From: Max Reitz <[email protected]> The backup job must only copy areas that the copy_bitmap reports as dirty. This is always the case when using traditional non-offloading backup, because it copies each cluster separately. When offloading the copy operation, we sometimes copy more than one cluster at a time, but we only check whether the first one is dirty.
Therefore, whenever copy offloading is possible, the backup job currently produces wrong output when the guest writes to an area of which an inner part has already been backed up, because that inner part will be re-copied. Fixes: 9ded4a0114968e98b41494fc035ba14f84cdf700 Signed-off-by: Max Reitz <[email protected]> Reviewed-by: Vladimir Sementsov-Ogievskiy <[email protected]> Message-id: [email protected] Cc: [email protected] Signed-off-by: Max Reitz <[email protected]> (cherry picked from commit 4a5b91ca024fc6fd87021c54655af76a35f2ef1e) Signed-off-by: Michael Roth <[email protected]> --- block/backup.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/block/backup.c b/block/backup.c index d1b94a6dbe..f67c208cf0 100644 --- a/block/backup.c +++ b/block/backup.c @@ -204,22 +204,31 @@ static int coroutine_fn backup_do_cow(BackupBlockJob *job, cow_request_begin(&cow_request, job, start, end); while (start < end) { + int64_t dirty_end; + if (!hbitmap_get(job->copy_bitmap, start)) { trace_backup_do_cow_skip(job, start); start += job->cluster_size; continue; /* already copied */ } + dirty_end = hbitmap_next_zero(job->copy_bitmap, start, (end - start)); + if (dirty_end < 0) { + dirty_end = end; + } + trace_backup_do_cow_process(job, start); if (job->use_copy_range) { - ret = backup_cow_with_offload(job, start, end, is_write_notifier); + ret = backup_cow_with_offload(job, start, dirty_end, + is_write_notifier); if (ret < 0) { job->use_copy_range = false; } } if (!job->use_copy_range) { - ret = backup_cow_with_bounce_buffer(job, start, end, is_write_notifier, + ret = backup_cow_with_bounce_buffer(job, start, dirty_end, + is_write_notifier, error_is_read, &bounce_buffer); } if (ret < 0) { -- 2.17.1
