On Fri, Oct 18, 2019 at 12:49:46PM -0400, Johannes Weiner wrote:
> On Fri, Oct 18, 2019 at 09:37:54AM -0700, Song Liu wrote:
> > In collapse_file(), after locking the page, it is necessary to recheck
> > that the page is up-to-date. Add PageUptodate() check for both shmem THP
> > and file THP.
> >
> > Current khugepaged should not try to collapse dirty file THP, because it
> > is limited to read only text. Add a PageDirty check and warning for file
> > THP. This is added after page_mapping() check, because if the page is
> > truncated, it might be dirty.
> >
> > Fixes: 99cb0dbd47a1 ("mm,thp: add read-only THP support for (non-shmem) FS")
> > Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
> > Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
> > Cc: Hugh Dickins <hughd@xxxxxxxxxx>
> > Cc: William Kucharski <william.kucharski@xxxxxxxxxx>
> > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> > Signed-off-by: Song Liu <songliubraving@xxxxxx>
>
> Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
We should also be able to remove the unlocked tests for those two
conditions, right?
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 0a1b4b484ac5..a3ef6ce86bfa 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1601,17 +1601,6 @@ static void collapse_file(struct mm_struct *mm,
result = SCAN_FAIL;
goto xa_unlocked;
}
- } else if (!PageUptodate(page)) {
- xas_unlock_irq(&xas);
- wait_on_page_locked(page);
- if (!trylock_page(page)) {
- result = SCAN_PAGE_LOCK;
- goto xa_unlocked;
- }
- get_page(page);
- } else if (PageDirty(page)) {
- result = SCAN_FAIL;
- goto xa_locked;
} else if (trylock_page(page)) {
get_page(page);
xas_unlock_irq(&xas);
