Re: [PATCH] io_uring/uring_cmd: ensure that device supports IOPOLL

[Jens Axboe <axboe@kernel.dk>]

On 3/9/23 2:27 AM, Kanchan Joshi wrote:
> On Wed, Mar 08, 2023 at 09:30:56AM -0700, Jens Axboe wrote:
>> It's possible for a file type to support uring commands, but not
>> pollable ones. Hence before issuing one of those, we should check
>> that it is supported and error out upfront if it isn't.
> 
> Indeed, I missed that altogether.
> 
> Reviewed-by: Kanchan Joshi <joshi.k@samsung.com>

FWIW, I changed it a bit so we can fold that check in with the
other IOPOLL section. I added your Reviewed-by still, here's the
v2:

commit 03b3d6be73e81ddb7c2930d942cdd17f4cfd5ba5
Author: Jens Axboe <axboe@kernel.dk>
Date:   Wed Mar 8 09:26:13 2023 -0700

    io_uring/uring_cmd: ensure that device supports IOPOLL
    
    It's possible for a file type to support uring commands, but not
    pollable ones. Hence before issuing one of those, we should check
    that it is supported and error out upfront if it isn't.
    
    Cc: stable@vger.kernel.org
    Fixes: 5756a3a7e713 ("io_uring: add iopoll infrastructure for io_uring_cmd")
    Link: https://github.com/axboe/liburing/issues/816
    Reviewed-by: Kanchan Joshi <joshi.k@samsung.com>
    Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/io_uring/uring_cmd.c b/io_uring/uring_cmd.c
index 446a189b78b0..2e4c483075d3 100644
--- a/io_uring/uring_cmd.c
+++ b/io_uring/uring_cmd.c
@@ -108,7 +108,7 @@ int io_uring_cmd(struct io_kiocb *req, unsigned int issue_flags)
 	struct file *file = req->file;
 	int ret;
 
-	if (!req->file->f_op->uring_cmd)
+	if (!file->f_op->uring_cmd)
 		return -EOPNOTSUPP;
 
 	ret = security_uring_cmd(ioucmd);
@@ -120,6 +120,8 @@ int io_uring_cmd(struct io_kiocb *req, unsigned int issue_flags)
 	if (ctx->flags & IORING_SETUP_CQE32)
 		issue_flags |= IO_URING_F_CQE32;
 	if (ctx->flags & IORING_SETUP_IOPOLL) {
+		if (!file->f_op->uring_cmd_iopoll)
+			return -EOPNOTSUPP;
 		issue_flags |= IO_URING_F_IOPOLL;
 		req->iopoll_completed = 0;
 		WRITE_ONCE(ioucmd->cookie, NULL);

-- 
Jens Axboe