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[libvirt] [PATCH 01/12] qemu: Add a hash table for the shared disks



This introduces a hash table for qemu driver, to store the shared
disk's info as (@disk_path, { ref_count, @orig_cdbfilter}). @ref_count
is the number of domains which shares the disk. @orig_cdbfilter is
the original cdbfilter setting of the shared disk, it will be used
to restore the the disk's cdbfilter setting to original value by
later patches.

* src/qemu/qemu_conf.h: (Add member 'sharedDisks' of type
                         virHashTablePtr; New struct qemuSharedDiskEntry;
                         Declare helpers qemuAddSharedDisk,
                         qemuRemoveSharedDisk)
* src/qemu/qemu_conf.c (Implement the two helpers)
* src/qemu/qemu_process.c (Update 'sharedDisks' when domain
                           starting and shutdown)
* src/qemu/qemu_driver.c (Update 'sharedDisks' when attaching
                          or detaching disk).

0 is passed for orig_cdbfilter temporarily, later patches will update
it.
---
 src/qemu/qemu_conf.c    |   48 +++++++++++++++++++++++++++++++++++++++++++++++
 src/qemu/qemu_conf.h    |   18 +++++++++++++++++
 src/qemu/qemu_driver.c  |   17 ++++++++++++++++
 src/qemu/qemu_process.c |   17 +++++++++++++++-
 4 files changed, 99 insertions(+), 1 deletions(-)

diff --git a/src/qemu/qemu_conf.c b/src/qemu/qemu_conf.c
index 8d380a1..2b21186 100644
--- a/src/qemu/qemu_conf.c
+++ b/src/qemu/qemu_conf.c
@@ -556,3 +556,51 @@ qemuDriverCloseCallbackRunAll(virQEMUDriverPtr driver,
 
     virHashForEach(driver->closeCallbacks, qemuDriverCloseCallbackRun, &data);
 }
+
+/* Increase ref count if the entry already exists, otherwise
+ * add a new entry.
+ */
+int
+qemuAddSharedDisk(virHashTablePtr sharedDisks,
+                  const char *disk_path,
+                  int orig_cdbfilter)
+{
+    qemuSharedDiskEntryPtr entry = NULL;
+
+    if ((entry = virHashLookup(sharedDisks, disk_path))) {
+        entry->ref++;
+    } else {
+        if (VIR_ALLOC(entry) < 0)
+            return -1;
+
+        entry->ref = 1;
+        entry->orig_cdbfilter = orig_cdbfilter;
+
+        if (virHashAddEntry(sharedDisks, disk_path, entry))
+            return -1;
+    }
+
+    return 0;
+}
+
+/* Decrease the ref count if the entry already exists, otherwise
+ * remove the entry.
+ */
+int
+qemuRemoveSharedDisk(virHashTablePtr sharedDisks,
+                     const char *disk_path)
+{
+    qemuSharedDiskEntryPtr entry = NULL;
+
+    if (!(entry = virHashLookup(sharedDisks, disk_path)))
+        return -1;
+
+    if (entry->ref != 1) {
+        entry->ref--;
+    } else {
+        if (virHashRemoveEntry(sharedDisks, disk_path) < 0)
+            return -1;
+    }
+
+    return 0;
+}
diff --git a/src/qemu/qemu_conf.h b/src/qemu/qemu_conf.h
index d0d25ce..df901f6 100644
--- a/src/qemu/qemu_conf.h
+++ b/src/qemu/qemu_conf.h
@@ -147,6 +147,8 @@ struct _virQEMUDriver {
     /* The devices which is are not in use by the host or any guest. */
     pciDeviceList *inactivePciHostdevs;
 
+    virHashTablePtr sharedDisks;
+
     virBitmapPtr reservedRemotePorts;
 
     virSysinfoDefPtr hostsysinfo;
@@ -193,6 +195,13 @@ struct qemuDomainDiskInfo {
     int io_status;
 };
 
+typedef struct qemuSharedDiskEntry qemuSharedDiskEntry;
+typedef qemuSharedDiskEntry *qemuSharedDiskEntryPtr;
+struct qemuSharedDiskEntry {
+    size_t ref; /* ref count of the shared disk */
+    int orig_cdbfilter; /* Original disk's cdbfilter setting */
+};
+
 typedef virDomainObjPtr (*qemuDriverCloseCallback)(virQEMUDriverPtr driver,
                                                    virDomainObjPtr vm,
                                                    virConnectPtr conn);
@@ -211,4 +220,13 @@ qemuDriverCloseCallback qemuDriverCloseCallbackGet(virQEMUDriverPtr driver,
 void qemuDriverCloseCallbackRunAll(virQEMUDriverPtr driver,
                                    virConnectPtr conn);
 
