linux-kernel - Re: vmalloc with GFP

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Message-ID: <20180717124930.GB30926@dhcp22.suse.cz>
Date:   Tue, 17 Jul 2018 14:49:30 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     "Theodore Y. Ts'o" <tytso@....edu>
Cc:     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 Tue 24-04-18 14:35:36, Theodore Ts'o wrote:
> On Tue, Apr 24, 2018 at 10:27:12AM -0600, Michal Hocko wrote:
> > fs/ext4/xattr.c
> > 
> > What to do about this? Well, there are two things. Firstly, it would be
> > really great to double check whether the GFP_NOFS is really needed. I
> > cannot judge that because I am not familiar with the code.
> 
> *Most* of the time it's not needed, but there are times when it is.
> We could be more smart about sending down GFP_NOFS only when it is
> needed.  If we are sending too many GFP_NOFS's allocations such that
> it's causing heartburn, we could fix this.  (xattr commands are rare
> enough that I dind't think it was worth it to modulate the GFP flags
> for this particular case, but we could make it be smarter if it would
> help.)

There still seem to be ext4_kvmalloc(NOFS) callers in the ext4 code. Do
you have any plans to get rid of those?
-- 
Michal Hocko
SUSE Labs