io_uring/kbuf: cleanup passing back cflags

We have various functions calculating the CQE cflags we need to pass
back, but it's all the same everywhere. Make a number of the putting
functions void, and just have the two main helps for this, io_put_kbuf()
and io_put_kbuf_comp() calculate the actual mask and pass it back.

While at it, cleanup how we put REQ_F_BUFFER_RING buffers. Before
this change, we would call into __io_put_kbuf() only to go right back
in to the header defined functions. As clearing this type of buffer
is just re-assigning the buf_index and incrementing the head, this
is very wasteful.
Signed-off-by: Jens Axboe <axboe@kernel.dk>

io_uring/kbuf.c

@@ -102,10 +102,8 @@ bool io_kbuf_recycle_legacy(struct io_kiocb *req, unsigned issue_flags)
 	return true;
 }
 
-unsigned int __io_put_kbuf(struct io_kiocb *req, unsigned issue_flags)
+void __io_put_kbuf(struct io_kiocb *req, unsigned issue_flags)
 {
-	unsigned int cflags;
-
 	/*
 	 * We can add this buffer back to two lists:
 	 *
@@ -118,21 +116,17 @@ unsigned int __io_put_kbuf(struct io_kiocb *req, unsigned issue_flags)
 	 * We migrate buffers from the comp_list to the issue cache list
 	 * when we need one.
 	 */
-	if (req->flags & REQ_F_BUFFER_RING) {
-		/* no buffers to recycle for this case */
-		cflags = __io_put_kbuf_list(req, NULL);
-	} else if (issue_flags & IO_URING_F_UNLOCKED) {
+	if (issue_flags & IO_URING_F_UNLOCKED) {
 		struct io_ring_ctx *ctx = req->ctx;
 
 		spin_lock(&ctx->completion_lock);
-		cflags = __io_put_kbuf_list(req, &ctx->io_buffers_comp);
+		__io_put_kbuf_list(req, &ctx->io_buffers_comp);
 		spin_unlock(&ctx->completion_lock);
 	} else {
 		lockdep_assert_held(&req->ctx->uring_lock);
 
-		cflags = __io_put_kbuf_list(req, &req->ctx->io_buffers_cache);
+		__io_put_kbuf_list(req, &req->ctx->io_buffers_cache);
 	}
-	return cflags;
 }
 
 static void __user *io_provided_buffer_select(struct io_kiocb *req, size_t *len,

io_uring/kbuf.h

@@ -57,7 +57,7 @@ int io_register_pbuf_status(struct io_ring_ctx *ctx, void __user *arg);
 
 void io_kbuf_mmap_list_free(struct io_ring_ctx *ctx);
 
-unsigned int __io_put_kbuf(struct io_kiocb *req, unsigned issue_flags);
+void __io_put_kbuf(struct io_kiocb *req, unsigned issue_flags);
 
 bool io_kbuf_recycle_legacy(struct io_kiocb *req, unsigned issue_flags);
 
@@ -108,41 +108,54 @@ static inline bool io_kbuf_recycle(struct io_kiocb *req, unsigned issue_flags)
 	return false;
 }
 
-static inline unsigned int __io_put_kbuf_list(struct io_kiocb *req,
-					      struct list_head *list)
+static inline void __io_put_kbuf_ring(struct io_kiocb *req)
 {
-	unsigned int ret = IORING_CQE_F_BUFFER | (req->buf_index << IORING_CQE_BUFFER_SHIFT);
-
-	if (req->flags & REQ_F_BUFFER_RING) {
 	if (req->buf_list) {
 		req->buf_index = req->buf_list->bgid;
 		req->buf_list->head++;
 	}
 	req->flags &= ~REQ_F_BUFFER_RING;
+}
+
+static inline void __io_put_kbuf_list(struct io_kiocb *req,
+				      struct list_head *list)
+{
+	if (req->flags & REQ_F_BUFFER_RING) {
+		__io_put_kbuf_ring(req);
 	} else {
 		req->buf_index = req->kbuf->bgid;
 		list_add(&req->kbuf->list, list);
 		req->flags &= ~REQ_F_BUFFER_SELECTED;
 	}
-
-	return ret;
 }
 
 static inline unsigned int io_put_kbuf_comp(struct io_kiocb *req)
 {
+	unsigned int ret;
+
 	lockdep_assert_held(&req->ctx->completion_lock);
 
 	if (!(req->flags & (REQ_F_BUFFER_SELECTED|REQ_F_BUFFER_RING)))
 		return 0;
-	return __io_put_kbuf_list(req, &req->ctx->io_buffers_comp);
+
+	ret = IORING_CQE_F_BUFFER | (req->buf_index << IORING_CQE_BUFFER_SHIFT);
+	__io_put_kbuf_list(req, &req->ctx->io_buffers_comp);
+	return ret;
 }
 
 static inline unsigned int io_put_kbuf(struct io_kiocb *req,
 				       unsigned issue_flags)
 {
+	unsigned int ret;
 
-	if (!(req->flags & (REQ_F_BUFFER_SELECTED|REQ_F_BUFFER_RING)))
+	if (!(req->flags & (REQ_F_BUFFER_RING | REQ_F_BUFFER_SELECTED)))
 		return 0;
-	return __io_put_kbuf(req, issue_flags);
+
+	ret = IORING_CQE_F_BUFFER | (req->buf_index << IORING_CQE_BUFFER_SHIFT);
+	if (req->flags & REQ_F_BUFFER_RING)
+		__io_put_kbuf_ring(req);
+	else
+		__io_put_kbuf(req, issue_flags);
+	return ret;
 }
 #endif