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[libvirt] [PATCH 3/6] 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    |  111 +++++++++++++++++++++++++++++++++++++++--------
 src/qemu/qemu_conf.h    |   22 ++++++++--
 src/qemu/qemu_driver.c  |   18 ++++++-
 src/qemu/qemu_process.c |    4 +-
 4 files changed, 128 insertions(+), 27 deletions(-)

diff --git a/src/qemu/qemu_conf.c b/src/qemu/qemu_conf.c
index 6e735c6..790f5a1 100644
--- a/src/qemu/qemu_conf.c
+++ b/src/qemu/qemu_conf.c
@@ -832,10 +832,9 @@ 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;
 
     if (!(sysfs_path = virGetUnprivSGIOSysfsPath(disk->src, NULL))) {
@@ -858,7 +857,7 @@ 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) {
@@ -884,14 +883,39 @@ 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)
+{
+    int i;
+
+    for (i = 0; i < entry->ref; i++) {
+        if (STREQ(entry->domains[i], name)) {
+            if (idx)
+                *idx = i;
+            return true;
+        }
+    }
+
+    return false;
+}
+
+/* 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;
     char *key = NULL;
     int ret = -1;
 
@@ -909,11 +933,34 @@ 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 ((VIR_REALLOC_N(entry->domains, entry->ref + 1) < 0) ||
+            !(entry->domains[entry->ref++] = strdup(name))) {
+            virReportOOMError();
+            goto cleanup;
+        }
+
+        if (virHashUpdateEntry(driver->sharedDisks, key, entry) < 0)
+            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;
     }
 
@@ -923,16 +970,24 @@ 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;
     char *key = NULL;
     int ret = -1;
+    int idx;
 
     if (disk->type != VIR_DOMAIN_DISK_TYPE_BLOCK ||
         !disk->shared || !disk->src)
@@ -941,11 +996,31 @@ 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 (idx != entry->ref - 1)
+            memmove(&entry->domains[idx],
+                    &entry->domains[idx + 1],
+                    sizeof(*entry->domains) * (entry->ref - idx - 1));
+
+        if (VIR_REALLOC_N(entry->domains, entry->ref - 1) < 0) {
+            virReportOOMError();
+            goto cleanup;
+        }
+
+        entry->ref--;
+
+        if (virHashUpdateEntry(driver->sharedDisks, key, entry) < 0)
             goto cleanup;
     } else {
         if (virHashRemoveEntry(driver->sharedDisks, key) < 0)
diff --git a/src/qemu/qemu_conf.h b/src/qemu/qemu_conf.h
index 1685cf6..6240e2c 100644
--- a/src/qemu/qemu_conf.h
+++ b/src/qemu/qemu_conf.h
@@ -275,13 +275,27 @@ qemuDriverCloseCallback qemuDriverCloseCallbackGet(virQEMUDriverPtr driver,
 void qemuDriverCloseCallbackRunAll(virQEMUDriverPtr driver,
                                    virConnectPtr conn);
 
-int qemuAddSharedDisk(virQEMUDriverPtr driver,
-                      virDomainDiskDefPtr disk)
+typedef struct _qemuSharedDiskEntry qemuSharedDiskEntry;
+typedef qemuSharedDiskEntry *qemuSharedDiskEntryPtr;
+struct _qemuSharedDiskEntry {
+    size_t ref;
+    char **domains; /* array of domain names */
+};
+
+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);
 
diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 86f9674..527c671 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -577,6 +577,18 @@ qemuDomainFindMaxID(virDomainObjPtr vm,
 }
 
 
+static void
+qemuSharedDisksFree(void *payload, const void *name ATTRIBUTE_UNUSED)
+{
+    qemuSharedDiskEntryPtr entry = (qemuSharedDiskEntryPtr)payload;
+    int i;
+
+    for (i = 0; i < entry->ref; i++) {
+        VIR_FREE(entry->domains[i]);
+    }
+    VIR_FREE(entry->domains);
+}
+
 /**
  * qemuStartup:
  *
@@ -718,7 +730,7 @@ qemuStartup(bool privileged,
     if ((qemu_driver->inactivePciHostdevs = virPCIDeviceListNew()) == NULL)
         goto error;
 
-    if (!(qemu_driver->sharedDisks = virHashCreate(30, NULL)))
+    if (!(qemu_driver->sharedDisks = virHashCreate(30, qemuSharedDisksFree)))
         goto error;
 
     if (privileged) {
@@ -5877,7 +5889,7 @@ 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);
 
@@ -6001,7 +6013,7 @@ 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);
     }
diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c
index 6ffb680..f46bc62 100644
--- a/src/qemu/qemu_process.c
+++ b/src/qemu/qemu_process.c
@@ -3909,7 +3909,7 @@ 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)
@@ -4318,7 +4318,7 @@ 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 */
-- 
1.7.7.6


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