linux-kernel - Re: [PATCH] netfs: Fix setting of BDP

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Date: Tue, 21 May 2024 21:05:47 +0100
From: David Howells <dhowells@...hat.com>
To: Jens Axboe <axboe@...nel.dk>
Cc: dhowells@...hat.com, Steve French <stfrench@...rosoft.com>,
    Jeff Layton <jlayton@...nel.org>,
    Enzo Matsumiya <ematsumiya@...e.de>,
    Matthew Wilcox <willy@...radead.org>,
    Christian Brauner <brauner@...nel.org>, netfs@...ts.linux.dev,
    v9fs@...ts.linux.dev, linux-afs@...ts.infradead.org,
    linux-cifs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
    linux-kernel@...r.kernel.org
Subject: Re: [PATCH] netfs: Fix setting of BDP_ASYNC from iocb flags

Jens Axboe <axboe@...nel.dk> wrote:

> On 5/21/24 9:54 AM, David Howells wrote:
> > Jens Axboe <axboe@...nel.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.

David