[libvirt] [PATCH v4 11/23] lock_driver: Introduce VIR_LOCK_MANAGER_ACQUIRE_ROLLBACK

[Michal Privoznik]

Soon there will be a virtlockd client that wants to either lock
all the resources or none (in order to avoid virtlockd killing
the client on connection close). Because on the RPC layer we can
only acquire one resource at a time, we have to perform a
rollback once we hit a resource that can't be acquired.

Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
---
 src/locking/lock_driver.h       |  4 ++
 src/locking/lock_driver_lockd.c | 84 +++++++++++++++++++++++++++++------------
 2 files changed, 64 insertions(+), 24 deletions(-)

diff --git a/src/locking/lock_driver.h b/src/locking/lock_driver.h
index 9be0abcfba..8d236471d4 100644
--- a/src/locking/lock_driver.h
+++ b/src/locking/lock_driver.h
@@ -67,6 +67,10 @@ typedef enum {
     VIR_LOCK_MANAGER_ACQUIRE_REGISTER_ONLY = (1 << 0),
     /* Prevent further lock/unlock calls from this process */
     VIR_LOCK_MANAGER_ACQUIRE_RESTRICT = (1 << 1),
+    /* In case when acquiring more resources which one of them
+     * can't be acquired, perform a rollback and release all
+     * resources acquired so far. */
+    VIR_LOCK_MANAGER_ACQUIRE_ROLLBACK = (1 << 2),
 } virLockManagerAcquireFlags;
 
 typedef enum {
diff --git a/src/locking/lock_driver_lockd.c b/src/locking/lock_driver_lockd.c
index cb294ac694..3068a72507 100644
--- a/src/locking/lock_driver_lockd.c
+++ b/src/locking/lock_driver_lockd.c
@@ -729,6 +729,34 @@ static int virLockManagerLockDaemonAddResource(virLockManagerPtr lock,
 }
 
 
+static int virLockManagerLockDaemonReleaseImpl(virNetClientPtr client,
+                                               virNetClientProgramPtr program,
+                                               int *counter,
+                                               virLockManagerLockDaemonResourcePtr res)
+{
+    virLockSpaceProtocolReleaseResourceArgs args;
+
+    memset(&args, 0, sizeof(args));
+
+    args.path = res->lockspace;
+    args.name = res->name;
+    args.flags = res->flags;
+
+    args.flags &=
+        ~(VIR_LOCK_SPACE_PROTOCOL_ACQUIRE_RESOURCE_SHARED |
+          VIR_LOCK_SPACE_PROTOCOL_ACQUIRE_RESOURCE_AUTOCREATE |
+          VIR_LOCK_SPACE_PROTOCOL_ACQUIRE_RESOURCE_METADATA);
+
+    return virNetClientProgramCall(program,
+                                   client,
+                                   (*counter)++,
+                                   VIR_LOCK_SPACE_PROTOCOL_PROC_RELEASE_RESOURCE,
+                                   0, NULL, NULL, NULL,
+                                   (xdrproc_t)xdr_virLockSpaceProtocolReleaseResourceArgs, &args,
+                                   (xdrproc_t)xdr_void, NULL);
+}
+
+
 static int virLockManagerLockDaemonAcquire(virLockManagerPtr lock,
                                            const char *state ATTRIBUTE_UNUSED,
                                            unsigned int flags,
@@ -739,10 +767,13 @@ static int virLockManagerLockDaemonAcquire(virLockManagerPtr lock,
     virNetClientProgramPtr program = NULL;
     int counter = 0;
     int rv = -1;
+    ssize_t i;
+    ssize_t lastGood = -1;
     virLockManagerLockDaemonPrivatePtr priv = lock->privateData;
 
     virCheckFlags(VIR_LOCK_MANAGER_ACQUIRE_REGISTER_ONLY |
-                  VIR_LOCK_MANAGER_ACQUIRE_RESTRICT, -1);
+                  VIR_LOCK_MANAGER_ACQUIRE_RESTRICT |
+                  VIR_LOCK_MANAGER_ACQUIRE_ROLLBACK, -1);
 
