[PATCH RFC 0/2] dm-mp netlink events

[PATCH RFC 0/2] dm-mp netlink events

[Mike Anderson]

This patch series creates a dm-mp hardware handler that sends netlink
messages when a hardware handlers error function is called. The skb
mempool in this patch is derived / copied from
drivers/scsi/scsi_transport_iscsi.c.

Currently I have created this support in a hardware handler to reduce the
impact on other code, but this code could easily be moved to
dm-mpath.c::do_end_io or higher if desired. The events will also contain
better information once the scsi error mapping patches are done.

This patch series contains:
	1 A hardware handler that sends events over netlink (dm-evt)
	2 A sample user space program to receive / display events.
	  (dm_evtd)

-andmike
--
Michael Anderson
andmike@us.ibm.com

[PATCH RFC 1/2] dm-mp dm_evt hardware handler

[Mike Anderson]

This patch adds a dm-mp hardware handler the sends events over netlink
when its error function is called.

Signed-off-by: Mike Anderson <andmike@us.ibm.com>

---
 drivers/md/Kconfig      |    5 
 drivers/md/Makefile     |    1 
 drivers/md/dm-evt.c     |  330 ++++++++++++++++++++++++++++++++++++++++++++++++
 drivers/md/dm-mpath.c   |   18 --
 drivers/md/dm-mpath.h   |   19 ++
 include/linux/dm-evt.h  |   46 ++++++
 include/linux/netlink.h |    1 
 7 files changed, 402 insertions(+), 18 deletions(-)

