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[dm-devel] [Patch] multipath-tools: rdac path checked leads to I/O hang when volumes are unmapped from storage.



Hi,

We are seeing I/O hang when volumes (configured with rdac path checker) are unmapped from the storage. Expected is I/O should fail. Please see the syslog snippet below:

Oct  15 14:40:43 linux kernel: sd 6:0:0:0: queueing MODE_SELECT command.
Oct  15 14:40:43 linux kernel: sd 6:0:0:0: MODE_SELECT failed with sense 0x59100.
Oct  15 14:40:43 linux kernel: end_request: I/O error, dev sdh, sector 18509824
Oct  15 14:40:43 linux kernel: device-mapper: multipath: Failing path 8:112.
Oct  15 14:40:43 linux kernel: end_request: I/O error, dev sdh, sector 0
Oct  15 14:40:43 linux kernel: end_request: I/O error, dev sdh, sector 18512896
Oct  15 14:40:43 linux kernel: end_request: I/O error, dev sdh, sector 18511872
Oct  15 14:40:43 linux kernel: end_request: I/O error, dev sdh, sector 18510848
Oct  15 14:40:43 linux multipathd: 8:112: mark as failed
Oct  15 14:40:43 linux multipathd: 3600a0b800029ea52000097bc4acde51e: Entering recovery mode: max_retries=30
Oct  15 14:40:44 linux multipathd: 3600a0b800029eb0a0000f2af4acde4d1: queue_if_no_path enabled
Oct  15 14:40:44 linux multipathd: 3600a0b800029eb0a0000f2af4acde4d1: Recovered to normal mode
Oct  15 14:40:44 linux kernel: sd 5:0:0:1: queueing MODE_SELECT command.
Oct  15 14:40:44 linux kernel: sd 5:0:0:1: MODE_SELECT failed with sense 0x59100.
Oct  15 14:40:44 linux kernel: end_request: I/O error, dev sdc, sector 0
Oct  15 14:40:44 linux kernel: device-mapper: multipath: Failing path 8:32.
Oct  15 14:40:44 linux kernel: end_request: I/O error, dev sdc, sector 16089088
Oct  15 14:40:44 linux kernel: end_request: I/O error, dev sdc, sector 16090112
Oct  15 14:40:44 linux kernel: end_request: I/O error, dev sdc, sector 16091136
Oct  15 14:40:44 linux kernel: end_request: I/O error, dev sdc, sector 16092160
Oct  15 14:40:44 linux multipathd: 8:32: mark as failed

Below is the patch that fix this issue. When devices are unmapped from storage, rdac patch checker sets the path state for those devices as ghost. As a reason dm issues mode select to failover path group and fails with 0x59100, which eventually ends up with ping pong between path groups resulting in I/O hang. In rdac path checker, we need to check if devices are not connected, mark it as failed. This patch adds check for Peripheral Qualifier (PQ) & Peripheral Device type(PDT) of Inquiry data and fails the path if either 1) PQ is set to 0x1 or 2) PQ set to 0x11 and PDT set to 0x1F.


Signed-off-by: Vijay Chauhan <vijay chauhan lsi com>
Reviewed-by: Babu Moger <babu moger lsi com>

---

--- multipath-tools/libmultipath/checkers/rdac.c.orig	2009-10-20 23:01:50.000000000 +0530
+++ multipath-tools/libmultipath/checkers/rdac.c	2009-10-20 23:49:31.000000000 +0530
@@ -91,7 +91,8 @@ do_inq(int sg_fd, unsigned int pg_op, vo
 
 struct volume_access_inq
 {
-	char dontcare0[8];
+	char PQ_PDT;
+	char dontcare0[7];
 	char avtcvp;
 	char dontcare1[39];
 };
@@ -105,6 +106,11 @@ libcheck_check (struct checker * c)
 	if (0 != do_inq(c->fd, 0xC9, &inq, sizeof(struct volume_access_inq))) {
 		MSG(c, MSG_RDAC_DOWN);
 		return PATH_DOWN;
+	} else {
+		if ((inq.PQ_PDT & 0x20) || (inq.PQ_PDT & 0x7f)) {
+			/* LUN not connected*/
+			return PATH_DOWN;
+		}
 	}
 
 	if (inq.avtcvp & 0x1) {

--


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