From: Michal Hocko <mhocko@kernel.org>
To: Dave Chinner <david@fromorbit.com>
Cc: Jonathan Corbet <corbet@lwn.net>,
LKML <linux-kernel@vger.kernel.org>,
linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
"Darrick J. Wong" <darrick.wong@oracle.com>,
David Sterba <dsterba@suse.cz>
Subject: Re: [PATCH] doc: document scope NOFS, NOIO APIs
Date: Fri, 25 May 2018 10:16:24 +0200 [thread overview]
Message-ID: <20180525081624.GH11881@dhcp22.suse.cz> (raw)
In-Reply-To: <20180524221715.GY10363@dastard>
On Fri 25-05-18 08:17:15, Dave Chinner wrote:
> On Thu, May 24, 2018 at 01:43:41PM +0200, Michal Hocko wrote:
[...]
> > +FS/IO code then simply calls the appropriate save function right at the
> > +layer where a lock taken from the reclaim context (e.g. shrinker) and
> > +the corresponding restore function when the lock is released. All that
> > +ideally along with an explanation what is the reclaim context for easier
> > +maintenance.
>
> This paragraph doesn't make much sense to me. I think you're trying
> to say that we should call the appropriate save function "before
> locks are taken that a reclaim context (e.g a shrinker) might
> require access to."
>
> I think it's also worth making a note about recursive/nested
> save/restore stacking, because it's not clear from this description
> that this is allowed and will work as long as inner save/restore
> calls are fully nested inside outer save/restore contexts.
Any better?
-FS/IO code then simply calls the appropriate save function right at the
-layer where a lock taken from the reclaim context (e.g. shrinker) and
-the corresponding restore function when the lock is released. All that
-ideally along with an explanation what is the reclaim context for easier
-maintenance.
+FS/IO code then simply calls the appropriate save function before any
+lock shared with the reclaim context is taken. The corresponding
+restore function when the lock is released. All that ideally along with
+an explanation what is the reclaim context for easier maintenance.
+
+Please note that the proper pairing of save/restore function allows nesting
+so memalloc_noio_save is safe to be called from an existing NOIO or NOFS scope.
What about __vmalloc(GFP_NOFS)
==============================
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2018-05-25 8:16 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20180424183536.GF30619@thunk.org>
2018-05-24 11:43 ` [PATCH] doc: document scope NOFS, NOIO APIs Michal Hocko
2018-05-24 14:33 ` Shakeel Butt
2018-05-24 14:47 ` Michal Hocko
2018-05-24 16:37 ` Randy Dunlap
2018-05-25 7:52 ` Michal Hocko
2018-05-28 7:21 ` Nikolay Borisov
2018-05-29 8:22 ` Michal Hocko
2018-05-28 11:32 ` Vlastimil Babka
2018-05-24 20:52 ` Jonathan Corbet
2018-05-25 8:11 ` Michal Hocko
2018-05-24 22:17 ` Dave Chinner
2018-05-24 23:25 ` Theodore Y. Ts'o
2018-05-25 8:16 ` Michal Hocko [this message]
2018-05-27 12:47 ` Mike Rapoport
2018-05-28 9:21 ` Michal Hocko
2018-05-28 16:10 ` Randy Dunlap
2018-05-29 8:21 ` Michal Hocko
2018-05-27 23:48 ` Dave Chinner
2018-05-28 9:19 ` Michal Hocko
2018-05-28 22:32 ` Dave Chinner
2018-05-29 8:18 ` Michal Hocko
2018-05-29 8:26 ` [PATCH v2] " Michal Hocko
2018-05-29 10:22 ` Dave Chinner
2018-05-29 11:50 ` Mike Rapoport
2018-05-29 11:51 ` Jonathan Corbet
2018-05-29 12:37 ` Michal Hocko
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