[PATCH RFC 0/4] dm-netlink events

[PATCH RFC 0/4] dm-netlink events

[Mike Anderson]

This is an update of my previous patch to add netlink event support to dm
multipath. I have moved the dm netlink support out of a hardware handler
and into a dm-netlink support file. I have changed the event messages to
use netlink attributes which should allow for more flexibility in event
message content over time.

This patch series adds a file called dm-netlink to the drivers/md
directory to provide netlink support for dm events.

The skb mempool in this patch is derived / copied from
drivers/scsi/scsi_transport_iscsi.c.

This patch series contains:
1 Core dm netlink support (dm-netlink).
2 Calls to dm-netlink for path failure / reinstate events.
3 A sample user space program to receive / display events (dm_nld).

I have ran path failure testing on a small config.
I ran the sample program as a 32 bit and 64 bit app against a 64 bit
kernel.

Currently on path failures the blkerr is hard coded until that error
support is complete.

Example out:
1.) Path failure.
Msg Type: 17 Recevied
Event Type: 1 Version: 6
[Event]: SEQNUM: 7, Time: Tue Nov 29 21:50:47 2005, DMNAME: 8:160, BLKERR:
0x5a5a5a5a

2.) Path reinstate
Msg Type: 17 Recevied
Event Type: 2 Version: 6
[Event]: SEQNUM: 12, Time: Tue Nov 29 21:51:57 2005, DMNAME: 8:48


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

[PATCH RFC 1/4] dm-netlink skeleton support

[Mike Anderson]

This patch adds a dm-netlink skeleton support to the Makefile, Kconfig,
and the dm directory. This base dm-netlink file only contains the mempool
support.

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

 drivers/md/Kconfig      |    6 ++
 drivers/md/Makefile     |    3 +
 drivers/md/dm-netlink.c |  144 ++++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/netlink.h |    1 
 4 files changed, 154 insertions(+)

Index: linux-2.6.15-rc1-patched/drivers/md/dm-netlink.c
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ linux-2.6.15-rc1-patched/drivers/md/dm-netlink.c	2005-11-29 23:50:01.000000000 -0800
@@ -0,0 +1,144 @@
+/*
+ * Device Mapper Netlink Support (dm-netlink)
+ *
+ * Copyright (C) 2005 IBM Corporation
+ * 	Author: Mike Anderson <andmike@us.ibm.com>
+ * 	skb mempool derived from drivers/scsi/scsi_transport_iscsi.c
+ *
+ * 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.
+ *
+ */
+#include <linux/module.h>
+#include <linux/mempool.h>
+#include <linux/time.h>
+#include <linux/jiffies.h>
+#include <linux/security.h>
+#include <net/sock.h>
+#include <net/netlink.h>
+
+#define MIN_EVT_SKBS	16
+#define HIWAT_EVT_SKBS	32
+#define EVT_SKB_SIZE	NLMSG_SPACE(128)
+
+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 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->size = size;
+	zp->hiwat = hiwat;
+	zp->allocated = 0;
+	INIT_LIST_HEAD(&zp->freequeue);
+	spin_lock_init(&zp->freelock);
+
+	zp->pool = mempool_create(min_nr, mempool_zone_alloc_skb,
+				  mempool_zone_free_skb, zp);
+	if (!zp->pool)
+		return -ENOMEM;
+
+	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;
+}
+
+int __init dm_nl_init(void)
+{
+	int err;
+
+	err = mempool_zone_init(&z_dm_evt, EVT_SKB_SIZE,
+				MIN_EVT_SKBS, HIWAT_EVT_SKBS);
+	if (!err)
+		printk(KERN_DEBUG "dm-netlink version 0.0.1 loaded\n");
+
+	return err;
+
+}
+
+void dm_nl_exit(void)
+{
+	mempool_destroy(z_dm_evt.pool);
+}
Index: linux-2.6.15-rc1-patched/include/linux/netlink.h
===================================================================
--- linux-2.6.15-rc1-patched.orig/include/linux/netlink.h	2005-11-11 18:51:47.000000000 -0800
+++ linux-2.6.15-rc1-patched/include/linux/netlink.h	2005-11-29 22:48:29.000000000 -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			17	/* Device Mapper */
 
