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dkim=pass header.d=google.com header.s=20210112 header.b=MsY086PN; spf=pass (imf30.hostedemail.com: domain of shakeelb@google.com designates 209.85.128.175 as permitted sender) smtp.mailfrom=shakeelb@google.com; dmarc=pass (policy=reject) header.from=google.com X-Rspamd-Server: rspam02 X-HE-Tag: 1669228480-47240 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 Wed, Nov 23, 2022 at 10:18 AM Johannes Weiner wrote: > > rmap changes (mapping and unmapping) of a page currently take > lock_page_memcg() to serialize 1) update of the mapcount and the > cgroup mapped counter with 2) cgroup moving the page and updating the > old cgroup and the new cgroup counters based on page_mapped(). > > Before b2052564e66d ("mm: memcontrol: continue cache reclaim from > offlined groups"), we used to reassign all pages that could be found > on a cgroup's LRU list on deletion - something that rmap didn't > naturally serialize against. Since that commit, however, the only > pages that get moved are those mapped into page tables of a task > that's being migrated. In that case, the pte lock is always held (and > we know the page is mapped), which keeps rmap changes at bay already. > > The additional lock_page_memcg() by rmap is redundant. Remove it. > > Signed-off-by: Johannes Weiner Acked-by: Shakeel Butt