On Mon, 2010-03-29 at 20:49 +0200, Peter Zijlstra wrote: > On Mon, 2010-03-29 at 20:37 +0200, Andrea Arcangeli wrote: > > From: Andrea Arcangeli <aarcange@xxxxxxxxxx> > > > > PG_buddy can be converted to page->_count == -1. So the PG_compound_lock can be > > added to page->flags without overflowing (because of the section bits > > increasing) with CONFIG_X86_PAE=y. > > This seems to break the assumption that all free pages have a zero page > count relied upon by things like page_cache_get_speculative(). > > What if a page-cache pages gets freed and used as a head in the buddy > list while a concurrent lockless page-cache lookup tries to get a page > ref? And here goes me wanting to hijack it for PG_arch_2 :-) Is there any other page flag we could hijack ? I need it only when the page is allocated, so a flag that's only used when the page sits in the buddy would be fine. Cheers, Ben. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>