On Wed, Jul 02, 2014 at 12:30:57AM -0400, Naoya Horiguchi wrote: > On Tue, Jul 01, 2014 at 11:15:40PM +0300, Kirill A. Shutemov wrote: > > On Tue, Jul 01, 2014 at 02:50:21PM -0400, Naoya Horiguchi wrote: > > > On Tue, Jul 01, 2014 at 09:07:39PM +0300, Kirill A. Shutemov wrote: > > > > Why do we need this special case for hugetlb page ->index? Why not use > > > > PAGE_SIZE units there too? Or I miss something? > > > > > > hugetlb pages are never split, so we use larger page cache size for > > > hugetlbfs file (to avoid large sparse page cache tree.) > > > > For transparent huge page cache I would like to have native support in > > page cache radix-tree: since huge pages are always naturally aligned we > > can create a leaf node for it several (RADIX_TREE_MAP_SHIFT - > > HPAGE_PMD_ORDER) levels up by tree, which would cover all indexes in the > > range the huge page represents. This approach should fit hugetlb too. And > > -1 special case for hugetlb. > > But I'm not sure when I'll get time to play with this... > > So I'm OK that hugetlb page should have ->index in PAGE_CACHE_SIZE > when transparent huge page is merged. I may try to write patches > on top of your tree after I've done a few series in my work queue. > > In order to fix the current problem, I suggest a page_to_pgoff() as a > short-term workaround. I found a few other call sites which can call > on hugepage, so this function help us track such callers. > The similar function seems to be introduced in your transparent huge > page cache tree (page_cache_index()). So this function will be finally > overwritten with it. > > Thanks, > Naoya Horiguchi > --- > From: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx> > Date: Tue, 1 Jul 2014 21:38:22 -0400 > Subject: [PATCH v2] rmap: fix pgoff calculation to handle hugepage correctly > > I triggered VM_BUG_ON() in vma_address() when I try to migrate an anonymous > hugepage with mbind() in the kernel v3.16-rc3. This is because pgoff's > calculation in rmap_walk_anon() fails to consider compound_order() only to > have an incorrect value. > > This patch introduces page_to_pgoff(), which gets the page's offset in > PAGE_CACHE_SIZE. Kirill pointed out that page cache tree should natively > handle hugepages, and in order to make hugetlbfs fit it, page->index of > hugetlbfs page should be in PAGE_CACHE_SIZE. This is beyond this patch, > but page_to_pgoff() contains the point to be fixed in a single function. > > Signed-off-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx> Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> -- Kirill A. Shutemov -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>