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



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#678372

Signed-off-by: Lon Hohberger <lhh redhat com>
---
 cman/qdisk/Makefile  |    2 +-
 cman/qdisk/disk.h    |    6 ++++++
 cman/qdisk/iostate.c |   16 +++++++++++++---
 cman/qdisk/iostate.h |    4 +++-
 cman/qdisk/main.c    |   45 ++++++++++++++++++++++++++++++++++++++++++---
 5 files changed, 65 insertions(+), 8 deletions(-)

diff --git a/cman/qdisk/Makefile b/cman/qdisk/Makefile
index 68e20cd..e3bb5f7 100644
--- a/cman/qdisk/Makefile
+++ b/cman/qdisk/Makefile
@@ -40,7 +40,7 @@ ${TARGET1}: ${SHAREDOBJS} ${OBJS1}
 	$(CC) -o $@ $^ $(EXTRA_LDFLAGS) $(LDFLAGS)
 
 ${TARGET2}: ${SHAREDOBJS} ${OBJS2}
-	$(CC) -o $@ $^ $(LDFLAGS)
+	$(CC) -o $@ $^ $(EXTRA_LDFLAGS) $(LDFLAGS)
 
 depends:
 	$(MAKE) -C ../lib all
diff --git a/cman/qdisk/disk.h b/cman/qdisk/disk.h
index 93d15fe..fd80fa6 100644
--- a/cman/qdisk/disk.h
+++ b/cman/qdisk/disk.h
@@ -273,6 +273,12 @@ 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_init(qd_ctx *ctx, cman_handle_t ch_admin,
diff --git a/cman/qdisk/iostate.c b/cman/qdisk/iostate.c
index 0199da4..06c6831 100644
--- a/cman/qdisk/iostate.c
+++ b/cman/qdisk/iostate.c
@@ -1,9 +1,12 @@
 #include <pthread.h>
+#include <libcman.h>
 #include <iostate.h>
 #include <unistd.h>
 #include <time.h>
 #include <sys/time.h>
 #include <liblogthread.h>
+#include <stdint.h>
+#include "platform.h"
 #include "iostate.h"
 
 static iostate_t main_state = 0;
@@ -26,7 +29,7 @@ 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 +68,8 @@ 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 +101,11 @@ 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, 178, 0);
+
 		/* Don't log things twice */
 		if (logged_incarnation == current_main_incarnation)
 			continue;
@@ -114,7 +124,7 @@ io_nanny_thread(void *arg)
 
 
 int
-io_nanny_start(int timeout)
+io_nanny_start(cman_handle_t ch, int timeout)
 {
 	int ret;
 
@@ -124,7 +134,7 @@ 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 a90e82c..d613d84 100644
--- a/cman/qdisk/main.c
+++ b/cman/qdisk/main.c
@@ -915,7 +915,8 @@ cman_wait(cman_handle_t ch, struct timeval *_tv)
 static void
 process_cman_event(cman_handle_t handle, void *private, int reason, int arg)
 {
-	qd_ctx *ctx = (qd_ctx *)private;
+	qd_priv_t *qp = (qd_priv_t *)private;
+	qd_ctx *ctx = qp->ctx;
 
 	switch(reason) {
 	case CMAN_REASON_PORTOPENED:
@@ -1926,6 +1927,33 @@ check_stop_cman(qd_ctx *ctx)
 do { static int _logged=0; if (!_logged) { _logged=1; logt_print(level, fmt, ##args); } } while(0)
 
 
+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) {
+		logt_print(LOG_NOTICE, "qdiskd on node %d reports hung %s()\n", nodeid,
+			   state_to_string(dstate));
+		ni[nodeid-1].ni_misses = 0;
+	}
+}
+
+
 int
 main(int argc, char **argv)
 {
@@ -1939,6 +1967,7 @@ 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");
@@ -2001,13 +2030,23 @@ main(int argc, char **argv)
 
 	/* For cman notifications we need two sockets - one for events,
 	   one for config change callbacks */
-	ch_user = cman_init(&ctx);
+	qp.ctx = &ctx;
+	qp.ni = &ni[0];
+	qp.ni_len = MAX_NODES_DISK;
+
+	ch_user = cman_init(&qp);
         if (cman_start_notification(ch_user, process_cman_event) != 0) {
 		logt_print(LOG_CRIT, "Could not register with CMAN: %s\n",
 			   strerror(errno));
 		goto out;
 	}
 
+	if (cman_start_recv_data(ch_user, qdisk_whine, 178) != 0) {
+		logt_print(LOG_CRIT, "Could not register with CMAN: %s\n",
+			   strerror(errno));
+		goto out;
+	}
+
 	memset(&me, 0, sizeof(me));
 	if (cman_get_node(ch_admin, CMAN_NODEID_US, &me) < 0) {
 		logt_print(LOG_CRIT, "Could not determine local node ID: %s\n",
@@ -2108,7 +2147,7 @@ main(int argc, char **argv)
 		}
 	}
 
-	io_nanny_start(ctx.qc_tko * ctx.qc_interval);
+	io_nanny_start(ch_user, ctx.qc_tko * ctx.qc_interval);
 
 	if (quorum_loop(&ctx, ni, MAX_NODES_DISK) == 0) {
 		/* Only clean up if we're exiting w/o error) */
-- 
1.7.7.6


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