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authorLiang Li <liliang.opensource@gmail.com>2018-03-13 08:12:16 -0400
committerKevin Wolf <kwolf@redhat.com>2018-03-19 12:01:39 +0100
commitb76e4458b1eb3c32e9824fe6aa51f67d2b251748 (patch)
tree457f190a9d5e03863a5a2b750611badf101183ce /hmp-commands.hx
parent1cfeaf386e3727df0e057710d61593ca515dd07b (diff)
downloadqemu-b76e4458b1eb3c32e9824fe6aa51f67d2b251748.tar.gz
block/mirror: change the semantic of 'force' of block-job-cancel
When doing drive mirror to a low speed shared storage, if there was heavy BLK IO write workload in VM after the 'ready' event, drive mirror block job can't be canceled immediately, it would keep running until the heavy BLK IO workload stopped in the VM. Libvirt depends on the current block-job-cancel semantics, which is that when used without a flag after the 'ready' event, the command blocks until data is in sync. However, these semantics are awkward in other situations, for example, people may use drive mirror for realtime backups while still wanting to use block live migration. Libvirt cannot start a block live migration while another drive mirror is in progress, but the user would rather abandon the backup attempt as broken and proceed with the live migration than be stuck waiting for the current drive mirror backup to finish. The drive-mirror command already includes a 'force' flag, which libvirt does not use, although it documented the flag as only being useful to quit a job which is paused. However, since quitting a paused job has the same effect as abandoning a backup in a non-paused job (namely, the destination file is not in sync, and the command completes immediately), we can just improve the documentation to make the force flag obviously useful. Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Jeff Cody <jcody@redhat.com> Cc: Kevin Wolf <kwolf@redhat.com> Cc: Max Reitz <mreitz@redhat.com> Cc: Eric Blake <eblake@redhat.com> Cc: John Snow <jsnow@redhat.com> Reported-by: Huaitong Han <huanhuaitong@didichuxing.com> Signed-off-by: Huaitong Han <huanhuaitong@didichuxing.com> Signed-off-by: Liang Li <liliangleo@didichuxing.com> Signed-off-by: Jeff Cody <jcody@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Diffstat (limited to 'hmp-commands.hx')
-rw-r--r--hmp-commands.hx3
1 files changed, 2 insertions, 1 deletions
diff --git a/hmp-commands.hx b/hmp-commands.hx
index 1723cbe1df..35d862a5d2 100644
--- a/hmp-commands.hx
+++ b/hmp-commands.hx
@@ -106,7 +106,8 @@ ETEXI
.args_type = "force:-f,device:B",
.params = "[-f] device",
.help = "stop an active background block operation (use -f"
- "\n\t\t\t if the operation is currently paused)",
+ "\n\t\t\t if you want to abort the operation immediately"
+ "\n\t\t\t instead of keep running until data is in sync)",
.cmd = hmp_block_job_cancel,
},