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authorTejun Heo <tj@kernel.org>2009-06-22 06:56:24 +0400
committerTejun Heo <tj@kernel.org>2009-06-22 06:56:24 +0400
commite59a1bb2fdfb745c685f5b40ffbed126331d3223 (patch)
treef2916a898b56f70554160f33be2252d15347fe8b /arch/x86/mm/pageattr.c
parent992f4c1c2c1583cef3296ec4bf5205843a9a5f3d (diff)
downloadlinux-e59a1bb2fdfb745c685f5b40ffbed126331d3223.tar.xz
x86: fix pageattr handling for lpage percpu allocator and re-enable it
lpage allocator aliases a PMD page for each cpu and returns whatever is unused to the page allocator. When the pageattr of the recycled pages are changed, this makes the two aliases point to the overlapping regions with different attributes which isn't allowed and known to cause subtle data corruption in certain cases. This can be handled in simliar manner to the x86_64 highmap alias. pageattr code should detect if the target pages have PMD alias and split the PMD alias and synchronize the attributes. pcpur allocator is updated to keep the allocated PMD pages map sorted in ascending address order and provide pcpu_lpage_remapped() function which binary searches the array to determine whether the given address is aliased and if so to which address. pageattr is updated to use pcpu_lpage_remapped() to detect the PMD alias and split it up as necessary from cpa_process_alias(). Jan Beulich spotted the original problem and incorrect usage of vaddr instead of laddr for lookup. With this, lpage percpu allocator should work correctly. Re-enable it. [ Impact: fix subtle lpage pageattr bug and re-enable lpage ] Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Jan Beulich <JBeulich@novell.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'arch/x86/mm/pageattr.c')
-rw-r--r--arch/x86/mm/pageattr.c21
1 files changed, 20 insertions, 1 deletions
diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index 2ab058b0947d..1b734d7a8966 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -11,6 +11,7 @@
#include <linux/interrupt.h>
#include <linux/seq_file.h>
#include <linux/debugfs.h>
+#include <linux/pfn.h>
#include <asm/e820.h>
#include <asm/processor.h>
@@ -682,7 +683,7 @@ static int cpa_process_alias(struct cpa_data *cpa)
{
struct cpa_data alias_cpa;
unsigned long laddr = (unsigned long)__va(cpa->pfn << PAGE_SHIFT);
- unsigned long vaddr;
+ unsigned long vaddr, remapped;
int ret;
if (cpa->pfn >= max_pfn_mapped)
@@ -737,6 +738,24 @@ static int cpa_process_alias(struct cpa_data *cpa)
}
#endif
+ /*
+ * If the PMD page was partially used for per-cpu remapping,
+ * the recycled area needs to be split and modified. Because
+ * the area is always proper subset of a PMD page
+ * cpa->numpages is guaranteed to be 1 for these areas, so
+ * there's no need to loop over and check for further remaps.
+ */
+ remapped = (unsigned long)pcpu_lpage_remapped((void *)laddr);
+ if (remapped) {
+ WARN_ON(cpa->numpages > 1);
+ alias_cpa = *cpa;
+ alias_cpa.vaddr = &remapped;
+ alias_cpa.flags &= ~(CPA_PAGES_ARRAY | CPA_ARRAY);
+ ret = __change_page_attr_set_clr(&alias_cpa, 0);
+ if (ret)
+ return ret;
+ }
+
return 0;
}