The patch titled
Check for PageSlab in arch flush_dcache_page to avoid triggering VM_BUG_ON
has been added to the -mm tree. Its filename is
check-for-pageslab-in-arch-flush_dcache_page-to-avoid-triggering-vm_bug_on.patch
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: Check for PageSlab in arch flush_dcache_page to avoid triggering VM_BUG_ON
From: Christoph Lameter <clameter@xxxxxxx>
We added a VM_BUG_ON in include/linux/mm.h to detect page cache functions
used on slab pages. However, arches that have virtual caches may call
flush_dcache_page for slab pages since they may have been put on scatter
gather lists.
Modify the functions in the affected arches to check for PageSlab() and use
a NULL mapping if such a page is encountered. This may only be necessary
for parisc and arm since sparc64 and xtensa do not scan over processes
mapping a page but I have modified those two arches also for correctnesses
sake since they use page_mapping() in flush_dcache_page().
If we have done that then we no longer need to return a NULL mapping in
page_mapping() for slab pages (Its a bit strange to have that given the
earlier VM_BUG_ON(PageSlab(page)).
Signed-off-by: Christoph Lameter <clameter@xxxxxxx>
Cc: Russell King <rmk@xxxxxxxxxxxxxxxx>
Cc: Kyle McMartin <kyle@xxxxxxxxxxx>
Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
Cc: Christian Zankel <chris@xxxxxxxxxx>
Cc: Hugh Dickins <hugh@xxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/arm/mm/flush.c | 12 +++++++++++-
arch/parisc/kernel/cache.c | 11 ++++++++++-
arch/sparc64/mm/init.c | 10 +++++++++-
arch/xtensa/mm/init.c | 11 ++++++++++-
include/linux/mm.h | 4 ----
5 files changed, 40 insertions(+), 8 deletions(-)
diff -puN arch/arm/mm/flush.c~check-for-pageslab-in-arch-flush_dcache_page-to-avoid-triggering-vm_bug_on arch/arm/mm/flush.c
--- a/arch/arm/mm/flush.c~check-for-pageslab-in-arch-flush_dcache_page-to-avoid-triggering-vm_bug_on
+++ a/arch/arm/mm/flush.c
@@ -188,7 +188,17 @@ static void __flush_dcache_aliases(struc
*/
void flush_dcache_page(struct page *page)
{
- struct address_space *mapping = page_mapping(page);
+ struct address_space *mapping;
+
+ /*
+ * This function is special in that a page struct obtained via
+ * virt_to_page from a slab object may be passed to it. However, slab
+ * allocators may use the mapping field for their own purposes. As a
+ * result mapping may be != NULL here although the page is not mapped.
+ * Slab objects are never mapped into user space so use NULL for that
+ * special case.
+ */
+ mapping = PageSlab(page) ? NULL : page_mapping(page);
#ifndef CONFIG_SMP
if (mapping && !mapping_mapped(mapping))
diff -puN arch/parisc/kernel/cache.c~check-for-pageslab-in-arch-flush_dcache_page-to-avoid-triggering-vm_bug_on arch/parisc/kernel/cache.c
--- a/arch/parisc/kernel/cache.c~check-for-pageslab-in-arch-flush_dcache_page-to-avoid-triggering-vm_bug_on
+++ a/arch/parisc/kernel/cache.c
@@ -339,7 +339,7 @@ __flush_cache_page(struct vm_area_struct
void flush_dcache_page(struct page *page)
{
- struct address_space *mapping = page_mapping(page);
+ struct address_space *mapping;
struct vm_area_struct *mpnt;
struct prio_tree_iter iter;
unsigned long offset;
@@ -347,6 +347,15 @@ void flush_dcache_page(struct page *page
pgoff_t pgoff;
unsigned long pfn = page_to_pfn(page);
+ /*
+ * This function is special in that a page struct obtained via
+ * virt_to_page from a slab object may be passed to it. However, slab
+ * allocators may use the mapping field for their own purposes. As a
+ * result mapping may be != NULL here although the page is not mapped.
+ * Slab objects are never mapped into user space so use NULL for that
+ * special case.
+ */
+ mapping = PageSlab(page) ? NULL : page_mapping(page);
if (mapping && !mapping_mapped(mapping)) {
set_bit(PG_dcache_dirty, &page->flags);
diff -puN arch/sparc64/mm/init.c~check-for-pageslab-in-arch-flush_dcache_page-to-avoid-triggering-vm_bug_on arch/sparc64/mm/init.c
--- a/arch/sparc64/mm/init.c~check-for-pageslab-in-arch-flush_dcache_page-to-avoid-triggering-vm_bug_on
+++ a/arch/sparc64/mm/init.c
@@ -339,7 +339,15 @@ void flush_dcache_page(struct page *page
this_cpu = get_cpu();
- mapping = page_mapping(page);
+ /*
+ * This function is special in that a page struct obtained via
+ * virt_to_page from a slab object may be passed to it. However, slab
+ * allocators may use the mapping field for their own purposes. As a
+ * result mapping may be != NULL here although the page is not mapped.
+ * Slab objects are never mapped into user space so use NULL for that
+ * special case.
