[libvirt] [PATCH v3 2/4] qemu: block: use the delete flag to delete snapshot images if requested

[Pavel Mores]

When blockcommit finishes successfully, one of the
qemuBlockJobProcessEventCompletedCommit() and
qemuBlockJobProcessEventCompletedActiveCommit() event handlers is called.
This is where the delete flag (stored in qemuBlockJobCommitData since the
previous commit) can actually be used to delete the committed snapshot
images if requested.

We use virFileRemove() instead of a simple unlink() to cover the case where
the image to be removed is on an NFS volume.  To acquire the uid/gid arguments
for the virFileRemove() call, we call qemuDomainGetImageIds() which was
previously static in its file so we first have to export it.

Signed-off-by: Pavel Mores <pmores at redhat.com>
---
 src/qemu/qemu_blockjob.c | 39 +++++++++++++++++++++++++++++++++++++++
 src/qemu/qemu_domain.c   |  2 +-
 src/qemu/qemu_domain.h   |  6 ++++++
 3 files changed, 46 insertions(+), 1 deletion(-)

diff --git a/src/qemu/qemu_blockjob.c b/src/qemu/qemu_blockjob.c
index 7d94a6ce38..1bf23dac3c 100644
--- a/src/qemu/qemu_blockjob.c
+++ b/src/qemu/qemu_blockjob.c
@@ -965,6 +965,37 @@ qemuBlockJobProcessEventCompletedPull(virQEMUDriverPtr driver,
 }
 
 
+/**
+ * Helper for qemuBlockJobProcessEventCompletedCommit() and
+ * qemuBlockJobProcessEventCompletedActiveCommit().  Relies on adjustments
+ * these functions perform on the 'backingStore' chain to function correctly.
+ *
+ * TODO look into removing backing store for non-local snapshots too
+ */
+static void
+qemuBlockJobUnlinkCommittedStorage(virQEMUDriverPtr driver,
+                                   virDomainObjPtr vm,
+                                   virDomainDiskDefPtr disk,
+                                   virStorageSourcePtr top)
+{
+    virStorageSourcePtr p = top;
+    virQEMUDriverConfigPtr cfg = virQEMUDriverGetConfig(driver);
+    uid_t uid;
+    gid_t gid;
+
+    for (; p != NULL; p = p->backingStore) {
+        if (virStorageSourceIsLocalStorage(p)) {
+
+            qemuDomainGetImageIds(cfg, vm, p, disk->src, &uid, &gid);
+
+            if (virFileRemove(p->path, uid, gid) < 0) {
+                VIR_WARN("Unable to remove snapshot image file %s (%s)",
+                         p->path, g_strerror(errno));
+            }
+        }
+    }
+}
+
 /**
  * qemuBlockJobProcessEventCompletedCommit:
  * @driver: qemu driver object
@@ -1031,6 +1062,10 @@ qemuBlockJobProcessEventCompletedCommit(virQEMUDriverPtr driver,
     job->data.commit.topparent->backingStore = job->data.commit.base;
 
     qemuBlockJobEventProcessConcludedRemoveChain(driver, vm, asyncJob, job->data.commit.top);
+
+    if (job->data.commit.deleteCommittedImages)
+        qemuBlockJobUnlinkCommittedStorage(driver, vm, job->disk, job->data.commit.top);
+
     virObjectUnref(job->data.commit.top);
     job->data.commit.top = NULL;
 
@@ -1121,6 +1156,10 @@ qemuBlockJobProcessEventCompletedActiveCommit(virQEMUDriverPtr driver,
     job->disk->src->readonly = job->data.commit.top->readonly;
 
     qemuBlockJobEventProcessConcludedRemoveChain(driver, vm, asyncJob, job->data.commit.top);
+
+    if (job->data.commit.deleteCommittedImages)
+        qemuBlockJobUnlinkCommittedStorage(driver, vm, job->disk, job->data.commit.top);
+
     virObjectUnref(job->data.commit.top);
     job->data.commit.top = NULL;
     /* the mirror element does not serve functional purpose for the commit job */
diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
index 262b74d1ab..07bf8f5a54 100644
--- a/src/qemu/qemu_domain.c
+++ b/src/qemu/qemu_domain.c
@@ -10133,7 +10133,7 @@ qemuDomainCleanupRun(virQEMUDriverPtr driver,
     priv->ncleanupCallbacks_max = 0;
 }
 
-static void
+void
 qemuDomainGetImageIds(virQEMUDriverConfigPtr cfg,
                       virDomainObjPtr vm,
                       virStorageSourcePtr src,
diff --git a/src/qemu/qemu_domain.h b/src/qemu/qemu_domain.h
index 98a9540275..f66610c7d3 100644
--- a/src/qemu/qemu_domain.h
+++ b/src/qemu/qemu_domain.h
@@ -834,6 +834,12 @@ bool qemuDomainDiskChangeSupported(virDomainDiskDefPtr disk,
 const char *qemuDomainDiskNodeFormatLookup(virDomainObjPtr vm,
                                            const char *disk);
 
+void qemuDomainGetImageIds(virQEMUDriverConfigPtr cfg,
+                      virDomainObjPtr vm,
+                      virStorageSourcePtr src,
+                      virStorageSourcePtr parentSrc,
+                      uid_t *uid, gid_t *gid);
+
 int qemuDomainStorageFileInit(virQEMUDriverPtr driver,
                               virDomainObjPtr vm,
                               virStorageSourcePtr src,
-- 
2.21.0