Messages in this thread | | | Date | Fri, 03 Jan 2014 15:17:16 -0500 | From | Sasha Levin <> | Subject | Re: [PATCH] mm/mlock: fix BUG_ON unlocked page for nolinear VMAs |
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On 12/18/2013 04:43 PM, Andrew Morton wrote: > On Wed, 18 Dec 2013 17:23:03 +0800 Wanpeng Li <liwanp@linux.vnet.ibm.com> wrote: > >>>> diff --git a/mm/rmap.c b/mm/rmap.c >>>> index 55c8b8d..1e24813 100644 >>>> --- a/mm/rmap.c >>>> +++ b/mm/rmap.c >>>> @@ -1347,6 +1347,7 @@ static int try_to_unmap_cluster(unsigned long cursor, unsigned int *mapcount, >>>> unsigned long end; >>>> int ret = SWAP_AGAIN; >>>> int locked_vma = 0; >>>> + int we_locked = 0; >>>> >>>> address = (vma->vm_start + cursor) & CLUSTER_MASK; >>>> end = address + CLUSTER_SIZE; >>>> @@ -1385,9 +1386,15 @@ static int try_to_unmap_cluster(unsigned long cursor, unsigned int *mapcount, >>>> BUG_ON(!page || PageAnon(page)); >>>> >>>> if (locked_vma) { >>>> - mlock_vma_page(page); /* no-op if already mlocked */ >>>> - if (page == check_page) >>>> + if (page != check_page) { >>>> + we_locked = trylock_page(page); >>> >>> If it's not us who has the page already locked, but somebody else, he >>> might unlock it at this point and then the BUG_ON in mlock_vma_page() >>> will trigger again. > > yes, this patch is pretty weak. > >> Any better idea is appreciated. ;-) > > Remove the BUG_ON() from mlock_vma_page()? Why was it added? > isolate_lru_page() and putback_lru_page() and *might* require > the page be locked, but I don't immediately see issues?
Ping? This BUG() is triggerable in 3.13-rc6 right now.
Thanks, Sasha
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