Index: sas-2.6-patched/drivers/md/dm-evt.c
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ sas-2.6-patched/drivers/md/dm-evt.c	2005-11-08 23:14:36.000000000 -0800
@@ -0,0 +1,330 @@
+/*
+ * Device Mapper Event Handler (dm-evt)
+ *
+ * Copyright (C) 2005 IBM Corporation
+ * Copyright (C) 2005 Mike Anderson <andmike@us.ibm.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *
+ * skb mempool derived from drivers/scsi/scsi_transport_iscsi.c
+ *
+ */
+#include <linux/module.h>
+#include <linux/mempool.h>
+#include <net/tcp.h>
+#include <linux/dm-evt.h>
+#include <linux/time.h>
+#include "dm.h"
+#include "dm-hw-handler.h"
+
+#define MIN_NR_EVT_SKBS	16
+#define HIWAT_EVT_SKBS 32
+
+struct mempool_zone {
+	mempool_t *pool;
+	int allocated;
+	int size;
+	int hiwat;
+	struct list_head freequeue;
+	spinlock_t freelock;
+};
+
+static struct mempool_zone z_dm_evt;
+
+static struct sock *dm_evt_sock;
+static int dm_evt_daemon_pid;
+
+static inline struct list_head *skb_to_lh(struct sk_buff *skb)
+{
+	return (struct list_head *)&skb->cb;
+}
+
+static void* mempool_zone_alloc_skb(unsigned int gfp_mask,
+				    void *pool_data)
+{
+	struct mempool_zone *zone = pool_data;
+
+	return alloc_skb(zone->size, gfp_mask);
+}
+
+static void mempool_zone_free_skb(void *element, void *pool_data)
+{
+	kfree_skb(element);
+}
+
+static void
+mempool_zone_complete(struct mempool_zone *zone, int release_all)
+{
+	unsigned long flags;
+	struct list_head *lh, *n;
+
+	spin_lock_irqsave(&zone->freelock, flags);
+	if (zone->allocated) {
+		list_for_each_safe(lh, n, &zone->freequeue) {
+			struct sk_buff *skb =
+				(struct sk_buff *)((char *)lh -
+				 offsetof(struct sk_buff, cb));
+			if (skb_shared(skb)) {
+				if (release_all)
+					kfree_skb(skb);
+				else
+					continue;
+			}
+
+			list_del(skb_to_lh(skb));
+			mempool_free(skb, zone->pool);
+			--zone->allocated;
+
+		}
+	}
+	spin_unlock_irqrestore(&zone->freelock, flags);
+}
+
+static int mempool_zone_init(struct mempool_zone *zp, unsigned size,
+			     int min_nr, unsigned hiwat)
+{
+	zp->pool = mempool_create(min_nr, mempool_zone_alloc_skb,
+				  mempool_zone_free_skb, zp);
+	if (!zp->pool)
+		return -ENOMEM;
+
+	zp->size = size;
+	zp->hiwat = hiwat;
+	zp->allocated = 0;
+	INIT_LIST_HEAD(&zp->freequeue);
+	spin_lock_init(&zp->freelock);
+
+	return 0;
+}
+
+static struct sk_buff* mempool_zone_get_skb(struct mempool_zone *zone)
+{
+	struct sk_buff *skb;
+	unsigned long flags;
+
+	/* Check for ones we can complete before we alloc */
+	mempool_zone_complete(zone, 0);
+
+	skb = mempool_alloc(zone->pool, GFP_ATOMIC);
+	if (skb) {
+		skb_get(skb);
+		spin_lock_irqsave(&z_dm_evt.freelock, flags);
+		list_add(skb_to_lh(skb), &z_dm_evt.freequeue);
+		++zone->allocated;
+		spin_unlock_irqrestore(&z_dm_evt.freelock, flags);
+	}
+	return skb;
+}
+
+static int dm_evt_create(struct hw_handler *hwh, unsigned argc, char **argv)
+{
+	return 0;
+}
+
+static void dm_evt_destroy(struct hw_handler *hwh)
+{
+	return;
+}
+
+#ifndef BLKERR_IO
+#define BLKERR_IO 0x5A5A5A5A
+#endif
+
+static int dm_evt_send_nl_evt(struct path *path, struct bio *bio)
+{
+	struct sk_buff	*skb;
+	struct nlmsghdr	*nlh;
+	struct dm_evt_msg *dm_evt;
+	struct timeval tv;
+	int err = -ENOMEM;
+	unsigned int blk_err = BLKERR_IO;
+
+	if (!dm_evt_sock || !dm_evt_daemon_pid)
+		return 0;
+
+	skb = mempool_zone_get_skb(&z_dm_evt);
+	if (!skb)
+		goto out;
+
+	nlh = NLMSG_PUT(skb, dm_evt_daemon_pid, 0, DM_EVENT_PATH_ERR,
+			sizeof(*dm_evt));
+	dm_evt = NLMSG_DATA(nlh);
+	strncpy(dm_evt->dm_name, path->dev->name, sizeof(dm_evt->dm_name));
+	do_gettimeofday(&tv);
+	dm_evt->tv_sec = tv.tv_sec;
+	dm_evt->tv_usec = tv.tv_usec;
+	dm_evt->u.patherr.blk_err = blk_err;
+
+	nlh = (struct nlmsghdr *) skb->data;
+
+	err = netlink_unicast(dm_evt_sock, skb, dm_evt_daemon_pid,
+			      MSG_DONTWAIT);
+	if (err < 0)
+		goto unicast_failure;
+	return err;
+
+unicast_failure:
+nlmsg_failure:
+	kfree_skb(skb);
+	mempool_zone_complete(&z_dm_evt, 0);
+out:
+	DMERR("%s: failed %d", __FUNCTION__, err);
+	return err;
+
+}
+
+
+static unsigned dm_evt_error(struct hw_handler *hwh, struct bio *bio)
+{
+	int err;
+	union map_info *info;
+	struct mpath_io *mpio;
