mm: Avoid putting a bad page back on the LRU

Prevent a page with a physical memory error from being placed back on the LRU. A new page flag bit is added. PG_memerror is given bit 32 and is only defined on 64 bit architectures. This avoids burning a page flag bit on 32 bit architectures. "BadPages:" is added to the output of /proc/meminfo to display the amount of memory marked bad (on 64 bit architectures).

---
 fs/proc/proc_misc.c        |    6 ++++++
 include/linux/kernel.h     |    1 +
 include/linux/page-flags.h |   23 +++++++++++++++++++++++
 include/linux/swap.h       |    1 +
 mm/migrate.c               |    3 +++
 mm/page_alloc.c            |   45 +++++++++++----------------------------------
 mm/swap.c                  |    4 ++++
 7 files changed, 49 insertions(+), 34 deletions(-)

Index: test/mm/swap.c
=================================--- test.orig/mm/swap.c 2008-04-25 15:22:11.204934760 -0500
+++ test/mm/swap.c 2008-04-25 15:42:02.806263586 -0500
@@ -208,6 +208,8 @@ void lru_cache_add(struct page *page)
struct pagevec *pvec = &get_cpu_var(lru_add_pvecs);

page_cache_get(page);
+ if (unlikely(PageMemError(page)))
+ return; /* Don't add bad pages to the page list */
if (!pagevec_add(pvec, page))
__pagevec_lru_add(pvec);
put_cpu_var(lru_add_pvecs);
@@ -218,6 +220,8 @@ void lru_cache_add_active(struct page *p
struct pagevec *pvec = &get_cpu_var(lru_add_active_pvecs);

page_cache_get(page);
+ if (unlikely(PageMemError(page)))
+ return; /* Don't add bad pages to the page list */
if (!pagevec_add(pvec, page))
__pagevec_lru_add_active(pvec);
put_cpu_var(lru_add_active_pvecs);
Index: test/mm/page_alloc.c
=================================--- test.orig/mm/page_alloc.c 2008-04-25 15:22:11.196933787 -0500
+++ test/mm/page_alloc.c 2008-04-25 15:42:02.818265056 -0500
@@ -70,6 +70,7 @@ unsigned long totalram_pages __read_most
unsigned long totalreserve_pages __read_mostly; long nr_swap_pages;
int percpu_pagelist_fraction;
+unsigned int totalbad_pages;

#ifdef CONFIG_HUGETLB_PAGE_SIZE_VARIABLE
int pageblock_order __read_mostly;
@@ -236,16 +237,7 @@ 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();
- page->flags &= ~(1 << PG_lru |
- 1 << PG_private |
- 1 << PG_locked |
- 1 << PG_active |
- 1 << PG_dirty |
- 1 << PG_reclaim |
- 1 << PG_slab |
- 1 << PG_swapcache |
- 1 << PG_writeback |
- 1 << PG_buddy );
+ page->flags &= ~(PAGE_FLAGS_RECLAIM);
set_page_count(page, 0);
reset_page_mapcount(page);
page->mapping = NULL;
@@ -462,16 +454,7 @@ static inline int free_pages_check(struc
(page->mapping != NULL) | (page_get_page_cgroup(page) != NULL) | (page_count(page) != 0) |
- (page->flags & (
- 1 << PG_lru |
- 1 << PG_private |
- 1 << PG_locked |
- 1 << PG_active |
- 1 << PG_slab |
- 1 << PG_swapcache |
- 1 << PG_writeback |
- 1 << PG_reserved |
- 1 << PG_buddy ))))
+ (page->flags & (PAGE_FLAGS_RESERVE))))
bad_page(page);
if (PageDirty(page))
__ClearPageDirty(page);
@@ -612,24 +595,14 @@ static int prep_new_page(struct page *pa
(page->mapping != NULL) | (page_get_page_cgroup(page) != NULL) | (page_count(page) != 0) |
- (page->flags & (
- 1 << PG_lru |
- 1 << PG_private |
- 1 << PG_locked |
- 1 << PG_active |
- 1 << PG_dirty |
- 1 << PG_slab |
- 1 << PG_swapcache |
- 1 << PG_writeback |
- 1 << PG_reserved |
- 1 << PG_buddy ))))
+ (page->flags & (PAGE_FLAGS_DIRTY))))
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.
+ * For now, we report if PG_reserved or PG_memerror was found set, but
+ * do not clear it, and do not allocate the page: as a safety net.
*/
- if (PageReserved(page))
+ if (PageReserved(page) || PageMemError(page))
return 1;

page->flags &= ~(1 << PG_uptodate | 1 << PG_error | 1 << PG_readahead |
@@ -1762,6 +1735,7 @@ void si_meminfo(struct sysinfo *val)
val->totalhigh = totalhigh_pages;
val->freehigh = nr_free_highpages();
val->mem_unit = PAGE_SIZE;
+ val->badpages = totalbad_pages;
}

EXPORT_SYMBOL(si_meminfo);
@@ -2478,6 +2452,9 @@ static void setup_zone_migrate_reserve(s

/* Blocks with reserved pages will never free, skip them. */ if (PageReserved(page))
+ continue;
+ /* Blocks with error pages will never free, skip them. */
+ if (PageMemError(page))
continue;

block_migratetype = get_pageblock_migratetype(page);
Index: test/include/linux/kernel.h
=================================--- test.orig/include/linux/kernel.h 2008-04-25 15:22:07.640501421 -0500
+++ test/include/linux/kernel.h 2008-04-25 15:42:02.826266036 -0500
@@ -412,6 +412,7 @@ struct sysinfo {
unsigned long totalhigh; /* Total high memory size */
unsigned long freehigh; /* Available high memory size */
unsigned int mem_unit; /* Memory unit size in bytes */
+ unsigned int badpages; /* Number of bad (PG_memerror) pages */
char _f[20-2*sizeof(long)-sizeof(int)]; /* Padding: libc5 uses this.. */
};

