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Message-ID: <6c7676ae-f0a3-4a9d-bcfa-f6fa0a03c928@kernel.dk>
Date: Tue, 21 May 2024 14:09:16 -0600
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Subject: Re: [PATCH] netfs: Fix setting of BDP_ASYNC from iocb flags
To: David Howells <dhowells@redhat.com>
Cc: Steve French <stfrench@microsoft.com>, Jeff Layton <jlayton@kernel.org>,
 Enzo Matsumiya <ematsumiya@suse.de>, Matthew Wilcox <willy@infradead.org>,
 Christian Brauner <brauner@kernel.org>, netfs@lists.linux.dev,
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 linux-kernel@vger.kernel.org
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 <322229.1716321947@warthog.procyon.org.uk>
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From: Jens Axboe <axboe@kernel.dk>
In-Reply-To: <322229.1716321947@warthog.procyon.org.uk>
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On 5/21/24 2:05 PM, David Howells wrote:
> Jens Axboe <axboe@kernel.dk> wrote:
> 
>> On 5/21/24 9:54 AM, David Howells wrote:
>>> Jens Axboe <axboe@kernel.dk> wrote:
>>>
>>>> However, I'll note that BDP_ASYNC is horribly named, it should be
>>>> BDP_NOWAIT instead. But that's a separate thing, fix looks correct
>>>> as-is.
>>>
>>> I thought IOCB_NOWAIT was related to RWF_NOWAIT, but apparently not from the
>>> code.
>>
>> It is, something submitted with RWF_NOWAIT should have IOCB_NOWAIT set.
>> But RWF_NOWAIT isn't the sole user of IOCB_NOWAIT, and no assumptions
>> should be made about whether something is sync or async based on whether
>> or not RWF_NOWAIT is set. Those aren't related other than _some_ proper
>> async IO will have IOCB_NOWAIT set, and others will not.
> 
> Are you sure?  RWF_NOWAIT seems to set IOCB_NOIO.

As it should, no-wait should imply not blocking on other IO. This is
completely orthogonal to whether or not it's async or sync IO.

I have a distinct feeling we're talking past each other :-)

-- 
Jens Axboe