diff options
| author | Hugh Dickins <hughd@google.com> | 2018-07-20 17:53:45 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2018-07-21 12:50:46 -0700 |
| commit | e1f1b1572e8db87a56609fd05bef76f98f0e456a (patch) | |
| tree | 97c419c35f7bea38037c6ffa77017fa6ddf1232c /mm/huge_memory.c | |
| parent | 35033ab988c396ad7bce3b6d24060c16a9066db8 (diff) | |
| download | lwn-e1f1b1572e8db87a56609fd05bef76f98f0e456a.tar.gz lwn-e1f1b1572e8db87a56609fd05bef76f98f0e456a.zip | |
mm/huge_memory.c: fix data loss when splitting a file pmd
__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>
Diffstat (limited to 'mm/huge_memory.c')
| -rw-r--r-- | mm/huge_memory.c | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 1cd7c1a57a14..25346bd99364 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2084,6 +2084,8 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, 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); |