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Subject: Re: [PATCH v2] mm/mremap: Don't account pages in vma_to_resize()
To:     Dmitry Safonov <dima@arista.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Brian Geffon <bgeffon@google.com>
Cc:     linux-kernel@vger.kernel.org,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Andy Lutomirski <luto@kernel.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Chen Wandun <chenwandun@huawei.com>,
        Dan Carpenter <dan.carpenter@oracle.com>,
        Dan Williams <dan.j.williams@intel.com>,
        Dave Jiang <dave.jiang@intel.com>,
        Hugh Dickins <hughd@google.com>,
        Ingo Molnar <mingo@redhat.com>, Jason Gunthorpe <jgg@ziepe.ca>,
        John Hubbard <jhubbard@nvidia.com>,
        Kefeng Wang <wangkefeng.wang@huawei.com>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        Minchan Kim <minchan@kernel.org>,
        Ralph Campbell <rcampbell@nvidia.com>,
        Russell King <linux@armlinux.org.uk>,
        Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
        Thomas Gleixner <tglx@linutronix.de>,
        Vishal Verma <vishal.l.verma@intel.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        Wei Yongjun <weiyongjun1@huawei.com>,
        Will Deacon <will@kernel.org>
References: <20210721131320.522061-1-dima@arista.com>
 <77e28552-7a13-0981-f921-cd027cb73525@gmail.com>
 <20210721130551.bbdeae56ca3ec2d0f28b0bac@linux-foundation.org>
 <48ba72b8-3da2-e438-6148-5ec22172d475@arista.com>
From:   Dmitry Safonov <0x7f454c46@gmail.com>
Message-ID: <59c2146d-210a-bbf9-0f2f-36e1e79688e7@gmail.com>
Date:   Wed, 21 Jul 2021 21:18:30 +0100
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On 7/21/21 9:08 PM, Dmitry Safonov wrote:
> On 7/21/21 9:05 PM, Andrew Morton wrote:
>> On Wed, 21 Jul 2021 14:21:54 +0100 Dmitry Safonov <0x7f454c46@gmail.com> wrote:
>>
>>>> Let's not do this.
>>>> Account memory in mremap() fast-path for growing VMAs or in move_vma()
>>>> for actually moving things. The same simpler way as it's done by
>>>> vm_stat_account(), but with a difference to call
>>>> security_vm_enough_memory_mm() before copying/adjusting VMA.
>>>>
>>>> Originally noticed by Chen Wandun:
>>>> https://lkml.kernel.org/r/20210717101942.120607-1-chenwandun@huawei.com
>>>
>>> The patch by Chen Wandun still makes sense with this v2.
>>> Heh :-)
>>
>> Should
>> https://lkml.kernel.org/r/20210717101942.120607-1-chenwandun@huawei.com
>> still be applied then?  Did you ack it?
>>
> 
> Yes, please keep that patch with
> Acked-by: Dmitry Safonov <dima@arista.com>
> 
> This one comes on the top to correct accounting for MREMAP_DONTUNMAP.

Please, also wait for reviews for this one.
I think it's correct and simplifies the complex code, but now I look
into the code again, I see that:
:	/*
:	 * MREMAP_DONTUNMAP is always a move and it does not allow resizing
:	 * in the process.
:	 */
:	if (flags & MREMAP_DONTUNMAP &&
:			(!(flags & MREMAP_MAYMOVE) || old_len != new_len))
:		return ret;

So, this part can be dropped:
> Fixes: e346b3813067 ("mm/mremap: add MREMAP_DONTUNMAP to mremap()")

But I think the patch still makes sense.

Brian, can I have your review on it?

Thanks,
          Dmitry