Adds the ability to monitor the nbdkit process so that we can take
action in case the child exits unexpectedly.
When the nbdkit process exits, we pause the vm, restart nbdkit, and then
resume the vm. This allows the vm to continue working in the event of a
nbdkit failure.
Eventually we may want to generalize this functionality since we may
need something similar for e.g. qemu-storage-daemon, etc.
The process is monitored with the pidfd_open() syscall if it exists
(since linux 5.3). Otherwise it resorts to checking whether the process
is alive once a second. The one-second time period was chosen somewhat
arbitrarily.
Signed-off-by: Jonathon Jongsma <jjongsma@xxxxxxxxxx>
---
meson.build | 7 ++
src/qemu/qemu_domain.c | 1 +
src/qemu/qemu_domain.h | 1 +
src/qemu/qemu_driver.c | 18 ++++++
src/qemu/qemu_nbdkit.c | 137 ++++++++++++++++++++++++++++++++++++++--
src/qemu/qemu_nbdkit.h | 8 ++-
src/qemu/qemu_process.c | 13 +++-
src/qemu/qemu_process.h | 3 +
8 files changed, 180 insertions(+), 8 deletions(-)
diff --git a/meson.build b/meson.build
index 965ada483b..8da3b59070 100644
--- a/meson.build
+++ b/meson.build
@@ -682,6 +682,13 @@ symbols = [
[ 'sched.h', 'cpu_set_t' ],
]
+if host_machine.system() == 'linux'
+ symbols += [
+ # process management
+ [ 'sys/syscall.h', 'SYS_pidfd_open' ],
+ ]
+endif
+
foreach symbol : symbols
if cc.has_header_symbol(symbol[0], symbol[1], args: '-D_GNU_SOURCE', prefix: symbol.get(2, ''))
conf.set('WITH_DECL_@0@'.format(symbol[1].to_upper()), 1)
diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
index 46fe5a1cf4..2b8ece8f19 100644
--- a/src/qemu/qemu_domain.c
+++ b/src/qemu/qemu_domain.c
@@ -11511,6 +11511,7 @@ qemuProcessEventFree(struct qemuProcessEvent *event)
case QEMU_PROCESS_EVENT_PR_DISCONNECT:
case QEMU_PROCESS_EVENT_UNATTENDED_MIGRATION:
case QEMU_PROCESS_EVENT_RESET:
+ case QEMU_PROCESS_EVENT_NBDKIT_EXITED:
case QEMU_PROCESS_EVENT_LAST:
break;
}
diff --git a/src/qemu/qemu_domain.h b/src/qemu/qemu_domain.h
index ddd20e67b4..f018b45eb6 100644
--- a/src/qemu/qemu_domain.h
+++ b/src/qemu/qemu_domain.h
@@ -465,6 +465,7 @@ typedef enum {
QEMU_PROCESS_EVENT_MEMORY_DEVICE_SIZE_CHANGE,
QEMU_PROCESS_EVENT_UNATTENDED_MIGRATION,
QEMU_PROCESS_EVENT_RESET,
+ QEMU_PROCESS_EVENT_NBDKIT_EXITED,
QEMU_PROCESS_EVENT_LAST
} qemuProcessEventType;
diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index ad8428948b..46e089fe0f 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -4040,6 +4040,21 @@ processResetEvent(virQEMUDriver *driver,
}
+
+
+static void
+processNbdkitExitedEvent(virDomainObj *vm,
+ qemuNbdkitProcess *nbdkit)
+{
+ if (virDomainObjBeginJob(vm, VIR_JOB_MODIFY) < 0)
+ return;
+
+ qemuNbdkitProcessRestart(nbdkit, vm);
+
+ virDomainObjEndJob(vm);
+}
+
+
static void qemuProcessEventHandler(void *data, void *opaque)
{
struct qemuProcessEvent *processEvent = data;
