[dm-devel] [PATCH] multipath-tools:fix unexport/export LUN access permission multipath can't restore

[Wuchongyun]

Hi Christophe, Hannes, Martin, Xose and Benjamin,

We meet below issue when doing the unexport/export LUN's access permission test, this patch is a method to fix this issue.
If it is convenient for some of you, please help to review this patch, thanks.

fix unexport/export LUN access permission multipath can't restore

Issue:
(1)Export LUN1 to host1,Create multipath, LUN1 have two paths: sda and
sdb;
(2)Unexport LUN1 to host1, host1 can't access LUN1.Kernel produce change
uevent for sda and sdb, then uev_update_path been called, which will
found the path's wwid have changed and set flag pp->wwid_changed
, checker thread's check_path() found this flag will set those paths
failed and report to DM, and then this multipath failed.
(3)export LUN1 to host1 again. Kernel produce the change uevents, but
those uevents are not belong to LUN1(not sda and sdb).
So LUN1's related devices' status(wwid) not been updated by uevent when
regain this LUN's permission and this multipath will not restore anymore.

Through some experiments we found that:
unexport/export LUN to host, kernel may not produce the change uevent
for the right devices. It may be other devices, and the result may
different.
Get wwid by "/lib/udev/scsi_id --whitelisted --device=/dev/%n"will always
get the latest wwid: when no access permission return a invalid wwid,
when access restore return the origial right wwid.

If we meet this situation above issue will happen:
when unexporting LUN we get the right change uevent and refresh this
path's wwid to a valid value(HP 3PAR is 30000000000000000);
When exporting LUN to the host again we get the other devices' change
uevents, then we have no chance to refresh the changed paths'wwid, and
this multipath will not restore even it's LUN access permissions have
been restored.

This patch can fix this issue by:
In check_path() if found flag pp->wwid_changed is set, compare the wwid
gotten by scsi_id and the wwid gotten by udev(current get_uid). If the
value is not equal, it most likely we got the access permissions or device
valid again, scsi_id's wwid may restored, we should produce a change uevent
to fresh this device's status.

Signed-off-by: Chongyun Wu <wu.chongyun at h3c.com>
---
 libmultipath/defaults.h |    1 +
 multipathd/main.c       |   51 +++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 52 insertions(+)

diff --git a/libmultipath/defaults.h b/libmultipath/defaults.h
index c9e3411..895d3a1 100644
--- a/libmultipath/defaults.h
+++ b/libmultipath/defaults.h
@@ -3,6 +3,7 @@
  * and the TEMPLATE in libmultipath/hwtable.c
  */
 #define DEFAULT_UID_ATTRIBUTE	"ID_SERIAL"
+#define DEFAULT_GETUID		"/lib/udev/scsi_id --whitelisted --device=/dev/%n"
 #define DEFAULT_UDEVDIR		"/dev"
 #define DEFAULT_MULTIPATHDIR	"/" LIB_STRING "/multipath"
 #define DEFAULT_SELECTOR	"service-time 0"
diff --git a/multipathd/main.c b/multipathd/main.c
index 27cf234..dedc7d2 100644
--- a/multipathd/main.c
+++ b/multipathd/main.c
@@ -937,6 +937,9 @@ uev_update_path (struct uevent *uev, struct vectors * vecs)
 	if (pp) {
 		struct multipath *mpp = pp->mpp;
 
+		udev_device_unref(pp->udev);
+		pp->udev = udev_device_ref(uev->udev);
+
 		if (disable_changed_wwids &&
 		    (strlen(pp->wwid) || pp->wwid_changed)) {
 			char wwid[WWID_SIZE];
@@ -1578,6 +1581,54 @@ check_path (struct vectors * vecs, struct path * pp, int ticks)
 		condlog(2, "%s: path wwid has changed. Refusing to use",
 			pp->dev);
 		newstate = PATH_DOWN;
+
+		/*
+		 * compare the wwid gotten form scsi_id with the wwid which
+		 * gotten form udev. maybe the path wwid have been restored
+		 * by LUN been exported to the host again or another
+		 * operations making the wwid different form udev database.
+		 * If so, should trigger change uevent to refresh this
+		 * path's udev datebase.
+		*/
+		char wwid_old[WWID_SIZE];
+		char wwid_form_scsi_id[WWID_SIZE];
+		char wwid_form_udev[WWID_SIZE];
+		char buff[CALLOUT_MAX_SIZE];
+		char *getuid_old = NULL;
+
+		memset(wwid_form_scsi_id, 0, WWID_SIZE);
+		memset(wwid_form_udev, 0, WWID_SIZE);
+
+		/* save this path's  wwid and getuid*/
+		strcpy(wwid_old, pp->wwid);
+		if (pp->getuid) {
+			getuid_old = buff;
+			strcpy(getuid_old, pp->getuid);
+		}
+
+		/* using /lib/udev/scsi_id to get wwid */
+		pp->getuid = DEFAULT_GETUID;
+		get_uid(pp, PATH_UP, pp->udev);
+		strcpy(wwid_form_scsi_id, pp->wwid);
+		/* using udev to get wwid */
+		pp->getuid = NULL;
+		get_uid(pp, PATH_UP, pp->udev);
+		strcpy(wwid_form_udev, pp->wwid);
+
+		if (0 != strcmp(wwid_form_scsi_id, wwid_form_udev)) {
+			sysfs_attr_set_value(pp->udev, "uevent", "change",
+				strlen("change"));
+			condlog(2, "%s: wwid inconsistent triggering change "
+				"event to refresh udev database", pp->dev);
+		}
+
+		/* change this path's wwid and getuid back*/
+		strcpy(pp->wwid, wwid_old);
+		if (getuid_old) {
+			strcpy(pp->getuid, getuid_old);
+		} else {
+			pp->getuid = getuid_old;
+		}
 	}
 
 	if (newstate == PATH_WILD || newstate == PATH_UNCHECKED) {
-- 
1.7.9.5