+	struct path *path;
+
+	info = dm_get_mapinfo(bio);
+	mpio = info->ptr;
+	path = &mpio->pgpath->path;
+
+	if (path->is_active) {
+		err = dm_evt_send_nl_evt(path, bio);
+	}
+
+	return MP_FAIL_PATH;
+}
+
+#define RCV_SKB_FAIL(err) do { netlink_ack(skb, nlh, (err)); return; } while (0)
+
+static void dm_evt_rcv_msg(struct sk_buff *skb)
+{
+	int pid, flags;
+	struct nlmsghdr *nlh = (struct nlmsghdr *) skb->data;
+
+	if (skb->len >= NLMSG_SPACE(0)) {
+
+		if (nlh->nlmsg_len < sizeof(*nlh) ||
+			skb->len < nlh->nlmsg_len) {
+			return;
+		}
+		pid = nlh->nlmsg_pid;
+		flags = nlh->nlmsg_flags;
+
+		if (security_netlink_recv(skb))
+			RCV_SKB_FAIL(-EPERM);
+
+		if (dm_evt_daemon_pid) {
+			if (dm_evt_daemon_pid != pid) {
+				RCV_SKB_FAIL(-EBUSY);
+			}
+		} else {
+			dm_evt_daemon_pid = pid;
+		}
+
+		if (flags & NLM_F_ACK)
+			netlink_ack(skb, nlh, 0);
+	}
+}
+
+static void dm_evt_rcv(struct sock *sk, int len)
+{
+	struct sk_buff *skb;
+	unsigned int qlen;
+
+	for (qlen = skb_queue_len(&sk->sk_receive_queue); qlen; qlen--) {
+		skb = skb_dequeue(&sk->sk_receive_queue);
+		dm_evt_rcv_msg(skb);
+		kfree_skb(skb);
+	}
+}
+
+static int dm_evt_rcv_nl_event(struct notifier_block *this, unsigned long event, void *ptr)
+{
+	struct netlink_notify *n = ptr;
+
+	if (event == NETLINK_URELEASE &&
+	    n->protocol == NETLINK_DM_EVENT && n->pid) {
+		if ( n->pid == dm_evt_daemon_pid  ) {
+			dm_evt_daemon_pid = 0;
+		}
+		mempool_zone_complete(&z_dm_evt, 1);
+	}
+
+	return NOTIFY_DONE;
+}
+
+static struct hw_handler_type dm_evt_hwh = {
+	.name = "dm-evt",
+	.module = THIS_MODULE,
+	.create = dm_evt_create,
+	.destroy = dm_evt_destroy,
+	.error = dm_evt_error,
+};
+
+static struct notifier_block dm_evt_nl_notifier = {
+	.notifier_call  = dm_evt_rcv_nl_event,
+};
+
+static int __init dm_evt_init(void)
+{
+	int err;
+
+	err = netlink_register_notifier(&dm_evt_nl_notifier);
+	if (err)
+		return err;
+
+	dm_evt_sock = netlink_kernel_create(NETLINK_DM_EVENT, 0,
+					    dm_evt_rcv, THIS_MODULE);
+	if (!dm_evt_sock) {
+		err = -ENOBUFS;
+		goto unregister_notifier;
+	}
+
+	err = mempool_zone_init(&z_dm_evt, NLMSG_SPACE(sizeof(struct
+							      dm_evt_msg)),
+				MIN_NR_EVT_SKBS, HIWAT_EVT_SKBS);
+	if (err)
+		goto release_socket;
+
+	err = dm_register_hw_handler(&dm_evt_hwh);
+	if (err)
+		goto release_zone;
+
+	DMINFO("dm-evt version 0.0.2 loaded");
+
+	return err;
+
+release_zone:
+	mempool_destroy(z_dm_evt.pool);
+release_socket:
+	sock_release(dm_evt_sock->sk_socket);
+unregister_notifier:
+	netlink_unregister_notifier(&dm_evt_nl_notifier);
+	DMERR("%s: failed %d", __FUNCTION__, err);
+	return err;
+}
+
+static void __exit dm_evt_exit(void)
+{
+	dm_unregister_hw_handler(&dm_evt_hwh);
+	mempool_destroy(z_dm_evt.pool);
+	sock_release(dm_evt_sock->sk_socket);
+	netlink_unregister_notifier(&dm_evt_nl_notifier);
+}
+
+module_init(dm_evt_init);
+module_exit(dm_evt_exit);
+
+MODULE_DESCRIPTION(DM_NAME "dm-evt multipath hwh");
+MODULE_AUTHOR("Mike Anderson <andmike@us.ibm.com>");
+MODULE_LICENSE("GPL");
Index: sas-2.6-patched/drivers/md/Makefile
===================================================================
--- sas-2.6-patched.orig/drivers/md/Makefile	2005-11-02 13:59:04.000000000 -0800
+++ sas-2.6-patched/drivers/md/Makefile	2005-11-02 13:59:31.000000000 -0800
@@ -34,6 +34,7 @@ obj-$(CONFIG_BLK_DEV_DM)	+= dm-mod.o
 obj-$(CONFIG_DM_CRYPT)		+= dm-crypt.o
 obj-$(CONFIG_DM_MULTIPATH)	+= dm-multipath.o dm-round-robin.o
 obj-$(CONFIG_DM_MULTIPATH_EMC)	+= dm-emc.o
+obj-$(CONFIG_DM_MULTIPATH_EVT)	+= dm-evt.o
 obj-$(CONFIG_DM_SNAPSHOT)	+= dm-snapshot.o
 obj-$(CONFIG_DM_MIRROR)		+= dm-mirror.o
 obj-$(CONFIG_DM_ZERO)		+= dm-zero.o
Index: sas-2.6-patched/include/linux/netlink.h
===================================================================
--- sas-2.6-patched.orig/include/linux/netlink.h	2005-11-02 13:59:04.000000000 -0800
+++ sas-2.6-patched/include/linux/netlink.h	2005-11-02 13:59:31.000000000 -0800
@@ -21,6 +21,7 @@
 #define NETLINK_DNRTMSG		14	/* DECnet routing messages */
 #define NETLINK_KOBJECT_UEVENT	15	/* Kernel messages to userspace */
 #define NETLINK_GENERIC		16
+#define NETLINK_DM_EVENT	17	/* DM Event */
 
