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);
 

include/libzfs.h

@@ -203,6 +203,7 @@ extern void zfs_save_arguments(int argc, char **, char *, int);
 extern int zpool_log_history(libzfs_handle_t *, const char *);
 
 extern int libzfs_errno(libzfs_handle_t *);
+extern const char *libzfs_error_init(int);
 extern const char *libzfs_error_action(libzfs_handle_t *);
 extern const char *libzfs_error_description(libzfs_handle_t *);
 extern int zfs_standard_error(libzfs_handle_t *, int, const char *);
@@ -749,7 +750,6 @@ extern int zfs_nicestrtonum(libzfs_handle_t *, const char *, uint64_t *);
 #define	STDERR_VERBOSE	0x02
 
 int libzfs_run_process(const char *, char **, int flags);
-int libzfs_load_module(const char *);
 
 /*
  * Given a device or file, determine if it is part of a pool.

lib/libzfs/libzfs_util.c

@@ -58,6 +58,31 @@ libzfs_errno(libzfs_handle_t *hdl)
 	return (hdl->libzfs_error);
 }
 
+const char *
+libzfs_error_init(int error)
+{
+	switch (error) {
+	case ENXIO:
+		return (dgettext(TEXT_DOMAIN, "The ZFS modules are not "
+		    "loaded.\nTry running '/sbin/modprobe zfs' as root "
+		    "to load them.\n"));
+	case ENOENT:
+		return (dgettext(TEXT_DOMAIN, "The /dev/zfs device is "
+		    "missing and must be created.\nTry running 'udevadm "
+		    "trigger' as root to create it.\n"));
+	case ENOEXEC:
+		return (dgettext(TEXT_DOMAIN, "The ZFS modules cannot be "
+		    "auto-loaded.\nTry running '/sbin/modprobe zfs' as "
+		    "root to manually load them.\n"));
+	case EACCES:
+		return (dgettext(TEXT_DOMAIN, "Permission denied the "
+		    "ZFS utilities must be run as root.\n"));
+	default:
+		return (dgettext(TEXT_DOMAIN, "Failed to initialize the "
+		    "libzfs library.\n"));
+	}
+}
+
 const char *
 libzfs_error_action(libzfs_handle_t *hdl)
 {
@@ -628,7 +653,7 @@ int
 libzfs_run_process(const char *path, char *argv[], int flags)
 {
 	pid_t pid;
-	int rc, devnull_fd;
+	int error, devnull_fd;
 
 	pid = vfork();
 	if (pid == 0) {
@@ -650,9 +675,9 @@ libzfs_run_process(const char *path, char *argv[], int flags)
 	} else if (pid > 0) {
 		int status;
 
-		while ((rc = waitpid(pid, &status, 0)) == -1 &&
+		while ((error = waitpid(pid, &status, 0)) == -1 &&
 			errno == EINTR);
-		if (rc < 0 || !WIFEXITED(status))
+		if (error < 0 || !WIFEXITED(status))
 			return (-1);
 
 		return (WEXITSTATUS(status));
@@ -670,7 +695,7 @@ libzfs_run_process(const char *path, char *argv[], int flags)
  * - ZFS_MODULE_LOADING="YES|yes|ON|on" - Attempt to load modules.
  * - ZFS_MODULE_TIMEOUT="<seconds>"     - Seconds to wait for ZFS_DEV
  */
-int
+static int
 libzfs_load_module(const char *module)
 {
 	char *argv[4] = {"/sbin/modprobe", "-q", (char *)module, (char *)0};
@@ -739,9 +764,7 @@ libzfs_init(void)
 
 	error = libzfs_load_module(ZFS_DRIVER);
 	if (error) {
-		(void) fprintf(stderr, gettext("Failed to load ZFS module "
+		errno = error;
-		    "stack.\nLoad the module manually by running "
-		    "'insmod <location>/zfs.ko' as root.\n"));
 		return (NULL);
 	}
 
@@ -750,13 +773,6 @@ libzfs_init(void)
 	}
 
 	if ((hdl->libzfs_fd = open(ZFS_DEV, O_RDWR)) < 0) {
-		(void) fprintf(stderr, gettext("Unable to open %s: %s.\n"),
-		    ZFS_DEV, strerror(errno));
-		if (errno == ENOENT)
-			(void) fprintf(stderr,
-			    gettext("Verify the ZFS module stack is "
-			    "loaded by running '/sbin/modprobe zfs'.\n"));
-
 		free(hdl);
 		return (NULL);
 	}
@@ -767,8 +783,6 @@ libzfs_init(void)
 	if ((hdl->libzfs_mnttab = fopen(MNTTAB, "r")) == NULL) {
 #endif
 		(void) close(hdl->libzfs_fd);
-		(void) fprintf(stderr,
-		    gettext("mtab is not present at %s.\n"), MNTTAB);
 		free(hdl);
 		return (NULL);
 	}