| From e1f1b1572e8db87a56609fd05bef76f98f0e456a Mon Sep 17 00:00:00 2001 |
| From: Hugh Dickins <hughd@google.com> |
| Date: Fri, 20 Jul 2018 17:53:45 -0700 |
| Subject: mm/huge_memory.c: fix data loss when splitting a file pmd |
| |
| From: Hugh Dickins <hughd@google.com> |
| |
| commit e1f1b1572e8db87a56609fd05bef76f98f0e456a upstream. |
| |
| __split_huge_pmd_locked() must check if the cleared huge pmd was dirty, |
| and propagate that to PageDirty: otherwise, data may be lost when a huge |
| tmpfs page is modified then split then reclaimed. |
| |
| How has this taken so long to be noticed? Because there was no problem |
| when the huge page is written by a write system call (shmem_write_end() |
| calls set_page_dirty()), nor when the page is allocated for a write fault |
| (fault_dirty_shared_page() calls set_page_dirty()); but when allocated for |
| a read fault (which MAP_POPULATE simulates), no set_page_dirty(). |
| |
| Link: http://lkml.kernel.org/r/alpine.LSU.2.11.1807111741430.1106@eggly.anvils |
| Fixes: d21b9e57c74c ("thp: handle file pages in split_huge_pmd()") |
| Signed-off-by: Hugh Dickins <hughd@google.com> |
| Reported-by: Ashwin Chaugule <ashwinch@google.com> |
| Reviewed-by: Yang Shi <yang.shi@linux.alibaba.com> |
| Reviewed-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> |
| Cc: "Huang, Ying" <ying.huang@intel.com> |
| 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: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| mm/huge_memory.c | 2 ++ |
| 1 file changed, 2 insertions(+) |
| |
| --- a/mm/huge_memory.c |
| +++ b/mm/huge_memory.c |
| @@ -1642,6 +1642,8 @@ static void __split_huge_pmd_locked(stru |
| if (vma_is_dax(vma)) |
| return; |
| page = pmd_page(_pmd); |
| + if (!PageDirty(page) && pmd_dirty(_pmd)) |
| + set_page_dirty(page); |
| if (!PageReferenced(page) && pmd_young(_pmd)) |
| SetPageReferenced(page); |
| page_remove_rmap(page, true); |