Index: test/include/linux/swap.h
=================================--- test.orig/include/linux/swap.h 2008-04-25 15:22:08.040550056 -0500
+++ test/include/linux/swap.h 2008-04-25 15:42:02.854269468 -0500
@@ -165,6 +165,7 @@ extern unsigned long totalreserve_pages;
extern long nr_swap_pages;
extern unsigned int nr_free_buffer_pages(void); extern unsigned int nr_free_pagecache_pages(void);
+extern unsigned int totalbad_pages;

/* Definition of global_page_state not available yet */ #define nr_free_pages() global_page_state(NR_FREE_PAGES)
Index: test/mm/migrate.c
=================================--- test.orig/mm/migrate.c 2008-04-25 15:22:11.192933300 -0500
+++ test/mm/migrate.c 2008-04-28 13:27:48.686601486 -0500
@@ -368,6 +368,7 @@ static void migrate_page_copy(struct pag
{
copy_highpage(newpage, page);

+ /* Do not migrate PG_memerror to the new page */
if (PageError(page))
SetPageError(newpage);
if (PageReferenced(page))
@@ -714,6 +715,8 @@ unlock:
*/
list_del(&page->lru);
move_to_lru(page);
+ if (PageMemError(page))
+ totalbad_pages++;
}

move_newpage:
Index: test/fs/proc/proc_misc.c
=================================--- test.orig/fs/proc/proc_misc.c 2008-04-25 15:22:04.684142013 -0500
+++ test/fs/proc/proc_misc.c 2008-04-25 15:42:02.890273879 -0500
@@ -179,6 +179,9 @@ static int meminfo_read_proc(char *page,
"PageTables: %8lu kB\n"
"NFS_Unstable: %8lu kB\n"
"Bounce: %8lu kB\n"
+#if (BITS_PER_LONG > 32)
+ "BadPages: %8u kB\n"
+#endif
"CommitLimit: %8lu kB\n"
"Committed_AS: %8lu kB\n"
"VmallocTotal: %8lu kB\n"
@@ -210,6 +213,9 @@ static int meminfo_read_proc(char *page,
K(global_page_state(NR_PAGETABLE)), K(global_page_state(NR_UNSTABLE_NFS)), K(global_page_state(NR_BOUNCE)),
+#if (BITS_PER_LONG > 32)
+ K(i.badpages),
+#endif
K(allowed),
K(committed),
(unsigned long)VMALLOC_TOTAL >> 10,
Index: test/include/linux/page-flags.h
=================================--- test.orig/include/linux/page-flags.h 2008-04-25 15:22:07.868529143 -0500
+++ test/include/linux/page-flags.h 2008-04-25 15:42:02.914276820 -0500
@@ -48,6 +48,9 @@
* PG_buddy is set to indicate that the page is free and in the buddy system
* (see mm/page_alloc.c).
*
+ * PG_memerror indicates a physical memory error on the page. The page
+ * should not be reused (ie put on the LRU).
+ *
*/

/*
@@ -106,6 +109,7 @@
* 63 32 0
*/
#define PG_uncached 31 /* Page has been mapped as uncached */
+#define PG_memerror 32 /* Page has a physical memory error */
#endif

/*
@@ -307,5 +311,24 @@ static inline void set_page_writeback(st
{
test_set_page_writeback(page);
}
+
+#if (BITS_PER_LONG > 32)
+#define PageMemError(page) test_bit(PG_memerror, &(page)->flags)
+#define SetPageMemError(page) set_bit(PG_memerror, &(page)->flags)
+#define ClearPageMemError(page) clear_bit(PG_memerror, &(page)->flags)
+#define PAGE_FLAGS (1 << PG_lru | 1 << PG_private | 1 << PG_locked | \

+			 1 << PG_buddy | 1 << PG_writeback | \
+			 1 << PG_slab  | 1 << PG_swapcache | 1 << PG_active | \

+ 1UL << PG_memerror)
+#else
+#define PageMemError(page) 0
+#define PAGE_FLAGS (1 << PG_lru | 1 << PG_private | 1 << PG_locked | \

+			 1 << PG_buddy | 1 << PG_writeback | \
+			 1 << PG_slab  | 1 << PG_swapcache | 1 << PG_active)

+#endif
+#define PAGE_FLAGS_RECLAIM (PAGE_FLAGS | 1 << PG_reclaim | 1 << PG_dirty)
+#define PAGE_FLAGS_RESERVE (PAGE_FLAGS | 1 << PG_reserved)
+#define PAGE_FLAGS_DIRTY (PAGE_FLAGS | 1 << PG_reserved | 1 << PG_dirty)
+

#endif /* PAGE_FLAGS_H */

Russ Anderson, OS RAS/Partitioning Project Lead  
SGI - Silicon Graphics Inc          [email protected]

not if you also reduce the padding ??

OK. The only reason badpages was added was to print the number of page pages in /proc/meminfo. I'll go with plan B, a badmem driver for displaying bad page info.

Russ Anderson, OS RAS/Partitioning Project Lead  
SGI - Silicon Graphics Inc          [email protected]