On Fri, Jan 21, 2011 at 06:36:18PM +0100, Andrea Arcangeli wrote: > On Fri, Jan 21, 2011 at 10:11:03AM -0600, Christoph Lameter wrote: > > On Thu, 20 Jan 2011, Andrea Arcangeli wrote: > > > > > Which following putback_lru_page()? You mean > > > putback_lru_page(newpage)? That is for the newly allocated page > > > (allocated at the very top, so always needed), it's not relevant to > > > the page_count(page) = 1. The page_count 1 is hold by the caller, so > > > it's leaking memory right now (for everything but compaction). > > > > Ahh yes we removed the putback_lru_pages call from migrate_pages() > > and broke the existing release logic. The caller has to call > > putback_release_pages() as per commit > > putback_lru_paeges > > > cf608ac19c95804dc2df43b1f4f9e068aa9034ab > > That is the very commit that introduced the two bugs that I've fixed > by code review. > > > > > If that is still the case then we still have the double free. > > The caller only calls putback_lru_pages if ret != 0 (the two cases you > refer to happen with ret = 0). > > Even if caller unconditionally calls putback_lru_pages (kind of what > compaction did), it can't double free because migrate_pages already > unlinked the pages before calling putback_lru_page(page), so there's > no way to do a double free (however if the caller unconditionally > called putback_lru_pages there would be no memleak to fix, but it > doesn't). > > > Could we please document the calling conventions exactly in the source? > > Right now it says that the caller should call putback_lru_pages(). > > The caller should call putback_lru_pages only if ret != 0. Minchan > this is your commit we're discussing can you check the commentary? No problem. I will send the patch. Thanks Adnrea, Christoph. > > Thanks! > Andrea > -- Kind regards, Minchan Kim -- 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/ . Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>