 #define MAX_LINKS 32		
 
Index: linux-2.6.15-rc1-patched/drivers/md/Makefile
===================================================================
--- linux-2.6.15-rc1-patched.orig/drivers/md/Makefile	2005-08-28 17:51:43.000000000 -0700
+++ linux-2.6.15-rc1-patched/drivers/md/Makefile	2005-11-29 22:48:29.000000000 -0800
@@ -37,6 +37,9 @@ obj-$(CONFIG_DM_MULTIPATH_EMC)	+= dm-emc
 obj-$(CONFIG_DM_SNAPSHOT)	+= dm-snapshot.o
 obj-$(CONFIG_DM_MIRROR)		+= dm-mirror.o
 obj-$(CONFIG_DM_ZERO)		+= dm-zero.o
+ifeq ($(CONFIG_DM_NL_SUPPORT),y)
+  dm-mod-objs += dm-netlink.o
+endif
 
 quiet_cmd_unroll = UNROLL  $@
       cmd_unroll = $(PERL) $(srctree)/$(src)/unroll.pl $(UNROLL) \
Index: linux-2.6.15-rc1-patched/drivers/md/Kconfig
===================================================================
--- linux-2.6.15-rc1-patched.orig/drivers/md/Kconfig	2005-06-17 17:21:30.000000000 -0700
+++ linux-2.6.15-rc1-patched/drivers/md/Kconfig	2005-11-29 22:48:29.000000000 -0800
@@ -236,5 +236,11 @@ config DM_MULTIPATH_EMC
 	---help---
 	  Multipath support for EMC CX/AX series hardware.
 
+config DM_NL_SUPPORT
+	bool "DM Netlink Support (EXPERIMENTAL)"
+	depends on  BLK_DEV_DM && EXPERIMENTAL
+	---help---
+	  Netlink events for dm devices.
+
 endmenu
 

Re: [PATCH RFC 2/4] dm-netlink netlink support

[Mike Anderson]

This patch adds netlink support to dm-netlink. It also adds support for
using netlink attributes for the event messages.

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

 drivers/md/dm-netlink.c    |  188 ++++++++++++++++++++++++++++++++++++++++++++-
 drivers/md/dm-netlink.h    |   40 +++++++++
 include/linux/dm-netlink.h |   46 +++++++++++
 3 files changed, 272 insertions(+), 2 deletions(-)

Index: linux-2.6.15-rc1-patched/drivers/md/dm-netlink.c
===================================================================
--- linux-2.6.15-rc1-patched.orig/drivers/md/dm-netlink.c	2005-11-29 23:13:59.000000000 -0800
+++ linux-2.6.15-rc1-patched/drivers/md/dm-netlink.c	2005-11-29 23:28:06.000000000 -0800
@@ -27,6 +27,7 @@
 #include <linux/security.h>
 #include <net/sock.h>
 #include <net/netlink.h>
+#include <linux/dm-netlink.h>
 
 #define MIN_EVT_SKBS	16
 #define HIWAT_EVT_SKBS	32
@@ -125,20 +126,203 @@ static struct sk_buff* mempool_zone_get_
 	return skb;
 }
 
