qemu: Record names of domain which uses the shared disk in hash table

The hash entry is changed from "ref" to {ref, @domains}. With this, the
caller can simply call qemuRemoveSharedDisk, without afraid of removing
the entry belongs to other domains. qemuProcessStart will obviously
benifit from it on error codepath (which calls qemuProcessStop to do
the cleanup).

src/qemu/qemu_conf.c

@@ -824,6 +824,11 @@ qemuDriverCloseCallbackRunAll(virQEMUDriverPtr driver,
     qemuDriverUnlock(driver);
 }
 
+struct _qemuSharedDiskEntry {
+    size_t ref;
+    char **domains; /* array of domain names */
+};
+
 /* Construct the hash key for sharedDisks as "major:minor" */
 char *
 qemuGetSharedDiskKey(const char *disk_path)
@@ -858,10 +863,9 @@ static int
 qemuCheckSharedDisk(virHashTablePtr sharedDisks,
                     virDomainDiskDefPtr disk)
 {
-    int val;
-    size_t *ref = NULL;
     char *sysfs_path = NULL;
     char *key = NULL;
+    int val;
     int ret = 0;
 
     /* The only conflicts between shared disk we care about now
@@ -881,7 +885,6 @@ qemuCheckSharedDisk(virHashTablePtr sharedDisks,
     if (!virFileExists(sysfs_path))
         goto cleanup;
 
-
     if (!(key = qemuGetSharedDiskKey(disk->src))) {
         ret = -1;
         goto cleanup;
@@ -890,7 +893,7 @@ qemuCheckSharedDisk(virHashTablePtr sharedDisks,
     /* It can't be conflict if no other domain is
      * is sharing it.
      */
-    if (!(ref = virHashLookup(sharedDisks, key)))
+    if (!(virHashLookup(sharedDisks, key)))
         goto cleanup;
 
     if (virGetDeviceUnprivSGIO(disk->src, NULL, &val) < 0) {
@@ -916,14 +919,84 @@ cleanup:
     return ret;
 }
 
-/* Increase ref count if the entry already exists, otherwise
- * add a new entry.
+bool
+qemuSharedDiskEntryDomainExists(qemuSharedDiskEntryPtr entry,
+                                const char *name,
+                                int *idx)
+{
+    size_t i;
+
+    for (i = 0; i < entry->ref; i++) {
+        if (STREQ(entry->domains[i], name)) {
+            if (idx)
+                *idx = i;
+            return true;
+        }
+    }
+
+    return false;
+}
+
+void
+qemuSharedDiskEntryFree(void *payload, const void *name ATTRIBUTE_UNUSED)
+{
+    qemuSharedDiskEntryPtr entry = payload;
+    size_t i;
+
+    for (i = 0; i < entry->ref; i++) {
+        VIR_FREE(entry->domains[i]);
+    }
+    VIR_FREE(entry->domains);
+    VIR_FREE(entry);
+}
+
+static qemuSharedDiskEntryPtr
+qemuSharedDiskEntryCopy(const qemuSharedDiskEntryPtr entry)
+{
+    qemuSharedDiskEntryPtr ret = NULL;
+    size_t i;
+
+    if (VIR_ALLOC(ret) < 0) {
+        virReportOOMError();
+        return NULL;
+    }
+
+    if (VIR_ALLOC_N(ret->domains, entry->ref) < 0) {
+        virReportOOMError();
+        goto cleanup;
+    }
+
+    for (i = 0; i < entry->ref; i++) {
+        if (!(ret->domains[i] = strdup(entry->domains[i]))) {
+            virReportOOMError();
+            goto cleanup;
+        }
+        ret->ref++;
+    }
+
+    return ret;
+
+cleanup:
+    qemuSharedDiskEntryFree(ret, NULL);
+    return NULL;
+}
+
+/* qemuAddSharedDisk:
+ * @driver: Pointer to qemu driver struct
+ * @disk: The disk def
+ * @name: The domain name
+ *
+ * Increase ref count and add the domain name into the list which
+ * records all the domains that use the shared disk if the entry
+ * already exists, otherwise add a new entry.
  */
 int
 qemuAddSharedDisk(virQEMUDriverPtr driver,
-                  virDomainDiskDefPtr disk)
+                  virDomainDiskDefPtr disk,
+                  const char *name)
 {
-    size_t *ref = NULL;
+    qemuSharedDiskEntry *entry = NULL;
+    qemuSharedDiskEntry *new_entry = NULL;
     char *key = NULL;
     int ret = -1;
 
