[PATCH v2 1/9] nvme-discover: lookup existing persistent controllers

[mwilck at suse.com]

From: Hannes Reinecke <hare at suse.de>

If persistent controller connections are present they should be
preferred even if no --device option is given on the commandline.

To avoid selecting a temporary non-persistent controller the
'kato' attribute is checked; any controller for which the
attribute is '0' will be skipped. This logic is not applied on
older kernels that don't support the 'kato' attribute. On these
kernels, we just have to assume that the encountered discovery
controller is persistent.

Signed-off-by: Hannes Reinecke <hare at suse.de>
Signed-off-by: Martin Wilck <mwilck at suse.de>
Signed-off-by: Martin Wilck <mwilck at suse.com>
---
 fabrics.c | 55 ++++++++++++++++++++++++++++++++-----------------------
 1 file changed, 32 insertions(+), 23 deletions(-)

diff --git a/fabrics.c b/fabrics.c
index 227773d..bdd0679 100644
--- a/fabrics.c
+++ b/fabrics.c
@@ -303,6 +303,7 @@ static bool ctrl_matches_connectargs(char *name, struct connect_args *args)
 	bool found = false;
 	char *path, *addr;
 	int ret;
+	bool persistent = true;
 
 	ret = asprintf(&path, "%s/%s", SYS_NVME, name);
 	if (ret < 0)
@@ -320,7 +321,30 @@ static bool ctrl_matches_connectargs(char *name, struct connect_args *args)
 	cargs.trsvcid = parse_conn_arg(addr, ' ', conarg_trsvcid);
 	cargs.host_traddr = parse_conn_arg(addr, ' ', conarg_host_traddr);
 
-	if (!strcmp(cargs.subsysnqn, args->subsysnqn) &&
+	if (!strcmp(cargs.subsysnqn, NVME_DISC_SUBSYS_NAME)) {
+		char *kato_str = nvme_get_ctrl_attr(path, "kato"), *p;
+		unsigned int kato = 0;
+
+		/*
+		 * When looking up discovery controllers we have to skip
+		 * any non-persistent controllers (ie those with a zero
+		 * kato value). Otherwise the controller will vanish from
+		 * underneath us as they are owned by another program.
+		 *
+		 * On older kernels, the 'kato' attribute isn't present.
+		 * Assume a persistent controller for these installations.
+		 */
+		if (kato_str) {
+			kato = strtoul(kato_str, &p, 0);
+			if (p == kato_str)
+				kato = 0;
+			free(kato_str);
+			persistent = (kato != 0);
+		}
+	}
+
+	if (persistent &&
+	    !strcmp(cargs.subsysnqn, args->subsysnqn) &&
 	    !strcmp(cargs.transport, args->transport) &&
 	    (!strcmp(cargs.traddr, args->traddr) ||
 	     !strcmp(args->traddr, "none")) &&
@@ -1346,30 +1370,15 @@ static int do_discover(char *argstr, bool connect, enum nvme_print_flags flags)
 	char *dev_name;
 	int instance, numrec = 0, ret, err;
 	int status = 0;
+	struct connect_args *cargs;
 
-	if (cfg.device) {
-		struct connect_args *cargs;
+	cargs = extract_connect_args(argstr);
+	if (!cargs)
+		return -ENOMEM;
 
-		cargs = extract_connect_args(argstr);
-		if (!cargs)
-			return -ENOMEM;
-
-		/*
-		 * if the cfg.device passed in matches the connect args
-		 *    cfg.device is left as-is
-		 * else if there exists a controller that matches the
-		 *         connect args
-		 *    cfg.device is the matching ctrl name
-		 * else if no ctrl matches the connect args
-		 *    cfg.device is set to null. This will attempt to
-		 *    create a new ctrl.
-		 * endif
-		 */
-		if (!ctrl_matches_connectargs(cfg.device, cargs))
-			cfg.device = find_ctrl_with_connectargs(cargs);
-
-		free_connect_args(cargs);
-	}
+	if (!cfg.device || !ctrl_matches_connectargs(cfg.device, cargs))
+		cfg.device = find_ctrl_with_connectargs(cargs);
+	free_connect_args(cargs);
 
 	if (!cfg.device) {
 		instance = add_ctrl(argstr);
-- 
2.30.1