Add ping_monitor() to mdadm --wait

The action we are waiting for may not be complete until the monitor has
had a chance to take action on the result.

The following script can now remove the device on the first attempt,
versus a few attempts with the original Wait():
#!/bin/bash
#export MDADM_NO_MDMON=1
export IMSM_DEVNAME_AS_SERIAL=1
./mdadm -Ss
./mdadm --zero-superblock /dev/loop[0-3]
echo 2 > /proc/sys/dev/raid/speed_limit_max
./mdadm --create /dev/imsm /dev/loop[0-3] -n 4 -e imsm -a md
./mdadm --create /dev/md/r1 /dev/loop[0-3] -n 4 -l 5 --force -a mdp
./mdadm --fail /dev/md/r1 /dev/loop3
./mdadm --wait /dev/md/r1
x=0
while  ! ./mdadm --remove /dev/imsm /dev/loop3 > /dev/null 2>&1
do
        x=$((x+1))
done
echo "removed after $x attempts"
./mdadm --add /dev/imsm /dev/loop3

Include 2 small cleanups:
* remove the almost open coded fd2devnum() in Wait() by introducing a
  new utility routine stat2devnum()
* teach connect_monitor() to parse the container device from a subarray
  string

Signed-off-by: Dan Williams <dan.j.williams@intel.com>

1 files changed, 14 insertions, 7 deletions

diff --git a/util.c b/util.c
index 60fe6c0..7fe835a 100644
--- a/util.c
+++ b/util.c
@@ -1022,17 +1022,24 @@ int devname2devnum(char *name)
 	return num;
 }
 
-int fd2devnum(int fd)
+int stat2devnum(struct stat *st)
 {
-	struct stat stb;
-	if (fstat(fd, &stb) == 0 &&
-	    (S_IFMT&stb.st_mode)==S_IFBLK) {
-		if (major(stb.st_rdev) == MD_MAJOR)
-			return minor(stb.st_rdev);
+	if ((S_IFMT & st->st_mode) == S_IFBLK) {
+		if (major(st->st_rdev) == MD_MAJOR)
+			return minor(st->st_rdev);
 		else
-			return -1- (minor(stb.st_rdev)>>6);
+			return -1- (minor(st->st_rdev)>>6);
 	}
 	return -1;
+
+}
+
+int fd2devnum(int fd)
+{
+	struct stat stb;
+	if (fstat(fd, &stb) == 0)
+		return stat2devnum(&stb);
+	return -1;
 }
 
 int mdmon_running(int devnum)