Simplify lru_add_page_tail(), there are actually only two cases possible:
split_huge_page_to_list(), with list supplied and head isolated from lru
by its caller; or split_huge_page(), with NULL list and head on lru -
because when head is racily isolated from lru, the isolator's reference
will stop the split from getting any further than its page_ref_freeze().
So decide between the two cases by "list", but add VM_WARN_ON()s to
verify that they match our lru expectations.
[Hugh Dickins: rewrite commit log]
Signed-off-by: Alex Shi <alex.shi@xxxxxxxxxxxxxxxxx>
Reviewed-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Acked-by: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Kirill A. Shutemov <kirill@xxxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Mika Penttilä <mika.penttila@xxxxxxxxxxxx>
Cc: linux-mm@xxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
---
mm/huge_memory.c | 20 ++++++--------------
1 file changed, 6 insertions(+), 14 deletions(-)
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 60726eb26840..79318d7f7d5d 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2356,24 +2356,16 @@ static void lru_add_page_tail(struct page *head, struct page *tail,
VM_BUG_ON_PAGE(PageLRU(tail), head);
lockdep_assert_held(&lruvec_pgdat(lruvec)->lru_lock);
- if (!list)
- SetPageLRU(tail);
-
- if (likely(PageLRU(head)))
- list_add_tail(&tail->lru, &head->lru);
- else if (list) {
+ if (list) {
/* page reclaim is reclaiming a huge page */
+ VM_WARN_ON(PageLRU(head));
get_page(tail);
list_add_tail(&tail->lru, list);
} else {
- /*
- * Head page has not yet been counted, as an hpage,
- * so we must account for each subpage individually.
- *
- * Put tail on the list at the correct position
- * so they all end up in order.
- */
- add_page_to_lru_list_tail(tail, lruvec, page_lru(tail));
+ /* head is still on lru (and we have it frozen) */
+ VM_WARN_ON(!PageLRU(head));
+ SetPageLRU(tail);
+ list_add_tail(&tail->lru, &head->lru);
}
}
--
1.8.3.1