+static struct sock *dm_nl_sock;
+static int dm_nl_daemon_pid;
+
+static u64 dm_evt_seqnum;
+static DEFINE_SPINLOCK(sequence_lock);
+
+static struct sk_buff *dm_nl_build_path_msg(char* dm_name, int type,
+					     int blk_err)
+{
+	struct sk_buff	*skb;
+	struct nlmsghdr	*nlh;
+	struct dm_nl_msghdr *dm_nlh;
+	u64 seq;
+	struct timeval tv;
+	int err = -ENOBUFS;
+
+	skb = mempool_zone_get_skb(&z_dm_evt);
+	if (!skb) {
+		printk(KERN_ERR "%s: mempool_zone_get_skb %d\n",
+		       __FUNCTION__, err);
+		err = -ENOMEM;
+		goto out;
+	}
+
+	nlh = nlmsg_put(skb, dm_nl_daemon_pid, 0, DM_EVT,
+			NLMSG_ALIGN(sizeof(*dm_nlh)), 0);
+	if (!nlh)
+		goto nla_put_failure;
+
+	dm_nlh = nlmsg_data(nlh);
+	dm_nlh->type = type;
+	dm_nlh->version = DM_E_ATTR_MAX;
+
+	spin_lock(&sequence_lock);
+	seq = ++dm_evt_seqnum;
+	spin_unlock(&sequence_lock);
+	do_gettimeofday(&tv);
+
+	NLA_PUT_U64(skb, DM_E_ATTR_SEQNUM, seq);
+	NLA_PUT_U64(skb, DM_E_ATTR_TSSEC, tv.tv_sec);
+	NLA_PUT_U64(skb, DM_E_ATTR_TSUSEC, tv.tv_usec);
+	NLA_PUT_STRING(skb, DM_E_ATTR_DMNAME, dm_name);
+
+	if (blk_err)
+		NLA_PUT_U32(skb, DM_E_ATTR_BLKERR, blk_err);
+
+	nlmsg_end(skb, nlh);
+
+	return skb;
+
+nla_put_failure:
+	printk(KERN_ERR "%s: nla_put_failure\n",
+	       __FUNCTION__);
+	/* reduce skb users so zone_complete can free */
+	kfree_skb(skb);
+	mempool_zone_complete(&z_dm_evt, 0);
+out:
+	return ERR_PTR(err);
+
+}
+
+static inline void dm_nl_unicast(struct sk_buff *skb)
+{
+	int err;
+
+	if (!dm_nl_sock || !dm_nl_daemon_pid)
+		return;
+
+	err = nlmsg_unicast(dm_nl_sock, skb, dm_nl_daemon_pid);
+	if (err < 0)
+		printk(KERN_ERR "%s: nlmsg_unicast %d\n", __FUNCTION__,
+		       err);
+}
+
+void dm_nl_path_fail(char* dm_name, int blk_err)
+{
+	struct sk_buff *msg;
+	msg = dm_nl_build_path_msg(dm_name, DM_EVT_FAIL_PATH, blk_err);
+
+	if (!IS_ERR(msg))
+		dm_nl_unicast(msg);
+}
+
+EXPORT_SYMBOL(dm_nl_path_fail);
+
+void dm_nl_path_reinstate(char* dm_name)
+{
+	struct sk_buff *msg;
+	msg = dm_nl_build_path_msg(dm_name, DM_EVT_REINSTATE_PATH, 0);
+
+	if (!IS_ERR(msg))
+		dm_nl_unicast(msg);
+}
+
+EXPORT_SYMBOL(dm_nl_path_reinstate);
+
+#define RCV_SKB_FAIL(err) do { netlink_ack(skb, nlh, (err)); return; } while (0)
+
+static void dm_nl_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_nl_daemon_pid) {
+			if (dm_nl_daemon_pid != pid) {
+				RCV_SKB_FAIL(-EBUSY);
+			}
+		} else {
+			dm_nl_daemon_pid = pid;
+		}
+
+		if (flags & NLM_F_ACK)
+			netlink_ack(skb, nlh, 0);
+	}
+}
+
+static void dm_nl_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_nl_rcv_msg(skb);
+		kfree_skb(skb);
+	}
+}
+
+static int dm_nl_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 && n->pid) {
+		if ( n->pid == dm_nl_daemon_pid  ) {
+			dm_nl_daemon_pid = 0;
+		}
+		mempool_zone_complete(&z_dm_evt, 1);
+	}
+
+	return NOTIFY_DONE;
+}
+
+static struct notifier_block dm_nl_nl_notifier = {
+	.notifier_call  = dm_nl_rcv_nl_event,
+};
+
+static struct sock *dm_nl_sock;
+static int dm_nl_daemon_pid;
+
 int __init dm_nl_init(void)
 {
 	int err;
 
