From: Vlastimil Babka <vbabka@suse.cz>
To: Hugh Dickins <hughd@google.com>,
Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@suse.com>,
"Kirill A. Shutemov" <kirill@shutemov.name>,
Matthew Wilcox <willy@infradead.org>,
David Hildenbrand <david@redhat.com>,
Alistair Popple <apopple@nvidia.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Rik van Riel <riel@surriel.com>,
Suren Baghdasaryan <surenb@google.com>,
Yu Zhao <yuzhao@google.com>, Greg Thelen <gthelen@google.com>,
Shakeel Butt <shakeelb@google.com>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH 02/13] mm/munlock: delete FOLL_MLOCK and FOLL_POPULATE
Date: Thu, 10 Feb 2022 12:35:19 +0100 [thread overview]
Message-ID: <1699e1b3-0508-4561-a7ec-052f382ca3c8@suse.cz> (raw)
In-Reply-To: <2b5eee76-183f-bd97-2e9d-f5ff8df63db@google.com>
On 2/6/22 22:32, Hugh Dickins wrote:
> If counting page mlocks, we must not double-count: follow_page_pte() can
> tell if a page has already been Mlocked or not, but cannot tell if a pte
> has already been counted or not: that will have to be done when the pte
> is mapped in (which lru_cache_add_inactive_or_unevictable() already tracks
> for new anon pages, but there's no such tracking yet for others).
>
> Delete all the FOLL_MLOCK code - faulting in the missing pages will do
> all that is necessary, without special mlock_vma_page() calls from here.
>
> But then FOLL_POPULATE turns out to serve no purpose - it was there so
> that its absence would tell faultin_page() not to faultin page when
> setting up VM_LOCKONFAULT areas; but if there's no special work needed
> here for mlock, then there's no work at all here for VM_LOCKONFAULT.
>
> Have I got that right? I've not looked into the history, but see that
> FOLL_POPULATE goes back before VM_LOCKONFAULT: did it serve a different
> purpose before? Ah, yes, it was used to skip the old stack guard page.
>
> And is it intentional that COW is not broken on existing pages when
> setting up a VM_LOCKONFAULT area? I can see that being argued either
> way, and have no reason to disagree with current behaviour.
Yeah I think it's consistent with the two usecases stated for VM_LOCKONFAULT:
https://lore.kernel.org/all/1441720742-7803-1-git-send-email-emunson@akamai.com/
> Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
next prev parent reply other threads:[~2022-02-10 11:35 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-06 21:27 [PATCH 00/13] mm/munlock: rework of mlock+munlock page handling Hugh Dickins
2022-02-06 21:30 ` [PATCH 01/13] mm/munlock: delete page_mlock() and all its works Hugh Dickins
2022-02-09 18:31 ` Vlastimil Babka
2022-02-09 22:28 ` Hugh Dickins
2022-02-10 9:52 ` Vlastimil Babka
2022-02-14 6:52 ` Hugh Dickins
2022-02-14 6:59 ` [PATCH v2 " Hugh Dickins
2022-02-14 10:07 ` Vlastimil Babka
2022-02-06 21:32 ` [PATCH 02/13] mm/munlock: delete FOLL_MLOCK and FOLL_POPULATE Hugh Dickins
2022-02-10 11:35 ` Vlastimil Babka [this message]
2022-02-06 21:34 ` [PATCH 03/13] mm/munlock: delete munlock_vma_pages_all(), allow oomreap Hugh Dickins
2022-02-10 15:30 ` Vlastimil Babka
2022-02-06 21:36 ` [PATCH 04/13] mm/munlock: rmap call mlock_vma_page() munlock_vma_page() Hugh Dickins
2022-02-11 10:29 ` Vlastimil Babka
2022-02-14 7:05 ` [PATCH v2 " Hugh Dickins
2022-02-06 21:38 ` [PATCH 05/13] mm/munlock: replace clear_page_mlock() by final clearance Hugh Dickins
2022-02-11 11:42 ` Vlastimil Babka
2022-02-06 21:38 ` [PATCH 00/13] mm/munlock: rework of mlock+munlock page handling Matthew Wilcox
2022-02-07 18:20 ` Hugh Dickins
2022-02-06 21:40 ` [PATCH 06/13] mm/munlock: maintain page->mlock_count while unevictable Hugh Dickins
2022-02-11 12:27 ` Vlastimil Babka
2022-02-14 5:42 ` Hugh Dickins
2022-02-11 18:07 ` Vlastimil Babka
2022-02-14 6:28 ` Hugh Dickins
2022-02-06 21:42 ` [PATCH 07/13] mm/munlock: mlock_pte_range() when mlocking or munlocking Hugh Dickins
2022-02-11 16:45 ` Vlastimil Babka
2022-02-14 6:32 ` Hugh Dickins
2022-02-14 7:09 ` [PATCH v2 " Hugh Dickins
2022-02-06 21:43 ` [PATCH 08/13] mm/migrate: __unmap_and_move() push good newpage to LRU Hugh Dickins
2022-02-11 17:19 ` Vlastimil Babka
2022-02-06 21:45 ` [PATCH 09/13] mm/munlock: delete smp_mb() from __pagevec_lru_add_fn() Hugh Dickins
2022-02-11 17:43 ` Vlastimil Babka
2022-02-06 21:47 ` [PATCH 10/13] mm/munlock: mlock_page() munlock_page() batch by pagevec Hugh Dickins
2022-02-09 8:15 ` Geert Uytterhoeven
2022-02-09 15:45 ` Hugh Dickins
2022-02-11 18:26 ` Vlastimil Babka
2022-02-14 7:15 ` [PATCH v2 " Hugh Dickins
2022-02-06 21:49 ` [PATCH 11/13] mm/munlock: page migration needs mlock pagevec drained Hugh Dickins
2022-02-11 18:49 ` Vlastimil Babka
2022-02-14 5:34 ` Hugh Dickins
2022-02-14 7:17 ` [PATCH v2 " Hugh Dickins
2022-02-06 21:51 ` [PATCH 12/13] mm/thp: collapse_file() do try_to_unmap(TTU_BATCH_FLUSH) Hugh Dickins
2022-02-06 21:53 ` [PATCH 13/13] mm/thp: shrink_page_list() avoid splitting VM_LOCKED THP Hugh Dickins
[not found] ` <20220207033518.2602-1-hdanton@sina.com>
2022-02-07 18:46 ` [PATCH 07/13] mm/munlock: mlock_pte_range() when mlocking or munlocking Hugh Dickins
2022-02-09 15:35 ` [PATCH 00/13] mm/munlock: rework of mlock+munlock page handling Michal Hocko
2022-02-09 16:21 ` Hugh Dickins
2022-02-09 21:01 ` Michal Hocko
2022-02-09 22:59 ` Hugh Dickins
2022-02-10 7:49 ` Michal Hocko
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