@@ -4097,6 +4112,9 @@ static void qemuProcessEventHandler(void *data, void *opaque)
case QEMU_PROCESS_EVENT_RESET:
processResetEvent(driver, vm);
break;
+ case QEMU_PROCESS_EVENT_NBDKIT_EXITED:
+ processNbdkitExitedEvent(vm, processEvent->data);
+ break;
case QEMU_PROCESS_EVENT_LAST:
break;
}
diff --git a/src/qemu/qemu_nbdkit.c b/src/qemu/qemu_nbdkit.c
index df638e99c0..c3fa349922 100644
--- a/src/qemu/qemu_nbdkit.c
+++ b/src/qemu/qemu_nbdkit.c
@@ -19,6 +19,7 @@
#include <config.h>
#include <glib.h>
+#include <sys/syscall.h>
#include "vircommand.h"
#include "virerror.h"
@@ -33,6 +34,7 @@
#include "qemu_nbdkit.h"
#define LIBVIRT_QEMU_NBDKITPRIV_H_ALLOW
#include "qemu_nbdkitpriv.h"
+#include "qemu_process.h"
#include "qemu_security.h"
#include <fcntl.h>
@@ -611,6 +613,106 @@ qemuNbdkitCapsCacheNew(const char *cachedir)
}
+void
+qemuNbdkitProcessRestart(qemuNbdkitProcess *proc,
+ virDomainObj *vm)
+{
+ qemuDomainObjPrivate *vmpriv = vm->privateData;
+ virQEMUDriver *driver = vmpriv->driver;
+
+ /* clean up resources associated with process */
+ qemuNbdkitProcessStop(proc);
+
+ if (qemuNbdkitProcessStart(proc, vm, driver) < 0)
+ VIR_WARN("Unable to restart nbkdit process");
+}
+
+
+typedef struct {
+ qemuNbdkitProcess *proc;
+ virDomainObj *vm;
+} qemuNbdkitProcessEventData;
+
+
+static qemuNbdkitProcessEventData*
+qemuNbdkitProcessEventDataNew(qemuNbdkitProcess *proc,
+ virDomainObj *vm)
+{
+ qemuNbdkitProcessEventData *d = g_new(qemuNbdkitProcessEventData, 1);
+ d->proc = proc;
+ d->vm = virObjectRef(vm);
+ return d;
+}
+
+
+static void
+qemuNbdkitProcessEventDataFree(qemuNbdkitProcessEventData *d)
+{
+ virObjectUnref(d->vm);
+ g_free(d);
+}
+
+
+#if WITH_DECL_SYS_PIDFD_OPEN
+static void
+qemuNbdkitProcessPidfdCb(int watch G_GNUC_UNUSED,
+ int fd,
+ int events G_GNUC_UNUSED,
+ void *opaque)
+{
+ qemuNbdkitProcessEventData *d = opaque;
+
+ VIR_FORCE_CLOSE(fd);
+ VIR_DEBUG("nbdkit process %i died", d->proc->pid);
+ /* submit an event so that it is handled in the per-vm event thread */
+ qemuProcessHandleNbdkitExit(d->proc, d->vm);
+}
+#endif /* WITH_DECL_SYS_PIDFD_OPEN */
+
+
+static int
+qemuNbdkitProcessStartMonitor(qemuNbdkitProcess *proc,
+ virDomainObj *vm)
+{
+#if WITH_DECL_SYS_PIDFD_OPEN
+ int pidfd;
+
+ pidfd = syscall(SYS_pidfd_open, proc->pid, 0);
+ if (pidfd < 0) {
+ virReportSystemError(errno, _("pidfd_open failed for %1$i"), proc->pid);
+ return -1;
+ }
+
+ proc->eventwatch = virEventAddHandle(pidfd,
+ VIR_EVENT_HANDLE_READABLE,
+ qemuNbdkitProcessPidfdCb,
+ qemuNbdkitProcessEventDataNew(proc, vm),
+ (virFreeCallback)qemuNbdkitProcessEventDataFree);
+
+ VIR_DEBUG("Monitoring nbdkit process %i for exit", proc->pid);
+
+ return 0;
+#else
+ /* This should not be reachable */
+ virReportError(VIR_ERR_NO_SUPPORT, "%s",
+ _("pidfd_open system call required for nbdkit support"));
+ return -1;
