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Subject: Re: [PATCH] bfs: add sanity check at bfs_fill_super().
To: Tigran Aivazian <aivazian.tigran@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
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From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
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Date: Wed, 13 Jun 2018 22:33:08 +0900
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On 2018/05/10 8:53, Andrew Morton wrote:
> On Thu, 10 May 2018 08:46:18 +0900 Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp> wrote:
> 
>>> page-allocation-fauilure warning and a nice backtrace, etc.  Why
>>> suppress all of that and add our custom warning instead?
>>
>> the intent of this patch is to avoid panic() by panic_on_warn == 1
>> due to hitting
>>
>> struct kmem_cache *kmalloc_slab(size_t size, gfp_t flags)
>> {
>>         unsigned int index;
>>
>>         if (unlikely(size > KMALLOC_MAX_SIZE)) {
>>                 WARN_ON_ONCE(!(flags & __GFP_NOWARN)); /* <= this line */
>>                 return NULL;
>>         }
>>
>> when size to allocate is controlled by the filesystem image.
> 
> Well, the same could happen with many many memory-allocation sites. 
> What's special about BFS?  If someone sets panic_on_warn=1 then
> presumably this panic is the behaviour they wanted in this case.
> 

Tigran, this patch is stalling. Do we want to apply this? Or, ignore as invalid?

errors=panic mount option for ext4 case was ignored as invalid.
http://lkml.kernel.org/r/CACT4Y+Z+2YW_VALJzzQr6hLsviA=dXk3iFqwVf+P5zqojeC9Zg@mail.gmail.com

But I prefer avoiding crashes if we can fix it.