In many cases, if collect_longterm_unpinnable_folios() does need to drain the LRU cache to release a reference, the cache in question is on this same CPU, and much more efficiently drained by a preliminary local lru_add_drain(), than the later cross-CPU lru_add_drain_all(). Marked for stable, to counter the increase in lru_add_drain_all()s from "mm/gup: check ref_count instead of lru before migration". Note for clean backports: can take 6.16 commit a03db236aebf ("gup: optimize longterm pin_user_pages() for large folio") first. Signed-off-by: Hugh Dickins Cc: --- mm/gup.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/mm/gup.c b/mm/gup.c index 82aec6443c0a..9f7c87f504a9 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -2291,6 +2291,8 @@ static unsigned long collect_longterm_unpinnable_folios( struct folio *folio; long i = 0; + lru_add_drain(); + for (folio = pofs_get_folio(pofs, i); folio; folio = pofs_next_folio(folio, pofs, &i)) { -- 2.51.0