Re: [libvirt] [PATCH] blockcommit: document semantics of committing active layer

Signed-off-by: Eric Blake <eblake(a)redhat.com&gt; --- This patch should probably be backported, even if later patches in the series are not, so that users avoid getting hung. include/libvirt/libvirt.h.in | 12 ++++++---- src/libvirt.c | 55 +++++++++++++++++++++++++++++--------------- src/qemu/qemu_driver.c | 9 ++++++++ 3 files changed, 54 insertions(+), 22 deletions(-) diff --git a/include/libvirt/libvirt.h.in b/include/libvirt/libvirt.h.in index 260c971..127de11 100644 --- a/include/libvirt/libvirt.h.in +++ b/include/libvirt/libvirt.h.in

@@ -2588,6 +2590,8 @@ typedef enum { VIR_DOMAIN_BLOCK_COMMIT_DELETE = 1 << 1, /* Delete any files that are now invalid after their contents have been committed */ + VIR_DOMAIN_BLOCK_COMMIT_ACTIVE = 1 << 2, /* Allow a two-phase commit when + top is the active layer */

} virDomainBlockCommitFlags; int virDomainBlockCommit(virDomainPtr dom, const char *disk, const char *base,

diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c index 55b4755..75c59e0 100644 --- a/src/qemu/qemu_driver.c +++ b/src/qemu/qemu_driver.c

@@ -15423,6 +15424,14 @@ qemuDomainBlockCommit(virDomainPtr dom, &top_parent))) goto endjob; + /* XXX Should we auto-pivot when COMMIT_ACTIVE is not specified? */ + if (topSource == &disk->src && !(flags & VIR_DOMAIN_BLOCK_COPY_ACTIVE)) {

+ virReportError(VIR_ERR_INVALID_ARG, + _("commit of '%s' active layer requires active flag"), + disk->dst); + goto endjob; + } + if (!topSource->backingStore) { virReportError(VIR_ERR_INVALID_ARG, _("top '%s' in chain for '%s' has no backing file"),