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cachestat: do not flush stats in recency check
syzbot detects that cachestat() is flushing stats, which can sleep, in its
RCU read section (see [1]). This is done in the workingset_test_recent()
step (which checks if the folio's eviction is recent).
Move the stat flushing step to before the RCU read section of cachestat,
and skip stat flushing during the recency check.
[1]: https://lore.kernel.org/cgroups/000000000000f71227061bdf97e0@google.com/
Link: https://lkml.kernel.org/r/20240627201737.3506959-1-nphamcs@gmail.com
Fixes: b006847222
("mm: workingset: move the stats flush into workingset_test_recent()")
Signed-off-by: Nhat Pham <nphamcs@gmail.com>
Reported-by: syzbot+b7f13b2d0cc156edf61a@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/cgroups/000000000000f71227061bdf97e0@google.com/
Debugged-by: Johannes Weiner <hannes@cmpxchg.org>
Suggested-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: David Hildenbrand <david@redhat.com>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Kairui Song <kasong@tencent.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Cc: <stable@vger.kernel.org> [6.8+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
parent
9fd154ba92
commit
5a4d8944d6
@ -354,7 +354,8 @@ static inline swp_entry_t page_swap_entry(struct page *page)
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}
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}
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/* linux/mm/workingset.c */
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/* linux/mm/workingset.c */
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bool workingset_test_recent(void *shadow, bool file, bool *workingset);
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bool workingset_test_recent(void *shadow, bool file, bool *workingset,
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bool flush);
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void workingset_age_nonresident(struct lruvec *lruvec, unsigned long nr_pages);
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void workingset_age_nonresident(struct lruvec *lruvec, unsigned long nr_pages);
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void *workingset_eviction(struct folio *folio, struct mem_cgroup *target_memcg);
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void *workingset_eviction(struct folio *folio, struct mem_cgroup *target_memcg);
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void workingset_refault(struct folio *folio, void *shadow);
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void workingset_refault(struct folio *folio, void *shadow);
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@ -4248,6 +4248,9 @@ static void filemap_cachestat(struct address_space *mapping,
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XA_STATE(xas, &mapping->i_pages, first_index);
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XA_STATE(xas, &mapping->i_pages, first_index);
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struct folio *folio;
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struct folio *folio;
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/* Flush stats (and potentially sleep) outside the RCU read section. */
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mem_cgroup_flush_stats_ratelimited(NULL);
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rcu_read_lock();
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rcu_read_lock();
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xas_for_each(&xas, folio, last_index) {
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xas_for_each(&xas, folio, last_index) {
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int order;
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int order;
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@ -4311,7 +4314,7 @@ static void filemap_cachestat(struct address_space *mapping,
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goto resched;
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goto resched;
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}
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}
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#endif
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#endif
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if (workingset_test_recent(shadow, true, &workingset))
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if (workingset_test_recent(shadow, true, &workingset, false))
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cs->nr_recently_evicted += nr_pages;
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cs->nr_recently_evicted += nr_pages;
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goto resched;
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goto resched;
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@ -412,10 +412,12 @@ void *workingset_eviction(struct folio *folio, struct mem_cgroup *target_memcg)
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* @file: whether the corresponding folio is from the file lru.
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* @file: whether the corresponding folio is from the file lru.
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* @workingset: where the workingset value unpacked from shadow should
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* @workingset: where the workingset value unpacked from shadow should
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* be stored.
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* be stored.
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* @flush: whether to flush cgroup rstat.
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*
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*
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* Return: true if the shadow is for a recently evicted folio; false otherwise.
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* Return: true if the shadow is for a recently evicted folio; false otherwise.
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*/
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*/
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bool workingset_test_recent(void *shadow, bool file, bool *workingset)
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bool workingset_test_recent(void *shadow, bool file, bool *workingset,
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bool flush)
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{
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{
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struct mem_cgroup *eviction_memcg;
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struct mem_cgroup *eviction_memcg;
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struct lruvec *eviction_lruvec;
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struct lruvec *eviction_lruvec;
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@ -467,10 +469,16 @@ bool workingset_test_recent(void *shadow, bool file, bool *workingset)
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/*
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/*
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* Flush stats (and potentially sleep) outside the RCU read section.
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* Flush stats (and potentially sleep) outside the RCU read section.
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*
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* Note that workingset_test_recent() itself might be called in RCU read
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* section (for e.g, in cachestat) - these callers need to skip flushing
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* stats (via the flush argument).
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*
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* XXX: With per-memcg flushing and thresholding, is ratelimiting
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* XXX: With per-memcg flushing and thresholding, is ratelimiting
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* still needed here?
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* still needed here?
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*/
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*/
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mem_cgroup_flush_stats_ratelimited(eviction_memcg);
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if (flush)
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mem_cgroup_flush_stats_ratelimited(eviction_memcg);
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eviction_lruvec = mem_cgroup_lruvec(eviction_memcg, pgdat);
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eviction_lruvec = mem_cgroup_lruvec(eviction_memcg, pgdat);
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refault = atomic_long_read(&eviction_lruvec->nonresident_age);
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refault = atomic_long_read(&eviction_lruvec->nonresident_age);
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@ -558,7 +566,7 @@ void workingset_refault(struct folio *folio, void *shadow)
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mod_lruvec_state(lruvec, WORKINGSET_REFAULT_BASE + file, nr);
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mod_lruvec_state(lruvec, WORKINGSET_REFAULT_BASE + file, nr);
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if (!workingset_test_recent(shadow, file, &workingset))
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if (!workingset_test_recent(shadow, file, &workingset, true))
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return;
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return;
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folio_set_active(folio);
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folio_set_active(folio);
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