+ mm-huge_memory-fix-split-assumption-of-page-size.patch added to -mm tree

+ mm-huge_memory-fix-split-assumption-of-page-size.patch added to -mm tree

[akpm]

The patch titled
     Subject: mm/huge_memory: fix split assumption of page size
has been added to the -mm tree.  Its filename is
     mm-huge_memory-fix-split-assumption-of-page-size.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/mm-huge_memory-fix-split-assumption-of-page-size.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/mm-huge_memory-fix-split-assumption-of-page-size.patch

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------------------------------------------------------
From: "Kirill A. Shutemov" <kirill@shutemov.name>
Subject: mm/huge_memory: fix split assumption of page size

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.

Link: https://lkml.kernel.org/r/20200908195539.25896-6-willy@infradead.org
Signed-off-by: Kirill A. Shutemov <kirill@shutemov.name>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Huang Ying <ying.huang@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/huge_memory.c |   15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

--- a/mm/huge_memory.c~mm-huge_memory-fix-split-assumption-of-page-size
+++ a/mm/huge_memory.c
@@ -2309,13 +2309,13 @@ 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);
 	}
 }
@@ -2390,6 +2390,7 @@ static void __split_huge_page(struct pag
 	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);
@@ -2405,7 +2406,7 @@ static void __split_huge_page(struct pag
 		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) {
@@ -2425,7 +2426,7 @@ static void __split_huge_page(struct pag
 
 	ClearPageCompound(head);
 
-	split_page_owner(head, HPAGE_PMD_NR);
+	split_page_owner(head, nr);
 
 	/* See comment in __split_huge_page_tail() */
 	if (PageAnon(head)) {
@@ -2444,9 +2445,9 @@ static void __split_huge_page(struct pag
 
 	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;
@@ -2700,7 +2701,7 @@ int split_huge_page_to_list(struct page
 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;
 	}
 
_

Patches currently in -mm which might be from kirill@shutemov.name are

mm-huge_memory-fix-total_mapcount-assumption-of-page-size.patch
mm-huge_memory-fix-split-assumption-of-page-size.patch