[Cluster-devel] [PATCH] qdiskd: Make multipath issues go away

[Fabio M. Di Nitto <fdinitto@redhat.com>]

From: Lon Hohberger <lhh@redhat.com>

Qdiskd hsitorically has required significant tuning to work around
delays which occur during multipath failover, overloaded I/O, and LUN
trespasses in both device-mapper-multipath and EMC PowerPath
environments.

This patch goes a very long way towards eliminating false evictions
when these conditions occur by making qdiskd whine to the other
cluster members when it detects hung system calls.  When a cluster
member whines, it indicates the source of the problem (which system
call is hung), and the act of receiving a whine from a host indicates
that qdiskd is operational, but that I/O is hung.  Hung I/O is different
from losing storage entirely (where you get I/O errors).

Possible problems:

- Receive queue getting very full, causing messages to become blocked on
a node where I/O is hung.  1) that would take a very long time, and 2)
node should get evicted at that point anyway.

Resolves: rhbz#782900

this version of the patch is a backport of:
e2937eb33f224f86904fead08499a6178868ca6a
34d2872fb7e60be1594158acaaeb8acd74f78d22

There is a minor change vs original patch based on how qdiskd
in RHEL5 handles cman connection. We add an extra call to cman_alive
in main qdisk_loop to make sure data are not stalled on the
cman port, and data_callback to qdiskd_whine executed.

Signed-off-by: Lon Hohberger <lhh@redhat.com>
Signed-off-by: Fabio M. Di Nitto <fdinitto@redhat.com>
---
 cman/daemon/cnxman-socket.h |    1 +
 cman/qdisk/Makefile         |    2 +-
 cman/qdisk/disk.h           |    6 ++++
 cman/qdisk/iostate.c        |   17 +++++++++++--
 cman/qdisk/iostate.h        |    4 ++-
 cman/qdisk/main.c           |   54 +++++++++++++++++++++++++++++++++++++++----
 6 files changed, 74 insertions(+), 10 deletions(-)

diff --git a/cman/daemon/cnxman-socket.h b/cman/daemon/cnxman-socket.h
index 351c97c..1d01b44 100644
--- a/cman/daemon/cnxman-socket.h
+++ b/cman/daemon/cnxman-socket.h
@@ -79,6 +79,7 @@
 #define CLUSTER_PORT_SERVICES    2
 #define CLUSTER_PORT_SYSMAN      10	/* Remote execution daemon */
 #define CLUSTER_PORT_CLVMD       11	/* Cluster LVM daemon */
+#define	CLUSTER_PORT_QDISKD	 178	/* Quorum disk daemon */
 
 /* Port numbers above this will be blocked when the cluster is inquorate or in
  * transition */
diff --git a/cman/qdisk/Makefile b/cman/qdisk/Makefile
index f58806b..9bfc486 100644
--- a/cman/qdisk/Makefile
+++ b/cman/qdisk/Makefile
@@ -32,7 +32,7 @@ qdiskd: disk.o crc32.o disk_util.o main.o score.o bitmap.o clulog.o \
 	gcc -o $@ $^ -lpthread -L../lib -L${ccslibdir} -lccs -lrt
 
 mkqdisk: disk.o crc32.o disk_util.o iostate.o \
-	 proc.o mkqdisk.o scandisk.o clulog.o gettid.o
+	 proc.o mkqdisk.o scandisk.o clulog.o gettid.o ../lib/libcman.a
 	gcc -o $@ $^ -lrt
 
 %.o: %.c
diff --git a/cman/qdisk/disk.h b/cman/qdisk/disk.h
index b784220..d491de1 100644
--- a/cman/qdisk/disk.h
+++ b/cman/qdisk/disk.h
@@ -290,6 +290,12 @@ typedef struct {
 	status_block_t ni_status;
 } node_info_t;
 
+typedef struct {
+	qd_ctx *ctx;
+	node_info_t *ni;
+	size_t ni_len;
+} qd_priv_t;
+
 int qd_write_status(qd_ctx *ctx, int nid, disk_node_state_t state,
 		    disk_msg_t *msg, memb_mask_t mask, memb_mask_t master);
 int qd_read_print_status(target_info_t *disk, int nid);
diff --git a/cman/qdisk/iostate.c b/cman/qdisk/iostate.c
index 65b4d50..eb74ad2 100644
--- a/cman/qdisk/iostate.c
+++ b/cman/qdisk/iostate.c
@@ -1,10 +1,14 @@
 #include <pthread.h>
+#include <libcman.h>
 #include <iostate.h>
 #include <unistd.h>
 #include <time.h>
 #include <sys/time.h>
 #include <clulog.h>
+#include <stdint.h>
+#include "platform.h"
 #include "iostate.h"
+#include "../daemon/cnxman-socket.h"
 
 static iostate_t main_state = 0;
 static int main_incarnation = 0;
@@ -26,7 +30,7 @@ static struct state_table io_state_table[] = {
 {	STATE_LSEEK,	"seek"	},
 {	-1,		NULL	} };
 
-static const char *
+const char *
 state_to_string(iostate_t state)
 {
 	static const char *ret = "unknown";
@@ -65,6 +69,8 @@ io_nanny_thread(void *arg)
 	iostate_t last_main_state = 0, current_main_state = 0;
 	int last_main_incarnation = 0, current_main_incarnation = 0;
 	int logged_incarnation = 0;
+	cman_handle_t ch = (cman_handle_t)arg;
+	int32_t whine_state;
 
 	/* Start with wherever we're at now */
 	pthread_mutex_lock(&state_mutex);
@@ -96,6 +102,11 @@ io_nanny_thread(void *arg)
 			continue;
 		}
 