 #define MAX_LINKS 32		
 
Index: sas-2.6-patched/include/linux/dm-evt.h
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ sas-2.6-patched/include/linux/dm-evt.h	2005-11-07 11:28:35.000000000 -0800
@@ -0,0 +1,46 @@
+/*
+ * Device Mapper Event Handler
+ *
+ * Copyright (C) 2005 IBM Corporation
+ * Copyright (C) 2005 Mike Anderson <andmike@us.ibm.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *
+ */
+#ifndef DM_EVENT_H
+#define DM_EVENT_H
+#include <linux/types.h>
+
+#define EVT_DM_NAME_LEN 16
+
+#define DM_EVENT_BASE	10
+enum dm_evt_e {
+	DM_EVENT_UNKOWN		= 0,
+	DM_EVENT_PATH_ERR	= DM_EVENT_BASE + 1,
+};
+
+struct dm_evt_msg {
+	uint8_t dm_name[EVT_DM_NAME_LEN];
+	uint64_t tv_sec;
+	uint64_t tv_usec;
+
+	union {
+		struct msg_path_err {
+			uint32_t blk_err; /* BLKERR Values */
+		} patherr;
+	} u;
+} __attribute__((aligned(sizeof(uint64_t))));
+
+#endif
Index: sas-2.6-patched/drivers/md/Kconfig
===================================================================
--- sas-2.6-patched.orig/drivers/md/Kconfig	2005-11-02 13:59:04.000000000 -0800
+++ sas-2.6-patched/drivers/md/Kconfig	2005-11-02 13:59:31.000000000 -0800
@@ -235,6 +235,11 @@ config DM_MULTIPATH_EMC
 	depends on DM_MULTIPATH && BLK_DEV_DM && EXPERIMENTAL
 	---help---
 	  Multipath support for EMC CX/AX series hardware.
+config DM_MULTIPATH_EVT
+	tristate "Generate netlink events for multipath failures"
+	depends on DM_MULTIPATH && BLK_DEV_DM && EXPERIMENTAL
+	---help---
+	  Multipath support for EMC CX/AX series hardware.
 
 endmenu
 
Index: sas-2.6-patched/drivers/md/dm-mpath.c
===================================================================
--- sas-2.6-patched.orig/drivers/md/dm-mpath.c	2005-11-02 13:59:04.000000000 -0800
+++ sas-2.6-patched/drivers/md/dm-mpath.c	2005-11-02 13:59:31.000000000 -0800
@@ -23,16 +23,6 @@
 
 #define MESG_STR(x) x, sizeof(x)
 
