| Message ID | alpine.LSU.2.11.1811261525080.2275@eggly.anvils (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | huge_memory,khugepaged tmpfs split/collapse fixes | expand |
On Mon, Nov 26, 2018 at 03:26:34PM -0800, Hugh Dickins wrote: > 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). > > Fixes: f3f0e1d2150b2 ("khugepaged: add support of collapse for tmpfs/shmem pages") > Signed-off-by: Hugh Dickins <hughd@google.com> > Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> > Cc: stable@vger.kernel.org # 4.8+ Ouch. Thanks for catching this. Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 65e82f665c7c..1c402d33547e 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();
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). Fixes: f3f0e1d2150b2 ("khugepaged: add support of collapse for tmpfs/shmem pages") Signed-off-by: Hugh Dickins <hughd@google.com> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: stable@vger.kernel.org # 4.8+ --- mm/khugepaged.c | 10 ++++++++++ 1 file changed, 10 insertions(+)