io-uring.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Pavel Begunkov <asml.silence@gmail.com>
To: Hao Xu <haoxu@linux.alibaba.com>, Jens Axboe <axboe@kernel.dk>
Cc: io-uring@vger.kernel.org, Joseph Qi <joseph.qi@linux.alibaba.com>
Subject: Re: [PATCH 2/2] io_uring: fix failed linkchain code logic
Date: Mon, 23 Aug 2021 18:12:58 +0100	[thread overview]
Message-ID: <7ae63962-51d6-13ff-0397-78cba6eee7f5@gmail.com> (raw)
In-Reply-To: <7a680e7a-801e-4515-e67c-a3849c581d02@gmail.com>

On 8/23/21 12:02 PM, Pavel Begunkov wrote:
> On 8/23/21 4:25 AM, Hao Xu wrote:
>> Given a linkchain like this:
>> req0(link_flag)-->req1(link_flag)-->...-->reqn(no link_flag)
>>
>> There is a problem:
>>  - if some intermediate linked req like req1 's submittion fails, reqs
>>    after it won't be cancelled.
>>
>>    - sqpoll disabled: maybe it's ok since users can get the error info
>>      of req1 and stop submitting the following sqes.
>>
>>    - sqpoll enabled: definitely a problem, the following sqes will be
>>      submitted in the next round.
>>
>> The solution is to refactor the code logic to:
>>  - if a linked req's submittion fails, just mark it and the head(if it
>>    exists) as REQ_F_FAIL. Leverage req->result to indicate whether it
>>    is failed or cancelled.
>>  - submit or fail the whole chain when we come to the end of it.
> 
> This looks good to me, a couple of comments below.
> 
> 
>> Signed-off-by: Hao Xu <haoxu@linux.alibaba.com>
>> ---
>>  fs/io_uring.c | 61 +++++++++++++++++++++++++++++++++++++--------------
>>  1 file changed, 45 insertions(+), 16 deletions(-)
>>
>> diff --git a/fs/io_uring.c b/fs/io_uring.c
>> index 44b1b2b58e6a..9ae8f2a5c584 100644
>> --- a/fs/io_uring.c
>> +++ b/fs/io_uring.c
>> @@ -1776,8 +1776,6 @@ static void io_preinit_req(struct io_kiocb *req, struct io_ring_ctx *ctx)
>>  	req->ctx = ctx;
>>  	req->link = NULL;
>>  	req->async_data = NULL;
>> -	/* not necessary, but safer to zero */
>> -	req->result = 0;
> 
> Please leave it. I'm afraid of leaking stack to userspace because
                                         ^^^^^
Don't know why I called it "stack", just kernel memory/data

> ->result juggling looks prone to errors. And preinit is pretty cold
> anyway.
> 

-- 
Pavel Begunkov

  reply	other threads:[~2021-08-23 17:13 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-23  3:25 [PATCH for-5.15 v2 0/2] fix failed linkchain code logic Hao Xu
2021-08-23  3:25 ` [PATCH 1/2] io_uring: remove redundant req_set_fail() Hao Xu
2021-08-23  3:25 ` [PATCH 2/2] io_uring: fix failed linkchain code logic Hao Xu
2021-08-23 11:02   ` Pavel Begunkov
2021-08-23 17:12     ` Pavel Begunkov [this message]
2021-08-23 18:45     ` Hao Xu
2021-08-27  9:46 [PATCH for-5.15 v3 0/2] " Hao Xu
2021-08-27  9:46 ` [PATCH 2/2] io_uring: " Hao Xu

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=7ae63962-51d6-13ff-0397-78cba6eee7f5@gmail.com \
    --to=asml.silence@gmail.com \
    --cc=axboe@kernel.dk \
    --cc=haoxu@linux.alibaba.com \
    --cc=io-uring@vger.kernel.org \
    --cc=joseph.qi@linux.alibaba.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).