debug-pagealloc: add support for highmem pages

This adds support for highmem pages poisoning and verification to the
debug-pagealloc feature for no-architecture support.

[akpm@linux-foundation.org: remove unneeded preempt_disable/enable]
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 10 insertions, 34 deletions

diff --git a/mm/debug-pagealloc.c b/mm/debug-pagealloc.c
index 2618933efdb3..7cea557407f4 100644
--- a/mm/debug-pagealloc.c
+++ b/mm/debug-pagealloc.c
@@ -1,6 +1,7 @@
 #include <linux/kernel.h>
 #include <linux/string.h>
 #include <linux/mm.h>
+#include <linux/highmem.h>
 #include <linux/page-debug-flags.h>
 #include <linux/poison.h>
 #include <linux/ratelimit.h>
@@ -20,28 +21,13 @@ 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;
+        void *addr = kmap_atomic(page);
 
-        if (PageHighMem(page)) {
-                poison_highpage(page);
-                return;
-        }
         set_page_poison(page);
-        addr = page_address(page);
         memset(addr, PAGE_POISON, PAGE_SIZE);
+        kunmap_atomic(addr);
 }
 
 static void poison_pages(struct page *page, int n)
@@ -86,27 +72,17 @@ 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;
+
+        if (!page_poison(page))
                 return;
-        }
-        if (page_poison(page)) {
-                void *addr = page_address(page);
 
-                check_poison_mem(addr, PAGE_SIZE);
-                clear_page_poison(page);
-        }
+        addr = kmap_atomic(page);
+        check_poison_mem(addr, PAGE_SIZE);
+        clear_page_poison(page);
+        kunmap_atomic(addr);
 }
 
 static void unpoison_pages(struct page *page, int n)