Re: [libvirt PATCH v7 24/35] qemu: Monitor nbdkit process for exit

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(a)redhat.com&gt; --- 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/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;

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

@@ -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);

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");

} /**

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

return 0; } + + +void qemuProcessHandleNbdkitExit(qemuNbdkitProcess *nbdkit, + virDomainObj *vm)

+{ + virObjectLock(vm); + qemuProcessEventSubmit(vm, QEMU_PROCESS_EVENT_NBDKIT_EXITED, 0, 0, nbdkit); + virObjectUnlock(vm); +}