[PATCH 05/11] mm/huge_memory: Fix split assumption of page size

Matthew Wilcox (Oracle)
2020-09-08T19:55:52Z

From: "Kirill A. Shutemov" <kirill@shutemov.name>

File THPs may now be of arbitrary size, and we can't rely on that size
after doing the split so remember the number of pages before we start
the split.

Signed-off-by: Kirill A. Shutemov <kirill@shutemov.name>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
mm/huge_memory.c | 15 ++++++++-------
1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index a882d770a812..7bf837c32e3f 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2302,13 +2302,13 @@ static void unmap_page(struct page *page)
VM_BUG_ON_PAGE(!unmap_success, page);
}

-static void remap_page(struct page *page)
+static void remap_page(struct page *page, unsigned int nr)
{
int i;
if (PageTransHuge(page)) {
remove_migration_ptes(page, page, true);
} else {
- for (i = 0; i < HPAGE_PMD_NR; i++)
+ for (i = 0; i < nr; i++)
remove_migration_ptes(page + i, page + i, true);
}
}
@@ -2383,6 +2383,7 @@ static void __split_huge_page(struct page *page, struct list_head *list,
struct lruvec *lruvec;
struct address_space *swap_cache = NULL;
unsigned long offset = 0;
+ unsigned int nr = thp_nr_pages(head);
int i;

lruvec = mem_cgroup_page_lruvec(head, pgdat);
@@ -2398,7 +2399,7 @@ static void __split_huge_page(struct page *page, struct list_head *list,
xa_lock(&swap_cache->i_pages);
}

- for (i = HPAGE_PMD_NR - 1; i >= 1; i--) {
+ for (i = nr - 1; i >= 1; i--) {
__split_huge_page_tail(head, i, lruvec, list);
/* Some pages can be beyond i_size: drop them from page cache */
if (head[i].index >= end) {
@@ -2418,7 +2419,7 @@ static void __split_huge_page(struct page *page, struct list_head *list,

ClearPageCompound(head);

- split_page_owner(head, HPAGE_PMD_NR);
+ split_page_owner(head, nr);

/* See comment in __split_huge_page_tail() */
if (PageAnon(head)) {
@@ -2437,9 +2438,9 @@ static void __split_huge_page(struct page *page, struct list_head *list,

spin_unlock_irqrestore(&pgdat->lru_lock, flags);

- remap_page(head);
+ remap_page(head, nr);

- for (i = 0; i < HPAGE_PMD_NR; i++) {
+ for (i = 0; i < nr; i++) {
struct page *subpage = head + i;
if (subpage == page)
continue;
@@ -2693,7 +2694,7 @@ int split_huge_page_to_list(struct page *page, struct list_head *list)
fail: if (mapping)
xa_unlock(&mapping->i_pages);
spin_unlock_irqrestore(&pgdata->lru_lock, flags);
- remap_page(head);
+ remap_page(head, thp_nr_pages(head));
ret = -EBUSY;
}

--
2.28.0