linux-kernel - Re: [PATCH v2] xfs: remove kmem_zalloc

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Message-ID: <20170314165745.GB28800@wotan.suse.de>
Date:   Tue, 14 Mar 2017 17:57:45 +0100
From:   "Luis R. Rodriguez" <mcgrof@...nel.org>
To:     "Darrick J. Wong" <darrick.wong@...cle.com>
Cc:     Brian Foster <bfoster@...hat.com>,
        Michal Hocko <mhocko@...nel.org>,
        Christoph Hellwig <hch@....de>,
        Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
        Xiong Zhou <xzhou@...hat.com>, linux-xfs@...r.kernel.org,
        linux-mm@...ck.org, LKML <linux-kernel@...r.kernel.org>,
        linux-fsdevel@...r.kernel.org, Michal Hocko <mhocko@...e.com>,
        Dave Chinner <david@...morbit.com>,
        sebastian.parschauer@...e.com, AlNovak@...e.com, jack@...e.cz
Subject: Re: [PATCH v2] xfs: remove kmem_zalloc_greedy

On Tue, Mar 07, 2017 at 04:35:28PM -0800, Darrick J. Wong wrote:
> The sole remaining caller of kmem_zalloc_greedy is bulkstat, which uses
> it to grab 1-4 pages for staging of inobt records.  The infinite loop in
> the greedy allocation function is causing hangs[1] in generic/269, so
> just get rid of the greedy allocator in favor of kmem_zalloc_large.
> This makes bulkstat somewhat more likely to ENOMEM if there's really no
> pages to spare, but eliminates a source of hangs.
> 
> [1] http://lkml.kernel.org/r/20170301044634.rgidgdqqiiwsmfpj%40XZHOUW.usersys.redhat.com
> 
> Signed-off-by: Darrick J. Wong <darrick.wong@...cle.com>
> ---
> v2: remove single-page fallback
> ---

Since this fixes a hang how about *at the very least* a respective Fixes tag ?
This fixes an existing hang so what are the stable considerations here ? I
realize the answer is not easy but figured its worth asking.

FWIW I trace kmem_zalloc_greedy()'s introduction back to 2006 77e4635ae1917
("[XFS] Add a greedy allocation interface, allocating within a min/max size
range.") through v2.6.19 days...

  Luis