diff options
Diffstat (limited to 'block/cow.c')
| -rw-r--r-- | block/cow.c | 19 |
1 files changed, 16 insertions, 3 deletions
diff --git a/block/cow.c b/block/cow.c index 4512806f5f..cd889e6512 100644 --- a/block/cow.c +++ b/block/cow.c @@ -106,7 +106,7 @@ static int cow_open(BlockDriverState *bs, QDict *options, int flags) * XXX(hch): right now these functions are extremely inefficient. * 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) +static inline int cow_set_bit(BlockDriverState *bs, int64_t bitnum, bool *first) { uint64_t offset = sizeof(struct cow_header_v2) + bitnum / 8; uint8_t bitmap; @@ -117,9 +117,21 @@ static inline int cow_set_bit(BlockDriverState *bs, int64_t bitnum) return ret; } + if (bitmap & (1 << (bitnum % 8))) { + return 0; + } + + if (*first) { + ret = bdrv_flush(bs->file); + if (ret < 0) { + return ret; + } + *first = false; + } + bitmap |= (1 << (bitnum % 8)); - ret = bdrv_pwrite_sync(bs->file, offset, &bitmap, sizeof(bitmap)); + ret = bdrv_pwrite(bs->file, offset, &bitmap, sizeof(bitmap)); if (ret < 0) { return ret; } @@ -181,9 +193,10 @@ static int cow_update_bitmap(BlockDriverState *bs, int64_t sector_num, { int error = 0; int i; + bool first = true; for (i = 0; i < nb_sectors; i++) { - error = cow_set_bit(bs, sector_num + i); + error = cow_set_bit(bs, sector_num + i, &first); if (error) { break; } |