diff options
| -rw-r--r-- | qemu-img.c | 32 |
1 files changed, 28 insertions, 4 deletions
diff --git a/qemu-img.c b/qemu-img.c index e4b84c4f56..89f1093d81 100644 --- a/qemu-img.c +++ b/qemu-img.c @@ -1065,6 +1065,28 @@ done: } /* + * Returns -1 if 'buf' contains only zeroes, otherwise the byte index + * of the first sector boundary within buf where the sector contains a + * non-zero byte. This function is robust to a buffer that is not + * sector-aligned. + */ +static int64_t find_nonzero(const uint8_t *buf, int64_t n) +{ + int64_t i; + int64_t end = QEMU_ALIGN_DOWN(n, BDRV_SECTOR_SIZE); + + for (i = 0; i < end; i += BDRV_SECTOR_SIZE) { + if (!buffer_is_zero(buf + i, BDRV_SECTOR_SIZE)) { + return i; + } + } + if (i < n && !buffer_is_zero(buf + i, n - end)) { + return i; + } + return -1; +} + +/* * Returns true iff the first sector pointed to by 'buf' contains at least * a non-NUL byte. * @@ -1189,7 +1211,9 @@ static int check_empty_sectors(BlockBackend *blk, int64_t sect_num, int sect_count, const char *filename, uint8_t *buffer, bool quiet) { - int pnum, ret = 0; + int ret = 0; + int64_t idx; + ret = blk_pread(blk, sect_num << BDRV_SECTOR_BITS, buffer, sect_count << BDRV_SECTOR_BITS); if (ret < 0) { @@ -1197,10 +1221,10 @@ static int check_empty_sectors(BlockBackend *blk, int64_t sect_num, sectors_to_bytes(sect_num), filename, strerror(-ret)); return ret; } - ret = is_allocated_sectors(buffer, sect_count, &pnum); - if (ret || pnum != sect_count) { + idx = find_nonzero(buffer, sect_count * BDRV_SECTOR_SIZE); + if (idx >= 0) { qprintf(quiet, "Content mismatch at offset %" PRId64 "!\n", - sectors_to_bytes(ret ? sect_num : sect_num + pnum)); + sectors_to_bytes(sect_num) + idx); return 1; } |