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Date: Wed, 9 May 2018 16:53:21 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
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        Tigran Aivazian <aivazian.tigran@gmail.com>,
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Subject: Re: [PATCH] bfs: add sanity check at bfs_fill_super().
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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.