+ */
+ mapping = PageSlab(page) ? NULL : page_mapping(page);
if (mapping && !mapping_mapped(mapping)) {
int dirty = test_bit(PG_dcache_dirty, &page->flags);
if (dirty) {
diff -puN arch/xtensa/mm/init.c~check-for-pageslab-in-arch-flush_dcache_page-to-avoid-triggering-vm_bug_on arch/xtensa/mm/init.c
--- a/arch/xtensa/mm/init.c~check-for-pageslab-in-arch-flush_dcache_page-to-avoid-triggering-vm_bug_on
+++ a/arch/xtensa/mm/init.c
@@ -433,7 +433,7 @@ void copy_user_page(void* to, void* from
void flush_dcache_page(struct page *page)
{
unsigned long addr = __pa(page_address(page));
- struct address_space *mapping = page_mapping(page);
+ struct address_space *mapping;
__flush_invalidate_dcache_page_phys(addr);
@@ -442,6 +442,15 @@ void flush_dcache_page(struct page *page
/* If this page hasn't been mapped, yet, handle I$/D$ coherency later.*/
#if 0
+ /*
+ * This function is special in that a page struct obtained via
+ * virt_to_page from a slab object may be passed to it. However, slab
+ * allocators may use the mapping field for their own purposes. As a
+ * result mapping may be != NULL although the page is not mapped.
+ * Slab objects are never mapped into user space so use NULL for that
+ * special case.
+ */
+ mapping = PageSlab(page) ? NULL : page_mapping(page);
if (mapping && !mapping_mapped(mapping))
clear_bit(PG_cache_clean, &page->flags);
else
diff -puN include/linux/mm.h~check-for-pageslab-in-arch-flush_dcache_page-to-avoid-triggering-vm_bug_on include/linux/mm.h
--- a/include/linux/mm.h~check-for-pageslab-in-arch-flush_dcache_page-to-avoid-triggering-vm_bug_on
+++ a/include/linux/mm.h
@@ -630,10 +630,6 @@ static inline struct address_space *page
VM_BUG_ON(PageSlab(page));
if (unlikely(PageSwapCache(page)))
mapping = &swapper_space;
-#ifdef CONFIG_SLUB
- else if (unlikely(PageSlab(page)))
- mapping = NULL;
-#endif
else if (unlikely((unsigned long)mapping & PAGE_MAPPING_ANON))
mapping = NULL;
return mapping;
_
Patches currently in -mm which might be from clameter@xxxxxxx are
check-for-pageslab-in-arch-flush_dcache_page-to-avoid-triggering-vm_bug_on.patch
pa-risc-use-page-allocator-instead-of-slab-allocator.patch
try-parent-numa_node-at-first-before-using-default-v2.patch
try-parent-numa_node-at-first-before-using-default-v2-fix.patch
sparsemem-clean-up-spelling-error-in-comments.patch
sparsemem-record-when-a-section-has-a-valid-mem_map.patch
generic-virtual-memmap-support-for-sparsemem.patch
x86_64-sparsemem_vmemmap-2m-page-size-support.patch
ia64-sparsemem_vmemmap-16k-page-size-support.patch
sparc64-sparsemem_vmemmap-support.patch
ppc64-sparsemem_vmemmap-support.patch
slubcearly_kmem_cache_node_alloc-shouldnt-be.patch
group-short-lived-and-reclaimable-kernel-allocations.patch
fix-calculation-in-move_freepages_block-for-counting-pages.patch
breakout-page_order-to-internalh-to-avoid-special-knowledge-of-the-buddy-allocator.patch
do-not-depend-on-max_order-when-grouping-pages-by-mobility.patch
print-out-statistics-in-relation-to-fragmentation-avoidance-to-proc-pagetypeinfo.patch
have-kswapd-keep-a-minimum-order-free-other-than-order-0.patch
only-check-absolute-watermarks-for-alloc_high-and-alloc_harder-allocations.patch
slub-exploit-page-mobility-to-increase-allocation-order.patch
slub-reduce-antifrag-max-order.patch
slub-slab-validation-move-tracking-information-alloc-outside-of-melstuff.patch
memory-unplug-v7-migration-by-kernel.patch
memory-unplug-v7-isolate_lru_page-fix.patch
intel-iommu-dmar-detection-and-parsing-logic.patch
intel-iommu-pci-generic-helper-function.patch
intel-iommu-clflush_cache_range-now-takes-size-param.patch
intel-iommu-iova-allocation-and-management-routines.patch
intel-iommu-intel-iommu-driver.patch
intel-iommu-avoid-memory-allocation-failures-in-dma-map-api-calls.patch
intel-iommu-intel-iommu-cmdline-option-forcedac.patch
intel-iommu-dmar-fault-handling-support.patch
intel-iommu-iommu-gfx-workaround.patch
intel-iommu-iommu-floppy-workaround.patch
revoke-core-code.patch
mm-implement-swap-prefetching.patch
rename-gfp_high_movable-to-gfp_highuser_movable-prefetch.patch
cpuset-zero-malloc-revert-the-old-cpuset-fix.patch
page-owner-tracking-leak-detector.patch
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