From: Hugh Dickins <hughd@google.com>
Date: Fri, 30 Nov 2018 14:10:35 -0800
Subject: mm/khugepaged: collapse_shmem() remember to clear holes
Git-commit: 2af8ff291848cc4b1cce24b6c943394eb2c761e8
Patch-mainline: v4.20-rc5
References: VM Functionality, bsc#1121599
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>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
---
mm/khugepaged.c | 10 ++++++++++
1 file changed, 10 insertions(+)
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1497,7 +1497,12 @@ tree_unlocked:
* Replacing old pages with new one has succeed, now we need to
* copy the content and free 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);
@@ -1507,6 +1512,11 @@ tree_unlocked:
ClearPageActive(page);
ClearPageUnevictable(page);
put_page(page);
+ index++;
+ }
+ while (index < end) {
+ clear_highpage(new_page + (index % HPAGE_PMD_NR));
+ index++;
}
local_irq_save(flags);