On 03/12/2018 10:13 PM, Jeff Cody wrote: > On Fri, Mar 02, 2018 at 11:20:55AM -0500, John Snow wrote: >> >> >> On 03/02/2018 10:39 AM, Eric Blake wrote: >>> On 02/26/2018 08:05 PM, Liang Li wrote: >>>> 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. >>> >>> How does this interact with John's ongoing work to redo block job >>> semantics: >>> https://lists.gnu.org/archive/html/qemu-devel/2018-02/msg06167.html >>> >>>> >>>> Cc: Paolo Bonzini <pbonz...@redhat.com> >>>> Cc: Jeff Cody <jc...@redhat.com> >>>> Cc: Kevin Wolf <kw...@redhat.com> >>>> Cc: Max Reitz <mre...@redhat.com> >>>> Cc: Eric Blake <ebl...@redhat.com> >>>> Cc: John Snow <js...@redhat.com> >>>> Reported-by: Huaitong Han <huanhuait...@didichuxing.com> >>>> Signed-off-by: Huaitong Han <huanhuait...@didichuxing.com> >>>> Signed-off-by: Liang Li <liliang...@didichuxing.com> >>>> --- >>> >>> But in isolation, the patch looks reasonable to me. >>> >>> Reviewed-by: Eric Blake <ebl...@redhat.com> >>> >> >> In fairness, this patch hit the list before mine did, so... >> >> I think it'll be OK to accommodate -- I think. It just changes the >> nature of how fast the cancellation happens in mirror, which shouldn't >> muck around with the general flow of job management in general. I think. >> >> Famous last words. >> > > I think Kevin's pulled your series in through his branch, and this patch > conflicts with it. Do we want to try to rebase this patch on top of your > series? >
Hey, Try the "review-reap" branch on my github. https://github.com/jnsnow/qemu.git Should just be a matter of extending the "force" flag to the user_cancel interface and passing the bools through. --js
