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From: Dennis Zhou <dennis@kernel.org>
To: Wang Yugui <wangyugui@e16-tech.com>
Cc: Vlastimil Babka <vbabka@suse.cz>,
	linux-mm@kvack.org, linux-btrfs@vger.kernel.org
Subject: Re: unexpected -ENOMEM from percpu_counter_init()
Date: Thu, 8 Apr 2021 02:44:38 +0000	[thread overview]
Message-ID: <YG5uFrWpwDHMhdR1@google.com> (raw)
In-Reply-To: <20210408072800.6C1F.409509F4@e16-tech.com>

On Thu, Apr 08, 2021 at 07:28:01AM +0800, Wang Yugui wrote:
> Hi,
> 
> > > > > upper caller:
> > > > >     nofs_flag = memalloc_nofs_save();
> > > > >     ret = btrfs_drew_lock_init(&root->snapshot_lock);
> > > > >     memalloc_nofs_restore(nofs_flag);
> > 
> > The issue is here. nofs is set which means percpu attempts an atomic
> > allocation. If it cannot find anything already allocated it isn't happy.
> > This was done before memalloc_nofs_{save/restore}() were pervasive.
> > 
> > Percpu should probably try to allocate some pages if possible even if
> > nofs is set.
> 
> Thanks.
> 
> I will wait for the patch, and then test it.
> 

I'm currently a bit busy with some other things. Adding support I don't
think will be much work, just a little bit tricky.

I recommend carrying what you have minus the change to reserved percpu
memory for now. If I'm the one to write it, I'll cc you.

Thanks,
Dennis


  reply	other threads:[~2021-04-08  2:44 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-01 10:51 Wang Yugui
2021-04-02  1:49 ` Wang Yugui
2021-04-07 12:35 ` Vlastimil Babka
2021-04-07 13:09   ` Wang Yugui
2021-04-07 14:56     ` Dennis Zhou
2021-04-07 23:28       ` Wang Yugui
2021-04-08  2:44         ` Dennis Zhou [this message]
2021-04-08  9:20           ` Wang Yugui
2021-04-08 13:48             ` Dennis Zhou
2021-04-08 14:28               ` Filipe Manana
2021-04-08 15:02                 ` Dennis Zhou
2021-04-09 11:39                   ` Filipe Manana
2021-04-09 13:39                     ` Dennis Zhou
2021-04-09 13:42                       ` Filipe Manana
2021-04-09  0:08               ` Wang Yugui
2021-04-09  2:14                 ` Dennis Zhou
2021-04-09  4:02                   ` Wang Yugui
2021-04-09  7:36                     ` Wang Yugui
2021-04-09  7:48                       ` Wang Yugui
2021-04-09 13:56                       ` Dennis Zhou
2021-04-10 15:29                         ` Wang Yugui
2021-04-10 15:52                           ` Dennis Zhou
2021-04-10 16:08                             ` Wang Yugui
2021-04-11 15:20                               ` Wang Yugui
2021-04-12  4:03                                 ` Dennis Zhou
2021-04-12  5:24                                   ` Wang Yugui
2021-04-09  9:52   ` Wang Yugui

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