+	err = netlink_register_notifier(&dm_nl_nl_notifier);
+	if (err)
+		return err;
+
+	dm_nl_sock = netlink_kernel_create(NETLINK_DM, 0,
+					    dm_nl_rcv, THIS_MODULE);
+	if (!dm_nl_sock) {
+		err = -ENOBUFS;
+		goto unregister_notifier;
+	}
+
 	err = mempool_zone_init(&z_dm_evt, EVT_SKB_SIZE,
 				MIN_EVT_SKBS, HIWAT_EVT_SKBS);
-	if (!err)
-		printk(KERN_DEBUG "dm-netlink version 0.0.1 loaded\n");
+	if (err)
+		goto release_socket;
+
+	printk(KERN_DEBUG "dm-netlink version 0.0.1 loaded\n");
 
 	return err;
 
+release_socket:
+	sock_release(dm_nl_sock->sk_socket);
+unregister_notifier:
+	netlink_unregister_notifier(&dm_nl_nl_notifier);
+	printk(KERN_ERR "%s: failed %d\n", __FUNCTION__, err);
+	return err;
 }
 
 void dm_nl_exit(void)
 {
 	mempool_destroy(z_dm_evt.pool);
+	sock_release(dm_nl_sock->sk_socket);
+	netlink_unregister_notifier(&dm_nl_nl_notifier);
 }
Index: linux-2.6.15-rc1-patched/include/linux/dm-netlink.h
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ linux-2.6.15-rc1-patched/include/linux/dm-netlink.h	2005-11-29 23:22:07.000000000 -0800
@@ -0,0 +1,46 @@
+/*
+ * Device Mapper Netlink Support
+ *
+ * Copyright (C) 2005 IBM Corporation
+ * 	Author: 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 LINUX_DM_NETLINK_H
+#define LINUX_DM_NETLINK_H
+
+enum dm_evt_attr {
+	DM_E_ATTR_SEQNUM	= 1,
+	DM_E_ATTR_TSSEC		= 2,
+	DM_E_ATTR_TSUSEC	= 3,
+	DM_E_ATTR_DMNAME	= 4,
+	DM_E_ATTR_BLKERR	= 5,
+	DM_E_ATTR_MAX,
+};
+
+#define DM_EVT NLMSG_MIN_TYPE + 0x1
+
+#define DM_EVT_FAIL_PATH 0x1
+#define DM_EVT_REINSTATE_PATH 0x2
+
+struct dm_nl_msghdr {
+	uint16_t type;
+	uint16_t version;
+	uint16_t reserved1;
+	uint16_t reserved2;
+} __attribute__((aligned(sizeof(uint64_t))));
+
+#endif /* LINUX_DM_NETLINK_H */
Index: linux-2.6.15-rc1-patched/drivers/md/dm-netlink.h
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ linux-2.6.15-rc1-patched/drivers/md/dm-netlink.h	2005-11-29 23:22:07.000000000 -0800
@@ -0,0 +1,40 @@
+/*
+ * Device Mapper Netlink Support
+ *
+ * Copyright (C) 2005 IBM Corporation
+ * 	Author: 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_NETLINK_H
+#define DM_NETLINK_H
+
+#ifdef CONFIG_DM_NL_SUPPORT
+void dm_nl_path_fail(char*, int);
+void dm_nl_path_reinstate(char*);
+#else
+static inline void dm_nl_path_fail(char* dm_name, int blk_err)
+{
+	return;
+}
+
+static inline void dm_nl_path_reinstate(char* dm_name)
+{
+	return;
+}
+#endif
+
+#endif /* DM_NETLINK_H */

[PATCH RFC 3/4] dm-mpath calls to dm-netlink

[Mike Anderson]

This patch adds a call to init dm_nl during dm init, and calls to dm_nl
functions for path failure / reinstate events.

