linux-kernel - Re: [PATCH] mm: add VM_STATIC flag to vmalloc and prevent from removing the areas

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Message-Id: <AC5E3048-6E2B-4DBE-80BA-AAE2D3EED969@gmail.com>
Date:   Wed, 12 Apr 2017 20:42:08 +0900
From:   Hoeun Ryu <hoeun.ryu@...il.com>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Andreas Dilger <adilger@...ger.ca>,
        Vlastimil Babka <vbabka@...e.cz>,
        Michal Hocko <mhocko@...e.com>,
        Chris Wilson <chris@...is-wilson.co.uk>,
        Ingo Molnar <mingo@...nel.org>, zijun_hu <zijun_hu@....com>,
        Matthew Wilcox <mawilcox@...rosoft.com>,
        Thomas Garnier <thgarnie@...gle.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        linux-arch@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: add VM_STATIC flag to vmalloc and prevent from removing the areas


> On Apr 12, 2017, at 3:02 PM, Christoph Hellwig <hch@...radead.org> wrote:
> 
>> On Wed, Apr 12, 2017 at 02:01:59PM +0900, Hoeun Ryu wrote:
>> vm_area_add_early/vm_area_register_early() are used to reserve vmalloc area
>> during boot process and those virtually mapped areas are never unmapped.
>> So `OR` VM_STATIC flag to the areas in vmalloc_init() when importing
>> existing vmlist entries and prevent those areas from being removed from the
>> rbtree by accident.
> 
> How would they be removed "by accident"?

I don't mean actual use-cases, but I just want to make it robust against like programming errors.