io_uring: rethink def->needs_async_data

needs_async_data controls allocation of async_data, and used in two
cases. 1) when async setup requires it (by io_req_prep_async() or
handler themselves), and 2) when op always needs additional space to
operate, like timeouts do.

Opcode preps already don't bother about the second case and do
allocation unconditionally, restrict needs_async_data to the first case
only and rename it into needs_async_setup.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
[axboe: update for IOPOLL fix]
Signed-off-by: Jens Axboe <axboe@kernel.dk>

fs/io_uring.c

@@ -849,8 +849,8 @@ struct io_op_def {
 	unsigned		pollout : 1;
 	/* op supports buffer selection */
 	unsigned		buffer_select : 1;
-	/* must always have async data allocated */
-	unsigned		needs_async_data : 1;
+	/* do prep async if is going to be punted */
+	unsigned		needs_async_setup : 1;
 	/* should block plug */
 	unsigned		plug : 1;
 	/* size of async data needed, if any */
@@ -864,7 +864,7 @@ static const struct io_op_def io_op_defs[] = {
 		.unbound_nonreg_file	= 1,
 		.pollin			= 1,
 		.buffer_select		= 1,
-		.needs_async_data	= 1,
+		.needs_async_setup	= 1,
 		.plug			= 1,
 		.async_size		= sizeof(struct io_async_rw),
 	},
@@ -873,7 +873,7 @@ static const struct io_op_def io_op_defs[] = {
 		.hash_reg_file		= 1,
 		.unbound_nonreg_file	= 1,
 		.pollout		= 1,
-		.needs_async_data	= 1,
+		.needs_async_setup	= 1,
 		.plug			= 1,
 		.async_size		= sizeof(struct io_async_rw),
 	},
@@ -907,7 +907,7 @@ static const struct io_op_def io_op_defs[] = {
 		.needs_file		= 1,
 		.unbound_nonreg_file	= 1,
 		.pollout		= 1,
-		.needs_async_data	= 1,
+		.needs_async_setup	= 1,
 		.async_size		= sizeof(struct io_async_msghdr),
 	},
 	[IORING_OP_RECVMSG] = {
@@ -915,11 +915,10 @@ static const struct io_op_def io_op_defs[] = {
 		.unbound_nonreg_file	= 1,
 		.pollin			= 1,
 		.buffer_select		= 1,
-		.needs_async_data	= 1,
+		.needs_async_setup	= 1,
 		.async_size		= sizeof(struct io_async_msghdr),
 	},
 	[IORING_OP_TIMEOUT] = {
-		.needs_async_data	= 1,
 		.async_size		= sizeof(struct io_timeout_data),
 	},
 	[IORING_OP_TIMEOUT_REMOVE] = {
@@ -932,14 +931,13 @@ static const struct io_op_def io_op_defs[] = {
 	},
 	[IORING_OP_ASYNC_CANCEL] = {},
 	[IORING_OP_LINK_TIMEOUT] = {
-		.needs_async_data	= 1,
 		.async_size		= sizeof(struct io_timeout_data),
 	},
 	[IORING_OP_CONNECT] = {
 		.needs_file		= 1,
 		.unbound_nonreg_file	= 1,
 		.pollout		= 1,
-		.needs_async_data	= 1,
+		.needs_async_setup	= 1,
 		.async_size		= sizeof(struct io_async_connect),
 	},
 	[IORING_OP_FALLOCATE] = {
@@ -3139,7 +3137,7 @@ static int io_setup_async_rw(struct io_kiocb *req, const struct iovec *iovec,
 			     const struct iovec *fast_iov,
 			     struct iov_iter *iter, bool force)
 {
-	if (!force && !io_op_defs[req->opcode].needs_async_data)
+	if (!force && !io_op_defs[req->opcode].needs_async_setup)
 		return 0;
 	if (!req->async_data) {
 		if (io_alloc_async_data(req)) {
@@ -5872,12 +5870,8 @@ static int io_req_prep_async(struct io_kiocb *req)
 {
 	switch (req->opcode) {
 	case IORING_OP_READV:
-	case IORING_OP_READ_FIXED:
-	case IORING_OP_READ:
 		return io_rw_prep_async(req, READ);
 	case IORING_OP_WRITEV:
-	case IORING_OP_WRITE_FIXED:
-	case IORING_OP_WRITE:
 		return io_rw_prep_async(req, WRITE);
 	case IORING_OP_SENDMSG:
 		return io_sendmsg_prep_async(req);
@@ -5891,11 +5885,10 @@ static int io_req_prep_async(struct io_kiocb *req)
 
 static int io_req_defer_prep(struct io_kiocb *req)
 {
-	if (!io_op_defs[req->opcode].needs_async_data)
-		return 0;
-	/* some opcodes init it during the inital prep */
-	if (req->async_data)
+	if (!io_op_defs[req->opcode].needs_async_setup)
 		return 0;
+	if (WARN_ON_ONCE(req->async_data))
+		return -EFAULT;
 	if (io_alloc_async_data(req))
 		return -EAGAIN;
 	return io_req_prep_async(req);