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

 drivers/md/dm-mpath.c |    9 ++++++---
 drivers/md/dm.c       |    2 ++
 drivers/md/dm.h       |    3 +++
 3 files changed, 11 insertions(+), 3 deletions(-)

Index: linux-2.6.15-rc1-patched/drivers/md/dm.h
===================================================================
--- linux-2.6.15-rc1-patched.orig/drivers/md/dm.h	2005-06-17 17:21:30.000000000 -0700
+++ linux-2.6.15-rc1-patched/drivers/md/dm.h	2005-11-29 23:32:32.000000000 -0800
@@ -192,4 +192,7 @@ void dm_stripe_exit(void);
 void *dm_vcalloc(unsigned long nmemb, unsigned long elem_size);
 union map_info *dm_get_mapinfo(struct bio *bio);
 
+int dm_nl_init(void);
+void dm_nl_exit(void);
+
 #endif
Index: linux-2.6.15-rc1-patched/drivers/md/dm.c
===================================================================
--- linux-2.6.15-rc1-patched.orig/drivers/md/dm.c	2005-10-27 18:52:10.000000000 -0700
+++ linux-2.6.15-rc1-patched/drivers/md/dm.c	2005-11-29 23:32:32.000000000 -0800
@@ -163,6 +163,7 @@ int (*_inits[])(void) __initdata = {
 	dm_linear_init,
 	dm_stripe_init,
 	dm_interface_init,
+	dm_nl_init,
 };
 
 void (*_exits[])(void) = {
@@ -171,6 +172,7 @@ void (*_exits[])(void) = {
 	dm_linear_exit,
 	dm_stripe_exit,
 	dm_interface_exit,
+	dm_nl_exit,
 };
 
 static int __init dm_init(void)
Index: linux-2.6.15-rc1-patched/drivers/md/dm-mpath.c
===================================================================
--- linux-2.6.15-rc1-patched.orig/drivers/md/dm-mpath.c	2005-10-27 18:52:10.000000000 -0700
+++ linux-2.6.15-rc1-patched/drivers/md/dm-mpath.c	2005-11-29 23:32:32.000000000 -0800
@@ -10,6 +10,7 @@
 #include "dm-hw-handler.h"
 #include "dm-bio-list.h"
 #include "dm-bio-record.h"
+#include "dm-netlink.h"
 
 #include <linux/ctype.h>
 #include <linux/init.h>
@@ -798,7 +799,7 @@ static int multipath_map(struct dm_targe
 /*
  * Take a path out of use.
  */
-static int fail_path(struct pgpath *pgpath)
+static int fail_path(struct pgpath *pgpath, struct bio *bio)
 {
 	unsigned long flags;
 	struct multipath *m = pgpath->pg->m;
@@ -819,6 +820,7 @@ static int fail_path(struct pgpath *pgpa
 	if (pgpath == m->current_pgpath)
 		m->current_pgpath = NULL;
 
+	dm_nl_path_fail(pgpath->path.dev->name, 0x5A5A5A5A);
 	queue_work(kmultipathd, &m->trigger_event);
 
 out:
@@ -858,6 +860,7 @@ static int reinstate_path(struct pgpath 
 	if (!m->nr_valid_paths++ && m->queue_size)
 		queue_work(kmultipathd, &m->process_queued_ios);
 
+	dm_nl_path_reinstate(pgpath->path.dev->name);
 	queue_work(kmultipathd, &m->trigger_event);
 
 out:
@@ -975,7 +978,7 @@ void dm_pg_init_complete(struct path *pa
 		err_flags |= MP_FAIL_PATH;
 
 	if (err_flags & MP_FAIL_PATH)
-		fail_path(pgpath);
+		fail_path(pgpath, NULL);
 
 	if (err_flags & MP_BYPASS_PG)
 		bypass_pg(m, pg, 1);
@@ -1027,7 +1030,7 @@ static int do_end_io(struct multipath *m
 
 	if (mpio->pgpath) {
 		if (err_flags & MP_FAIL_PATH)
-			fail_path(mpio->pgpath);
+			fail_path(mpio->pgpath, bio);
 
 		if (err_flags & MP_BYPASS_PG)
 			bypass_pg(m, mpio->pgpath->pg, 1);

