diff options
Diffstat (limited to 'block')
| -rw-r--r-- | block/cow.c | 98 |
1 files changed, 61 insertions, 37 deletions
diff --git a/block/cow.c b/block/cow.c index 1a48ac0cba..ec9a9f72fa 100644 --- a/block/cow.c +++ b/block/cow.c @@ -21,11 +21,9 @@ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN * THE SOFTWARE. */ -#ifndef _WIN32 #include "qemu-common.h" #include "block_int.h" #include "module.h" -#include <sys/mman.h> /**************************************************************/ /* COW block driver using file system holes */ @@ -45,9 +43,6 @@ struct cow_header_v2 { typedef struct BDRVCowState { int fd; - uint8_t *cow_bitmap; /* if non NULL, COW mappings are used first */ - uint8_t *cow_bitmap_addr; /* mmap address of cow_bitmap */ - int cow_bitmap_size; int64_t cow_sectors_offset; } BDRVCowState; @@ -68,6 +63,7 @@ static int cow_open(BlockDriverState *bs, const char *filename, int flags) BDRVCowState *s = bs->opaque; int fd; struct cow_header_v2 cow_header; + int bitmap_size; int64_t size; fd = open(filename, O_RDWR | O_BINARY | O_LARGEFILE); @@ -94,61 +90,92 @@ static int cow_open(BlockDriverState *bs, const char *filename, int flags) pstrcpy(bs->backing_file, sizeof(bs->backing_file), cow_header.backing_file); - /* mmap the bitmap */ - s->cow_bitmap_size = ((bs->total_sectors + 7) >> 3) + sizeof(cow_header); - s->cow_bitmap_addr = (void *)mmap(get_mmap_addr(s->cow_bitmap_size), - s->cow_bitmap_size, - PROT_READ | PROT_WRITE, - MAP_SHARED, s->fd, 0); - if (s->cow_bitmap_addr == MAP_FAILED) - goto fail; - s->cow_bitmap = s->cow_bitmap_addr + sizeof(cow_header); - s->cow_sectors_offset = (s->cow_bitmap_size + 511) & ~511; + bitmap_size = ((bs->total_sectors + 7) >> 3) + sizeof(cow_header); + s->cow_sectors_offset = (bitmap_size + 511) & ~511; return 0; fail: close(fd); return -1; } -static inline void cow_set_bit(uint8_t *bitmap, int64_t bitnum) +/* + * XXX(hch): right now these functions are extremly ineffcient. + * We should just read the whole bitmap we'll need in one go instead. + */ +static inline int cow_set_bit(BlockDriverState *bs, int64_t bitnum) { - bitmap[bitnum / 8] |= (1 << (bitnum%8)); + BDRVCowState *s = bs->opaque; + uint64_t offset = sizeof(struct cow_header_v2) + bitnum / 8; + uint8_t bitmap; + + if (pread(s->fd, &bitmap, sizeof(bitmap), offset) != + sizeof(bitmap)) { + return -errno; + } + + bitmap |= (1 << (bitnum % 8)); + + if (pwrite(s->fd, &bitmap, sizeof(bitmap), offset) != + sizeof(bitmap)) { + return -errno; + } + return 0; } -static inline int is_bit_set(const uint8_t *bitmap, int64_t bitnum) +static inline int is_bit_set(BlockDriverState *bs, int64_t bitnum) { - return !!(bitmap[bitnum / 8] & (1 << (bitnum%8))); -} + BDRVCowState *s = bs->opaque; + uint64_t offset = sizeof(struct cow_header_v2) + bitnum / 8; + uint8_t bitmap; + if (pread(s->fd, &bitmap, sizeof(bitmap), offset) != + sizeof(bitmap)) { + return -errno; + } + + return !!(bitmap & (1 << (bitnum % 8))); +} /* Return true if first block has been changed (ie. current version is * in COW file). Set the number of continuous blocks for which that * is true. */ -static inline int is_changed(uint8_t *bitmap, - int64_t sector_num, int nb_sectors, - int *num_same) +static int cow_is_allocated(BlockDriverState *bs, int64_t sector_num, + int nb_sectors, int *num_same) { int changed; - if (!bitmap || nb_sectors == 0) { + if (nb_sectors == 0) { *num_same = nb_sectors; return 0; } - changed = is_bit_set(bitmap, sector_num); + changed = is_bit_set(bs, sector_num); + if (changed < 0) { + return 0; /* XXX: how to return I/O errors? */ + } + for (*num_same = 1; *num_same < nb_sectors; (*num_same)++) { - if (is_bit_set(bitmap, sector_num + *num_same) != changed) + if (is_bit_set(bs, sector_num + *num_same) != changed) break; } return changed; } -static int cow_is_allocated(BlockDriverState *bs, int64_t sector_num, - int nb_sectors, int *pnum) +static int cow_update_bitmap(BlockDriverState *bs, int64_t sector_num, + int nb_sectors) { - BDRVCowState *s = bs->opaque; - return is_changed(s->cow_bitmap, sector_num, nb_sectors, pnum); + int error = 0; + int i; + + for (i = 0; i < nb_sectors; i++) { + error = cow_set_bit(bs, sector_num + i); + if (error) { + break; + } + } + + return error; } static int cow_read(BlockDriverState *bs, int64_t sector_num, @@ -158,7 +185,7 @@ static int cow_read(BlockDriverState *bs, int64_t sector_num, int ret, n; while (nb_sectors > 0) { - if (is_changed(s->cow_bitmap, sector_num, nb_sectors, &n)) { + if (cow_is_allocated(bs, sector_num, nb_sectors, &n)) { ret = pread(s->fd, buf, n * 512, s->cow_sectors_offset + sector_num * 512); if (ret != n * 512) @@ -184,21 +211,19 @@ static int cow_write(BlockDriverState *bs, int64_t sector_num, const uint8_t *buf, int nb_sectors) { BDRVCowState *s = bs->opaque; - int ret, i; + int ret; ret = pwrite(s->fd, buf, nb_sectors * 512, s->cow_sectors_offset + sector_num * 512); if (ret != nb_sectors * 512) return -1; - for (i = 0; i < nb_sectors; i++) - cow_set_bit(s->cow_bitmap, sector_num + i); - return 0; + + return cow_update_bitmap(bs, sector_num, nb_sectors); } static void cow_close(BlockDriverState *bs) { BDRVCowState *s = bs->opaque; - munmap((void *)s->cow_bitmap_addr, s->cow_bitmap_size); close(s->fd); } @@ -308,4 +333,3 @@ static void bdrv_cow_init(void) } block_init(bdrv_cow_init); -#endif |