In the func munlock_vma_page, comments mentained lru_lock needed for
serialization with split_huge_pages. But the page must be PageLocked
as well as pages in split_huge_page series funcs. Thus the PageLocked
is enough to serialize both funcs.
Further more, Hugh Dickins pointed: before splitting in
split_huge_page_to_list, the page was unmap_page() to remove pmd/ptes
which protect the page from munlock. Thus, no needs to guard
__split_huge_page_tail for mlock clean, just keep the lru_lock there for
isolation purpose.
LKP found a preempt issue on __mod_zone_page_state which need change
to mod_zone_page_state. Thanks!
Signed-off-by: Alex Shi <[email protected]>
Acked-by: Hugh Dickins <[email protected]>
Acked-by: Johannes Weiner <[email protected]>
Cc: Kirill A. Shutemov <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: [email protected]
Cc: [email protected]
---
mm/mlock.c | 26 +++++---------------------
1 file changed, 5 insertions(+), 21 deletions(-)
diff --git a/mm/mlock.c b/mm/mlock.c
index 884b1216da6a..796c726a0407 100644
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -187,40 +187,24 @@ static void __munlock_isolation_failed(struct page *page)
unsigned int munlock_vma_page(struct page *page)
{
int nr_pages;
- pg_data_t *pgdat = page_pgdat(page);
/* For try_to_munlock() and to serialize with page migration */
BUG_ON(!PageLocked(page));
-
VM_BUG_ON_PAGE(PageTail(page), page);
- /*
- * Serialize with any parallel __split_huge_page_refcount() which
- * might otherwise copy PageMlocked to part of the tail pages before
- * we clear it in the head page. It also stabilizes thp_nr_pages().
- */
- spin_lock_irq(&pgdat->lru_lock);
-
if (!TestClearPageMlocked(page)) {
/* Potentially, PTE-mapped THP: do not skip the rest PTEs */
- nr_pages = 1;
- goto unlock_out;
+ return 0;
}
nr_pages = thp_nr_pages(page);
- __mod_zone_page_state(page_zone(page), NR_MLOCK, -nr_pages);
+ mod_zone_page_state(page_zone(page), NR_MLOCK, -nr_pages);
- if (__munlock_isolate_lru_page(page, true)) {
- spin_unlock_irq(&pgdat->lru_lock);
+ if (!isolate_lru_page(page))
__munlock_isolated_page(page);
- goto out;
- }
- __munlock_isolation_failed(page);
-
-unlock_out:
- spin_unlock_irq(&pgdat->lru_lock);
+ else
+ __munlock_isolation_failed(page);
-out:
return nr_pages - 1;
}
--
1.8.3.1
On 11/5/20 9:55 AM, Alex Shi wrote:
> In the func munlock_vma_page, comments mentained lru_lock needed for
> serialization with split_huge_pages. But the page must be PageLocked
> as well as pages in split_huge_page series funcs. Thus the PageLocked
> is enough to serialize both funcs.
>
> Further more, Hugh Dickins pointed: before splitting in
> split_huge_page_to_list, the page was unmap_page() to remove pmd/ptes
> which protect the page from munlock. Thus, no needs to guard
> __split_huge_page_tail for mlock clean, just keep the lru_lock there for
> isolation purpose.
>
> LKP found a preempt issue on __mod_zone_page_state which need change
> to mod_zone_page_state. Thanks!
>
> Signed-off-by: Alex Shi <[email protected]>
> Acked-by: Hugh Dickins <[email protected]>
> Acked-by: Johannes Weiner <[email protected]>
> Cc: Kirill A. Shutemov <[email protected]>
> Cc: Vlastimil Babka <[email protected]>
> Cc: Andrew Morton <[email protected]>
> Cc: [email protected]
> Cc: [email protected]
Acked-by: Vlastimil Babka <[email protected]>
Nit below:
> ---
> mm/mlock.c | 26 +++++---------------------
> 1 file changed, 5 insertions(+), 21 deletions(-)
>
> diff --git a/mm/mlock.c b/mm/mlock.c
> index 884b1216da6a..796c726a0407 100644
> --- a/mm/mlock.c
> +++ b/mm/mlock.c
> @@ -187,40 +187,24 @@ static void __munlock_isolation_failed(struct page *page)
> unsigned int munlock_vma_page(struct page *page)
> {
> int nr_pages;
> - pg_data_t *pgdat = page_pgdat(page);
>
> /* For try_to_munlock() and to serialize with page migration */
Now the reasons for locking are expanded?
> BUG_ON(!PageLocked(page));
> -
> VM_BUG_ON_PAGE(PageTail(page), page);
>
> - /*
> - * Serialize with any parallel __split_huge_page_refcount() which
> - * might otherwise copy PageMlocked to part of the tail pages before
> - * we clear it in the head page. It also stabilizes thp_nr_pages().
> - */
> - spin_lock_irq(&pgdat->lru_lock);
> -
> if (!TestClearPageMlocked(page)) {
> /* Potentially, PTE-mapped THP: do not skip the rest PTEs */
> - nr_pages = 1;
> - goto unlock_out;
> + return 0;
> }
>
> nr_pages = thp_nr_pages(page);
> - __mod_zone_page_state(page_zone(page), NR_MLOCK, -nr_pages);
> + mod_zone_page_state(page_zone(page), NR_MLOCK, -nr_pages);
>
> - if (__munlock_isolate_lru_page(page, true)) {
> - spin_unlock_irq(&pgdat->lru_lock);
> + if (!isolate_lru_page(page))
> __munlock_isolated_page(page);
> - goto out;
> - }
> - __munlock_isolation_failed(page);
> -
> -unlock_out:
> - spin_unlock_irq(&pgdat->lru_lock);
> + else
> + __munlock_isolation_failed(page);
>
> -out:
> return nr_pages - 1;
> }
>
>