[PATCH RFC 4/4] Sample user space program (dm_nld)

[Mike Anderson]

 Sample program that receives dm netlink events and prints them out. This
 program uses the netlink library (libnl)
 http://people.suug.ch/~tgr/libnl/

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

 Makefile |   31 ++++++++++++
 dm_nld.c |  159 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 dm_nld.h |   53 +++++++++++++++++++++
 3 files changed, 243 insertions(+)

--- /dev/null	2005-11-13 12:06:42.576962000 -0800
+++ dm_nld/dm_nld.c	2005-11-29 21:03:14.000000000 -0800
@@ -0,0 +1,159 @@
+/*
+ * Device Mapper Netlink User Space Daemon (dm-nld)
+ *
+ * Copyright (C) 2005 IBM Corporation
+ * 	Author: 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 netlink interface
+ */
+
+#include <unistd.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <inttypes.h>
+#include <sys/socket.h>
+#include <sys/user.h>
+#include <asm/types.h>
+#include <linux/netlink.h>
+#include <time.h>
+#include "dm_nld.h"
+
+static struct nla_policy dm_e_attr_policy[DM_E_ATTR_MAX] = {
+	[DM_E_ATTR_SEQNUM]	= { .type = NLA_U64 },
+	[DM_E_ATTR_TSSEC]	= { .type = NLA_U64 },
+	[DM_E_ATTR_TSUSEC]	= { .type = NLA_U64 },
+	[DM_E_ATTR_DMNAME]	= { .type = NLA_STRING },
+	[DM_E_ATTR_BLKERR]	= { .type = NLA_U32 },
+};
+
+char * build_evt_msg(struct nlattr *dm_attr[])
+{
+	int n, size = 1024;
+	char *bmark, *str = NULL;
+
+	str = calloc(1, size);
+	if (!str)
+		goto out;
+	bmark = str;
+
+	n = snprintf(bmark, size, "[Event]:");
+	size -= n;
+	bmark += n;
+
+	if (dm_attr[DM_E_ATTR_SEQNUM] && size) {
+		n = snprintf(bmark, size, " SEQNUM: %" PRIu64,
+			     nla_get_u64(dm_attr[DM_E_ATTR_SEQNUM]));
+		size -= n;
+		bmark += n;
+	}
+
+	if (dm_attr[DM_E_ATTR_TSSEC] && size) {
+		const time_t t = nla_get_u64(dm_attr[DM_E_ATTR_TSSEC]),
+		n = snprintf(bmark, size, ", Time: %s", ctime(&t));
+		size -= n;
+		bmark += n - 1;
+	}
+
+	if (dm_attr[DM_E_ATTR_DMNAME] && size) {
+		n = snprintf(bmark, size, ", DMNAME: %s", (char *)
+			     nla_data(dm_attr[DM_E_ATTR_DMNAME]));
+		size -= n;
+		bmark += n;
+	}
+
+	if (dm_attr[DM_E_ATTR_BLKERR] && size) {
+		n = snprintf(bmark, size, ", BLKERR: 0x%x",
+			     nla_get_u32(dm_attr[DM_E_ATTR_BLKERR]));
+	}
+
+out:
+	return str;
+}
+
+int main (int argc, char *argv[])
+{
+	int err = -1;
+	struct sockaddr_nl addr;
+	struct nlmsghdr *nlh;
+	struct dm_nl_msghdr *dm_nlh;
+	unsigned char *msg;
+	char *evt_str = NULL;
+	struct nlattr *dm_attr[DM_E_ATTR_MAX];
+
+	struct nl_handle *handle;
+
+	handle = nl_handle_alloc();
+	if (!handle)
+		goto handle_out;
+
