linux-ext4 - Re: vmalloc with GFP

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Message-ID: <20180510055825.GB32366@dhcp22.suse.cz>
Date:   Thu, 10 May 2018 07:58:25 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     "Darrick J. Wong" <darrick.wong@...cle.com>
Cc:     "Theodore Y. Ts'o" <tytso@....edu>,
        LKML <linux-kernel@...r.kernel.org>,
        Artem Bityutskiy <dedekind1@...il.com>,
        Richard Weinberger <richard@....at>,
        David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        Boris Brezillon <boris.brezillon@...e-electrons.com>,
        Marek Vasut <marek.vasut@...il.com>,
        Cyrille Pitchen <cyrille.pitchen@...ev4u.fr>,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        Steven Whitehouse <swhiteho@...hat.com>,
        Bob Peterson <rpeterso@...hat.com>,
        Trond Myklebust <trond.myklebust@...marydata.com>,
        Anna Schumaker <anna.schumaker@...app.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Philippe Ombredanne <pombredanne@...b.com>,
        Kate Stewart <kstewart@...uxfoundation.org>,
        Mikulas Patocka <mpatocka@...hat.com>,
        linux-mtd@...ts.infradead.org, linux-ext4@...r.kernel.org,
        cluster-devel@...hat.com, linux-nfs@...r.kernel.org,
        linux-mm@...ck.org
Subject: Re: vmalloc with GFP_NOFS

On Wed 09-05-18 15:02:31, Darrick J. Wong wrote:
> On Wed, May 09, 2018 at 11:04:47PM +0200, Michal Hocko wrote:
> > On Wed 09-05-18 08:13:51, Darrick J. Wong wrote:
[...]
> > > > FS resp. IO submitting code paths have to be careful when allocating
> > > 
> > > Not sure what 'FS resp. IO' means here -- 'FS and IO' ?
> > > 
> > > (Or is this one of those things where this looks like plain English text
> > > but in reality it's some sort of markup that I'm not so familiar with?)
> > > 
> > > Confused because I've seen 'resp.' used as shorthand for
> > > 'responsible'...
> > 
> > Well, I've tried to cover both. Filesystem and IO code paths which
> > allocate while in sensitive context. IO submission is kinda clear but I
> > am not sure what a general term for filsystem code paths would be. I
> > would be greatful for any hints here.
> 
> "Code paths in the filesystem and IO stacks must be careful when
> allocating memory to prevent recursion deadlocks caused by direct memory
> reclaim calling back into the FS or IO paths and blocking on already
> held resources (e.g. locks)." ?

Great, thanks!
-- 
Michal Hocko
SUSE Labs