[dm-devel] [PATCH 2/2] multipathd: skip spurious event message for blacklisted paths

[Mauricio Faria de Oliveira]

Currently, multipath still prints the 'spurious uevent, path not found'
message if a path is blacklisted by something different than a devnode
in the 'change' uevent handling. (uev_trigger() calls filter_devnode()).

Thus blacklisting by device vendor/product and wwid still renders that
message in the system log -- since it's verbosity level 0 -- for paths
that are explicitly marked to be ignored.

This problem happens on common scenarios such as creating filesystems
on a blacklisted device (e.g., mkfs.* /dev/sdX), which is usually run
several times on test environments, and the error message may mislead
the error checker/monitor tools with false negatives.

This patch resolves this problem by calling/checking path_discover()
for PATHINFO_SKIPPED with just enough device information flags for
blacklist verification -- and it prints a debug message (verbosity
level 3) instead of an error message since this case is not an error.

Even though it introduces a bit of overhead to get the path info,
it is only exercised in the error/non-default path -- so not a problem.

Test-case (on QEMU):

  /etc/multipath.conf:

  blacklist {
      device {
          vendor "QEMU"
       }
  }

  # multipathd -d &
  ...
  Dec 10 08:06:27 | sda: (QEMU:QEMU HARDDISK) vendor/product blacklisted
  ...

  # mkfs.ext3 -F /dev/sda
  ...

  Dec 10 08:07:05 | sda: spurious uevent, path not found

With the patch applied, no message is printed by default.
It's still possible to get the event logged for debug with '-v3':

  Dec 10 09:08:51 | sda: spurious uevent, path blacklisted

Reported-by: Yueh Chyong (Ida) Jackson <idaj at us.ibm.com>
Signed-off-by: Mauricio Faria de Oliveira <mauricfo at linux.vnet.ibm.com>
---
 multipathd/main.c | 22 +++++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)

diff --git a/multipathd/main.c b/multipathd/main.c
index d6f081f..364fecb 100644
--- a/multipathd/main.c
+++ b/multipathd/main.c
@@ -1010,8 +1010,28 @@ uev_update_path (struct uevent *uev, struct vectors * vecs)
 	}
 out:
 	lock_cleanup_pop(vecs->lock);
-	if (!pp)
+	if (!pp) {
+		/* If the path is blacklisted, print a debug/non-default verbosity message. */
+		if (uev->udev) {
+			int flag = DI_BLACKLIST | DI_SYSFS | DI_WWID;
+			struct udev_device *udevice;
+
+			udevice = udev_device_ref(uev->udev);
+			conf = get_multipath_config();
+
+			retval = path_discover(NULL, conf, udevice, flag);
+
+			put_multipath_config(conf);
+			udev_device_unref(uev->udev);
+
+			if (retval == PATHINFO_SKIPPED) {
+				condlog(3, "%s: spurious uevent, path blacklisted", uev->kernel);
+				return 0;
+			}
+		}
+
 		condlog(0, "%s: spurious uevent, path not found", uev->kernel);
+	}
 
 	return retval;
 }
-- 
2.7.4