+	nl_disable_sequence_check(handle);
+
+	err = nl_connect(handle, NETLINK_DM);
+	if (err < 0)
+		goto connect_out;
+
+	err = nl_send_simple(handle, NLMSG_NOOP, 0, NULL, 0);
+	if (err < 0)
+		goto simple_out;
+
+	memset(&addr, 0, sizeof(addr));
+	addr.nl_family = AF_NETLINK;
+	addr.nl_pid = 0;
+	addr.nl_groups = 0;
+
+	do {
+		err = nl_recv(handle, &addr, &msg);
+		if (err <= 0)
+			break;
+		nlh = (struct nlmsghdr *) msg;
+		fprintf(stdout, "Msg Type: %d Recevied\n",
+			nlh->nlmsg_type);
+		if (nlh->nlmsg_type == DM_EVT) {
+			dm_nlh = nlmsg_data(nlh);
+			fprintf(stdout, "Event Type: %d Version: %d\n",
+				dm_nlh->type, dm_nlh->version);
+			
+			err = nla_parse(dm_attr, DM_E_ATTR_MAX - 1,
+					nlmsg_attrdata(nlh, 
+						sizeof(struct dm_nl_msghdr)),
+					nlmsg_attrlen(nlh, 
+					      sizeof(struct dm_nl_msghdr)),
+					dm_e_attr_policy);
+			if (err < 0)
+				break;
+
+			evt_str = build_evt_msg(dm_attr);
+			if (evt_str)
+				fprintf(stdout, "%s\n", evt_str);
+		}
+
+		free(evt_str);
+		free(msg);
+	} while (1);
+
+simple_out:
+	nl_close(handle);
+connect_out:
+	nl_handle_destroy(handle);
+handle_out:
+	exit(err == 0 ? 0 : 1);
+}
--- /dev/null	2005-11-13 12:06:42.576962000 -0800
+++ dm_nld/dm_nld.h	2005-11-23 01:23:56.000000000 -0800
@@ -0,0 +1,53 @@
+/*
+ * Device Mapper Netlink Daemon
+ *
+ * Copyright (C) 2005 IBM Corporation
+ * 	Author: 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_NLD_H
+#define DM_NLD_H
+#include <stdint.h>
+#include <netlink/attr.h>
+#include <netlink/msg.h>
+
+enum dm_evt_attr {
+	DM_E_ATTR_SEQNUM	= 1,
+	DM_E_ATTR_TSSEC		= 2,
+	DM_E_ATTR_TSUSEC	= 3,
+	DM_E_ATTR_DMNAME	= 4,
+	DM_E_ATTR_BLKERR	= 5,
+	DM_E_ATTR_MAX,
+};
+
+#ifndef NLMSG_MIN_TYPE
+#define NLMSG_MIN_TYPE 0x10
+#endif
+
+#define DM_EVT NLMSG_MIN_TYPE + 0x1
+
+#define DM_EVT_FAIL_PATH 0x1
+#define DM_EVT_REINSTATE_PATH 0x2
+
+struct dm_nl_msghdr {
+	uint16_t type;
+	uint16_t version;
+	uint16_t reserved1;
+	uint16_t reserved2;
+} __attribute__((aligned(sizeof(uint64_t))));
+
+#endif /* DM_NLD_H */
--- /dev/null	2005-11-13 12:06:42.576962000 -0800
+++ dm_nld/Makefile	2005-11-23 01:37:40.000000000 -0800
@@ -0,0 +1,31 @@
+# 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         = $(CROSS_COMPILE)objdump
+
+CFLAGS		+= -fno-builtin -Wall -Wchar-subscripts -Wundef \
+		   -Wstrict-prototypes -Wpointer-arith -Wsign-compare
+CFLAGS		+= -DNETLINK_DM=17
+
+LDFLAGS		= -lnl
+ifeq ($(strip $(DEBUG)),true)
+CFLAGS		+= -O1 -g
+else
+CFLAGS		+= -Os
+endif
+
+PROGRAM	= dm_nld
+
+all: $(PROGRAM)
+
+dm_evtd: dm_nld.o
+	$(CC) $^ -o $@
+
+clean:
+	rm -f *.o $(PROGRAM)