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Subject[PATCH 2/4] debug-pagealloc: add support for highmem pages
Date
This adds support for highmem pages poisoning and verification to the
debug-pagealloc feature for no-architecture support.

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
---
mm/debug-pagealloc.c | 61 ++++++++++++++++++++++++-------------------------
1 files changed, 30 insertions(+), 31 deletions(-)

diff --git a/mm/debug-pagealloc.c b/mm/debug-pagealloc.c
index a4b6d70..5afe80c 100644
--- a/mm/debug-pagealloc.c
+++ b/mm/debug-pagealloc.c
@@ -1,5 +1,6 @@
#include <linux/kernel.h>
#include <linux/mm.h>
+#include <linux/highmem.h>
#include <linux/page-debug-flags.h>
#include <linux/poison.h>
#include <linux/ratelimit.h>
@@ -19,28 +20,25 @@ static inline bool page_poison(struct page *page)
return test_bit(PAGE_DEBUG_FLAG_POISON, &page->debug_flags);
}

-static void poison_highpage(struct page *page)
-{
- /*
- * Page poisoning for highmem pages is not implemented.
- *
- * This can be called from interrupt contexts.
- * So we need to create a new kmap_atomic slot for this
- * application and it will need interrupt protection.
- */
-}
-
static void poison_page(struct page *page)
{
void *addr;
-
- if (PageHighMem(page)) {
- poison_highpage(page);
- return;
+ unsigned long flags;
+ bool highmem = PageHighMem(page);
+
+ if (highmem) {
+ local_irq_save(flags);
+ addr = kmap_atomic(page);
+ } else {
+ addr = page_address(page);
}
set_page_poison(page);
- addr = page_address(page);
memset(addr, PAGE_POISON, PAGE_SIZE);
+
+ if (highmem) {
+ kunmap_atomic(addr);
+ local_irq_restore(flags);
+ }
}

static void poison_pages(struct page *page, int n)
@@ -88,26 +86,27 @@ static void check_poison_mem(unsigned char *mem, size_t bytes)
dump_stack();
}

-static void unpoison_highpage(struct page *page)
-{
- /*
- * See comment in poison_highpage().
- * Highmem pages should not be poisoned for now
- */
- BUG_ON(page_poison(page));
-}
-
static void unpoison_page(struct page *page)
{
- if (PageHighMem(page)) {
- unpoison_highpage(page);
+ void *addr;
+ unsigned long flags;
+ bool highmem = PageHighMem(page);
+
+ if (!page_poison(page))
return;
+
+ if (highmem) {
+ local_irq_save(flags);
+ addr = kmap_atomic(page);
+ } else {
+ addr = page_address(page);
}
- if (page_poison(page)) {
- void *addr = page_address(page);
+ check_poison_mem(addr, PAGE_SIZE);
+ clear_page_poison(page);

- check_poison_mem(addr, PAGE_SIZE);
- clear_page_poison(page);
+ if (highmem) {
+ kunmap_atomic(addr);
+ local_irq_restore(flags);
}
}

--
1.7.4.4


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