block: Fix dirty bitmap in bdrv_co_discard
Unsetting dirty globally with discard is not very correct. The discard may zero out sectors (depending on can_write_zeroes_with_unmap), we should replicate this change to destination side to make sure that the guest sees the same data. Calling bdrv_reset_dirty also troubles mirror job because the hbitmap iterator doesn't expect unsetting of bits after current position. So let's do it the opposite way which fixes both problems: set the dirty bits if we are to discard it. Reported-by: wangxiaolong@ucloud.cn Signed-off-by: NFam Zheng <famz@redhat.com> Reviewed-by: NPaolo Bonzini <pbonzini@redhat.com> Reviewed-by: NEric Blake <eblake@redhat.com> Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>
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