Sasha Levin has shown oopses on
ffffea0003480048 and
ffffea0003480008 at
mm/memory.c:1132, running Trinity on different 3.16-rc-next kernels:
where zap_pte_range() checks page->mapping to see if PageAnon(page).
Those addresses fit struct pages for pfns d2001 and d2000, and in each
dump a register or a stack slot showed
d2001730 or
d2000730: pte flags
0x730 are PCD ACCESSED PROTNONE SPECIAL IOMAP; and Sasha's e820 map has
a hole between
cfffffff and
100000000, which would need special access.
Commit
c46a7c817e66 ("x86: define _PAGE_NUMA by reusing software bits on
the PMD and PTE levels") has broken vm_normal_page(): a PROTNONE SPECIAL
pte no longer passes the pte_special() test, so zap_pte_range() goes on
to try to access a non-existent struct page.
Fix this by refining pte_special() (SPECIAL with PRESENT or PROTNONE) to
complement pte_numa() (SPECIAL with neither PRESENT nor PROTNONE). A
hint that this was a problem was that
c46a7c817e66 added pte_numa() test
to vm_normal_page(), and moved its is_zero_pfn() test from slow to fast
path: This was papering over a pte_special() snag when the zero page was
encountered during zap. This patch reverts vm_normal_page() to how it
was before, relying on pte_special().
It still appears that this patch may be incomplete: aren't there other
places which need to be handling PROTNONE along with PRESENT? For
example, pte_mknuma() clears _PAGE_PRESENT and sets _PAGE_NUMA, but on a
PROT_NONE area, that would make it pte_special(). This is side-stepped
by the fact that NUMA hinting faults skipped PROT_NONE VMAs and there
are no grounds where a NUMA hinting fault on a PROT_NONE VMA would be
interesting.
Fixes: c46a7c817e66 ("x86: define _PAGE_NUMA by reusing software bits on the PMD and PTE levels")
Reported-by: Sasha Levin <sasha.levin@oracle.com>
Tested-by: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Mel Gorman <mgorman@suse.de>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Cyrill Gorcunov <gorcunov@gmail.com>
Cc: Matthew Wilcox <matthew.r.wilcox@intel.com>
Cc: <stable@vger.kernel.org> [3.16]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
static inline int pte_special(pte_t pte)
{
- return (pte_flags(pte) & (_PAGE_PRESENT|_PAGE_SPECIAL)) ==
- (_PAGE_PRESENT|_PAGE_SPECIAL);
+ /*
+ * See CONFIG_NUMA_BALANCING pte_numa in include/asm-generic/pgtable.h.
+ * On x86 we have _PAGE_BIT_NUMA == _PAGE_BIT_GLOBAL+1 ==
+ * __PAGE_BIT_SOFTW1 == _PAGE_BIT_SPECIAL.
+ */
+ return (pte_flags(pte) & _PAGE_SPECIAL) &&
+ (pte_flags(pte) & (_PAGE_PRESENT|_PAGE_PROTNONE));
}
static inline unsigned long pte_pfn(pte_t pte)
unsigned long pfn = pte_pfn(pte);
if (HAVE_PTE_SPECIAL) {
- if (likely(!pte_special(pte) || pte_numa(pte)))
+ if (likely(!pte_special(pte)))
goto check_pfn;
if (vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP))
return NULL;
}
}
+ if (is_zero_pfn(pfn))
+ return NULL;
check_pfn:
if (unlikely(pfn > highest_memmap_pfn)) {
print_bad_pte(vma, addr, pte, NULL);
return NULL;
}
- if (is_zero_pfn(pfn))
- return NULL;
-
/*
* NOTE! We still have PageReserved() pages in the page tables.
* eg. VDSO mappings can cause them to exist.