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Date: Tue, 2 Oct 2018 16:54:02 +0900
From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Subject: Re: [PATCH] mm: Avoid swapping in interrupt context
Message-ID: <20181002075402.GI598@jagdpanzerIV>
References: <1538387115-2363-1-git-send-email-amhetre@nvidia.com>
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To: Ashish Mhetre <amhetre@nvidia.com>
Cc: linux-mm@kvack.org, akpm@linux-foundation.org, vdumpa@nvidia.com, Snikam@nvidia.com, Sri Krishna chowdary <schowdary@nvidia.com>

On (10/01/18 15:15), Ashish Mhetre wrote:
> From: Sri Krishna chowdary <schowdary@nvidia.com>
> 
> Pages can be swapped out from interrupt context as well.

Well, if you do kmalloc(GFP_KERNEL) from IRQ then that's the bug
you need to fix in the first place.

> ZRAM uses zsmalloc allocator to make room for these pages.
> 
> But zsmalloc is not made to be used from interrupt context.
> This can result in a kernel Oops.

Most like not just "can" but "will" result in panic(). We have
BUG_ON(in_interrupt()) in zsmalloc.

	-ss