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[172.10.233.147]) by smtp.gmail.com with ESMTPSA id h135sm7396281oib.50.2020.09.21.23.13.19 (version=TLS1 cipher=ECDHE-ECDSA-AES128-SHA bits=128/128); Mon, 21 Sep 2020 23:13:21 -0700 (PDT) Date: Mon, 21 Sep 2020 23:13:17 -0700 (PDT) From: Hugh Dickins X-X-Sender: hugh@eggly.anvils To: Alex Shi cc: akpm@linux-foundation.org, mgorman@techsingularity.net, tj@kernel.org, hughd@google.com, khlebnikov@yandex-team.ru, daniel.m.jordan@oracle.com, willy@infradead.org, hannes@cmpxchg.org, lkp@intel.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, shakeelb@google.com, iamjoonsoo.kim@lge.com, richard.weiyang@gmail.com, kirill@shutemov.name, alexander.duyck@gmail.com, rong.a.chen@intel.com, mhocko@suse.com, vdavydov.dev@gmail.com, shy828301@gmail.com, "Kirill A. Shutemov" , Vlastimil Babka Subject: Re: [PATCH v18 25/32] mm/mlock: remove lru_lock on TestClearPageMlocked in munlock_vma_page In-Reply-To: <1598273705-69124-26-git-send-email-alex.shi@linux.alibaba.com> Message-ID: References: <1598273705-69124-1-git-send-email-alex.shi@linux.alibaba.com> <1598273705-69124-26-git-send-email-alex.shi@linux.alibaba.com> User-Agent: Alpine 2.11 (LSU 23 2013-08-11) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, 24 Aug 2020, Alex Shi wrote: > In the func munlock_vma_page, the page must be PageLocked as well as > pages in split_huge_page series funcs. Thus the PageLocked is enough > to serialize both funcs. > > So we could relief the TestClearPageMlocked/hpage_nr_pages which are not > necessary under lru lock. > > As to another munlock func __munlock_pagevec, which no PageLocked > protection and should remain lru protecting. > > Signed-off-by: Alex Shi I made some comments on the mlock+munlock situation last week: I won't review this 24/32 and 25/32 now, but will take a look at your github tree tomorrow instead. Perhaps I'll find you have already done the fixes, perhaps I'll find you have merged these back into earlier patches. And I won't be reviewing beyond this point: this is enough for now, I think. Hugh > Cc: Kirill A. Shutemov > Cc: Vlastimil Babka > Cc: Andrew Morton > Cc: linux-mm@kvack.org > Cc: linux-kernel@vger.kernel.org > --- > mm/mlock.c | 41 +++++++++++++++-------------------------- > 1 file changed, 15 insertions(+), 26 deletions(-) > > diff --git a/mm/mlock.c b/mm/mlock.c > index 0448409184e3..46a05e6ec5ba 100644 > --- a/mm/mlock.c > +++ b/mm/mlock.c > @@ -69,9 +69,9 @@ void clear_page_mlock(struct page *page) > * > * See __pagevec_lru_add_fn for more explanation. > */ > - if (!isolate_lru_page(page)) { > + if (!isolate_lru_page(page)) > putback_lru_page(page); > - } else { > + else { > /* > * We lost the race. the page already moved to evictable list. > */ > @@ -178,7 +178,6 @@ static void __munlock_isolation_failed(struct page *page) > unsigned int munlock_vma_page(struct page *page) > { > int nr_pages; > - struct lruvec *lruvec; > > /* For try_to_munlock() and to serialize with page migration */ > BUG_ON(!PageLocked(page)); > @@ -186,37 +185,22 @@ unsigned int munlock_vma_page(struct page *page) > VM_BUG_ON_PAGE(PageTail(page), page); > > /* > - * Serialize split tail pages in __split_huge_page_tail() which > - * might otherwise copy PageMlocked to part of the tail pages before > - * we clear it in the head page. It also stabilizes thp_nr_pages(). > - * TestClearPageLRU can't be used here to block page isolation, since > - * out of lock clear_page_mlock may interfer PageLRU/PageMlocked > - * sequence, same as __pagevec_lru_add_fn, and lead the page place to > - * wrong lru list here. So relay on PageLocked to stop lruvec change > - * in mem_cgroup_move_account(). > + * Serialize split tail pages in __split_huge_page_tail() by > + * lock_page(); Do TestClearPageMlocked/PageLRU sequence like > + * clear_page_mlock(). > */ > - lruvec = lock_page_lruvec_irq(page); > - > - if (!TestClearPageMlocked(page)) { > + if (!TestClearPageMlocked(page)) > /* Potentially, PTE-mapped THP: do not skip the rest PTEs */ > - nr_pages = 1; > - goto unlock_out; > - } > + return 0; > > nr_pages = thp_nr_pages(page); > __mod_zone_page_state(page_zone(page), NR_MLOCK, -nr_pages); > > - if (__munlock_isolate_lru_page(page, lruvec, true)) { > - unlock_page_lruvec_irq(lruvec); > + if (!isolate_lru_page(page)) > __munlock_isolated_page(page); > - goto out; > - } > - __munlock_isolation_failed(page); > - > -unlock_out: > - unlock_page_lruvec_irq(lruvec); > + else > + __munlock_isolation_failed(page); > > -out: > return nr_pages - 1; > } > > @@ -305,6 +289,11 @@ static void __munlock_pagevec(struct pagevec *pvec, struct zone *zone) > > /* block memcg change in mem_cgroup_move_account */ > lock_page_memcg(page); > + /* > + * Serialize split tail pages in __split_huge_page_tail() which > + * might otherwise copy PageMlocked to part of the tail pages > + * before we clear it in the head page. > + */ > lruvec = relock_page_lruvec_irq(page, lruvec); > if (TestClearPageMlocked(page)) { > /* > -- > 1.8.3.1 > >