-/* Path properties */
-struct pgpath {
-	struct list_head list;
-
-	struct priority_group *pg;	/* Owning PG */
-	unsigned fail_count;		/* Cumulative failure count */
-
-	struct path path;
-};
-
 #define path_to_pgpath(__pgp) container_of((__pgp), struct pgpath, path)
 
 /*
@@ -88,14 +78,6 @@ struct multipath {
 	mempool_t *mpio_pool;
 };
 
-/*
- * Context information attached to each bio we process.
- */
-struct mpath_io {
-	struct pgpath *pgpath;
-	struct dm_bio_details details;
-};
-
 typedef int (*action_fn) (struct pgpath *pgpath);
 
 #define MIN_IOS 256	/* Mempool size */
Index: sas-2.6-patched/drivers/md/dm-mpath.h
===================================================================
--- sas-2.6-patched.orig/drivers/md/dm-mpath.h	2005-11-02 13:59:04.000000000 -0800
+++ sas-2.6-patched/drivers/md/dm-mpath.h	2005-11-02 13:59:31.000000000 -0800
@@ -8,6 +8,7 @@
 
 #ifndef	DM_MPATH_H
 #define	DM_MPATH_H
+#include "dm-bio-record.h"
 
 struct dm_dev;
 
@@ -19,6 +20,24 @@ struct path {
 	void *hwhcontext;	/* For hw-handler use */
 };
 
+/* Path properties */
+struct pgpath {
+	struct list_head list;
+
+	struct priority_group *pg;	/* Owning PG */
+	unsigned fail_count;		/* Cumulative failure count */
+
+	struct path path;
+};
+
+/*
+ * Context information attached to each bio we process.
+ */
+struct mpath_io {
+	struct pgpath *pgpath;
+	struct dm_bio_details details;
+};
+
 /* Callback for hwh_pg_init_fn to use when complete */
 void dm_pg_init_complete(struct path *path, unsigned err_flags);
 

[PATCH RFC 2/2] user space program for dm-evt netlink messages

[Mike Anderson]

 This patch adds a user space program the listens for netlink messages
 sent by the dm-mp dm_evt hardware handler.

 Signed-off-by: Mike Anderson <andmike@us.ibm.com>

 ---

 Makefile  |   30 ++++++++++
 dm_evtd.c |  177 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 dm_evtd.h |   46 ++++++++++++++++
 3 files changed, 253 insertions(+)

