From 49b0638502da097c15d46cd4e871dbaa022caf7c Mon Sep 17 00:00:00 2001 From: Suren Baghdasaryan Date: Fri, 4 Aug 2023 08:27:19 -0700 Subject: mm: enable page walking API to lock vmas during the walk walk_page_range() and friends often operate under write-locked mmap_lock. With introduction of vma locks, the vmas have to be locked as well during such walks to prevent concurrent page faults in these areas. Add an additional member to mm_walk_ops to indicate locking requirements for the walk. The change ensures that page walks which prevent concurrent page faults by write-locking mmap_lock, operate correctly after introduction of per-vma locks. With per-vma locks page faults can be handled under vma lock without taking mmap_lock at all, so write locking mmap_lock would not stop them. The change ensures vmas are properly locked during such walks. A sample issue this solves is do_mbind() performing queue_pages_range() to queue pages for migration. Without this change a concurrent page can be faulted into the area and be left out of migration. Link: https://lkml.kernel.org/r/20230804152724.3090321-2-surenb@google.com Signed-off-by: Suren Baghdasaryan Suggested-by: Linus Torvalds Suggested-by: Jann Horn Cc: David Hildenbrand Cc: Davidlohr Bueso Cc: Hugh Dickins Cc: Johannes Weiner Cc: Laurent Dufour Cc: Liam Howlett Cc: Matthew Wilcox (Oracle) Cc: Michal Hocko Cc: Michel Lespinasse Cc: Peter Xu Cc: Vlastimil Babka Cc: Signed-off-by: Andrew Morton --- mm/memcontrol.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'mm/memcontrol.c') diff --git a/mm/memcontrol.c b/mm/memcontrol.c index e8ca4bdcb03c..315fd5f45e3c 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -6024,6 +6024,7 @@ static int mem_cgroup_count_precharge_pte_range(pmd_t *pmd, static const struct mm_walk_ops precharge_walk_ops = { .pmd_entry = mem_cgroup_count_precharge_pte_range, + .walk_lock = PGWALK_RDLOCK, }; static unsigned long mem_cgroup_count_precharge(struct mm_struct *mm) @@ -6303,6 +6304,7 @@ put: /* get_mctgt_type() gets & locks the page */ static const struct mm_walk_ops charge_walk_ops = { .pmd_entry = mem_cgroup_move_charge_pte_range, + .walk_lock = PGWALK_RDLOCK, }; static void mem_cgroup_move_charge(void) -- cgit