diff options
| -rw-r--r-- | extent_io.c | 2 | ||||
| -rw-r--r-- | extent_io.h | 19 | ||||
| -rw-r--r-- | kerncompat.h | 3 |
3 files changed, 22 insertions, 2 deletions
diff --git a/extent_io.c b/extent_io.c index c99d3627..d956c573 100644 --- a/extent_io.c +++ b/extent_io.c @@ -889,5 +889,5 @@ void memset_extent_buffer(struct extent_buffer *eb, char c, int extent_buffer_test_bit(struct extent_buffer *eb, unsigned long start, unsigned long nr) { - return test_bit(nr, (unsigned long *)(eb->data + start)); + return le_test_bit(nr, (u8 *)eb->data + start); } diff --git a/extent_io.h b/extent_io.h index a9a73535..94a42bf5 100644 --- a/extent_io.h +++ b/extent_io.h @@ -49,6 +49,25 @@ #define BLOCK_GROUP_DIRTY EXTENT_DIRTY +/* + * The extent buffer bitmap operations are done with byte granularity instead of + * word granularity for two reasons: + * 1. The bitmaps must be little-endian on disk. + * 2. Bitmap items are not guaranteed to be aligned to a word and therefore a + * single word in a bitmap may straddle two pages in the extent buffer. + */ +#define BIT_BYTE(nr) ((nr) / BITS_PER_BYTE) +#define BYTE_MASK ((1 << BITS_PER_BYTE) - 1) +#define BITMAP_FIRST_BYTE_MASK(start) \ + ((BYTE_MASK << ((start) & (BITS_PER_BYTE - 1))) & BYTE_MASK) +#define BITMAP_LAST_BYTE_MASK(nbits) \ + (BYTE_MASK >> (-(nbits) & (BITS_PER_BYTE - 1))) + +static inline int le_test_bit(int nr, const u8 *addr) +{ + return 1U & (addr[BIT_BYTE(nr)] >> (nr & (BITS_PER_BYTE-1))); +} + struct btrfs_fs_info; struct extent_io_tree { diff --git a/kerncompat.h b/kerncompat.h index 378f0552..c9b9b797 100644 --- a/kerncompat.h +++ b/kerncompat.h @@ -55,7 +55,8 @@ #define gfp_t int #define get_cpu_var(p) (p) #define __get_cpu_var(p) (p) -#define BITS_PER_LONG (__SIZEOF_LONG__ * 8) +#define BITS_PER_BYTE 8 +#define BITS_PER_LONG (__SIZEOF_LONG__ * BITS_PER_BYTE) #define __GFP_BITS_SHIFT 20 #define __GFP_BITS_MASK ((int)((1 << __GFP_BITS_SHIFT) - 1)) #define GFP_KERNEL 0 |