Btrfs-progs: fall back to the v1 ioctl if the new balance ioctl fails

This only falls back if the plain version of balance start is used.
Any args make us report the ioctl isn't supported.

Signed-off-by: Chris Mason <chris.mason@oracle.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

1 files changed, 32 insertions, 6 deletions

diff --git a/cmds-balance.c b/cmds-balance.c
index a6886a06..5fb2fda9 100644
--- a/cmds-balance.c
+++ b/cmds-balance.c
@@ -270,7 +270,18 @@ static void dump_ioctl_balance_args(struct btrfs_ioctl_balance_args *args)
 	}
 }
 
-static int do_balance(const char *path, struct btrfs_ioctl_balance_args *args)
+static int do_balance_v1(int fd)
+{
+	struct btrfs_ioctl_vol_args args;
+	int ret;
+
+	memset(&args, 0, sizeof(args));
+	ret = ioctl(fd, BTRFS_IOC_BALANCE, &args);
+	return ret;
+}
+
+static int do_balance(const char *path, struct btrfs_ioctl_balance_args *args,
+		      int nofilters)
 {
 	int fd;
 	int ret;
@@ -284,29 +295,44 @@ static int do_balance(const char *path, struct btrfs_ioctl_balance_args *args)
 
 	ret = ioctl(fd, BTRFS_IOC_BALANCE_V2, args);
 	e = errno;
-	close(fd);
 
 	if (ret < 0) {
+		/*
+		 * older kernels don't have the new balance ioctl, try the
+		 * old one.  But, the old one doesn't know any filters, so
+		 * don't fall back if they tried to use the fancy new things
+		 */
+		if (e == ENOTTY && nofilters) {
+			ret = do_balance_v1(fd);
+			if (ret == 0)
+				goto out;
+			e = errno;
+		}
+
 		if (e == ECANCELED) {
 			if (args->state & BTRFS_BALANCE_STATE_PAUSE_REQ)
 				fprintf(stderr, "balance paused by user\n");
 			if (args->state & BTRFS_BALANCE_STATE_CANCEL_REQ)
 				fprintf(stderr, "balance canceled by user\n");
+			ret = 0;
 		} else {
 			fprintf(stderr, "ERROR: error during balancing '%s' "
 				"- %s\n", path, strerror(e));
 			if (e != EINPROGRESS)
 				fprintf(stderr, "There may be more info in "
 					"syslog - try dmesg | tail\n");
-			return 19;
+			ret = 19;
 		}
 	} else {
 		printf("Done, had to relocate %llu out of %llu chunks\n",
 		       (unsigned long long)args->stat.completed,
 		       (unsigned long long)args->stat.considered);
+		ret = 0;
 	}
 
-	return 0;
+out:
+	close(fd);
+	return ret;
 }
 
 static const char * const cmd_balance_start_usage[] = {
@@ -438,7 +464,7 @@ static int cmd_balance_start(int argc, char **argv)
 	if (verbose)
 		dump_ioctl_balance_args(&args);
 
-	return do_balance(argv[optind], &args);
+	return do_balance(argv[optind], &args, nofilters);
 }
 
 static const char * const cmd_balance_pause_usage[] = {
@@ -677,7 +703,7 @@ int cmd_balance(int argc, char **argv)
 		memset(&args, 0, sizeof(args));
 		args.flags |= BTRFS_BALANCE_TYPE_MASK;
 
-		return do_balance(argv[1], &args);
+		return do_balance(argv[1], &args, 1);
 	}
 
 	return handle_command_group(&balance_cmd_group, argc, argv);