The patch below does not apply to the 6.6-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y git checkout FETCH_HEAD git cherry-pick -x 1aaf8c122918aa8897605a9aa1e8ed6600d6f930 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2025021008-recharger-fastball-ffab@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 1aaf8c122918aa8897605a9aa1e8ed6600d6f930 Mon Sep 17 00:00:00 2001 From: Zhaoyang Huang zhaoyang.huang@unisoc.com Date: Tue, 21 Jan 2025 10:01:59 +0800 Subject: [PATCH] mm: gup: fix infinite loop within __get_longterm_locked

We can run into an infinite loop in __get_longterm_locked() when collect_longterm_unpinnable_folios() finds only folios that are isolated from the LRU or were never added to the LRU. This can happen when all folios to be pinned are never added to the LRU, for example when vm_ops->fault allocated pages using cma_alloc() and never added them to the LRU.

Fix it by simply taking a look at the list in the single caller, to see if anything was added.

[zhaoyang.huang@unisoc.com: move definition of local] Link: https://lkml.kernel.org/r/20250122012604.3654667-1-zhaoyang.huang@unisoc.com Link: https://lkml.kernel.org/r/20250121020159.3636477-1-zhaoyang.huang@unisoc.com Fixes: 67e139b02d99 ("mm/gup.c: refactor check_and_migrate_movable_pages()") Signed-off-by: Zhaoyang Huang zhaoyang.huang@unisoc.com Reviewed-by: John Hubbard jhubbard@nvidia.com Reviewed-by: David Hildenbrand david@redhat.com Suggested-by: David Hildenbrand david@redhat.com Acked-by: David Hildenbrand david@redhat.com Cc: Aijun Sun aijun.sun@unisoc.com Cc: Alistair Popple apopple@nvidia.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org

diff --git a/mm/gup.c b/mm/gup.c index 9aaf338cc1f4..3883b307780e 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -2320,13 +2320,13 @@ static void pofs_unpin(struct pages_or_folios *pofs) /* * Returns the number of collected folios. Return value is always >= 0. */ -static unsigned long collect_longterm_unpinnable_folios( +static void collect_longterm_unpinnable_folios( struct list_head *movable_folio_list, struct pages_or_folios *pofs) { - unsigned long i, collected = 0; struct folio *prev_folio = NULL; bool drain_allow = true; + unsigned long i;

for (i = 0; i < pofs->nr_entries; i++) { struct folio *folio = pofs_get_folio(pofs, i); @@ -2338,8 +2338,6 @@ static unsigned long collect_longterm_unpinnable_folios( if (folio_is_longterm_pinnable(folio)) continue;

- collected++; - if (folio_is_device_coherent(folio)) continue;

@@ -2361,8 +2359,6 @@ static unsigned long collect_longterm_unpinnable_folios( NR_ISOLATED_ANON + folio_is_file_lru(folio), folio_nr_pages(folio)); } - - return collected; }

/* @@ -2439,11 +2435,9 @@ static long check_and_migrate_movable_pages_or_folios(struct pages_or_folios *pofs) { LIST_HEAD(movable_folio_list); - unsigned long collected;

- collected = collect_longterm_unpinnable_folios(&movable_folio_list, - pofs); - if (!collected) + collect_longterm_unpinnable_folios(&movable_folio_list, pofs); + if (list_empty(&movable_folio_list)) return 0;

return migrate_longterm_unpinnable_folios(&movable_folio_list, pofs);