Messages in this thread | | | Subject | Re: [REGRESSION] !PageLocked(page) assertion with tcpdump | From | Laura Abbott <> | Date | Wed, 10 Aug 2016 13:03:54 -0700 |
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On 08/10/2016 09:13 AM, Kirill A. Shutemov wrote: > On Wed, Aug 10, 2016 at 07:33:38AM -0700, Laura Abbott wrote: >> Hi, >> >> There have been several reports[1] of assertions tripping when using >> tcpdump on the latest master: >> >> [ 1013.718212] device wlp2s0 entered promiscuous mode >> [ 1013.736003] page:ffffea0004380000 count:2 mapcount:0 mapping: >> (null) index:0x0 compound_mapcount: 0 >> [ 1013.736013] flags: 0x17ffffc0004000(head) >> [ 1013.736017] page dumped because: VM_BUG_ON_PAGE(!PageLocked(page)) >> [ 1013.736044] ------------[ cut here ]------------ >> [ 1013.736091] kernel BUG at mm/rmap.c:1288! > > The patch below should do the trick. > > From 8026e3a2cecb7cdd3a63ebc266fb359ef7ec965b Mon Sep 17 00:00:00 2001 > From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> > Date: Wed, 10 Aug 2016 18:51:54 +0300 > Subject: [PATCH] mm, rmap: fix false positive VM_BUG() in page_add_file_rmap() > > PageTransCompound() doesn't distinguish THP from from any other type of > compound pages. This can lead to false-positive VM_BUG_ON() in > page_add_file_rmap() if called on compound page from a driver[1]. > > I think we can exclude such cases by checking if the page belong to a > mapping. > > The VM_BUG_ON_PAGE() is downgraded to VM_WARN_ON_ONCE(). This path > should not cause any harm to non-THP page, but good to know if we step > on anything else. > > [1] http://lkml.kernel.org/r/c711e067-0bff-a6cb-3c37-04dfe77d2db1@redhat.com > > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> > Reported-by: Laura Abbott <labbott@redhat.com>
Tested-by: Laura Abbott <labbott@redhat.com>
> --- > mm/rmap.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/mm/rmap.c b/mm/rmap.c > index eee844997bd8..f071d6f7a986 100644 > --- a/mm/rmap.c > +++ b/mm/rmap.c > @@ -1286,8 +1286,9 @@ void page_add_file_rmap(struct page *page, bool compound) > else > __inc_node_page_state(page, NR_FILE_PMDMAPPED); > } else { > - if (PageTransCompound(page)) { > - VM_BUG_ON_PAGE(!PageLocked(page), page); > + if (PageTransCompound(page) && page_mapping(page)) { > + VM_WARN_ON_ONCE(!PageLocked(page)); > + > SetPageDoubleMap(compound_head(page)); > if (PageMlocked(page)) > clear_page_mlock(compound_head(page)); >
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