badpage: keep any bad page out of circulation

Until now the bad_page() checkers have special-cased PageReserved, keeping
those pages out of circulation thereafter.  Now extend the special case to
all: we want to keep ANY page with bad state out of circulation - the
"free" page may well be in use by something.

Leave the bad state of those pages untouched, for examination by
debuggers; except for PageBuddy - leaving that set would risk bringing the
page back.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index b90a74d..bd33025 100644 (file)
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -231,9 +231,9 @@ static void bad_page(struct page *page)
        printk(KERN_EMERG "Trying to fix it up, but a reboot is needed\n"
                KERN_EMERG "Backtrace:\n");
        dump_stack();
-       set_page_count(page, 0);
-       reset_page_mapcount(page);
-       page->mapping = NULL;
+
+       /* Leave bad fields for debug, except PageBuddy could make trouble */
+       __ClearPageBuddy(page);
        add_taint(TAINT_BAD_PAGE);
 }
 
@@ -290,25 +290,31 @@ void prep_compound_gigantic_page(struct page *page, unsigned long order)
 }
 #endif
 
-static void destroy_compound_page(struct page *page, unsigned long order)
+static int destroy_compound_page(struct page *page, unsigned long order)
 {
        int i;
        int nr_pages = 1 << order;
+       int bad = 0;
 
-       if (unlikely(compound_order(page) != order))
+       if (unlikely(compound_order(page) != order) ||
+           unlikely(!PageHead(page))) {
                bad_page(page);
+               bad++;
+       }
 
-       if (unlikely(!PageHead(page)))
-                       bad_page(page);
        __ClearPageHead(page);
+
        for (i = 1; i < nr_pages; i++) {
                struct page *p = page + i;
 
-               if (unlikely(!PageTail(p) |
-                               (p->first_page != page)))
+               if (unlikely(!PageTail(p) | (p->first_page != page))) {
                        bad_page(page);
+                       bad++;
+               }
                __ClearPageTail(p);
        }
+
+       return bad;
 }
 
 static inline void prep_zero_page(struct page *page, int order, gfp_t gfp_flags)
@@ -428,7 +434,8 @@ static inline void __free_one_page(struct page *page,
        int migratetype = get_pageblock_migratetype(page);
 
        if (unlikely(PageCompound(page)))
-               destroy_compound_page(page, order);
+               if (unlikely(destroy_compound_page(page, order)))
+                       return;
 
        page_idx = page_to_pfn(page) & ((1 << MAX_ORDER) - 1);
 
@@ -465,15 +472,10 @@ static inline int free_pages_check(struct page *page)
        if (unlikely(page_mapcount(page) |
                (page->mapping != NULL)  |
                (page_count(page) != 0)  |
-               (page->flags & PAGE_FLAGS_CHECK_AT_FREE)))
+               (page->flags & PAGE_FLAGS_CHECK_AT_FREE))) {
                bad_page(page);
-       /*
-        * For now, we report if PG_reserved was found set, but do not
-        * clear it, and do not free the page.  But we shall soon need
-        * to do more, for when the ZERO_PAGE count wraps negative.
-        */
-       if (PageReserved(page))
                return 1;
+       }
        if (page->flags & PAGE_FLAGS_CHECK_AT_PREP)
                page->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
        return 0;
@@ -521,11 +523,11 @@ static void __free_pages_ok(struct page *page, unsigned int order)
 {
        unsigned long flags;
        int i;
-       int reserved = 0;
+       int bad = 0;
 
        for (i = 0 ; i < (1 << order) ; ++i)
-               reserved += free_pages_check(page + i);
-       if (reserved)
+               bad += free_pages_check(page + i);
+       if (bad)
                return;
 
        if (!PageHighMem(page)) {
@@ -610,17 +612,11 @@ static int prep_new_page(struct page *page, int order, gfp_t gfp_flags)
        if (unlikely(page_mapcount(page) |
                (page->mapping != NULL)  |
                (page_count(page) != 0)  |
-               (page->flags & PAGE_FLAGS_CHECK_AT_PREP)))
+               (page->flags & PAGE_FLAGS_CHECK_AT_PREP))) {
                bad_page(page);
-
-       /*
-        * For now, we report if PG_reserved was found set, but do not
-        * clear it, and do not allocate the page: as a safety net.
-        */
-       if (PageReserved(page))
                return 1;
+       }
 
-       page->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
        set_page_private(page, 0);
        set_page_refcounted(page);