Messages in this thread | | | Date | Wed, 16 Jul 2014 01:07:18 +0400 | Subject | Re: [PATCH] mm: do not call do_fault_around for non-linear fault | From | Konstantin Khlebnikov <> |
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On Wed, Jul 16, 2014 at 12:42 AM, Andrew Morton <akpm@linux-foundation.org> wrote: > On Tue, 15 Jul 2014 15:58:32 +0400 Konstantin Khlebnikov <k.khlebnikov@samsung.com> wrote: > >> From: Konstantin Khlebnikov <koct9i@gmail.com> >> >> Faulting around non-linear page-fault has no sense and >> breaks logic in do_fault_around because pgoff is shifted. >> > > Please be a lot more careful with the changelogs? This one failed to > describe the effects of the bug, failed to adequately describe the bug > itself, failed to describe the offending commits and failed to identify > which kernel versions need the patch.
Sorry for that. I thought I had already lost that bug-fixing race.
> > Sigh. I went back and assembled the necessary information, below. > Please check it. > > > > From: Konstantin Khlebnikov <koct9i@gmail.com> > Subject: mm: do not call do_fault_around for non-linear fault > > Ingo Korb reported that "repeated mapping of the same file on tmpfs using > remap_file_pages sometimes triggers a BUG at mm/filemap.c:202 when the > process exits". He bisected the bug to d7c1755179b82d ("mm: implement > ->map_pages for shmem/tmpfs"), although the bug was actually added by > 8c6e50b0290c4 ("mm: introduce vm_ops->map_pages()"). > > Problem is caused by calling do_fault_around for _non-linear_ faiult. In > this case pgoff is shifted and might become negative during calculation. > > Faulting around non-linear page-fault has no sense and breaks logic in > do_fault_around because pgoff is shifted. > > Signed-off-by: Konstantin Khlebnikov <koct9i@gmail.com> > Reported-by: "Ingo Korb" <ingo.korb@tu-dortmund.de> > Tested-by: "Ingo Korb" <ingo.korb@tu-dortmund.de> > Cc: Hugh Dickins <hughd@google.com> > Cc: Sasha Levin <sasha.levin@oracle.com> > Cc: Dave Jones <davej@redhat.com> > Cc: Ning Qu <quning@google.com> > Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> > Cc: <stable@vger.kernel.org> [3.15.x] > Signed-off-by: Andrew Morton <akpm@linux-foundation.org> > --- > > mm/memory.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff -puN mm/memory.c~mm-do-not-call-do_fault_around-for-non-linear-fault mm/memory.c > --- a/mm/memory.c~mm-do-not-call-do_fault_around-for-non-linear-fault > +++ a/mm/memory.c > @@ -2882,7 +2882,8 @@ static int do_read_fault(struct mm_struc > * if page by the offset is not ready to be mapped (cold cache or > * something). > */ > - if (vma->vm_ops->map_pages && fault_around_pages() > 1) { > + if (vma->vm_ops->map_pages && !(flags & FAULT_FLAG_NONLINEAR) && > + fault_around_pages() > 1) { > pte = pte_offset_map_lock(mm, pmd, address, &ptl); > do_fault_around(vma, address, pte, pgoff, flags); > if (!pte_same(*pte, orig_pte)) > _ >
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