From: Alistair Popple <apopple@nvidia•com>
To: Mike Kravetz <mike.kravetz@oracle•com>
Cc: "Michal Hocko" <mhocko@suse•com>,
"Jérôme Glisse" <jglisse@redhat•com>,
linux-mm@kvack•org, linux-kernel@vger•kernel.org,
linuxppc-dev@lists•ozlabs.org, linux-riscv@lists•infradead.org,
linux-s390@vger•kernel.org, netdev@vger•kernel.org,
"David Hildenbrand" <david@redhat•com>,
"Peter Xu" <peterx@redhat•com>,
"Nadav Amit" <nadav.amit@gmail•com>,
"Matthew Wilcox" <willy@infradead•org>,
"Vlastimil Babka" <vbabka@suse•cz>,
"Rik van Riel" <riel@surriel•com>,
"Will Deacon" <will@kernel•org>,
"Michael Ellerman" <mpe@ellerman•id.au>,
"Palmer Dabbelt" <palmer@dabbelt•com>,
"Christian Borntraeger" <borntraeger@linux•ibm.com>,
"Dave Hansen" <dave.hansen@linux•intel.com>,
"Christian Brauner" <brauner@kernel•org>,
"Eric Dumazet" <edumazet@google•com>,
"Andrew Morton" <akpm@linux-foundation•org>
Subject: Re: [RFC PATCH] mm: remove zap_page_range and change callers to use zap_vma_page_range
Date: Thu, 05 Jan 2023 12:14:36 +1100 [thread overview]
Message-ID: <87bkndvks7.fsf@nvidia.com> (raw)
In-Reply-To: <Y6C6B08nTWusK3RI@monkey>
Mike Kravetz <mike.kravetz@oracle•com> writes:
> On 12/19/22 13:06, Michal Hocko wrote:
>> On Fri 16-12-22 11:20:12, Mike Kravetz wrote:
>> > zap_page_range was originally designed to unmap pages within an address
>> > range that could span multiple vmas. While working on [1], it was
>> > discovered that all callers of zap_page_range pass a range entirely within
>> > a single vma. In addition, the mmu notification call within zap_page
>> > range does not correctly handle ranges that span multiple vmas as calls
>> > should be vma specific.
>>
>> Could you spend a sentence or two explaining what is wrong here?
>
> Hmmmm? My assumption was that the range passed to mmu_notifier_range_init()
> was supposed to be within the specified vma. When looking into the notifier
> routines, I could not find any documentation about the usage of the vma within
> the mmu_notifier_range structure. It was introduced with commit bf198b2b34bf
> "mm/mmu_notifier: pass down vma and reasons why mmu notifier is happening".
> However, I do not see this being used today.
>
> Of course, I could be missing something, so adding Jérôme.
The only use for mmu_notifier_range->vma I can find is in
mmu_notifier_range_update_to_read_only() which was introduced in
c6d23413f81b ("mm/mmu_notifier: mmu_notifier_range_update_to_read_only()
helper"). However there are no users of that symbol so I think we can
remove it along with the mmu_notifier_range->vma field.
I will put togeather a patch to do that.
>>
>> > Instead of fixing zap_page_range, change all callers to use the new
>> > routine zap_vma_page_range. zap_vma_page_range is just a wrapper around
>> > zap_page_range_single passing in NULL zap details. The name is also
>> > more in line with other exported routines that operate within a vma.
>> > We can then remove zap_page_range.
>>
>> I would stick with zap_page_range_single rather than adding a new
>> wrapper but nothing really critical.
>
> I am fine with doing that as well. My only reason for the wrapper is that all
> callers outside mm/memory.c would pass in NULL zap details.
>
>>
>> > Also, change madvise_dontneed_single_vma to use this new routine.
>> >
>> > [1] https://lore.kernel.org/linux-mm/20221114235507.294320-2-mike.kravetz@oracle.com/
>> > Suggested-by: Peter Xu <peterx@redhat•com>
>> > Signed-off-by: Mike Kravetz <mike.kravetz@oracle•com>
>>
>> Other than that LGTM
>> Acked-by: Michal Hocko <mhocko@suse•com>
>>
>> Thanks!
>
> Thanks for taking a look.
next prev parent reply other threads:[~2023-01-05 1:21 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-12-16 19:20 [RFC PATCH] mm: remove zap_page_range and change callers to use zap_vma_page_range Mike Kravetz
2022-12-19 12:06 ` Michal Hocko
2022-12-19 19:22 ` Mike Kravetz
2023-01-05 1:14 ` Alistair Popple [this message]
2022-12-20 17:38 ` Peter Xu
2022-12-21 3:15 ` Michael Ellerman
2022-12-23 16:27 ` Christoph Hellwig
2022-12-23 21:22 ` Mike Kravetz
2022-12-29 16:22 ` Palmer Dabbelt
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