From: Andrea Parri <andrea.parri@amarulasolutions.com>
To: David Howells <dhowells@redhat.com>
Cc: 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
Date: Mon, 26 Nov 2018 17:56:06 +0100 [thread overview]
Message-ID: <20181126165606.GA11282@andrea> (raw)
In-Reply-To: <26942.1543249596@warthog.procyon.org.uk>
On Mon, Nov 26, 2018 at 04:26:36PM +0000, David Howells wrote:
> 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.
Sure. My point was: those operations are currently not atomic _and_
they provide no ordering; I think that the above commit message does
a good work in explaining *why* we need atomicity, but can't say the
same for the memory-ordering requirement.
Andrea
>
> David
next prev parent reply other threads:[~2018-11-26 16:56 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-17 14:23 [PATCH 0/4] FS-Cache: Miscellaneous fixes David Howells
2018-10-17 14:23 ` [PATCH 1/4] cachefiles: fix the race between cachefiles_bury_object() and rmdir(2) David Howells
2018-10-17 14:23 ` [PATCH 2/4] fscache: Fix race in fscache_op_complete() due to split atomic_sub & read David Howells
2018-10-17 15:11 ` Andrea Parri
2018-10-17 15:32 ` David Howells
2018-10-17 16:48 ` Andrea Parri
2018-11-26 16:26 ` David Howells
2018-11-26 16:56 ` Andrea Parri [this message]
2018-11-28 14:43 ` David Howells
2018-11-28 20:45 ` Andrea Parri
2018-10-17 14:23 ` [PATCH 3/4] fscache: Fix incomplete initialisation of inline key space David Howells
2018-10-17 14:23 ` [PATCH 4/4] fscache: Fix out of bound read in long cookie keys David Howells
2018-10-18 10:03 ` [PATCH 0/4] FS-Cache: Miscellaneous fixes Greg KH
-- strict thread matches above, loose matches on Subject: below --
2018-10-17 14:16 David Howells
2018-10-17 14:17 ` [PATCH 2/4] fscache: Fix race in fscache_op_complete() due to split atomic_sub & read David Howells
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