[mdadm PATCH 2/2] fix mdmon takeover

[Luca Berra <bluca@comedia.it>]

there are two cases that would result in two mdmon processes for the
same array
takeover not detecting pid file in ALT_RUN
if running mdmon a second time without "--takeover"

Signed-off-by: Luca Berra <bluca@comedia.it>
---
  mdmon.c |   10 +++++++++-
  msg.c   |    2 +-
  util.c  |    4 ++--
  3 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/mdmon.c b/mdmon.c
index d593ebc..a2b7946 100644
--- a/mdmon.c
+++ b/mdmon.c
@@ -441,7 +441,6 @@ static int mdmon(char *devname, int devnum, int must_fork, int takeover)
  	sigaction(SIGPIPE, &act, NULL);
  
  	if (takeover) {
-		pid_dir = VAR_RUN;
  		victim = mdmon_pid(container->devnum);
  		if (victim < 0) {
  			pid_dir = ALT_RUN;
@@ -453,6 +452,15 @@ static int mdmon(char *devname, int devnum, int must_fork, int takeover)
  
  	ignore = chdir("/");
  	if (victim < 0) {
+		pid_dir = ALT_RUN;
+		if (ping_monitor(container->devname) == 0) {
+			fprintf(stderr, "mdmon: %s already managed\n",
+				container->devname);
+			if (!takeover)
+				fprintf(stderr, "\trun mdmon --takeover instead\n");
+			exit(3);
+		}
+		pid_dir = VAR_RUN;
  		if (ping_monitor(container->devname) == 0) {
  			fprintf(stderr, "mdmon: %s already managed\n",
  				container->devname);
diff --git a/msg.c b/msg.c
index cc07b96..d2d8445 100644
--- a/msg.c
+++ b/msg.c
@@ -147,7 +147,7 @@ int connect_monitor(char *devname)
  	int pos;
  	char *c;
  
-	pos = sprintf(path, "%s/", VAR_RUN);
+	pos = sprintf(path, "%s/", pid_dir);
  	if (is_subarray(devname)) {
  		devname++;
  		c = strchr(devname, '/');
diff --git a/util.c b/util.c
index 1def2a0..2fe566d 100644
--- a/util.c
+++ b/util.c
@@ -1475,11 +1475,11 @@ int mdmon_pid(int devnum)
  	fd = open(path, O_RDONLY | O_NOATIME, 0);
  
  	if (fd < 0)
-		return 0;
+		return -1;
  	n = read(fd, pid, 9);
  	close(fd);
  	if (n <= 0)
-		return 0;
+		return -1;
  	return atoi(pid);
  }
  
-- 
1.7.0

-- 
Luca Berra -- bluca@comedia.it
         Communication Media & Services S.r.l.
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