> -----Original Message----- > From: owner-linux-mm@xxxxxxxxx [mailto:owner-linux-mm@xxxxxxxxx] On > Behalf Of Wanpeng Li > Sent: Tuesday, December 17, 2013 3:27 AM > To: Sasha Levin > Cc: Bob Liu; Andrew Morton; linux-mm@xxxxxxxxx; Michel Lespinasse; > npiggin@xxxxxxx; Motohiro Kosaki JP; riel@xxxxxxxxxx > Subject: Re: mm: kernel BUG at mm/mlock.c:82! > > Hi Sasha, > On Tue, Dec 17, 2013 at 01:46:54AM -0500, Sasha Levin wrote: > >On 12/17/2013 12:39 AM, Bob Liu wrote: > >>cc'd more people. > >> > >>On 12/17/2013 09:04 AM, Sasha Levin wrote: > >>>Hi all, > >>> > >>>While fuzzing with trinity inside a KVM tools guest running latest > >>>-next kernel, I've stumbled on the following spew. > >>> > >>>Codewise, it's pretty straightforward. In try_to_unmap_cluster(): > >>> > >>> page = vm_normal_page(vma, address, *pte); > >>> BUG_ON(!page || PageAnon(page)); > >>> > >>> if (locked_vma) { > >>> mlock_vma_page(page); /* no-op if already > >>>mlocked */ > >>> if (page == check_page) > >>> ret = SWAP_MLOCK; > >>> continue; /* don't unmap */ > >>> } > >>> > >>>And the BUG triggers once we see that 'page' isn't locked. > >>> > >> > >>Yes, I didn't see any place locked the corresponding page in > >>try_to_unmap_cluster(). > >> > >>I'm afraid adding lock_page() over there may cause potential deadlock. > >>How about just remove the BUG_ON() in mlock_vma_page()? > > > >Welp, it's been there for 5 years now - there should be a good reason to > justify removing it. > > > > Page should be locked before invoke try_to_unmap(), this check can't be > removed since this bug is just triggered by confirm !check page hold page > lock in virtual scan during nolinear VMAs pages aging. Avoid to confirm !check > page hold page lock is acceptable. That's a try_to_unmap()'s assumption and it already have BUG_ON(!PageLocked(page)). We can remove wrong BUG_ON from mlock_vma_page() simply. Mlock_vma_page() doesn't depend on page-locked. -- 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