+		/* Whine on CMAN api */
+		whine_state = (int32_t)current_main_state;
+		swab32(whine_state);
+		cman_send_data(ch, &whine_state, sizeof(int32_t), 0, CLUSTER_PORT_QDISKD, 0);
+
 		/* Don't log things twice */
 		if (logged_incarnation == current_main_incarnation)
 			continue;
@@ -114,7 +125,7 @@ io_nanny_thread(void *arg)
 
 
 int
-io_nanny_start(int timeout)
+io_nanny_start(cman_handle_t ch, int timeout)
 {
 	int ret;
 
@@ -124,7 +135,7 @@ io_nanny_start(int timeout)
 	qdisk_timeout = timeout;
 	thread_active = 1;
 
-	ret = pthread_create(&io_nanny_tid, NULL, io_nanny_thread, NULL);
+	ret = pthread_create(&io_nanny_tid, NULL, io_nanny_thread, ch);
 	pthread_mutex_unlock(&state_mutex);
 
 	return ret;
diff --git a/cman/qdisk/iostate.h b/cman/qdisk/iostate.h
index 7dd7bf6..a65b1d4 100644
--- a/cman/qdisk/iostate.h
+++ b/cman/qdisk/iostate.h
@@ -11,7 +11,9 @@ typedef enum {
 
 void io_state(iostate_t state);
 
-int io_nanny_start(int timeout);
+int io_nanny_start(cman_handle_t ch, int timeout);
 int io_nanny_stop(void);
 
+const char * state_to_string(iostate_t state);
+
 #endif
diff --git a/cman/qdisk/main.c b/cman/qdisk/main.c
index 0d7bb3d..90d00ab 100644
--- a/cman/qdisk/main.c
+++ b/cman/qdisk/main.c
@@ -48,6 +48,7 @@
      (defined(LIBCMAN_VERSION) && LIBCMAN_VERSION < 2))
 #include <cluster/cnxman-socket.h>
 #endif
+#include "../daemon/cnxman-socket.h"
 
 int daemon_init(char *);
 int check_process_running(char *, pid_t *);
@@ -892,6 +893,11 @@ quorum_loop(qd_ctx *ctx, node_info_t *ni, int max)
 	
 	_running = 1;
 	while (_running) {
+		/* perform a forceful cman dispatch */
+		if (cman_alive(ctx->qc_ch) < 0) {
+			clulog(LOG_ERR, "cman: %s\n", strerror(errno));
+		}
+
 		/* XXX this was getuptime() in clumanager */
 		get_time(&oldtime, (ctx->qc_flags&RF_UPTIME));
 
@@ -1514,6 +1520,31 @@ check_stop_cman(qd_ctx *ctx)
 	}
 }
 
+static void
+qdisk_whine(cman_handle_t h, void *privdata, char *buf, int len,
+	    uint8_t port, int nodeid)
+{
+	int32_t dstate;
+	qd_priv_t *qp = (qd_priv_t *)privdata;
+	node_info_t *ni = qp->ni;
+
+	if (len != sizeof(dstate)) {
+		return;
+	}
+
+	dstate = *((int32_t*)buf);
+
+	if (nodeid == (qp->ctx->qc_my_id))
+		return;
+
+	swab32(dstate);
+
+	if (dstate) {
+		clulog(LOG_CRIT, "qdiskd on node %d reports hung %s()\n",
+		       state_to_string(dstate));
+		ni[nodeid-1].ni_misses = 0;
+	}
+}
 
 int
 main(int argc, char **argv)
@@ -1528,6 +1559,7 @@ main(int argc, char **argv)
 	char device[128];
 	pid_t pid;
 	quorum_header_t qh;
+	qd_priv_t qp;
 
 	if (check_process_running(argv[0], &pid) && pid !=getpid()) {
 		printf("QDisk services already running\n");
@@ -1559,10 +1591,16 @@ main(int argc, char **argv)
 		}
 	}
 
+	/* For cman notifications we need two sockets - one for events,
+	   one for config change callbacks */
+	qp.ctx = &ctx;
+	qp.ni = &ni[0];
+	qp.ni_len = MAX_NODES_DISK;
+
 #if (defined(LIBCMAN_VERSION) && LIBCMAN_VERSION >= 2)
-	ch = cman_admin_init(NULL);
+	ch = cman_admin_init(&qp);
 #else
-	ch = cman_init(NULL);
+	ch = cman_init(&qp);
 #endif
 	if (!ch) {
 		if (!foreground && !forked) {
@@ -1577,13 +1615,19 @@ main(int argc, char **argv)
 		do {
 			sleep(5);
 #if (defined(LIBCMAN_VERSION) && LIBCMAN_VERSION >= 2)
-			ch = cman_admin_init(NULL);
+			ch = cman_admin_init(&qp);
 #else
-			ch = cman_init(NULL);
+			ch = cman_init(&qp);
 #endif
 		} while (!ch);
 	}
 
+	if (cman_start_recv_data(ch, qdisk_whine, CLUSTER_PORT_QDISKD) != 0) {
+		clulog_and_print(LOG_CRIT, "Could not register with CMAN: %s\n",
+				 strerror(errno));
+		goto out;
+	}
+
 	memset(&me, 0, sizeof(me));
 	while (cman_get_node(ch, CMAN_NODEID_US, &me) < 0) {
 		if (!foreground && !forked) {
@@ -1696,7 +1740,7 @@ main(int argc, char **argv)
 		}
 	}
 
-	io_nanny_start(ctx.qc_tko * ctx.qc_interval);
+	io_nanny_start(ch, ctx.qc_tko * ctx.qc_interval);
 
 	if (quorum_loop(&ctx, ni, MAX_NODES_DISK) == 0)
 		cman_unregister_quorum_device(ctx.qc_ch);
-- 
1.7.7.6