From 2af8ff291848cc4b1cce24b6c943394eb2c761e8 Mon Sep 17 00:00:00 2001
From: Hugh Dickins <hughd@google.com>
Date: Fri, 30 Nov 2018 14:10:35 -0800
Subject: [PATCH] mm/khugepaged: collapse_shmem() remember to clear holes
Huge tmpfs testing reminds us that there is no __GFP_ZERO in the gfp
flags khugepaged uses to allocate a huge page - in all common cases it
would just be a waste of effort - so collapse_shmem() must remember to
clear out any holes that it instantiates.
The obvious place to do so, where they are put into the page cache tree,
is not a good choice: because interrupts are disabled there. Leave it
until further down, once success is assured, where the other pages are
copied (before setting PageUptodate).
Link: http://lkml.kernel.org/r/alpine.LSU.2.11.1811261525080.2275@eggly.anvils
Fixes: f3f0e1d2150b2 ("khugepaged: add support of collapse for tmpfs/shmem pages")
Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: <stable@vger.kernel.org> [4.8+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
mm/khugepaged.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 65e82f665c7c2..1c402d33547e4 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1467,7 +1467,12 @@ static void collapse_shmem(struct mm_struct *mm,
* Replacing old pages with new one has succeeded, now we
* need to copy the content and free the old pages.
*/
+ index = start;
list_for_each_entry_safe(page, tmp, &pagelist, lru) {
+ while (index < page->index) {
+ clear_highpage(new_page + (index % HPAGE_PMD_NR));
+ index++;
+ }
copy_highpage(new_page + (page->index % HPAGE_PMD_NR),
page);
list_del(&page->lru);
@@ -1477,6 +1482,11 @@ static void collapse_shmem(struct mm_struct *mm,
ClearPageActive(page);
ClearPageUnevictable(page);
put_page(page);
+ index++;
+ }
+ while (index < end) {
+ clear_highpage(new_page + (index % HPAGE_PMD_NR));
+ index++;
}
local_irq_disable();
--
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