From: Hoeun Ryu <hoeun.ryu@gmail.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: hch@infradead.org, khandual@linux.vnet.ibm.com,
Andrew Morton <akpm@linux-foundation.org>,
Roman Pen <r.peniaev@gmail.com>,
Andreas Dilger <adilger@dilger.ca>,
Andrey Ryabinin <aryabinin@virtuozzo.com>,
Chris Wilson <chris@chris-wilson.co.uk>,
Ingo Molnar <mingo@kernel.org>, zijun_hu <zijun_hu@htc.com>,
Matthew Wilcox <mawilcox@microsoft.com>,
Thomas Garnier <thgarnie@google.com>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
linux-arch@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] mm: add VM_STATIC flag to vmalloc and prevent from removing the areas
Date: Wed, 19 Apr 2017 14:32:14 +0900 [thread overview]
Message-ID: <CEE04495-95EF-4A98-A85F-5C3537072BCE@gmail.com> (raw)
In-Reply-To: <20170418065946.GB22360@dhcp22.suse.cz>
> On Apr 18, 2017, at 3:59 PM, Michal Hocko <mhocko@kernel.org> wrote:
>
>> On Tue 18-04-17 14:48:39, 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.
>
> Has this been a problem in the past or currently so that it is worth
> handling?
>
>> This flags can be also used by other vmalloc APIs to
>> specify that the area will never go away.
>
> Do we have a user for that?
>
>> This makes remove_vm_area() more robust against other kind of errors (eg.
>> programming errors).
>
> Well, yes it will help to prevent from vfree(early_mem) but we have 4
> users of vm_area_register_early so I am really wondering whether this is
> worth additional code. It would really help to understand your
> motivation for the patch if we were explicit about the problem you are
> trying to solve.
I just think that it would be good to make it robust against various kind of errors.
You might think that's not an enough reason to do so though.
>
> Thanks
>
> --
> Michal Hocko
> SUSE Labs
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next prev parent reply other threads:[~2017-04-19 5:32 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-18 5:48 Hoeun Ryu
2017-04-18 6:59 ` Michal Hocko
2017-04-19 5:32 ` Hoeun Ryu [this message]
-- strict thread matches above, loose matches on Subject: below --
2017-04-18 2:26 Hoeun Ryu
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