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From: Pavel Begunkov <[email protected]>
To: Jens Axboe <[email protected]>, [email protected]
Subject: [PATCH] io_uring: fix blocking inline submission
Date: Wed,  9 Jun 2021 12:07:25 +0100	[thread overview]
Message-ID: <d60270856b8a4560a639ef5f76e55eb563633599.1623236455.git.asml.silence@gmail.com> (raw)

There is a complaint against sys_io_uring_enter() blocking if it submits
stdin reads. The problem is in __io_file_supports_async(), which
sees that it's a cdev and allows it to be processed inline.

Punt char devices using generic rules of io_file_supports_async(),
including checking for presence of *_iter() versions of rw callbacks.
Apparently, it will affect most of cdevs with some exceptions like
null and zero devices.

Signed-off-by: Pavel Begunkov <[email protected]>
---

"...For now, just ensure that anything potentially problematic is done
inline". I believe this part is outdated, but what use cases we miss?
Anything that we care about?

IMHO the best option is to do like in this patch and add
(read,write)_iter(), to places we care about.

/dev/[u]random, consoles, any else?

 fs/io_uring.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 42380ed563c4..44d1859f0dfb 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2616,7 +2616,7 @@ static bool __io_file_supports_async(struct file *file, int rw)
 			return true;
 		return false;
 	}
-	if (S_ISCHR(mode) || S_ISSOCK(mode))
+	if (S_ISSOCK(mode))
 		return true;
 	if (S_ISREG(mode)) {
 		if (IS_ENABLED(CONFIG_BLOCK) &&
-- 
2.31.1


             reply	other threads:[~2021-06-09 11:08 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-09 11:07 Pavel Begunkov [this message]
2021-06-09 12:42 ` [PATCH] io_uring: fix blocking inline submission Hao Xu
2021-06-14 10:24   ` Pavel Begunkov
2021-06-09 15:07 ` Jens Axboe
2021-06-09 15:34   ` Pavel Begunkov
2021-06-09 15:36     ` Jens Axboe
2021-06-09 15:41       ` Pavel Begunkov
2021-06-09 15:43         ` Jens Axboe
2021-06-09 15:47           ` Pavel Begunkov
2021-06-14  9:30             ` Pavel Begunkov
2021-06-09 15:38 ` Pavel Begunkov

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