The patch titled Subject: mm/gup: local lru_add_drain() to avoid lru_add_drain_all() has been added to the -mm mm-new branch. Its filename is mm-gup-local-lru_add_drain-to-avoid-lru_add_drain_all.patch

This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...

This patch will later appear in the mm-new branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Note, mm-new is a provisional staging ground for work-in-progress patches, and acceptance into mm-new is a notification for others take notice and to finish up reviews. Please do not hesitate to respond to review feedback and post updated versions to replace or incrementally fixup patches in mm-new.

Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's

*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days

------------------------------------------------------ From: Hugh Dickins hughd@google.com Subject: mm/gup: local lru_add_drain() to avoid lru_add_drain_all() Date: Sun, 31 Aug 2025 02:08:26 -0700 (PDT)

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/165ccfdb-16b5-ac11-0d66-2984293590c8@google.com Signed-off-by: Hugh Dickins hughd@google.com Cc: stable@vger.kernel.org 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: David Hildenbrand david@redhat.com 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: 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 Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

mm/gup.c | 2 ++ 1 file changed, 2 insertions(+)

--- a/mm/gup.c~mm-gup-local-lru_add_drain-to-avoid-lru_add_drain_all +++ a/mm/gup.c @@ -2291,6 +2291,8 @@ static unsigned long collect_longterm_un struct folio *folio; long i = 0;

+ lru_add_drain(); + for (folio = pofs_get_folio(pofs, i); folio; folio = pofs_next_folio(folio, pofs, &i)) {

_

Patches currently in -mm which might be from hughd@google.com are

mm-fix-folio_expected_ref_count-when-pg_private_2.patch mm-gup-check-ref_count-instead-of-lru-before-migration.patch mm-gup-local-lru_add_drain-to-avoid-lru_add_drain_all.patch mm-revert-mm-gup-clear-the-lru-flag-of-a-page-before-adding-to-lru-batch.patch mm-revert-mm-vmscanc-fix-oom-on-swap-stress-test.patch mm-folio_may_be_cached-unless-folio_test_large.patch mm-lru_add_drain_all-do-local-lru_add_drain-first.patch