From: Michal Hocko <mhocko@kernel.org>
To: Nikolay Borisov <kernel@kyup.com>
Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>,
Theodore Ts'o <tytso@mit.edu>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
Dmitry Monakhov <dmonakhov@virtuozzo.com>,
Johannes Weiner <hannes@cmpxchg.org>,
linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org
Subject: Re: [PATCH RFC] ext4: use __GFP_NOFAIL in ext4_free_blocks()
Date: Thu, 25 Feb 2016 10:08:39 +0100 [thread overview]
Message-ID: <20160225090839.GC17573@dhcp22.suse.cz> (raw)
In-Reply-To: <56CEC2EC.5000506@kyup.com>
On Thu 25-02-16 11:01:32, Nikolay Borisov wrote:
>
>
> On 02/24/2016 07:09 PM, Konstantin Khlebnikov wrote:
> > This might be unexpected but pages allocated for sbi->s_buddy_cache are
> > charged to current memory cgroup. So, GFP_NOFS allocation could fail if
> > current task has been killed by OOM or if current memory cgroup has no
> > free memory left. Block allocator cannot handle such failures here yet.
> >
> > Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
>
> Adding new users of GFP_NOFAIL is deprecated.
This is not true. GFP_NOFAIL should be used where the allocation failure
is no tolleratable and it is much more preferrable to doing an opencoded
endless loop over page allocator.
> Where exactly does the
> block allocator fail, I skimmed the code and failing ext4_mb_load_buddy
> seems to be handled at all call sites. There are some BUG_ONs but from
> the comments there I guess they should occur when we try to find a page
> and not allocate a new one?
I have posted a similar patch last year:
http://lkml.kernel.org/r/1438768284-30927-6-git-send-email-mhocko@kernel.org
because I could see emergency reboots when GFP_NOFS allocations were
allowed to fail.
--
Michal Hocko
SUSE Labs
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next prev parent reply other threads:[~2016-02-25 9:08 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-24 17:09 [PATCH RFC] ext4: use __GFP_NOFAIL in ext4_free_blocks() Konstantin Khlebnikov
2016-02-25 9:01 ` Nikolay Borisov
2016-02-25 9:08 ` Michal Hocko [this message]
2016-02-25 9:12 ` Nikolay Borisov
2016-02-25 10:27 ` Michal Hocko
2016-03-13 21:30 ` Theodore Ts'o
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