On Thu, Mar 19, 2015 at 8:08 PM, Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> wrote: > Currently we take naive approach to page flags on compound -- we set the > flag on the page without consideration if the flag makes sense for tail > page or for compound page in general. This patchset try to sort this out > by defining per-flag policy on what need to be done if page-flag helper > operate on compound page. > > The last patch in patchset also sanitize usege of page->mapping for tail > pages. We don't define meaning of page->mapping for tail pages. Currently > it's always NULL, which can be inconsistent with head page and potentially > lead to problems. > > For now I catched one case of illigal usage of page flags or ->mapping: > sound subsystem allocates pages with __GFP_COMP and maps them with PTEs. > It leads to setting dirty bit on tail pages and access to tail_page's > ->mapping. I don't see any bad behaviour caused by this, but worth fixing > anyway. Do you mean call of set_page_dirty() from zap_pte_range() ? I think this should be replaced with vma operation: vma->vm_ops->set_page_dirty() > > This patchset makes more sense if you take my THP refcounting into > account: we will see more compound pages mapped with PTEs and we need to > define behaviour of flags on compound pages to avoid bugs. > > Kirill A. Shutemov (16): > mm: consolidate all page-flags helpers in <linux/page-flags.h> > page-flags: trivial cleanup for PageTrans* helpers > page-flags: introduce page flags policies wrt compound pages > page-flags: define PG_locked behavior on compound pages > page-flags: define behavior of FS/IO-related flags on compound pages > page-flags: define behavior of LRU-related flags on compound pages > page-flags: define behavior SL*B-related flags on compound pages > page-flags: define behavior of Xen-related flags on compound pages > page-flags: define PG_reserved behavior on compound pages > page-flags: define PG_swapbacked behavior on compound pages > page-flags: define PG_swapcache behavior on compound pages > page-flags: define PG_mlocked behavior on compound pages > page-flags: define PG_uncached behavior on compound pages > page-flags: define PG_uptodate behavior on compound pages > page-flags: look on head page if the flag is encoded in page->mapping > mm: sanitize page->mapping for tail pages > > fs/cifs/file.c | 8 +- > include/linux/hugetlb.h | 7 - > include/linux/ksm.h | 17 --- > include/linux/mm.h | 122 +---------------- > include/linux/page-flags.h | 317 ++++++++++++++++++++++++++++++++++----------- > include/linux/pagemap.h | 25 ++-- > include/linux/poison.h | 4 + > mm/filemap.c | 15 ++- > mm/huge_memory.c | 2 +- > mm/ksm.c | 2 +- > mm/memory-failure.c | 2 +- > mm/memory.c | 2 +- > mm/migrate.c | 2 +- > mm/page_alloc.c | 7 + > mm/shmem.c | 4 +- > mm/slub.c | 2 + > mm/swap_state.c | 4 +- > mm/util.c | 5 +- > mm/vmscan.c | 4 +- > mm/zswap.c | 4 +- > 20 files changed, 294 insertions(+), 261 deletions(-) > > -- > 2.1.4 > > -- > 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> -- 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>