--- /dev/null	2005-11-08 02:47:22.640591000 -0800
+++ dm_evtd/dm_evtd.c	2005-11-07 13:04:02.000000000 -0800
@@ -0,0 +1,177 @@
+/*
+ * Device Mapper Event User Space Daemon (dm-evtd)
+ *
+ * Copyright (C) 2005 IBM Corporation
+ * Copyright (C) 2005 Mike Anderson <andmike@us.ibm.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *
+ */
+/*
+ * This program is a proto example of using the dm-evt hardward handler
+ */
+
+#include <unistd.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <sys/socket.h>
+#include <sys/user.h>
+#include <asm/types.h>
+#include <linux/netlink.h>
+#include <time.h>
+#include "dm_evtd.h"
+
+static int socket_open(int *sock)
+{
+	struct sockaddr_nl snl;
+	int err = -1;
+
+	memset(&snl, 0x00, sizeof(snl));
+	snl.nl_family = AF_NETLINK;
+	snl.nl_pid = getpid();
+	snl.nl_groups = 0; /* not in mcast groups */
+
+	*sock = socket(PF_NETLINK, SOCK_DGRAM, NETLINK_DM_EVENT);
+	if (*sock == -1) {
+		fprintf(stderr, "%s: socket failed (%s)\n", __FUNCTION__,
+			strerror(errno));
+		goto sock_failed;
+	}
+
+	err = bind(*sock, (struct sockaddr *) &snl,
+		      sizeof(snl));
+	if (err < 0) {
+		fprintf(stderr, "%s: bind failed (%s)\n", __FUNCTION__,
+		       strerror(errno));
+		goto bind_failed;
+	}
+
+	return err;
+bind_failed:
+	close(*sock);
+sock_failed:
+	return err;
+}
+
+static int evt_connect(int socket, unsigned short type)
+{
+	struct nlmsghdr *nlh;
+	struct sockaddr_nl addr;
+	struct msghdr msg;
+	struct iovec iov;
+	int err = -1;
+
+	nlh = calloc(1, sizeof(*nlh));
+	if (!nlh) {
+		fprintf(stderr, "%s: calloc failed (%s)\n", __FUNCTION__,
+			strerror(errno));
+		goto calloc_failed;
+	}
+
+	nlh->nlmsg_len = NLMSG_SPACE(0);
+	nlh->nlmsg_pid = getpid();
+	nlh->nlmsg_flags = 0;
+	nlh->nlmsg_type = type;
+
+	memset(&addr, 0, sizeof(addr));
+	addr.nl_family = AF_NETLINK;
+	addr.nl_pid = 0;
+	addr.nl_groups = 0;
+
+	iov.iov_base = (void*)nlh;
+	iov.iov_len = nlh->nlmsg_len;
+
+	memset(&msg, 0, sizeof(msg));
+	msg.msg_name= (void*)&addr;
+	msg.msg_namelen = sizeof(addr);
+	msg.msg_iov = &iov;
+	msg.msg_iovlen = 1;
+
+	err = sendmsg(socket, &msg, 0);
+
+	if (err <= 0)
+		fprintf(stderr, "%s: sendmsg failed (%s)\n", __FUNCTION__,
+			strerror(errno));
+
+calloc_failed:
+	return err;
+}
+
+static int evt_read(int socket, char *data, int count, int flags)
+{
+	int err;
+	struct iovec iov;
+	static struct sockaddr_nl addr;
+	struct msghdr msg;
+
+	iov.iov_base = data;
+	iov.iov_len = count;
+	memset(iov.iov_base, 0, iov.iov_len);
+
+	memset(&addr, 0, sizeof(addr));
+	addr.nl_family = AF_NETLINK;
+	addr.nl_pid = 0;
+	addr.nl_groups = 0;
+
+	memset(&msg, 0, sizeof(msg));
+	msg.msg_name= (void*)&addr;
+	msg.msg_namelen = sizeof(addr);
+	msg.msg_iov = &iov;
+	msg.msg_iovlen = 1;
+
+	err = recvmsg(socket, &msg, flags);
+	if (err <= 0) {
+		fprintf(stderr, "%s: recvmsg failed (%s)\n", __FUNCTION__,
+			strerror(errno));
+	}
+
+	return err;
+}
+
+int main (int argc, char *argv[])
+{
+	int err, socket = -1;
+	void *msg;
+	struct dm_evt_msg *evt_msg;
+	struct nlmsghdr *nlh;
+
+	err = socket_open(&socket);
+	if (err)
+		exit(1);
+	err = evt_connect(socket, NLMSG_NOOP);
+
+	msg = calloc(1, NLMSG_SPACE(sizeof(struct dm_evt_msg)));
+	do {
+		err = evt_read(socket, msg, 
+			       NLMSG_SPACE(sizeof(struct dm_evt_msg)),
+			       0);
+		if (err <= 0)
+			break;
+		nlh = (struct nlmsghdr *)msg;
+		evt_msg = NLMSG_DATA(nlh);
+
+		fprintf(stdout,"[DM_EVT]: dm_name: %s, blk_err: 0x%x,"
+			" Time: %s", evt_msg->dm_name,
+			evt_msg->u.patherr.blk_err, 
+			ctime((time_t *)&evt_msg->tv_sec));
+
+		bzero(msg, NLMSG_SPACE(sizeof(struct dm_evt_msg)));
+	} while (1);
+
+	exit(err == 0 ? 0 : 1);
+}
--- /dev/null	2005-11-08 02:47:22.640591000 -0800
+++ dm_evtd/dm_evtd.h	2005-11-07 11:42:41.000000000 -0800
@@ -0,0 +1,46 @@
+/*
+ * Device Mapper Event Handler
+ *
+ * Copyright (C) 2005 IBM Corporation
+ * Copyright (C) 2005 Mike Anderson <andmike@us.ibm.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *
+ */
+#ifndef DM_EVENT_H
+#define DM_EVENT_H
+#include <stdint.h>
+
+#define EVT_DM_NAME_LEN 16
+
+#define DM_EVENT_BASE	10
+enum dm_evt_e {
+	DM_EVENT_UNKOWN		= 0,
+	DM_EVENT_PATH_ERR	= DM_EVENT_BASE + 1,
+};
+
+struct dm_evt_msg {
+	uint8_t dm_name[EVT_DM_NAME_LEN];
+	uint64_t tv_sec;
+	uint64_t tv_usec;
+
+	union {
+		struct msg_path_err {
+			uint32_t blk_err; /* BLKERR Values */
+		} patherr;
+	} u;
+} __attribute__((aligned(sizeof(uint64_t))));
+
+#endif
--- /dev/null	2005-11-08 02:47:22.640591000 -0800
+++ dm_evtd/Makefile	2005-11-08 22:13:36.000000000 -0800
@@ -0,0 +1,30 @@
+# Make variables (CC, etc...)
+AS              = $(CROSS_COMPILE)as
+LD              = $(CROSS_COMPILE)ld
+CC              = $(CROSS_COMPILE)gcc
+CPP             = $(CC) -E
+AR              = $(CROSS_COMPILE)ar
+NM              = $(CROSS_COMPILE)nm
+STRIP           = $(CROSS_COMPILE)strip
+OBJCOPY         = $(CROSS_COMPILE)objcopy
+OBJDUMP         = $(CROSS_COMPILE)objdump
+
+CFLAGS		+= -fno-builtin -Wall -Wchar-subscripts -Wundef \
+		   -Wstrict-prototypes -Wpointer-arith -Wsign-compare
+CFLAGS		+= -DNETLINK_DM_EVENT=17
+
+ifeq ($(strip $(DEBUG)),true)
+CFLAGS		+= -O1 -g
+else
+CFLAGS		+= -Os
+endif
+
+PROGRAM	= dm_evtd
+
+all: $(PROGRAM)
+
+dm_evtd: dm_evtd.o
+	$(CC) $^ -o $@
+
+clean:
+	rm -f *.o $(PROGRAM)