@@ -942,11 +1015,40 @@ qemuAddSharedDisk(virQEMUDriverPtr driver,
     if (!(key = qemuGetSharedDiskKey(disk->src)))
         goto cleanup;
 
-    if ((ref = virHashLookup(driver->sharedDisks, key))) {
-        if (virHashUpdateEntry(driver->sharedDisks, key, ++ref) < 0)
-             goto cleanup;
+    if ((entry = virHashLookup(driver->sharedDisks, key))) {
+        /* Nothing to do if the shared disk is already recorded
+         * in the table.
+         */
+        if (qemuSharedDiskEntryDomainExists(entry, name, NULL)) {
+            ret = 0;
+            goto cleanup;
+        }
+
+        if (!(new_entry = qemuSharedDiskEntryCopy(entry)))
+            goto cleanup;
+
+        if ((VIR_EXPAND_N(new_entry->domains, new_entry->ref, 1) < 0) ||
+            !(new_entry->domains[new_entry->ref - 1] = strdup(name))) {
+            qemuSharedDiskEntryFree(new_entry, NULL);
+            virReportOOMError();
+            goto cleanup;
+        }
+
+        if (virHashUpdateEntry(driver->sharedDisks, key, new_entry) < 0) {
+            qemuSharedDiskEntryFree(new_entry, NULL);
+            goto cleanup;
+        }
     } else {
-        if (virHashAddEntry(driver->sharedDisks, key, (void *)0x1))
+        if ((VIR_ALLOC(entry) < 0) ||
+            (VIR_ALLOC_N(entry->domains, 1) < 0) ||
+            !(entry->domains[0] = strdup(name))) {
+            virReportOOMError();
+            goto cleanup;
+        }
+
+        entry->ref = 1;
+
+        if (virHashAddEntry(driver->sharedDisks, key, entry))
             goto cleanup;
     }
 
@@ -957,16 +1059,25 @@ cleanup:
     return ret;
 }
 
-/* Decrease the ref count if the entry already exists, otherwise
- * remove the entry.
+/* qemuRemoveSharedDisk:
+ * @driver: Pointer to qemu driver struct
+ * @disk: The disk def
+ * @name: The domain name
+ *
+ * Decrease ref count and remove the domain name from the list which
+ * records all the domains that use the shared disk if ref is not 1,
+ * otherwise remove the entry.
  */
 int
 qemuRemoveSharedDisk(virQEMUDriverPtr driver,
-                     virDomainDiskDefPtr disk)
+                     virDomainDiskDefPtr disk,
+                     const char *name)
 {
-    size_t *ref = NULL;
+    qemuSharedDiskEntryPtr entry = NULL;
+    qemuSharedDiskEntryPtr new_entry = NULL;
     char *key = NULL;
     int ret = -1;
+    int idx;
 
     if (disk->type != VIR_DOMAIN_DISK_TYPE_BLOCK ||
         !disk->shared || !disk->src)
@@ -976,12 +1087,32 @@ qemuRemoveSharedDisk(virQEMUDriverPtr driver,
     if (!(key = qemuGetSharedDiskKey(disk->src)))
         goto cleanup;
 
-    if (!(ref = virHashLookup(driver->sharedDisks, key)))
+    if (!(entry = virHashLookup(driver->sharedDisks, key)))
         goto cleanup;
 
-    if (ref != (void *)0x1) {
-        if (virHashUpdateEntry(driver->sharedDisks, key, --ref) < 0)
+    /* Nothing to do if the shared disk is not recored in
+     * the table.
+     */
+    if (!qemuSharedDiskEntryDomainExists(entry, name, &idx)) {
+        ret = 0;
+        goto cleanup;
+    }
+
+    if (entry->ref != 1) {
+        if (!(new_entry = qemuSharedDiskEntryCopy(entry)))
+            goto cleanup;
+
+        if (idx != new_entry->ref - 1)
+            memmove(&new_entry->domains[idx],
+                    &new_entry->domains[idx + 1],
+                    sizeof(*new_entry->domains) * (new_entry->ref - idx - 1));
+
+        VIR_SHRINK_N(new_entry->domains, new_entry->ref, 1);
+
+        if (virHashUpdateEntry(driver->sharedDisks, key, new_entry) < 0){
+            qemuSharedDiskEntryFree(new_entry, NULL);
             goto cleanup;
+        }
     } else {
         if (virHashRemoveEntry(driver->sharedDisks, key) < 0)
             goto cleanup;

src/qemu/qemu_conf.h

@@ -272,16 +272,30 @@ qemuDriverCloseCallback qemuDriverCloseCallbackGet(virQEMUDriverPtr driver,
 void qemuDriverCloseCallbackRunAll(virQEMUDriverPtr driver,
                                    virConnectPtr conn);
 
