io_uring: kbuf: kill __io_kbuf_recycle()

__io_kbuf_recycle() is only called in io_kbuf_recycle(). Kill it and
tweak the code so that the legacy pbuf and ring pbuf code become clear

Signed-off-by: Hao Xu <howeyxu@tencent.com>
Link: https://lore.kernel.org/r/20220622055551.642370-1-hao.xu@linux.dev
Signed-off-by: Jens Axboe <axboe@kernel.dk>

io_uring/kbuf.c

@@ -37,36 +37,30 @@ static inline struct io_buffer_list *io_buffer_get_list(struct io_ring_ctx *ctx,
 	return xa_load(&ctx->io_bl_xa, bgid);
 }
 
-void __io_kbuf_recycle(struct io_kiocb *req, unsigned issue_flags)
+static int io_buffer_add_list(struct io_ring_ctx *ctx,
+			      struct io_buffer_list *bl, unsigned int bgid)
+{
+	bl->bgid = bgid;
+	if (bgid < BGID_ARRAY)
+		return 0;
+
+	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)
 {
 	struct io_ring_ctx *ctx = req->ctx;
 	struct io_buffer_list *bl;
 	struct io_buffer *buf;
 
 	/*
-	 * We don't need to recycle for REQ_F_BUFFER_RING, we can just clear
+	 * For legacy provided buffer mode, don't recycle if we already did
-	 * the flag and hence ensure that bl->head doesn't get incremented.
+	 * IO to this buffer. For ring-mapped provided buffer mode, we should
-	 * If the tail has already been incremented, hang on to it.
+	 * increment ring->head to explicitly monopolize the buffer to avoid
+	 * multiple use.
 	 */
-	if (req->flags & REQ_F_BUFFER_RING) {
+	if (req->flags & REQ_F_PARTIAL_IO)
-		if (req->buf_list) {
-			if (req->flags & REQ_F_PARTIAL_IO) {
-				/*
-				 * If we end up here, then the io_uring_lock has
-				 * been kept held since we retrieved the buffer.
-				 * For the io-wq case, we already cleared
-				 * req->buf_list when the buffer was retrieved,
-				 * hence it cannot be set here for that case.
-				 */
-				req->buf_list->head++;
-				req->buf_list = NULL;
-			} else {
-				req->buf_index = req->buf_list->bgid;
-				req->flags &= ~REQ_F_BUFFER_RING;
-			}
-		}
 		return;
-	}
 
 	io_ring_submit_lock(ctx, issue_flags);
 
@@ -77,16 +71,35 @@ void __io_kbuf_recycle(struct io_kiocb *req, unsigned issue_flags)
 	req->buf_index = buf->bgid;
 
 	io_ring_submit_unlock(ctx, issue_flags);
+	return;
 }
 
-static int io_buffer_add_list(struct io_ring_ctx *ctx,
+void io_kbuf_recycle_ring(struct io_kiocb *req)
-			      struct io_buffer_list *bl, unsigned int bgid)
 {
-	bl->bgid = bgid;
+	/*
-	if (bgid < BGID_ARRAY)
+	 * We don't need to recycle for REQ_F_BUFFER_RING, we can just clear
-		return 0;
+	 * the flag and hence ensure that bl->head doesn't get incremented.
-
+	 * If the tail has already been incremented, hang on to it.
-	return xa_err(xa_store(&ctx->io_bl_xa, bgid, bl, GFP_KERNEL));
+	 * The exception is partial io, that case we should increment bl->head
+	 * to monopolize the buffer.
+	 */
+	if (req->buf_list) {
+		if (req->flags & REQ_F_PARTIAL_IO) {
+			/*
+			 * If we end up here, then the io_uring_lock has
+			 * been kept held since we retrieved the buffer.
+			 * For the io-wq case, we already cleared
+			 * req->buf_list when the buffer was retrieved,
+			 * hence it cannot be set here for that case.
+			 */
+			req->buf_list->head++;
+			req->buf_list = NULL;
+		} else {
+			req->buf_index = req->buf_list->bgid;
+			req->flags &= ~REQ_F_BUFFER_RING;
+		}
+	}
+	return;
 }
 
 unsigned int __io_put_kbuf(struct io_kiocb *req, unsigned issue_flags)

io_uring/kbuf.h

@@ -35,7 +35,6 @@ struct io_buffer {
 
 void __user *io_buffer_select(struct io_kiocb *req, size_t *len,
 			      unsigned int issue_flags);
-void __io_kbuf_recycle(struct io_kiocb *req, unsigned issue_flags);
 void io_destroy_buffers(struct io_ring_ctx *ctx);
 
 int io_remove_buffers_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe);
@@ -49,6 +48,9 @@ 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);
+void io_kbuf_recycle_ring(struct io_kiocb *req);
+
 static inline bool io_do_buffer_select(struct io_kiocb *req)
 {
 	if (!(req->flags & REQ_F_BUFFER_SELECT))
@@ -58,18 +60,6 @@ static inline bool io_do_buffer_select(struct io_kiocb *req)
 
 static inline void io_kbuf_recycle(struct io_kiocb *req, unsigned issue_flags)
 {
-	if (!(req->flags & (REQ_F_BUFFER_SELECTED|REQ_F_BUFFER_RING)))
-		return;
-	/*
-	 * For legacy provided buffer mode, don't recycle if we already did
-	 * IO to this buffer. For ring-mapped provided buffer mode, we should
-	 * increment ring->head to explicitly monopolize the buffer to avoid
-	 * multiple use.
-	 */
-	if ((req->flags & REQ_F_BUFFER_SELECTED) &&
-	    (req->flags & REQ_F_PARTIAL_IO))
-		return;
-
 	/*
 	 * READV uses fields in `struct io_rw` (len/addr) to stash the selected
 	 * buffer data. However if that buffer is recycled the original request
@@ -78,7 +68,10 @@ static inline void io_kbuf_recycle(struct io_kiocb *req, unsigned issue_flags)
 	if (req->opcode == IORING_OP_READV)
 		return;
 
-	__io_kbuf_recycle(req, issue_flags);
+	if (req->flags & REQ_F_BUFFER_SELECTED)
+		io_kbuf_recycle_legacy(req, issue_flags);
+	if (req->flags & REQ_F_BUFFER_RING)
+		io_kbuf_recycle_ring(req);
 }
 
 static inline unsigned int __io_put_kbuf_list(struct io_kiocb *req,