Re: [PATCH] qemu: virtiofs: Stop virtiofsd when the qemu guest fails to start

[Daniel Henrique Barboza <danielhb413@xxxxxxxxx>]

On 11/10/20 2:04 AM, Masayoshi Mizuma wrote:
> From: Masayoshi Mizuma <m.mizuma@xxxxxxxxxxxxxx>
>
> A qemu guest which has virtiofs config fails to start if the previous
> starting failed because of invalid option or something.
> For example of the reproduction:
>
>    # virsh start guest
>    error: Failed to start domain guest
>    error: internal error: process exited while connecting to monitor: qemu-system-x86_64: -foo: invalid option
>
>    ... fix the option ...
>
>    # virsh start guest
>    error: Failed to start domain guest
>    error: Cannot open log file: '/var/log/libvirt/qemu/guest-fs0-virtiofsd.log': Device or resource busy
>    #
>
> That's because the virtiofsd which was executed on the former staring remains


s/staring/start ?


> and virtlogd keeps to opening the log file.
>
> Stop virtiofsd when the qemu guest fails to start.
>
> Signed-off-by: Masayoshi Mizuma <m.mizuma@xxxxxxxxxxxxxx>
> ---
>   src/qemu/qemu_domain.h   | 1 +
>   src/qemu/qemu_virtiofs.c | 5 +++++
>   2 files changed, 6 insertions(+)
>
> diff --git a/src/qemu/qemu_domain.h b/src/qemu/qemu_domain.h
> index ca041e207b..7d47c030bd 100644
> --- a/src/qemu/qemu_domain.h
> +++ b/src/qemu/qemu_domain.h
> @@ -426,6 +426,7 @@ struct _qemuDomainFSPrivate {
>       virObject parent;
>   
>       char *vhostuser_fs_sock;
> +    pid_t virtiofsd_pid;
>   };
>   
>   
> diff --git a/src/qemu/qemu_virtiofs.c b/src/qemu/qemu_virtiofs.c
> index 2e239cad66..8684219915 100644
> --- a/src/qemu/qemu_virtiofs.c
> +++ b/src/qemu/qemu_virtiofs.c
> @@ -250,6 +250,7 @@ qemuVirtioFSStart(virLogManagerPtr logManager,
>       }
>   
>       QEMU_DOMAIN_FS_PRIVATE(fs)->vhostuser_fs_sock = g_steal_pointer(&socket_path);
> +    QEMU_DOMAIN_FS_PRIVATE(fs)->virtiofsd_pid = pid;
>       ret = 0;
>   
>    cleanup:
> @@ -273,6 +274,7 @@ qemuVirtioFSStop(virQEMUDriverPtr driver G_GNUC_UNUSED,
>   {
>       g_autofree char *pidfile = NULL;
>       virErrorPtr orig_err;
> +    pid_t pid = QEMU_DOMAIN_FS_PRIVATE(fs)->virtiofsd_pid;
>   
>       virErrorPreserveLast(&orig_err);
>   
> @@ -286,6 +288,9 @@ qemuVirtioFSStop(virQEMUDriverPtr driver G_GNUC_UNUSED,
>               unlink(QEMU_DOMAIN_FS_PRIVATE(fs)->vhostuser_fs_sock);
>       }
>   
> +    if (virProcessKill(pid, 0) == 0)
> +        virProcessKillPainfully(pid, true);
> +


If you're adamant into killing 'pid' I suggest to just verify "if (pid)" and
then execute virProcessKillPainfully(), like is being done in virPidFileForceCleanupPath()
that is called right before.

Speaking of which, isn't virPidFileForceCleanupPath() responsible of killing
virtiofsd? If that's the case, the function is failing to do so in the scenario
you described, but it will succeed in all other cases. The result is that you'll
end up trying to kill the process twice.

Making a guess about what might be happening, if 'pidfile' does not exist in your error
scenario then virPidFileForceCleanupPath() is returning 0 but is doing nothing. This is
the case where your code might come in and kill the pid manually.



Thanks,

DHB


>    cleanup:
>       virErrorRestore(&orig_err);
>   }