From 4a5b91ca024fc6fd87021c54655af76a35f2ef1e Mon Sep 17 00:00:00 2001 From: Max Reitz Date: Thu, 1 Aug 2019 19:38:59 +0200 Subject: backup: Copy only dirty areas 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 Reviewed-by: Vladimir Sementsov-Ogievskiy Message-id: 20190801173900.23851-2-mreitz@redhat.com Cc: qemu-stable@nongnu.org Signed-off-by: Max Reitz --- block/backup.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) (limited to 'block/backup.c') diff --git a/block/backup.c b/block/backup.c index 715e1d3..1ee271f 100644 --- a/block/backup.c +++ b/block/backup.c @@ -202,22 +202,31 @@ 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) { -- cgit v1.1