6.6-stable review patch. If anyone has any objections, please let me know.
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From: Hugh Dickins hughd@google.com
[ Upstream commit a09a8a1fbb374e0053b97306da9dbc05bd384685 ]
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.
Link: https://lkml.kernel.org/r/66f2751f-283e-816d-9530-765db7edc465@google.com Signed-off-by: Hugh Dickins hughd@google.com Acked-by: David Hildenbrand david@redhat.com Cc: "Aneesh Kumar K.V" aneesh.kumar@kernel.org Cc: Axel Rasmussen axelrasmussen@google.com Cc: Chris Li chrisl@kernel.org Cc: Christoph Hellwig hch@infradead.org Cc: Jason Gunthorpe jgg@ziepe.ca Cc: Johannes Weiner hannes@cmpxchg.org Cc: John Hubbard jhubbard@nvidia.com Cc: Keir Fraser keirf@google.com Cc: Konstantin Khlebnikov koct9i@gmail.com Cc: Li Zhe lizhe.67@bytedance.com Cc: Matthew Wilcox (Oracle) willy@infradead.org Cc: Peter Xu peterx@redhat.com Cc: Rik van Riel riel@surriel.com Cc: Shivank Garg shivankg@amd.com Cc: Vlastimil Babka vbabka@suse.cz Cc: Wei Xu weixugc@google.com Cc: Will Deacon will@kernel.org Cc: yangge yangge1116@126.com Cc: Yuanchu Xie yuanchu@google.com Cc: Yu Zhao yuzhao@google.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org [ Resolved minor conflicts ] Signed-off-by: Hugh Dickins hughd@google.com Signed-off-by: Sasha Levin sashal@kernel.org --- mm/gup.c | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-)
diff --git a/mm/gup.c b/mm/gup.c index 00ac2df7164c3..5be764395e046 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -1953,7 +1953,7 @@ static unsigned long collect_longterm_unpinnable_pages( { unsigned long i, collected = 0; struct folio *prev_folio = NULL; - bool drain_allow = true; + int drained = 0;
for (i = 0; i < nr_pages; i++) { struct folio *folio = page_folio(pages[i]); @@ -1975,10 +1975,17 @@ static unsigned long collect_longterm_unpinnable_pages( continue; }
- if (drain_allow && folio_ref_count(folio) != - folio_expected_ref_count(folio) + 1) { + if (drained == 0 && + folio_ref_count(folio) != + folio_expected_ref_count(folio) + 1) { + lru_add_drain(); + drained = 1; + } + if (drained == 1 && + folio_ref_count(folio) != + folio_expected_ref_count(folio) + 1) { lru_add_drain_all(); - drain_allow = false; + drained = 2; }
if (!folio_isolate_lru(folio))