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| author | Nick Piggin <piggin@cyberone.com.au> | 2006-04-10 16:54:00 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2006-04-17 13:16:05 -0700 |
| commit | 2b53303840e1a8f1c7d007d988e8f497248ca270 (patch) | |
| tree | 855c466c03ca32099ad6bb983833e4011e3f90a7 /include | |
| parent | add92b7ade7eb528b7df6153f8bc773f5e2a80f1 (diff) | |
| download | lwn-2b53303840e1a8f1c7d007d988e8f497248ca270.tar.gz lwn-2b53303840e1a8f1c7d007d988e8f497248ca270.zip | |
[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>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/mm.h | 5 | ||||
| -rw-r--r-- | include/linux/page-flags.h | 8 |
2 files changed, 9 insertions, 4 deletions
diff --git a/include/linux/mm.h b/include/linux/mm.h index 498ff8778fb6..279446edd3c4 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 d52999c43336..d7ce72e433b4 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 @@ -319,6 +321,10 @@ 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) |