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Message-ID: <7f766982-5719-03bf-2d2e-044996e09f7a@huawei.com>
Date:   Mon, 17 Oct 2022 11:41:20 +0800
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Subject: Re: [PATCH] nfs-blkmapd: PID file read by systemd failed
From:   zhanchengbin <zhanchengbin1@huawei.com>
To:     <steved@redhat.com>
CC:     <linux-nfs@vger.kernel.org>, <liuzhiqiang26@huawei.com>,
        linfeilong <linfeilong@huawei.com>
References: <68672de3-9fb5-e90b-814f-850185762029@huawei.com>
In-Reply-To: <68672de3-9fb5-e90b-814f-850185762029@huawei.com>
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Precedence: bulk

friendly ping, thanks.

On 2022/10/11 17:33, zhanchengbin wrote:
> When started nfs-blkmap.service, the PID file can't be opened, The
> cause is that the child process does not create the PID file before
> the systemd reads the PID file.
> Adding "ExecStartPost=/bin/sleep 0.1" to
> /usr/lib/systemd/system/nfs-blkmap.service will probably solve this
> problem, However, there is no guarantee that the above solutions are
> effective under high cpu pressure.So replace the daemon function with
> the fork function, and put the behavior of creating the PID file in
> the parent process to solve the above problems.
> 
> Signed-off-by: zhanchengbin <zhanchengbin1@huawei.com>
> Reviewed-by: Zhiqiang Liu <liuzhiqiang26@huawei.com>
> ---
>   utils/blkmapd/device-discovery.c | 48 +++++++++++++++++++++-----------
>   1 file changed, 32 insertions(+), 16 deletions(-)
> 
> diff --git a/utils/blkmapd/device-discovery.c 
> b/utils/blkmapd/device-discovery.c
> index 2736ac89..4d97ac72 100644
> --- a/utils/blkmapd/device-discovery.c
> +++ b/utils/blkmapd/device-discovery.c
> @@ -507,28 +507,44 @@ int main(int argc, char **argv)
>       if (fg) {
>           openlog("blkmapd", LOG_PERROR, 0);
>       } else {
> -        if (daemon(0, 0) != 0) {
> -            fprintf(stderr, "Daemonize failed\n");
> +        pid_t pid = fork();
> +        if (pid < 0) {
> +            fprintf(stderr, "fork error\n");
>               exit(1);
> +        } else if (pid != 0) {
> +            pidfd = open(PID_FILE, O_WRONLY | O_CREAT, 0644);
> +            if (pidfd < 0) {
> +                fprintf(stderr, "Create pid file %s failed\n", PID_FILE);
> +                exit(1);
> +            }
> +
> +            if (lockf(pidfd, F_TLOCK, 0) < 0) {
> +                fprintf(stderr, "Already running; Exiting!");
> +                close(pidfd);
> +                exit(1);
> +            }
> +            if (ftruncate(pidfd, 0) < 0)
> +                fprintf(stderr, "ftruncate on %s failed: m\n", PID_FILE);
> +            sprintf(pidbuf, "%d\n", pid);
> +            if (write(pidfd, pidbuf, strlen(pidbuf)) != 
> (ssize_t)strlen(pidbuf))
> +                fprintf(stderr, "write on %s failed: m\n", PID_FILE);
> +            exit(0);
>           }
> 
> -        openlog("blkmapd", LOG_PID, 0);
> -        pidfd = open(PID_FILE, O_WRONLY | O_CREAT, 0644);
> -        if (pidfd < 0) {
> -            BL_LOG_ERR("Create pid file %s failed\n", PID_FILE);
> -            exit(1);
> +        (void)setsid();
> +        if (chdir("/")) {
> +            fprintf(stderr, "chdir error\n");
>           }
> +        int fd = open("/dev/null", O_RDWR, 0);
> +        if (fd >= 0) {
> +            (void)dup2(fd, STDIN_FILENO);
> +            (void)dup2(fd, STDOUT_FILENO);
> +            (void)dup2(fd, STDERR_FILENO);
> 
> -        if (lockf(pidfd, F_TLOCK, 0) < 0) {
> -            BL_LOG_ERR("Already running; Exiting!");
> -            close(pidfd);
> -            exit(1);
> +            (void)close(fd);
>           }
> -        if (ftruncate(pidfd, 0) < 0)
> -            BL_LOG_WARNING("ftruncate on %s failed: m\n", PID_FILE);
> -        sprintf(pidbuf, "%d\n", getpid());
> -        if (write(pidfd, pidbuf, strlen(pidbuf)) != 
> (ssize_t)strlen(pidbuf))
> -            BL_LOG_WARNING("write on %s failed: m\n", PID_FILE);
> +
> +        openlog("blkmapd", LOG_PID, 0);
>       }
> 
>       signal(SIGINT, sig_die);