-int qemuAddSharedDisk(virQEMUDriverPtr driver,
-                      virDomainDiskDefPtr disk)
+typedef struct _qemuSharedDiskEntry qemuSharedDiskEntry;
+typedef qemuSharedDiskEntry *qemuSharedDiskEntryPtr;
+
+bool qemuSharedDiskEntryDomainExists(qemuSharedDiskEntryPtr entry,
+                                     const char *name,
+                                     int *index)
     ATTRIBUTE_NONNULL(1) ATTRIBUTE_NONNULL(2);
 
+int qemuAddSharedDisk(virQEMUDriverPtr driver,
+                      virDomainDiskDefPtr disk,
+                      const char *name)
+    ATTRIBUTE_NONNULL(1) ATTRIBUTE_NONNULL(2) ATTRIBUTE_NONNULL(3);
+
 int qemuRemoveSharedDisk(virQEMUDriverPtr driver,
-                         virDomainDiskDefPtr disk)
-    ATTRIBUTE_NONNULL(1) ATTRIBUTE_NONNULL(2);
+                         virDomainDiskDefPtr disk,
+                         const char *name)
+    ATTRIBUTE_NONNULL(1) ATTRIBUTE_NONNULL(2) ATTRIBUTE_NONNULL(3);
+
 char * qemuGetSharedDiskKey(const char *disk_path)
     ATTRIBUTE_NONNULL(1);
 
+void qemuSharedDiskEntryFree(void *payload, const void *name)
+    ATTRIBUTE_NONNULL(1);
+
 int qemuDriverAllocateID(virQEMUDriverPtr driver);
 
 #endif /* __QEMUD_CONF_H */

src/qemu/qemu_driver.c

@@ -681,7 +681,7 @@ qemuStartup(bool privileged,
     if ((qemu_driver->inactivePciHostdevs = virPCIDeviceListNew()) == NULL)
         goto error;
 
-    if (!(qemu_driver->sharedDisks = virHashCreate(30, NULL)))
+    if (!(qemu_driver->sharedDisks = virHashCreate(30, qemuSharedDiskEntryFree)))
         goto error;
 
     if (privileged) {
@@ -5766,7 +5766,7 @@ qemuDomainAttachDeviceDiskLive(virConnectPtr conn,
     }
 
     if (ret == 0) {
-        if (qemuAddSharedDisk(driver, disk) < 0)
+        if (qemuAddSharedDisk(driver, disk, vm->def->name) < 0)
             VIR_WARN("Failed to add disk '%s' to shared disk table",
                      disk->src);
 
@@ -5890,7 +5890,7 @@ qemuDomainDetachDeviceDiskLive(virQEMUDriverPtr driver,
     }
 
     if (ret == 0) {
-        if (qemuRemoveSharedDisk(driver, disk) < 0)
+        if (qemuRemoveSharedDisk(driver, disk, vm->def->name) < 0)
              VIR_WARN("Failed to remove disk '%s' from shared disk table",
                       disk->src);
     }

src/qemu/qemu_process.c

@@ -3830,7 +3830,7 @@ int qemuProcessStart(virConnectPtr conn,
                            _("Raw I/O is not supported on this platform"));
 #endif
 
-        if (qemuAddSharedDisk(driver, disk) < 0)
+        if (qemuAddSharedDisk(driver, disk, vm->def->name) < 0)
             goto cleanup;
 
         if (qemuSetUnprivSGIO(disk) < 0)
@@ -4235,7 +4235,7 @@ void qemuProcessStop(virQEMUDriverPtr driver,
 
     for (i = 0; i < vm->def->ndisks; i++) {
         virDomainDiskDefPtr disk = vm->def->disks[i];
-        ignore_value(qemuRemoveSharedDisk(driver, disk));
+        ignore_value(qemuRemoveSharedDisk(driver, disk, vm->def->name));
     }
 
     /* Clear out dynamically assigned labels */