+int qemuAddSharedDisk(virHashTablePtr sharedDisks,
+                      const char *disk_path,
+                      int orig_cdbfilter)
+    ATTRIBUTE_NONNULL(1) ATTRIBUTE_NONNULL(2);
+
+int qemuRemoveSharedDisk(virHashTablePtr sharedDisks,
+                         const char *disk_path)
+    ATTRIBUTE_NONNULL(1) ATTRIBUTE_NONNULL(2);
+
 #endif /* __QEMUD_CONF_H */
diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index e099c5c..fdde74d 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -810,6 +810,9 @@ qemuStartup(bool privileged,
     if ((qemu_driver->inactivePciHostdevs = pciDeviceListNew()) == NULL)
         goto error;
 
+    if (!(qemu_driver->sharedDisks = virHashCreate(30, NULL)))
+        goto error;
+
     if (privileged) {
         if (chown(qemu_driver->libDir, qemu_driver->user, qemu_driver->group) < 0) {
             virReportSystemError(errno,
@@ -1064,6 +1067,7 @@ qemuShutdown(void) {
     pciDeviceListFree(qemu_driver->activePciHostdevs);
     pciDeviceListFree(qemu_driver->inactivePciHostdevs);
     usbDeviceListFree(qemu_driver->activeUsbHostdevs);
+    virHashFree(qemu_driver->sharedDisks);
     virCapabilitiesFree(qemu_driver->caps);
     qemuCapsCacheFree(qemu_driver->capsCache);
 
@@ -6035,6 +6039,12 @@ qemuDomainAttachDeviceDiskLive(virConnectPtr conn,
             VIR_WARN("Failed to teardown cgroup for disk path %s",
                      NULLSTR(disk->src));
     }
+
+    if (ret == 0 && disk->shared) {
+        if (qemuAddSharedDisk(driver->sharedDisks, disk->src, 0) < 0)
+            VIR_WARN("Failed to add disk '%s' to shared disk table",
+                     disk->src);
+    }
 end:
     if (cgroup)
         virCgroupFree(&cgroup);
@@ -6149,6 +6159,13 @@ qemuDomainDetachDeviceDiskLive(virQEMUDriverPtr driver,
                        virDomainDiskDeviceTypeToString(disk->type));
         break;
     }
+
+    if (ret == 0 && disk->shared) {
+        if (qemuRemoveSharedDisk(driver->sharedDisks, disk->src) < 0)
+             VIR_WARN("Failed to remove disk '%s' from shared disk table",
+                      disk->src);
+    }
+
     return ret;
 }
 
diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c
index ab04599..89152b8 100644
--- a/src/qemu/qemu_process.c
+++ b/src/qemu/qemu_process.c
@@ -3706,8 +3706,15 @@ int qemuProcessStart(virConnectPtr conn,
 
     /* in case a certain disk is desirous of CAP_SYS_RAWIO, add this */
     for (i = 0; i < vm->def->ndisks; i++) {
-        if (vm->def->disks[i]->rawio == 1)
+        virDomainDiskDefPtr disk = vm->def->disks[i];
+
+        if (disk->rawio == 1)
             virCommandAllowCap(cmd, CAP_SYS_RAWIO);
+
+        if (disk->shared) {
+            if (qemuAddSharedDisk(driver->sharedDisks, disk->src, 0) < 0)
+                goto cleanup;
+        }
     }
 
     virCommandSetPreExecHook(cmd, qemuProcessHook, &hookData);
@@ -4104,6 +4111,14 @@ void qemuProcessStop(virQEMUDriverPtr driver,
                                           flags & VIR_QEMU_PROCESS_STOP_MIGRATED);
     virSecurityManagerReleaseLabel(driver->securityManager, vm->def);
 
+    for (i = 0; i < vm->def->ndisks; i++) {
+        virDomainDiskDefPtr disk = vm->def->disks[i];
+
+        if (disk->shared) {
+            ignore_value(qemuRemoveSharedDisk(driver->sharedDisks, disk->src));
+        }
+    }
+
     /* Clear out dynamically assigned labels */
     for (i = 0; i < vm->def->nseclabels; i++) {
         if (vm->def->seclabels[i]->type == VIR_DOMAIN_SECLABEL_DYNAMIC) {
-- 
1.7.7.6


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