diff options
| -rw-r--r-- | fs/btrfs/extent_io.c | 149 | ||||
| -rw-r--r-- | fs/btrfs/extent_io.h | 6 |
2 files changed, 155 insertions, 0 deletions
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c index 3915c9473e94..324d38259d4b 100644 --- a/fs/btrfs/extent_io.c +++ b/fs/btrfs/extent_io.c @@ -5527,6 +5527,155 @@ void copy_extent_buffer(struct extent_buffer *dst, struct extent_buffer *src, } } +/* + * The extent buffer bitmap operations are done with byte granularity because + * 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))) + +/* + * eb_bitmap_offset() - calculate the page and offset of the byte containing the + * given bit number + * @eb: the extent buffer + * @start: offset of the bitmap item in the extent buffer + * @nr: bit number + * @page_index: return index of the page in the extent buffer that contains the + * given bit number + * @page_offset: return offset into the page given by page_index + * + * This helper hides the ugliness of finding the byte in an extent buffer which + * contains a given bit. + */ +static inline void eb_bitmap_offset(struct extent_buffer *eb, + unsigned long start, unsigned long nr, + unsigned long *page_index, + size_t *page_offset) +{ + size_t start_offset = eb->start & ((u64)PAGE_CACHE_SIZE - 1); + size_t byte_offset = BIT_BYTE(nr); + size_t offset; + + /* + * The byte we want is the offset of the extent buffer + the offset of + * the bitmap item in the extent buffer + the offset of the byte in the + * bitmap item. + */ + offset = start_offset + start + byte_offset; + + *page_index = offset >> PAGE_CACHE_SHIFT; + *page_offset = offset & (PAGE_CACHE_SIZE - 1); +} + +/** + * extent_buffer_test_bit - determine whether a bit in a bitmap item is set + * @eb: the extent buffer + * @start: offset of the bitmap item in the extent buffer + * @nr: bit number to test + */ +int extent_buffer_test_bit(struct extent_buffer *eb, unsigned long start, + unsigned long nr) +{ + char *kaddr; + struct page *page; + unsigned long i; + size_t offset; + + eb_bitmap_offset(eb, start, nr, &i, &offset); + page = eb->pages[i]; + WARN_ON(!PageUptodate(page)); + kaddr = page_address(page); + return 1U & (kaddr[offset] >> (nr & (BITS_PER_BYTE - 1))); +} + +/** + * extent_buffer_bitmap_set - set an area of a bitmap + * @eb: the extent buffer + * @start: offset of the bitmap item in the extent buffer + * @pos: bit number of the first bit + * @len: number of bits to set + */ +void extent_buffer_bitmap_set(struct extent_buffer *eb, unsigned long start, + unsigned long pos, unsigned long len) +{ + char *kaddr; + struct page *page; + unsigned long i; + size_t offset; + const unsigned int size = pos + len; + int bits_to_set = BITS_PER_BYTE - (pos % BITS_PER_BYTE); + unsigned int mask_to_set = BITMAP_FIRST_BYTE_MASK(pos); + + eb_bitmap_offset(eb, start, pos, &i, &offset); + page = eb->pages[i]; + WARN_ON(!PageUptodate(page)); + kaddr = page_address(page); + + while (len >= bits_to_set) { + kaddr[offset] |= mask_to_set; + len -= bits_to_set; + bits_to_set = BITS_PER_BYTE; + mask_to_set = ~0U; + if (++offset >= PAGE_CACHE_SIZE && len > 0) { + offset = 0; + page = eb->pages[++i]; + WARN_ON(!PageUptodate(page)); + kaddr = page_address(page); + } + } + if (len) { + mask_to_set &= BITMAP_LAST_BYTE_MASK(size); + kaddr[offset] |= mask_to_set; + } +} + + +/** + * extent_buffer_bitmap_clear - clear an area of a bitmap + * @eb: the extent buffer + * @start: offset of the bitmap item in the extent buffer + * @pos: bit number of the first bit + * @len: number of bits to clear + */ +void extent_buffer_bitmap_clear(struct extent_buffer *eb, unsigned long start, + unsigned long pos, unsigned long len) +{ + char *kaddr; + struct page *page; + unsigned long i; + size_t offset; + const unsigned int size = pos + len; + int bits_to_clear = BITS_PER_BYTE - (pos % BITS_PER_BYTE); + unsigned int mask_to_clear = BITMAP_FIRST_BYTE_MASK(pos); + + eb_bitmap_offset(eb, start, pos, &i, &offset); + page = eb->pages[i]; + WARN_ON(!PageUptodate(page)); + kaddr = page_address(page); + + while (len >= bits_to_clear) { + kaddr[offset] &= ~mask_to_clear; + len -= bits_to_clear; + bits_to_clear = BITS_PER_BYTE; + mask_to_clear = ~0U; + if (++offset >= PAGE_CACHE_SIZE && len > 0) { + offset = 0; + page = eb->pages[++i]; + WARN_ON(!PageUptodate(page)); + kaddr = page_address(page); + } + } + if (len) { + mask_to_clear &= BITMAP_LAST_BYTE_MASK(size); + kaddr[offset] &= ~mask_to_clear; + } +} + static inline bool areas_overlap(unsigned long src, unsigned long dst, unsigned long len) { unsigned long distance = (src > dst) ? src - dst : dst - src; diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h index c668f36898d3..9185a20081d7 100644 --- a/fs/btrfs/extent_io.h +++ b/fs/btrfs/extent_io.h @@ -309,6 +309,12 @@ void memmove_extent_buffer(struct extent_buffer *dst, unsigned long dst_offset, unsigned long src_offset, unsigned long len); void memset_extent_buffer(struct extent_buffer *eb, char c, unsigned long start, unsigned long len); +int extent_buffer_test_bit(struct extent_buffer *eb, unsigned long start, + unsigned long pos); +void extent_buffer_bitmap_set(struct extent_buffer *eb, unsigned long start, + unsigned long pos, unsigned long len); +void extent_buffer_bitmap_clear(struct extent_buffer *eb, unsigned long start, + unsigned long pos, unsigned long len); void clear_extent_buffer_dirty(struct extent_buffer *eb); int set_extent_buffer_dirty(struct extent_buffer *eb); int set_extent_buffer_uptodate(struct extent_buffer *eb); |