Add libzfs_error_init() function

All fprintf() error messages are moved out of the libzfs_init()
library function where they never belonged in the first place.  A
libzfs_error_init() function is added to provide useful error
messages for the most common causes of failure.

Additionally, in libzfs_run_process() the 'rc' variable was renamed
to 'error' for consistency with the rest of the code base.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Chris Dunlap <cdunlap@llnl.gov>
Signed-off-by: Richard Yao <ryao@gentoo.org>

cmd/mount_zfs/mount_zfs.c

@@ -473,8 +473,10 @@ main(int argc, char **argv)
 	if (zfsflags & ZS_ZFSUTIL)
 		zfsutil = 1;
 
-	if ((g_zfs = libzfs_init()) == NULL)
+	if ((g_zfs = libzfs_init()) == NULL) {
+		(void) fprintf(stderr, "%s", libzfs_error_init(errno));
 		return (MOUNT_SYSERR);
+	}
 
 	/* try to open the dataset to access the mount point */
 	if ((zhp = zfs_open(g_zfs, dataset,

cmd/zdb/zdb.c

@@ -3699,8 +3699,10 @@ main(int argc, char **argv)
 	zfs_vdev_async_read_max_active = 10;
 
 	kernel_init(FREAD);
-	if ((g_zfs = libzfs_init()) == NULL)
+	if ((g_zfs = libzfs_init()) == NULL) {
+		(void) fprintf(stderr, "%s", libzfs_error_init(errno));
 		return (1);
+	}
 
 	if (dump_all)
 		verbose = MAX(verbose, 1);

cmd/zfs/zfs_main.c

@@ -6708,8 +6708,10 @@ main(int argc, char **argv)
 	    (strcmp(cmdname, "--help") == 0))
 		usage(B_TRUE);
 
-	if ((g_zfs = libzfs_init()) == NULL)
+	if ((g_zfs = libzfs_init()) == NULL) {
+		(void) fprintf(stderr, "%s", libzfs_error_init(errno));
 		return (1);
+	}
 
 	mnttab_file = g_zfs->libzfs_mnttab;
 

cmd/zinject/zinject.c

@@ -572,8 +572,10 @@ main(int argc, char **argv)
 	int ret;
 	int flags = 0;
 
-	if ((g_zfs = libzfs_init()) == NULL)
+	if ((g_zfs = libzfs_init()) == NULL) {
+		(void) fprintf(stderr, "%s", libzfs_error_init(errno));
 		return (1);
+	}
 
 	libzfs_print_on_error(g_zfs, B_TRUE);
 

cmd/zpool/zpool_main.c

@@ -5919,8 +5919,10 @@ main(int argc, char **argv)
 	if ((strcmp(cmdname, "-?") == 0) || strcmp(cmdname, "--help") == 0)
 		usage(B_TRUE);
 
-	if ((g_zfs = libzfs_init()) == NULL)
+	if ((g_zfs = libzfs_init()) == NULL) {
+		(void) fprintf(stderr, "%s", libzfs_error_init(errno));
 		return (1);
+	}
 
 	libzfs_print_on_error(g_zfs, B_TRUE);