Re: [libvirt PATCH v5 25/32] 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_nbdkit.c | 147 ++++++++++++++++++++++++++++++++++++++-- src/qemu/qemu_nbdkit.h | 4 +- src/qemu/qemu_process.c | 4 +- 4 files changed, 155 insertions(+), 7 deletions(-)

diff --git a/src/qemu/qemu_nbdkit.c b/src/qemu/qemu_nbdkit.c index e6d3232a1e..74e2ceee19 100644 --- a/src/qemu/qemu_nbdkit.c +++ b/src/qemu/qemu_nbdkit.c

+#if WITH_DECL_SYS_PIDFD_OPEN + pidfd = syscall(SYS_pidfd_open, proc->pid, 0); + if (pidfd < 0) + return -1; + + proc->eventwatch = virEventAddHandle(pidfd, + VIR_EVENT_HANDLE_READABLE, + qemuNbdkitProcessPidfdCb, + qemuNbdkitProcessEventDataNew(proc, vm), + (virFreeCallback)qemuNbdkitProcessEventDataFree); +#else + /* fall back to checking once a second */ + proc->eventwatch = virEventAddTimeout(1000, + qemuNbdkitProcessTimeoutCb, + qemuNbdkitProcessEventDataNew(proc, vm), + (virFreeCallback)qemuNbdkitProcessEventDataFree);