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From: Qi Zheng In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT X-Stat-Signature: wnz8z3pqno33b7hpjej39jmf8pmdsaqc X-Rspam-User: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 6F8BD1C000F X-HE-Tag: 1766041042-713377 X-HE-Meta: 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 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: List-Subscribe: List-Unsubscribe: On 12/18/25 6:30 AM, Johannes Weiner wrote: > On Wed, Dec 17, 2025 at 03:27:43PM +0800, Qi Zheng wrote: >> From: Muchun Song >> >> In the near future, a folio will no longer pin its corresponding >> memory cgroup. So an lruvec returned by folio_lruvec() could be >> released without the rcu read lock or a reference to its memory >> cgroup. >> >> In the current patch, the rcu read lock is employed to safeguard >> against the release of the lruvec in workingset_refault(). >> >> This serves as a preparatory measure for the reparenting of the >> LRU pages. >> >> Signed-off-by: Muchun Song >> Signed-off-by: Qi Zheng >> Reviewed-by: Harry Yoo >> --- >> mm/workingset.c | 5 ++++- >> 1 file changed, 4 insertions(+), 1 deletion(-) >> >> diff --git a/mm/workingset.c b/mm/workingset.c >> index 445fc634196d8..427ca1a5625e8 100644 >> --- a/mm/workingset.c >> +++ b/mm/workingset.c >> @@ -560,11 +560,12 @@ void workingset_refault(struct folio *folio, void *shadow) >> * locked to guarantee folio_memcg() stability throughout. >> */ >> nr = folio_nr_pages(folio); >> + rcu_read_lock(); >> lruvec = folio_lruvec(folio); >> mod_lruvec_state(lruvec, WORKINGSET_REFAULT_BASE + file, nr); >> >> if (!workingset_test_recent(shadow, file, &workingset, true)) > > This might sleep. You have to get a reference here and unlock RCU. Indeed, this may sleep in css_rstat_flush(). Will do the following: get_mem_cgroup_from_folio(folio); lruvec = mem_cgroup_lruvec(memcg, folio_pgdat(folio)); /* xxx */ mem_cgroup_put(memcg);