[dm-devel] [PATCH]libmultipath/dmparser: add missing path with good status when sync state with dm kernel

[Chongyun Wu]

Hi Martin and Ben,

Cloud you help to view below patch, thanks.

>From b2786c81a78bf3868f300fd3177e852e718e7790 Mon Sep 17 00:00:00 2001
From: Chongyun Wu <wu.chongyun at h3c.com>
Date: Mon, 6 Jul 2020 11:22:21 +0800
Subject: [PATCH] libmultipath/dmparser: add missing path with good status
 when sync state with dm kernel

Add path back into deamon vecs->pathvecs when found path missing in
multipathd which can fix dm io blocked issue.

Test environment:
several hosts;
each host have 100+ multipath, each multipath have 1 to 4 paths.
run up/down storage network loop script for days.

Issue:
After several hours stop script, found some hosts have dm io blocked issue:
slave block device access well, but its dm device blocked.
36c0bfc0100a8d4a228214da50000003c dm-20 HUAWEI,XSG1
size=350G features='1 queue_if_no_path' hwhandler='0' wp=rw
`-+- policy='round-robin 0' prio=1 status=enabled
  |- 1:0:0:20  sdbk 67:224  failed ready running
multipathd show paths cannot found sdbk!

Test result:
With this patch, run script several days, io blocked issue
not found again.

This patch can fix this issue: when found path only missing in
multipathd but still in dm, check the missing path status if ok
try to add it back, and checker have chance to reinstate this
path and the dm io blocked issue will disappear.

Signed-off-by: Chongyun Wu <wu.chongyun at h3c.com>
---
 libmultipath/dmparser.c | 31 +++++++++++++++++++++++++++++++
 libmultipath/dmparser.h |  1 +
 2 files changed, 32 insertions(+)

diff --git a/libmultipath/dmparser.c b/libmultipath/dmparser.c
index b856a07f..2f90b17c 100644
--- a/libmultipath/dmparser.c
+++ b/libmultipath/dmparser.c
@@ -317,6 +317,12 @@ int disassemble_map(vector pathvec, char *params, struct multipath *mpp,
 				/* Only call this in multipath client mode */
 				if (!is_daemon && store_path(pathvec, pp))
 					goto out1;
+
+				/* Try to add good status path back to avoid
+				 * dm io blocked issue in special condition.
+				 */
+				if(add_missing_path(pathvec, devname))
+					condlog(2, "Try to add missing path %s failed", devname);
 			} else {
 				if (!strlen(pp->wwid) &&
 				    strlen(mpp->wwid))
@@ -569,3 +575,28 @@ int disassemble_status(char *params, struct multipath *mpp)
 	}
 	return 0;
 }
+
+/* Add missing good status path back to multipathd */
+int add_missing_path(vector pathvec, char *missing_dev)
+{
+	struct udev_device *udevice;
+	struct config *conf;
+	int ret = 0;
+				
+	condlog(2, "Cant't found path %s try to add it back if its state is up.", 
+			missing_dev);
+
+	udevice = udev_device_new_from_subsystem_sysname(udev, "block", missing_dev);
+	if (!udevice) {
+		condlog(0, "%s: can't find path form udev", missing_dev);
+		return 1;
+	}
+	conf = get_multipath_config();
+	pthread_cleanup_push(put_multipath_config, conf);
+	ret = store_pathinfo(pathvec, conf,
+						 udevice, DI_ALL | DI_BLACKLIST, NULL);
+	pthread_cleanup_pop(1);
+	udev_device_unref(udevice);
+
+	return ret;
+}
diff --git a/libmultipath/dmparser.h b/libmultipath/dmparser.h
index e1badb0b..515ca900 100644
--- a/libmultipath/dmparser.h
+++ b/libmultipath/dmparser.h
@@ -1,3 +1,4 @@
 int assemble_map (struct multipath *, char *, int);
 int disassemble_map (vector, char *, struct multipath *, int);
 int disassemble_status (char *, struct multipath *);
+int add_missing_path(vector pathvec, char *missing_dev);
-- 
2.12.1.windows.1


Best Regards，
Chongyun Wu