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From:   David Howells <dhowells@redhat.com>
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To:     Andrea Parri <andrea.parri@amarulasolutions.com>
Cc:     dhowells@redhat.com, gregkh@linux-foundation.org,
        Kiran Kumar Modukuri <kiran.modukuri@gmail.com>,
        viro@zeniv.linux.org.uk, sandeen@redhat.com,
        linux-cachefs@redhat.com, linux-fsdevel@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/4] fscache: Fix race in fscache_op_complete() due to split atomic_sub & read
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Date:   Mon, 26 Nov 2018 16:26:36 +0000
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Andrea Parri <andrea.parri@amarulasolutions.com> wrote:

> > > > Fix this by using atomic_sub_return() instead of two calls.
> > > 
> > > Seems a case for atomic_sub_return_relaxed()... why not?
> > 
> > Ummm...  In that case, should it be atomic_sub_return_release()?
> 
> Hard to tell for me: your diff./changelog is all I know about fs-cache
> ... (and this suggests -no-, given that atomic_sub() and atomic_read()
> provide no ordering...); good question though. ;-)

Yeah, that doesn't mean that it shouldn't be stricter than 'relaxed'.  It's
kind of like an unlock/release operation, so I think 'release' is probably the
minimum requirement.

David