Haiyue Wang <haiyue.wang@xxxxxxxxx> writes:
> The handling Non-LRU pages returned by follow_page() jumps directly, it
> doesn't call put_page() to handle the reference count, since 'FOLL_GET'
> flag for follow_page() has get_page() called. Fix the zone device page
> check by handling the page reference count correctly before returning.
>
> And as David reviewed, "device pages are never PageKsm pages". Drop this
> zone device page check for break_ksm().
>
> Fixes: 3218f8712d6b ("mm: handling Non-LRU pages returned by vm_normal_pages")
> Signed-off-by: Haiyue Wang <haiyue.wang@xxxxxxxxx>
LGTM, Thanks!
Reviewed-by: "Huang, Ying" <ying.huang@xxxxxxxxx>
> ---
> mm/huge_memory.c | 4 ++--
> mm/ksm.c | 12 +++++++++---
> mm/migrate.c | 10 +++++++---
> 3 files changed, 18 insertions(+), 8 deletions(-)
>
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 8a7c1b344abe..b2ba17c3dcd7 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -2963,10 +2963,10 @@ static int split_huge_pages_pid(int pid, unsigned long vaddr_start,
> /* FOLL_DUMP to ignore special (like zero) pages */
> page = follow_page(vma, addr, FOLL_GET | FOLL_DUMP);
>
> - if (IS_ERR_OR_NULL(page) || is_zone_device_page(page))
> + if (IS_ERR_OR_NULL(page))
> continue;
>
> - if (!is_transparent_hugepage(page))
> + if (is_zone_device_page(page) || !is_transparent_hugepage(page))
> goto next;
>
> total++;
> diff --git a/mm/ksm.c b/mm/ksm.c
> index 42ab153335a2..e26f57fc1f0e 100644
> --- a/mm/ksm.c
> +++ b/mm/ksm.c
> @@ -475,7 +475,7 @@ static int break_ksm(struct vm_area_struct *vma, unsigned long addr)
> cond_resched();
> page = follow_page(vma, addr,
> FOLL_GET | FOLL_MIGRATION | FOLL_REMOTE);
> - if (IS_ERR_OR_NULL(page) || is_zone_device_page(page))
> + if (IS_ERR_OR_NULL(page))
> break;
> if (PageKsm(page))
> ret = handle_mm_fault(vma, addr,
> @@ -560,12 +560,15 @@ static struct page *get_mergeable_page(struct rmap_item *rmap_item)
> goto out;
>
> page = follow_page(vma, addr, FOLL_GET);
> - if (IS_ERR_OR_NULL(page) || is_zone_device_page(page))
> + if (IS_ERR_OR_NULL(page))
> goto out;
> + if (is_zone_device_page(page))
> + goto out_putpage;
> if (PageAnon(page)) {
> flush_anon_page(vma, page, addr);
> flush_dcache_page(page);
> } else {
> +out_putpage:
> put_page(page);
> out:
> page = NULL;
> @@ -2308,11 +2311,13 @@ static struct rmap_item *scan_get_next_rmap_item(struct page **page)
> if (ksm_test_exit(mm))
> break;
> *page = follow_page(vma, ksm_scan.address, FOLL_GET);
> - if (IS_ERR_OR_NULL(*page) || is_zone_device_page(*page)) {
> + if (IS_ERR_OR_NULL(*page)) {
> ksm_scan.address += PAGE_SIZE;
> cond_resched();
> continue;
> }
> + if (is_zone_device_page(*page))
> + goto next_page;
> if (PageAnon(*page)) {
> flush_anon_page(vma, *page, ksm_scan.address);
> flush_dcache_page(*page);
> @@ -2327,6 +2332,7 @@ static struct rmap_item *scan_get_next_rmap_item(struct page **page)
> mmap_read_unlock(mm);
> return rmap_item;
> }
> +next_page:
> put_page(*page);
> ksm_scan.address += PAGE_SIZE;
> cond_resched();
> diff --git a/mm/migrate.c b/mm/migrate.c
> index 581dfaad9257..fee12cd2f294 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -1672,9 +1672,12 @@ static int add_page_for_migration(struct mm_struct *mm, unsigned long addr,
> goto out;
>
> err = -ENOENT;
> - if (!page || is_zone_device_page(page))
> + if (!page)
> goto out;
>
> + if (is_zone_device_page(page))
> + goto out_putpage;
> +
> err = 0;
> if (page_to_nid(page) == node)
> goto out_putpage;
> @@ -1868,8 +1871,9 @@ static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages,
> if (IS_ERR(page))
> goto set_status;
>
> - if (page && !is_zone_device_page(page)) {
> - err = page_to_nid(page);
> + if (page) {
> + err = !is_zone_device_page(page) ? page_to_nid(page)
> + : -ENOENT;
> if (foll_flags & FOLL_GET)
> put_page(page);
> } else {
