From 5c0e3066474b57c56ff0d88ca31d95bd14232fee Mon Sep 17 00:00:00 2001 From: Mel Gorman Date: Tue, 16 Oct 2007 01:25:56 -0700 Subject: Fix corruption of memmap on IA64 SPARSEMEM when mem_section is not a power of 2 There are problems in the use of SPARSEMEM and pageblock flags that causes problems on ia64. The first part of the problem is that units are incorrect in SECTION_BLOCKFLAGS_BITS computation. This results in a map_section's section_mem_map being treated as part of a bitmap which isn't good. This was evident with an invalid virtual address when mem_init attempted to free bootmem pages while relinquishing control from the bootmem allocator. The second part of the problem occurs because the pageblock flags bitmap is be located with the mem_section. The SECTIONS_PER_ROOT computation using sizeof (mem_section) may not be a power of 2 depending on the size of the bitmap. This renders masks and other such things not power of 2 base. This issue was seen with SPARSEMEM_EXTREME on ia64. This patch moves the bitmap outside of mem_section and uses a pointer instead in the mem_section. The bitmaps are allocated when the section is being initialised. Note that sparse_early_usemap_alloc() does not use alloc_remap() like sparse_early_mem_map_alloc(). The allocation required for the bitmap on x86, the only architecture that uses alloc_remap is typically smaller than a cache line. alloc_remap() pads out allocations to the cache size which would be a needless waste. Credit to Bob Picco for identifying the original problem and effecting a fix for the SECTION_BLOCKFLAGS_BITS calculation. Credit to Andy Whitcroft for devising the best way of allocating the bitmaps only when required for the section. [wli@holomorphy.com: warning fix] Signed-off-by: Bob Picco Signed-off-by: Andy Whitcroft Signed-off-by: Mel Gorman Cc: "Luck, Tony" Signed-off-by: William Irwin Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/mmzone.h | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) (limited to 'include/linux') diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index a8140a9a65e..9a5d5590bd3 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -748,7 +748,7 @@ extern struct zone *next_zone(struct zone *zone); #define PAGE_SECTION_MASK (~(PAGES_PER_SECTION-1)) #define SECTION_BLOCKFLAGS_BITS \ - ((SECTION_SIZE_BITS - (MAX_ORDER-1)) * NR_PAGEBLOCK_BITS) + ((1 << (PFN_SECTION_SHIFT - (MAX_ORDER-1))) * NR_PAGEBLOCK_BITS) #if (MAX_ORDER - 1 + PAGE_SHIFT) > SECTION_SIZE_BITS #error Allocator MAX_ORDER exceeds SECTION_SIZE @@ -769,7 +769,9 @@ struct mem_section { * before using it wrong. */ unsigned long section_mem_map; - DECLARE_BITMAP(pageblock_flags, SECTION_BLOCKFLAGS_BITS); + + /* See declaration of similar field in struct zone */ + unsigned long *pageblock_flags; }; #ifdef CONFIG_SPARSEMEM_EXTREME -- cgit v1.2.3