| Message ID | 20191018163754.3736610-1-songliubraving@fb.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] mm,thp: recheck each page before collapsing file THP | expand |
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@linux.intel.com> > Cc: Johannes Weiner <hannes@cmpxchg.org> > Cc: Hugh Dickins <hughd@google.com> > Cc: William Kucharski <william.kucharski@oracle.com> > Cc: Andrew Morton <akpm@linux-foundation.org> > Signed-off-by: Song Liu <songliubraving@fb.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org>
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@linux.intel.com> > > Cc: Johannes Weiner <hannes@cmpxchg.org> > > Cc: Hugh Dickins <hughd@google.com> > > Cc: William Kucharski <william.kucharski@oracle.com> > > Cc: Andrew Morton <akpm@linux-foundation.org> > > Signed-off-by: Song Liu <songliubraving@fb.com> > > Acked-by: Johannes Weiner <hannes@cmpxchg.org> 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);
> On Oct 18, 2019, at 9:58 AM, Johannes Weiner <hannes@cmpxchg.org> wrote: > > 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@linux.intel.com> >>> Cc: Johannes Weiner <hannes@cmpxchg.org> >>> Cc: Hugh Dickins <hughd@google.com> >>> Cc: William Kucharski <william.kucharski@oracle.com> >>> Cc: Andrew Morton <akpm@linux-foundation.org> >>> Signed-off-by: Song Liu <songliubraving@fb.com> >> >> Acked-by: Johannes Weiner <hannes@cmpxchg.org> > > We should also be able to remove the unlocked tests for those two > conditions, right? Yeah, I think we can remove them. Thanks, Song > > 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);
diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 0a1b4b484ac5..40c549302d36 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -1626,7 +1626,12 @@ static void collapse_file(struct mm_struct *mm, * without racing with truncate. */ VM_BUG_ON_PAGE(!PageLocked(page), page); - VM_BUG_ON_PAGE(!PageUptodate(page), page); + + /* double check the page is up to date */ + if (unlikely(!PageUptodate(page))) { + result = SCAN_FAIL; + goto out_unlock; + } /* * If file was truncated then extended, or hole-punched, before @@ -1642,6 +1647,15 @@ static void collapse_file(struct mm_struct *mm, goto out_unlock; } + /* + * khugepaged should not try to collapse dirty pages for + * file THP. Show warning if this somehow happens. + */ + if (WARN_ON_ONCE(!is_shmem && PageDirty(page))) { + result = SCAN_FAIL; + goto out_unlock; + } + if (isolate_lru_page(page)) { result = SCAN_DEL_PAGE_LRU; goto out_unlock;
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@linux.intel.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Hugh Dickins <hughd@google.com> Cc: William Kucharski <william.kucharski@oracle.com> Cc: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Song Liu <songliubraving@fb.com> --- Changes v1 => v2: Rearrange the checks per feedback from Johannes, Rik, and Kirill. --- mm/khugepaged.c | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-)