The patch titled
Subject: numa: fix /proc/<pid>/numa_maps for THP
has been added to the -mm tree. Its filename is
numa-fix-proc-pid-numa_maps-for-thp.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/numa-fix-proc-pid-numa_maps-for-thp.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/numa-fix-proc-pid-numa_maps-for-thp.patch
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------------------------------------------------------
From: Gerald Schaefer <gerald.schaefer@xxxxxxxxxx>
Subject: numa: fix /proc/<pid>/numa_maps for THP
In gather_pte_stats() a THP pmd is cast into a pte, which is wrong because
the layouts may differ depending on the architecture. On s390 this will
lead to inaccurate numa_maps accounting in /proc because of misguided
pte_present() and pte_dirty() checks on the fake pte.
On other architectures pte_present() and pte_dirty() may work by chance,
but there may be an issue with direct-access (dax) mappings w/o underlying
struct pages when HAVE_PTE_SPECIAL is set and THP is available. In
vm_normal_page() the fake pte will be checked with pte_special() and
because there is no "special" bit in a pmd, this will always return false
and the VM_PFNMAP | VM_MIXEDMAP checking will be skipped. On dax mappings
w/o struct pages, an invalid struct page pointer would then be returned
that can crash the kernel.
This patch fixes the numa_maps THP handling by introducing new "_pmd" variants
of the can_gather_numa_stats() and vm_normal_page() functions.
Signed-off-by: Gerald Schaefer <gerald.schaefer@xxxxxxxxxx>
Cc: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Cc: "Kirill A . Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Konstantin Khlebnikov <koct9i@xxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Jerome Marchand <jmarchan@xxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
Cc: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
Cc: Michael Holzheu <holzheu@xxxxxxxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> [4.3+]
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/proc/task_mmu.c | 33 ++++++++++++++++++++++++++++++---
include/linux/mm.h | 2 ++
mm/memory.c | 40 ++++++++++++++++++++++++++++++++++++++++
3 files changed, 72 insertions(+), 3 deletions(-)
diff -puN fs/proc/task_mmu.c~numa-fix-proc-pid-numa_maps-for-thp fs/proc/task_mmu.c
--- a/fs/proc/task_mmu.c~numa-fix-proc-pid-numa_maps-for-thp
+++ a/fs/proc/task_mmu.c
@@ -1518,6 +1518,32 @@ static struct page *can_gather_numa_stat
return page;
}
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+static struct page *can_gather_numa_stats_pmd(pmd_t pmd,
+ struct vm_area_struct *vma,
+ unsigned long addr)
+{
+ struct page *page;
+ int nid;
+
+ if (!pmd_present(pmd))
+ return NULL;
+
+ page = vm_normal_page_pmd(vma, addr, pmd);
+ if (!page)
+ return NULL;
+
+ if (PageReserved(page))
+ return NULL;
+
+ nid = page_to_nid(page);
+ if (!node_isset(nid, node_states[N_MEMORY]))
+ return NULL;
+
+ return page;
+}
+#endif
+
static int gather_pte_stats(pmd_t *pmd, unsigned long addr,
unsigned long end, struct mm_walk *walk)
{
@@ -1527,14 +1553,14 @@ static int gather_pte_stats(pmd_t *pmd,
pte_t *orig_pte;
pte_t *pte;
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
ptl = pmd_trans_huge_lock(pmd, vma);
if (ptl) {
- pte_t huge_pte = *(pte_t *)pmd;
struct page *page;
- page = can_gather_numa_stats(huge_pte, vma, addr);
+ page = can_gather_numa_stats_pmd(*pmd, vma, addr);
if (page)
- gather_stats(page, md, pte_dirty(huge_pte),
+ gather_stats(page, md, pmd_dirty(*pmd),
HPAGE_PMD_SIZE/PAGE_SIZE);
spin_unlock(ptl);
return 0;
@@ -1542,6 +1568,7 @@ static int gather_pte_stats(pmd_t *pmd,
if (pmd_trans_unstable(pmd))
return 0;
+#endif
orig_pte = pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
do {
struct page *page = can_gather_numa_stats(*pte, vma, addr);
diff -puN include/linux/mm.h~numa-fix-proc-pid-numa_maps-for-thp include/linux/mm.h
--- a/include/linux/mm.h~numa-fix-proc-pid-numa_maps-for-thp
+++ a/include/linux/mm.h
@@ -1140,6 +1140,8 @@ struct zap_details {
struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
pte_t pte);
+struct page *vm_normal_page_pmd(struct vm_area_struct *vma, unsigned long addr,
+ pmd_t pmd);
int zap_vma_ptes(struct vm_area_struct *vma, unsigned long address,
unsigned long size);
diff -puN mm/memory.c~numa-fix-proc-pid-numa_maps-for-thp mm/memory.c
--- a/mm/memory.c~numa-fix-proc-pid-numa_maps-for-thp
+++ a/mm/memory.c
@@ -789,6 +789,46 @@ out:
return pfn_to_page(pfn);
}
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+struct page *vm_normal_page_pmd(struct vm_area_struct *vma, unsigned long addr,
+ pmd_t pmd)
+{
+ unsigned long pfn = pmd_pfn(pmd);
+
+ /*
+ * There is no pmd_special() but there may be special pmds, e.g.
+ * in a direct-access (dax) mapping, so let's just replicate the
+ * !HAVE_PTE_SPECIAL case from vm_normal_page() here.
+ */
+ if (unlikely(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP))) {
+ if (vma->vm_flags & VM_MIXEDMAP) {
+ if (!pfn_valid(pfn))
+ return NULL;
+ goto out;
+ } else {
+ unsigned long off;
+ off = (addr - vma->vm_start) >> PAGE_SHIFT;
+ if (pfn == vma->vm_pgoff + off)
+ return NULL;
+ if (!is_cow_mapping(vma->vm_flags))
+ return NULL;
+ }
+ }
+
+ if (is_zero_pfn(pfn))
+ return NULL;
+ if (unlikely(pfn > highest_memmap_pfn))
+ return NULL;
+
+ /*
+ * NOTE! We still have PageReserved() pages in the page tables.
+ * eg. VDSO mappings can cause them to exist.
+ */
+out:
+ return pfn_to_page(pfn);
+}
+#endif
+
/*
* copy one vm_area from one task to the other. Assumes the page tables
* already present in the new task to be cleared in the whole range
_
Patches currently in -mm which might be from gerald.schaefer@xxxxxxxxxx are
numa-fix-proc-pid-numa_maps-for-thp.patch
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