diff options
author | Hugh Dickins <hughd@google.com> | 2022-02-15 03:34:46 +0100 |
---|---|---|
committer | Matthew Wilcox (Oracle) <willy@infradead.org> | 2022-02-17 17:57:10 +0100 |
commit | 2262ace60713348228b2abe0629e77091643d29e (patch) | |
tree | 8b4d0485ac4503e6df53e105b8aa3f5abaede659 /mm/swap.c | |
parent | mm/migrate: __unmap_and_move() push good newpage to LRU (diff) | |
download | linux-2262ace60713348228b2abe0629e77091643d29e.tar.xz linux-2262ace60713348228b2abe0629e77091643d29e.zip |
mm/munlock: delete smp_mb() from __pagevec_lru_add_fn()
My reading of comment on smp_mb__after_atomic() in __pagevec_lru_add_fn()
says that it can now be deleted; and that remains so when the next patch
is added.
Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Diffstat (limited to 'mm/swap.c')
-rw-r--r-- | mm/swap.c | 37 |
1 files changed, 9 insertions, 28 deletions
diff --git a/mm/swap.c b/mm/swap.c index 682a03301a2c..3f770b1ea2c1 100644 --- a/mm/swap.c +++ b/mm/swap.c @@ -1025,37 +1025,18 @@ static void __pagevec_lru_add_fn(struct folio *folio, struct lruvec *lruvec) VM_BUG_ON_FOLIO(folio_test_lru(folio), folio); + folio_set_lru(folio); /* - * A folio becomes evictable in two ways: - * 1) Within LRU lock [munlock_vma_page() and __munlock_pagevec()]. - * 2) Before acquiring LRU lock to put the folio on the correct LRU - * and then - * a) do PageLRU check with lock [check_move_unevictable_pages] - * b) do PageLRU check before lock [clear_page_mlock] - * - * (1) & (2a) are ok as LRU lock will serialize them. For (2b), we need - * following strict ordering: - * - * #0: __pagevec_lru_add_fn #1: clear_page_mlock - * - * folio_set_lru() folio_test_clear_mlocked() - * smp_mb() // explicit ordering // above provides strict - * // ordering - * folio_test_mlocked() folio_test_lru() + * Is an smp_mb__after_atomic() still required here, before + * folio_evictable() tests PageMlocked, to rule out the possibility + * of stranding an evictable folio on an unevictable LRU? I think + * not, because munlock_page() only clears PageMlocked while the LRU + * lock is held. * - * - * if '#1' does not observe setting of PG_lru by '#0' and - * fails isolation, the explicit barrier will make sure that - * folio_evictable check will put the folio on the correct - * LRU. Without smp_mb(), folio_set_lru() can be reordered - * after folio_test_mlocked() check and can make '#1' fail the - * isolation of the folio whose mlocked bit is cleared (#0 is - * also looking at the same folio) and the evictable folio will - * be stranded on an unevictable LRU. + * (That is not true of __page_cache_release(), and not necessarily + * true of release_pages(): but those only clear PageMlocked after + * put_page_testzero() has excluded any other users of the page.) */ - folio_set_lru(folio); - smp_mb__after_atomic(); - if (folio_evictable(folio)) { if (was_unevictable) __count_vm_events(UNEVICTABLE_PGRESCUED, nr_pages); |