linux-kernel - Re: [PATCH 1/4] fs, afs: convert afs_cell.usage from atomic_t to refcount

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Message-ID: <8877.1487784554@warthog.procyon.org.uk>
Date:   Wed, 22 Feb 2017 17:29:14 +0000
From:   David Howells <dhowells@...hat.com>
To:     "Reshetova, Elena" <elena.reshetova@...el.com>
Cc:     dhowells@...hat.com,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-afs@...ts.infradead.org" <linux-afs@...ts.infradead.org>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        Hans Liljestrand <ishkamiel@...il.com>,
        "Kees Cook" <keescook@...omium.org>,
        David Windsor <dwindsor@...il.com>
Subject: Re: [PATCH 1/4] fs, afs: convert afs_cell.usage from atomic_t to refcount_t

Reshetova, Elena <elena.reshetova@...el.com> wrote:

> Thank you very much David for testing the patches! 
> I guess for this one and other two patches it means that if we want to do the atomic_t --> refcount_t conversions, 
> we need to do +1 on the whole counting scheme to avoid issues around reaching zero.  
> Do you see this approach reasonable? I can give it a try, if it makes sense in your opinion. 

Or you could create a refcount_inc_may_resurrect() function that does allow
increment from 0.  Make it take a lock-check like the rcu functions do.

David