+#endif /* WITH_DECL_SYS_PIDFD_OPEN */
+}
+
+
+static void
+qemuNbdkitProcessStopMonitor(qemuNbdkitProcess *proc)
+{
+#if WITH_DECL_SYS_PIDFD_OPEN
+ if (proc->eventwatch > 0) {
+ virEventRemoveHandle(proc->eventwatch);
+ proc->eventwatch = 0;
+ }
+#endif /* WITH_DECL_SYS_PIDFD_OPEN */
+}
+
+
static qemuNbdkitProcess *
qemuNbdkitProcessNew(virStorageSource *source,
const char *pidfile,
@@ -658,9 +760,11 @@ qemuNbdkitReconnectStorageSource(virStorageSource *source,
static void
-qemuNbdkitStorageSourceManageProcessOne(virStorageSource *source)
+qemuNbdkitStorageSourceManageProcessOne(virStorageSource *source,
+ virDomainObj *vm)
{
qemuDomainStorageSourcePrivate *srcpriv = QEMU_DOMAIN_STORAGE_SOURCE_PRIVATE(source);
+ qemuDomainObjPrivate *vmpriv = vm->privateData;
qemuNbdkitProcess *proc;
if (!srcpriv)
@@ -671,6 +775,9 @@ qemuNbdkitStorageSourceManageProcessOne(virStorageSource *source)
if (!proc)
return;
+ if (!proc->caps)
+ proc->caps = qemuGetNbdkitCaps(vmpriv->driver);
+
if (proc->pid <= 0) {
if (virPidFileReadPath(proc->pidfile, &proc->pid) < 0) {
VIR_WARN("Unable to read pidfile '%s'", proc->pidfile);
@@ -678,8 +785,14 @@ qemuNbdkitStorageSourceManageProcessOne(virStorageSource *source)
}
}
- if (virProcessKill(proc->pid, 0) < 0)
+ if (virProcessKill(proc->pid, 0) < 0) {
VIR_WARN("nbdkit process %i is not alive", proc->pid);
+ qemuNbdkitProcessRestart(proc, vm);
+ return;
+ }
+
+ if (qemuNbdkitProcessStartMonitor(proc, vm) < 0)
+ VIR_WARN("unable monitor nbdkit process");
}
/**
@@ -692,11 +805,12 @@ qemuNbdkitStorageSourceManageProcessOne(virStorageSource *source)
* disk and is attempting to re-connect to active domains.
*/
void
-qemuNbdkitStorageSourceManageProcess(virStorageSource *source)
+qemuNbdkitStorageSourceManageProcess(virStorageSource *source,
+ virDomainObj *vm)
{
virStorageSource *backing;
for (backing = source; backing != NULL; backing = backing->backingStore)
- qemuNbdkitStorageSourceManageProcessOne(backing);
+ qemuNbdkitStorageSourceManageProcessOne(backing, vm);
}
@@ -708,6 +822,11 @@ qemuNbdkitInitStorageSource(qemuNbdkitCaps *caps,
uid_t user,
gid_t group)
{
+#if !WITH_DECL_SYS_PIDFD_OPEN
+ /* we need pidfd_open in order to monitor the process, so don't construct
+ * the object in this case so we'll fall back to qemu storage drivers */
+ return false;
+#else
qemuDomainStorageSourcePrivate *srcPriv = qemuDomainStorageSourcePrivateFetch(source);
g_autofree char *pidname = g_strdup_printf("nbdkit-%s.pid", alias);
g_autofree char *socketname = g_strdup_printf("nbdkit-%s.socket", alias);
@@ -751,6 +870,7 @@ qemuNbdkitInitStorageSource(qemuNbdkitCaps *caps,
srcPriv->nbdkitProcess = proc;
return true;
+#endif /* WITH_DECL_SYS_PIDFD_OPEN */
}
@@ -968,6 +1088,8 @@ qemuNbdkitProcessBuildCommand(qemuNbdkitProcess *proc)
void
qemuNbdkitProcessFree(qemuNbdkitProcess *proc)
{
+ qemuNbdkitProcessStopMonitor(proc);