     if (priv->type == VIR_LOCK_MANAGER_OBJECT_TYPE_DOMAIN &&
         priv->nresources == 0 &&
@@ -761,7 +792,6 @@ static int virLockManagerLockDaemonAcquire(virLockManagerPtr lock,
         goto cleanup;
 
     if (!(flags & VIR_LOCK_MANAGER_ACQUIRE_REGISTER_ONLY)) {
-        size_t i;
         for (i = 0; i < priv->nresources; i++) {
             virLockSpaceProtocolAcquireResourceArgs args;
 
@@ -779,6 +809,7 @@ static int virLockManagerLockDaemonAcquire(virLockManagerPtr lock,
                                         (xdrproc_t)xdr_virLockSpaceProtocolAcquireResourceArgs, &args,
                                         (xdrproc_t)xdr_void, NULL) < 0)
                 goto cleanup;
+            lastGood = i;
         }
     }
 
@@ -789,8 +820,30 @@ static int virLockManagerLockDaemonAcquire(virLockManagerPtr lock,
     rv = 0;
 
  cleanup:
-    if (rv != 0 && fd)
-        VIR_FORCE_CLOSE(*fd);
+    if (rv < 0) {
+        int saved_errno = errno;
+        virErrorPtr origerr;
+
+        virErrorPreserveLast(&origerr);
+        if (fd)
+            VIR_FORCE_CLOSE(*fd);
+
+        if (client && program &&
+            flags & VIR_LOCK_MANAGER_ACQUIRE_ROLLBACK &&
+            !(flags & VIR_LOCK_MANAGER_ACQUIRE_REGISTER_ONLY)) {
+            for (i = lastGood; i >= 0; i--) {
+                virLockManagerLockDaemonResourcePtr res = &priv->resources[i];
+
+                if (virLockManagerLockDaemonReleaseImpl(client, program,
+                                                        &counter, res) < 0)
+                    VIR_WARN("Unable to release resource lockspace=%s name=%s",
+                             res->lockspace, res->name);
+            }
+        }
+
+        virErrorRestore(&origerr);
+        errno = saved_errno;
+    }
     virNetClientClose(client);
     virObjectUnref(client);
     virObjectUnref(program);
@@ -818,27 +871,10 @@ static int virLockManagerLockDaemonRelease(virLockManagerPtr lock,
         goto cleanup;
 
     for (i = 0; i < priv->nresources; i++) {
-        virLockSpaceProtocolReleaseResourceArgs args;
+        virLockManagerLockDaemonResourcePtr res = &priv->resources[i];
 
-        memset(&args, 0, sizeof(args));
-
-        if (priv->resources[i].lockspace)
-            args.path = priv->resources[i].lockspace;
-        args.name = priv->resources[i].name;
-        args.flags = priv->resources[i].flags;
-
-        args.flags &=
-            ~(VIR_LOCK_SPACE_PROTOCOL_ACQUIRE_RESOURCE_SHARED |
-              VIR_LOCK_SPACE_PROTOCOL_ACQUIRE_RESOURCE_AUTOCREATE |
-              VIR_LOCK_SPACE_PROTOCOL_ACQUIRE_RESOURCE_METADATA);
-
-        if (virNetClientProgramCall(program,
-                                    client,
-                                    counter++,
-                                    VIR_LOCK_SPACE_PROTOCOL_PROC_RELEASE_RESOURCE,
-                                    0, NULL, NULL, NULL,
-                                    (xdrproc_t)xdr_virLockSpaceProtocolReleaseResourceArgs, &args,
-                                    (xdrproc_t)xdr_void, NULL) < 0)
+        if (virLockManagerLockDaemonReleaseImpl(client, program,
+                                                &counter, res) < 0)
             goto cleanup;
     }
 
-- 
2.16.4