[Devel] [PATCH] spfs: Main process wakes and kills its children on exit

[Kirill Tkhai]

Missed header. Actually it's v2

On 23.01.2018 12:41, Kirill Tkhai wrote:
> Stanislav Kinsburskiy says:
> 
> "SPFS manager has a special "--exit-with-spfs" options, which is used by CRIU.
>  The idea of the option is simple: force SPFS manager to exit, when it has some
>  SPFS processes among its children (i.e. spfs was mounted at least once),
>  but all these processes have exited for whatever reason (which usually happens
>  when restore has failed and spfs mounts where unmounted).
>  Although it works in overall (main SPFS manager process exits), its children
>  (responsible to SPFS replacement) may wait on FUTEX for "release" command
>  for corresponding SPFS mount and thus never stop until they are killed".
> 
> 1 spfs-manager
> 2   \_ spfs
> 3   \_ spfs-manager
> 4   \_ spfs
> 5   \_ spfs-manager
> 
> 2 and 3 are pair of a mount, and 4 and 5 are pair of another mount.
> The patch makes spfs-manager 1 kill 3 in case of 2 exited.
> 
> https://jira.sw.ru/browse/PSBM-80055
> 
> Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
> ---
>  manager/context.c |    4 ++++
>  manager/spfs.c    |    1 +
>  2 files changed, 5 insertions(+)
> 
> diff --git a/manager/context.c b/manager/context.c
> index 1eb37c9..4464a23 100644
> --- a/manager/context.c
> +++ b/manager/context.c
> @@ -53,6 +53,9 @@ static void cleanup_spfs_mount(struct spfs_manager_context_s *ctx,
>  		/* SPFS master was killed. We need to release the reference */
>  		spfs_release_mnt(info);
>  
> +	if (killed || WEXITSTATUS(status))
> +		kill(info->replacer, SIGKILL);
> +
>  	info->dead = true;
>  	del_spfs_info(ctx->spfs_mounts, info);
>  
> @@ -88,6 +91,7 @@ static void sigchld_handler(int signal, siginfo_t *siginfo, void *data)
>  				 * corresponding fd.
>  				 */
>  				spfs_release_mnt(info);
> +			info->replacer = -1;
>  		} else {
>  			info = find_spfs_by_pid(ctx->spfs_mounts, pid);
>  			if (info) {
> diff --git a/manager/spfs.c b/manager/spfs.c
> index 3e0f667..0b94587 100644
> --- a/manager/spfs.c
> +++ b/manager/spfs.c
> @@ -39,6 +39,7 @@ int create_spfs_info(const char *id,
>  		pr_err("failed to allocate\n");
>  		return -ENOMEM;
>  	}
> +	info->replacer = -1;
>  
>  	err = init_mount_info(&info->mnt, id, mountpoint, ns_mountpoint);
>  	if (err)
>