+
g_clear_pointer(&proc->pidfile, g_free);
g_clear_pointer(&proc->socketfile, g_free);
g_clear_object(&proc->caps);
@@ -1037,8 +1159,11 @@ qemuNbdkitProcessStart(qemuNbdkitProcess *proc,
goto error;
while (virTimeBackOffWait(&timebackoff)) {
- if (virFileExists(proc->socketfile))
+ if (virFileExists(proc->socketfile)) {
+ if (qemuNbdkitProcessStartMonitor(proc, vm) < 0)
+ goto error;
return 0;
+ }
if (virProcessKill(proc->pid, 0) == 0)
continue;
@@ -1069,6 +1194,8 @@ qemuNbdkitProcessStart(qemuNbdkitProcess *proc,
int
qemuNbdkitProcessStop(qemuNbdkitProcess *proc)
{
+ qemuNbdkitProcessStopMonitor(proc);
+
if (proc->pid < 0)
return 0;
diff --git a/src/qemu/qemu_nbdkit.h b/src/qemu/qemu_nbdkit.h
index 36a2219d82..f33b049d38 100644
--- a/src/qemu/qemu_nbdkit.h
+++ b/src/qemu/qemu_nbdkit.h
@@ -69,7 +69,8 @@ void
qemuNbdkitStopStorageSource(virStorageSource *src);
void
-qemuNbdkitStorageSourceManageProcess(virStorageSource *src);
+qemuNbdkitStorageSourceManageProcess(virStorageSource *src,
+ virDomainObj *vm);
bool
qemuNbdkitCapsGet(qemuNbdkitCaps *nbdkitCaps,
@@ -91,6 +92,7 @@ struct _qemuNbdkitProcess {
uid_t user;
gid_t group;
pid_t pid;
+ int eventwatch;
};
int
@@ -98,6 +100,10 @@ qemuNbdkitProcessStart(qemuNbdkitProcess *proc,
virDomainObj *vm,
virQEMUDriver *driver);
+void
+qemuNbdkitProcessRestart(qemuNbdkitProcess *proc,
+ virDomainObj *vm);
+
int
qemuNbdkitProcessStop(qemuNbdkitProcess *proc);
diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c
index d90990d8a5..1020c1a161 100644
--- a/src/qemu/qemu_process.c
+++ b/src/qemu/qemu_process.c
@@ -8993,10 +8993,10 @@ qemuProcessReconnect(void *opaque)
}
for (i = 0; i < obj->def->ndisks; i++)
- qemuNbdkitStorageSourceManageProcess(obj->def->disks[i]->src);
+ qemuNbdkitStorageSourceManageProcess(obj->def->disks[i]->src, obj);
if (obj->def->os.loader && obj->def->os.loader->nvram)
- qemuNbdkitStorageSourceManageProcess(obj->def->os.loader->nvram);
+ qemuNbdkitStorageSourceManageProcess(obj->def->os.loader->nvram, obj);
/* update domain state XML with possibly updated state in virDomainObj */
if (virDomainObjSave(obj, driver->xmlopt, cfg->stateDir) < 0)
@@ -9451,3 +9451,12 @@ qemuProcessQMPStart(qemuProcessQMP *proc)
return 0;
}
+
+
+void qemuProcessHandleNbdkitExit(qemuNbdkitProcess *nbdkit,
+ virDomainObj *vm)
+{
+ virObjectLock(vm);
+ qemuProcessEventSubmit(vm, QEMU_PROCESS_EVENT_NBDKIT_EXITED, 0, 0, nbdkit);
+ virObjectUnlock(vm);
+}
diff --git a/src/qemu/qemu_process.h b/src/qemu/qemu_process.h
index cae1b49756..86a60d29c9 100644
--- a/src/qemu/qemu_process.h
+++ b/src/qemu/qemu_process.h
@@ -237,3 +237,6 @@ void qemuProcessRefreshDiskProps(virDomainDiskDef *disk,
struct qemuDomainDiskInfo *info);
int qemuProcessSetupEmulator(virDomainObj *vm);
+
+void qemuProcessHandleNbdkitExit(qemuNbdkitProcess *nbdkit,
+ virDomainObj *vm);
--
2.41.0
