Date: Mon, 19 Dec 2016 14:06:19 -0800
From: "Darrick J. Wong" <darrick.wong@oracle.com>
To: Dave Chinner <david@fromorbit.com>
Cc: Michal Hocko <mhocko@kernel.org>, linux-mm@kvack.org,
        linux-fsdevel@vger.kernel.org,
        Andrew Morton <akpm@linux-foundation.org>,
        "Theodore Ts'o" <tytso@mit.edu>, Chris Mason <clm@fb.com>,
        David Sterba <dsterba@suse.cz>, Jan Kara <jack@suse.cz>,
        ceph-devel@vger.kernel.org, cluster-devel@redhat.com,
        linux-nfs@vger.kernel.org, logfs@logfs.org, linux-xfs@vger.kernel.org,
        linux-ext4@vger.kernel.org, linux-btrfs@vger.kernel.org,
        linux-mtd@lists.infradead.org, reiserfs-devel@vger.kernel.org,
        linux-ntfs-dev@lists.sourceforge.net,
        linux-f2fs-devel@lists.sourceforge.net, linux-afs@lists.infradead.org,
        LKML <linux-kernel@vger.kernel.org>, Michal Hocko <mhocko@suse.com>
Subject: Re: [PATCH 2/9] xfs: introduce and use KM_NOLOCKDEP to silence
 reclaim lockdep false positives
Message-ID: <20161219220619.GA7296@birch.djwong.org>
References: <20161215140715.12732-1-mhocko@kernel.org>
 <20161215140715.12732-3-mhocko@kernel.org>
 <20161219212413.GN4326@dastard>
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On Tue, Dec 20, 2016 at 08:24:13AM +1100, Dave Chinner wrote:
> On Thu, Dec 15, 2016 at 03:07:08PM +0100, Michal Hocko wrote:
> > From: Michal Hocko <mhocko@suse.com>
> > 
> > Now that the page allocator offers __GFP_NOLOCKDEP let's introduce
> > KM_NOLOCKDEP alias for the xfs allocation APIs. While we are at it
> > also change KM_NOFS users introduced by b17cb364dbbb ("xfs: fix missing
> > KM_NOFS tags to keep lockdep happy") and use the new flag for them
> > instead. There is really no reason to make these allocations contexts
> > weaker just because of the lockdep which even might not be enabled
> > in most cases.
> > 
> > Signed-off-by: Michal Hocko <mhocko@suse.com>
> 
> I'd suggest that it might be better to drop this patch for now -
> it's not necessary for the context flag changeover but does
> introduce a risk of regressions if the conversion is wrong.

I was just about to write in that while I didn't see anything obviously
wrong with the NOFS removals, I also don't know for sure that we can't
end up recursively in those code paths (specifically the directory
traversal thing).

--D

> Hence I think this is better as a completely separate series
> which audits and changes all the unnecessary KM_NOFS allocations
> in one go. I've never liked whack-a-mole style changes like this -
> do it once, do it properly....
> 
> Cheers,
> 
> Dave.
> -- 
> Dave Chinner
> david@fromorbit.com
> --
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