On Mon, Apr 09, 2012 at 21:52:20 -0600, Eric Blake wrote: > This is the bare minimum to end a copy job (of course, until a > later patch adds the ability to start a copy job, this patch > doesn't do much in isolation; I've just split the patches to > ease the review). Yeah, thanks for doing that. > This patch intentionally avoids SELinux, lock manager, and audit > actions, saving that for a later patch that affects the overall > lifecycle of a disk copy. In particular, I'm still fuzzy on the > exact qemu error semantics, and whether I need to make more of > an effort after a 'drive-reopen' fails. > > When a mirror job is started, cancelling the job safely reverts back > to the source disk, regardless of whether the destination is in > phase 1 (streaming, in which case the destination is worthless) or > phase 2 (mirroring, in which case the destination is sync'd up to > the source at the time of the cancel). Our existing code does just > fine in either phase, other than some bookkeeping cleanup. > > Pivoting the job requires the use of the new 'drive-reopen' command. > Here, failure of the command is potentially catastrophic to the > domain, since it rips out the old disk before attempting to open > the new one; if our recovery path of retrying the reopen on the > original source disk also fails, the domain is hosed. If only qemu > could get 'drive-reopen' inside 'transaction'... > > Interesting side note: while snapshot-create --disk-only creates a > copy of the disk at a point in time by moving the domain on to a > new file (the copy is the file now in the just-extended backing > chain), blockjob --abort of a copy job creates a copy of the disk > while keeping the domain on the original file. There may be > potential improvements to the snapshot code to exploit block copy > over multiple disks all at one point in time. And, if > 'block_job_cancel' were made part of 'transaction', you could > copy multiple disks at the same point in time without pausing > the domain. This also implies we may want to add a --quiesce > flag to the pivot operation, so that when breaking a mirror, the > side of the mirror that we are abandoning is at least in a stable > state with regards to guest I/O. > > * src/qemu/qemu_driver.c (qemuDomainBlockJobAbort): Accept new flag. > (qemuDomainBlockPivot): New helper function. > (qemuDomainBlockJobImpl): Implement it. > --- > src/qemu/qemu_driver.c | 115 +++++++++++++++++++++++++++++++++++++++++++++-- > 1 files changed, 110 insertions(+), 5 deletions(-) OK Jirka -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list