[PATCH 3/4] io_uring: early return for sparse buf table registration

[Pavel Begunkov <asml.silence@gmail.com>]

We don't need to do anything after io_rsrc_data_alloc() if the goal is
to create an empty buffer table, so just return earlier and clean up the
rest of io_sqe_buffers_register(). It should be particularly nice with
IORING_RSRC_REGISTER_SPARSE.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 io_uring/rsrc.c | 32 ++++++++++++++++----------------
 1 file changed, 16 insertions(+), 16 deletions(-)

diff --git a/io_uring/rsrc.c b/io_uring/rsrc.c
index d5e29536466c..958eee7b4a47 100644
--- a/io_uring/rsrc.c
+++ b/io_uring/rsrc.c
@@ -867,28 +867,28 @@ int io_sqe_buffers_register(struct io_ring_ctx *ctx, void __user *arg,
 	if (ret)
 		return ret;
 
-	if (!arg)
-		memset(iov, 0, sizeof(*iov));
+	if (!arg) {
+		ctx->buf_table = data;
+		return 0;
+	}
 
 	for (i = 0; i < nr_args; i++) {
 		struct io_rsrc_node *node;
 		u64 tag = 0;
 
-		if (arg) {
-			uvec = (struct iovec __user *) arg;
-			iov = iovec_from_user(uvec, 1, 1, &fast_iov, ctx->compat);
-			if (IS_ERR(iov)) {
-				ret = PTR_ERR(iov);
-				break;
-			}
-			ret = io_buffer_validate(iov);
-			if (ret)
-				break;
-			if (ctx->compat)
-				arg += sizeof(struct compat_iovec);
-			else
-				arg += sizeof(struct iovec);
+		uvec = (struct iovec __user *) arg;
+		iov = iovec_from_user(uvec, 1, 1, &fast_iov, ctx->compat);
+		if (IS_ERR(iov)) {
+			ret = PTR_ERR(iov);
+			break;
 		}
+		ret = io_buffer_validate(iov);
+		if (ret)
+			break;
+		if (ctx->compat)
+			arg += sizeof(struct compat_iovec);
+		else
+			arg += sizeof(struct iovec);
 
 		if (tags) {
 			if (copy_from_user(&tag, &tags[i], sizeof(tag))) {
-- 
2.48.1