7 @@ void io_kbuf_recycle_legacy(struct io_kiocb *req, unsigned issue_flags)
 	req->buf_index = buf->bgid;
 
 	io_ring_submit_unlock(ctx, issue_flags);
-	return;
+	return true;
 }
 
 unsigned int __io_put_kbuf(struct io_kiocb *req, unsigned issue_flags)

io_uring/kbuf.h

@@ -53,11 +53,11 @@ int io_unregister_pbuf_ring(struct io_ring_ctx *ctx, void __user *arg);
 
 unsigned int __io_put_kbuf(struct io_kiocb *req, unsigned issue_flags);
 
-void io_kbuf_recycle_legacy(struct io_kiocb *req, unsigned issue_flags);
+bool io_kbuf_recycle_legacy(struct io_kiocb *req, unsigned issue_flags);
 
 void *io_pbuf_get_address(struct io_ring_ctx *ctx, unsigned long bgid);
 
-static inline void io_kbuf_recycle_ring(struct io_kiocb *req)
+static inline bool io_kbuf_recycle_ring(struct io_kiocb *req)
 {
 	/*
 	 * We don't need to recycle for REQ_F_BUFFER_RING, we can just clear
@@ -80,8 +80,10 @@ static inline void io_kbuf_recycle_ring(struct io_kiocb *req)
 		} else {
 			req->buf_index = req->buf_list->bgid;
 			req->flags &= ~REQ_F_BUFFER_RING;
+			return true;
 		}
 	}
+	return false;
 }
 
 static inline bool io_do_buffer_select(struct io_kiocb *req)
@@ -91,12 +93,13 @@ static inline bool io_do_buffer_select(struct io_kiocb *req)
 	return !(req->flags & (REQ_F_BUFFER_SELECTED|REQ_F_BUFFER_RING));
 }
 
-static inline void io_kbuf_recycle(struct io_kiocb *req, unsigned issue_flags)
+static inline bool io_kbuf_recycle(struct io_kiocb *req, unsigned issue_flags)
 {
 	if (req->flags & REQ_F_BUFFER_SELECTED)
-		io_kbuf_recycle_legacy(req, issue_flags);
+		return io_kbuf_recycle_legacy(req, issue_flags);
 	if (req->flags & REQ_F_BUFFER_RING)
-		io_kbuf_recycle_ring(req);
+		return io_kbuf_recycle_ring(req);
+	return false;
 }
 
 static inline unsigned int __io_put_kbuf_list(struct io_kiocb *req,