Received-SPF: pass (google.com: domain of linux-nfs-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <68672de3-9fb5-e90b-814f-850185762029@huawei.com>
Date:   Tue, 11 Oct 2022 17:33:22 +0800
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101
 Thunderbird/91.3.2
From:   zhanchengbin <zhanchengbin1@huawei.com>
To:     <steved@redhat.com>
CC:     <linux-nfs@vger.kernel.org>, <liuzhiqiang26@huawei.com>,
        linfeilong <linfeilong@huawei.com>
Subject: [PATCH] nfs-blkmapd: PID file read by systemd failed
Content-Type: text/plain; charset="UTF-8"; format=flowed
Content-Transfer-Encoding: 7bit
Precedence: bulk

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);
-- 
2.27.0