linux-kernel - Re: btrfs crash when low on memory.

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Message-ID: <CAFDW0jJ2yHftRW5Kp8sc+uxNC3oS4AZKqG0Szz2rUyxeeA0+2Q@mail.gmail.com>
Date:	Wed, 27 Feb 2013 21:10:25 +0100
From:	Ahmet Inan <ainan@...hematik.uni-freiburg.de>
To:	Josef Bacik <jbacik@...ionio.com>
Cc:	Dave Jones <davej@...hat.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	"linux-btrfs@...r.kernel.org" <linux-btrfs@...r.kernel.org>
Subject: Re: btrfs crash when low on memory.

On Wed, Feb 27, 2013 at 7:26 PM, Josef Bacik <jbacik@...ionio.com> wrote:
> On Wed, Feb 27, 2013 at 07:31:11AM -0700, Ahmet Inan wrote:
>> > Yeah we have a lot of
>> >
>> > ptr = kmalloc();
>> > BUG_ON(ptr);
>> >
>> > everywhere.  I'll fix this one up but I really need to sit down and go through
>> > all of them and make sure we do the right thing in all these places.  Thanks,
>>
>> But what would be the right thing to do when you got no memory?
>> Spinlock until you can kmalloc? Pre-reserve some memory?
>>
>
> Return ENOMEM?  We have a way to abort transactions now, if it's in a horrible
> of enough spot we can just abort the transaction and let the user deal with the
> aftermath, it's nicer than panicing.  Thanks,

youre right. i am only afraid of silent corruption of data on aborts:
our guys here trigger OOM all the time with their compilers and
numerical codes (go figure).
and until now we had no more aborts / panics because of
"vm.min_free_kbytes = 65536" and thus no corruption.

my point is:
i like a freezing computer more than an corrupting computer, even if
its a server. reboot to the rescue.

Ahmet
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