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authorNick Piggin <piggin@cyberone.com.au>2006-04-10 11:21:48 +1000
committerLinus Torvalds <torvalds@g5.osdl.org>2006-04-10 10:16:37 -0700
commit676165a8af7167f488abdcce6851a9bc36e83254 (patch)
treea9b2b8dc155b48ce073b5ada31f2ac0694118e69 /include/linux
parentc3a9d6541f84ac3ff566982d08389b87c1c36b4e (diff)
[PATCH] Fix buddy list race that could lead to page lru list corruptions
Rohit found an obscure bug causing buddy list corruption. page_is_buddy is using a non-atomic test (PagePrivate && page_count == 0) to determine whether or not a free page's buddy is itself free and in the buddy lists. Each of the conjuncts may be true at different times due to unrelated conditions, so the non-atomic page_is_buddy test may find each conjunct to be true even if they were not both true at the same time (ie. the page was not on the buddy lists). Signed-off-by: Martin Bligh <mbligh@google.com> Signed-off-by: Rohit Seth <rohitseth@google.com> Signed-off-by: Nick Piggin <npiggin@suse.de> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'include/linux')
-rw-r--r--include/linux/mm.h5
-rw-r--r--include/linux/page-flags.h8
2 files changed, 9 insertions, 4 deletions
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 6aa016f1d3a..1154684209a 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -229,10 +229,9 @@ struct page {
unsigned long private; /* Mapping-private opaque data:
* usually used for buffer_heads
* if PagePrivate set; used for
- * swp_entry_t if PageSwapCache.
- * When page is free, this
+ * swp_entry_t if PageSwapCache;
* indicates order in the buddy
- * system.
+ * system if PG_buddy is set.
*/
struct address_space *mapping; /* If low bit clear, points to
* inode address_space, or NULL.
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 9ea629c02a4..547aac7696c 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -74,7 +74,9 @@
#define PG_mappedtodisk 16 /* Has blocks allocated on-disk */
#define PG_reclaim 17 /* To be reclaimed asap */
#define PG_nosave_free 18 /* Free, should not be written */
-#define PG_uncached 19 /* Page has been mapped as uncached */
+#define PG_buddy 19 /* Page is free, on buddy lists */
+
+#define PG_uncached 20 /* Page has been mapped as uncached */
/*
* Global page accounting. One instance per CPU. Only unsigned longs are
@@ -317,6 +319,10 @@ extern void __mod_page_state_offset(unsigned long offset, unsigned long delta);
#define SetPageNosaveFree(page) set_bit(PG_nosave_free, &(page)->flags)
#define ClearPageNosaveFree(page) clear_bit(PG_nosave_free, &(page)->flags)
+#define PageBuddy(page) test_bit(PG_buddy, &(page)->flags)
+#define __SetPageBuddy(page) __set_bit(PG_buddy, &(page)->flags)
+#define __ClearPageBuddy(page) __clear_bit(PG_buddy, &(page)->flags)
+
#define PageMappedToDisk(page) test_bit(PG_mappedtodisk, &(page)->flags)
#define SetPageMappedToDisk(page) set_bit(PG_mappedtodisk, &(page)->flags)
#define ClearPageMappedToDisk(page) clear_bit(PG_mappedtodisk, &(page)->flags)