On Wed, 18 Dec 2013 19:41:44 -0500 Sasha Levin <sasha.levin@xxxxxxxxxx> wrote: > On 12/18/2013 07:28 PM, Andrew Morton wrote: > > On Thu, 19 Dec 2013 08:16:35 +0800 Wanpeng Li <liwanp@xxxxxxxxxxxxxxxxxx> wrote: > > > >> page_get_anon_vma() called in page_referenced_anon() will lock and > >> increase the refcount of anon_vma, page won't be locked for anonymous > >> page. This patch fix it by skip check anonymous page locked. > >> > >> [ 588.698828] kernel BUG at mm/rmap.c:1663! > > > > Why is all this suddenly happening. Did we change something, or did a > > new test get added to trinity? > > Dave has improved mmap testing in trinity, maybe it's related? Dave, can you please summarise recent trinity changes for us? > > Or if there is no reason why the page must be locked for > > rmap_walk_ksm() and rmap_walk_file(), let's just remove rmap_walk()'s > > VM_BUG_ON()? And rmap_walk_ksm()'s as well - it's duplicative anyway. > > IMO, removing all these VM_BUG_ON()s (which is happening quite often recently) will > lead to having bugs sneak by causing obscure undetected corruption instead of > being very obvious through a BUG. > Well. a) My patch was functionally the same as the one Wanpeng proposed, only better ;) and b) we shouldn't just assert X because we observed that the existing code does X. If a particular function *needs* PageLocked(page) then sure, it can and should assert that the page is locked. Preferably with a comment explaining *why* PageLocked() is needed. That way we don't end up with years-old assertions which nobody understands any more, which is what we have now. -- 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>