On 1/20/25 1:26 AM, zhaoyang.huang wrote:
From: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>
Infinite loop within __get_longterm_locked detected in an unique usage
of pin_user_pages where the VA's pages are all unpinnable(vm_ops->fault
function allocate pages via cma_alloc for hardware purpose and leave them
out of LRU). Fixing this by have 'collected' reflect the actual number
of pages in movable_folio_list.
The above is rather terse, although perhaps by kernel standards it's OK.
Isn't this missing a Fixes tag?
Fixes: 67e139b02d994 ("mm/gup.c: refactor
check_and_migrate_movable_pages()")
Signed-off-by: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>
---
mm/gup.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/mm/gup.c b/mm/gup.c
index 3b75e631f369..2231ce7221f9 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -2341,8 +2341,6 @@ static unsigned long collect_longterm_unpinnable_folios(
if (folio_is_longterm_pinnable(folio))
continue;
- collected++;
-
if (folio_is_device_coherent(folio))
continue;
@@ -2359,6 +2357,8 @@ static unsigned long collect_longterm_unpinnable_folios(
if (!folio_isolate_lru(folio))
continue;
+ collected++;
+
Well, this seems correct to me. Somehow I talked myself into believing
that it was OK to do collected++ early, even though later on we skip
actually collecting the folio, thus miscounting things.
But now I believe it was just incorrect all along.
Reviewed-by: John Hubbard <jhubbard@xxxxxxxxxx>
thanks,
--
John Hubbard
