On Tue, Oct 11, 2016 at 05:58:15PM +0200, Jan Kara wrote: > On Thu 15-09-16 14:54:55, Kirill A. Shutemov wrote: > > invalidate_inode_page() has expectation about page_count() of the page > > -- if it's not 2 (one to caller, one to radix-tree), it will not be > > dropped. That condition almost never met for THPs -- tail pages are > > pinned to the pagevec. > > > > Let's drop them, before calling invalidate_inode_page(). > > > > Signed-off-by: Kirill A. Shutemov <kirill.shute...@linux.intel.com> > > --- > > mm/truncate.c | 11 +++++++++++ > > 1 file changed, 11 insertions(+) > > > > diff --git a/mm/truncate.c b/mm/truncate.c > > index a01cce450a26..ce904e4b1708 100644 > > --- a/mm/truncate.c > > +++ b/mm/truncate.c > > @@ -504,10 +504,21 @@ unsigned long invalidate_mapping_pages(struct > > address_space *mapping, > > /* 'end' is in the middle of THP */ > > if (index == round_down(end, HPAGE_PMD_NR)) > > continue; > > + /* > > + * invalidate_inode_page() expects > > + * page_count(page) == 2 to drop page from page > > + * cache -- drop tail pages references. > > + */ > > + get_page(page); > > + pagevec_release(&pvec); > > I'm not quite sure why this is needed. When you have multiorder entry in > the radix tree for your huge page, then you should not get more entries in > the pagevec for your huge page. What do I miss?
For compatibility reason find_get_entries() (which is called by pagevec_lookup_entries()) collects all subpages of huge page in the range (head/tails). See patch [07/41] So huge page, which is fully in the range it will be pinned up to PAGEVEC_SIZE times. -- Kirill A. Shutemov