Re: [PATCH RFC 0/2] dm-mp netlink events

[Christophe Varoqui]

On Tue, Nov 08, 2005 at 11:54:23PM -0800, Mike Anderson wrote:
> This patch series creates a dm-mp hardware handler that sends netlink
> messages when a hardware handlers error function is called. The skb
> mempool in this patch is derived / copied from
> drivers/scsi/scsi_transport_iscsi.c.
> 
> Currently I have created this support in a hardware handler to reduce the
> impact on other code, but this code could easily be moved to
> dm-mpath.c::do_end_io or higher if desired. The events will also contain
> better information once the scsi error mapping patches are done.
> 
> This patch series contains:
> 	1 A hardware handler that sends events over netlink (dm-evt)
> 	2 A sample user space program to receive / display events.
> 	  (dm_evtd)
> 
Would uevents work instead of yet another Netlink wire ?
The multipath daemon already listens for uevents ...

Regards,
cvaroqui

Re: [PATCH RFC 0/2] dm-mp netlink events

[Mike Anderson]

Christophe Varoqui <christophe.varoqui@free.fr> wrote:
> Would uevents work instead of yet another Netlink wire ?
> The multipath daemon already listens for uevents ...

I general similar information could have been sent using the uevents
netlink. Though changes would be needed in kobject_uevent to allow more
event data to be passed in the events environmental data. Also while we
could generate events against /sys/block/dm-* it might be more interesting
if we had more detailed kobjects in the sysfs tree to generate events
against, but that is a larger change.

The reason I decide to use a different netlink number was that I was trying
to use a event method that would have a higher chance of working under low
memory conditions (i.e. the skb mempool). I also used unicast instead of
broadcast. When using netlink_broadcast I could not control the memory
allocation in the skb_clone. While skb_clone just clones the header so it
would me a smaller allocation and you can pass in the flags for the
allocation I was still concerned that this might not work in low memory
cases.

-andmike
--
Michael Anderson
andmike@us.ibm.com