[PATCH rfc 2/6] nvme-cli: support persistent connections to a discovery controller

[jsmart2021@gmail.com (James Smart)]

From: Sagi Grimberg <sagi@grimberg.me>

Simply don't destroy the discovery controller after getting the
log pages. Note that persistent connection to a discovery subsystem
require to pass in a non-zero kato value, so if not provided we
simply use a default of 30 seconds kato.

Example:
  nvme connect-all ... --persistent

Signed-off-by: Sagi Grimberg <sagi at grimberg.me>
Reviewed-by: James Smart <jsmart2021 at gmail.com>
Reviewed-by: Hannes Reinecke <hare at suse.com>
Reviewed-by: Max Gurtovoy <maxg at mellanox.com>

---
resolved merge error
---
 fabrics.c | 15 ++++++++++++---
 fabrics.h |  2 ++
 2 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/fabrics.c b/fabrics.c
index cc91d00..c4bbe2c 100644
--- a/fabrics.c
+++ b/fabrics.c
@@ -65,6 +65,7 @@ static struct config {
 	int  disable_sqflow;
 	int  hdr_digest;
 	int  data_digest;
+	bool persistent;
 } cfg = { NULL };
 
 #define BUF_SIZE		4096
@@ -858,9 +859,11 @@ static int do_discover(char *argstr, bool connect)
 		return -errno;
 	ret = nvmf_get_log_page_discovery(dev_name, &log, &numrec);
 	free(dev_name);
-	err = remove_ctrl(instance);
-	if (err)
-		return err;
+	if (!cfg.persistent) {
+		err = remove_ctrl(instance);
+		if (err)
+			return err;
+	}
 
 	switch (ret) {
 	case DISC_OK:
@@ -936,6 +939,9 @@ static int discover_from_conf_file(const char *desc, char *argstr,
 		if (err)
 			continue;
 
+		if (cfg.persistent && !cfg.keep_alive_tmo)
+			cfg.keep_alive_tmo = NVMF_DEF_DISC_TMO;
+
 		err = build_options(argstr, BUF_SIZE);
 		if (err) {
 			ret = err;
@@ -978,6 +984,7 @@ int discover(const char *desc, int argc, char **argv, bool connect)
 		{"nr-write-queues", 'W', "LIST", CFG_INT, &cfg.nr_write_queues,    required_argument, "number of write queues to use (default 0)" },
 		{"nr-poll-queues",  'P', "LIST", CFG_INT, &cfg.nr_poll_queues,    required_argument, "number of poll queues to use (default 0)" },
 		{"queue-size",      'Q', "LIST", CFG_INT, &cfg.queue_size,      required_argument, "number of io queue elements to use (default 128)" },
+		{"persistent",  'p', "LIST", CFG_NONE, &cfg.persistent,  no_argument, "persistent discovery connection" },
 		{NULL},
 	};
 
@@ -992,6 +999,8 @@ int discover(const char *desc, int argc, char **argv, bool connect)
 		return discover_from_conf_file(desc, argstr,
 				command_line_options, connect);
 	} else {
+		if (cfg.persistent && !cfg.keep_alive_tmo)
+			cfg.keep_alive_tmo = NVMF_DEF_DISC_TMO;
 		ret = build_options(argstr, BUF_SIZE);
 		if (ret)
 			return ret;
diff --git a/fabrics.h b/fabrics.h
index 988f3ef..7c1664b 100644
--- a/fabrics.h
+++ b/fabrics.h
@@ -1,6 +1,8 @@
 #ifndef _DISCOVER_H
 #define _DISCOVER_H
 
+#define NVMF_DEF_DISC_TMO	30
+
 extern int discover(const char *desc, int argc, char **argv, bool connect);
 extern int connect(const char *desc, int argc, char **argv);
 extern int disconnect(const char *desc, int argc, char **argv);
-- 
2.13.7