[PATCH] btrfs-progs: filesystem-resize: make output more readable

[Sidong Yang <realwakka@gmail.com>]

This patch make output of filesystem-resize command more readable and
give detail information for users. This patch provides more information
about filesystem like below.

Before:
Resize '/mnt' of '1:-1G'

After:
Resize device id 1 (/dev/vdb) from 4.00GiB to 3.00GiB

Signed-off-by: Sidong Yang <realwakka@gmail.com>
---
 cmds/filesystem.c | 61 ++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 60 insertions(+), 1 deletion(-)

diff --git a/cmds/filesystem.c b/cmds/filesystem.c
index fac612b2..53e775b7 100644
--- a/cmds/filesystem.c
+++ b/cmds/filesystem.c
@@ -1084,6 +1084,14 @@ static int cmd_filesystem_resize(const struct cmd_struct *cmd,
 	int ret;
 	struct stat st;
 	bool enqueue = false;
+	struct btrfs_ioctl_fs_info_args fi_args;
+	struct btrfs_ioctl_dev_info_args *di_args = NULL;
+	char newsize[256];
+	char sign;
+	u64 inc_bytes;
+	u64 res_bytes;
+	int i, devid, dev_idx;
+	const char *res_str;
 
 	optind = 0;
 	while (1) {
@@ -1142,7 +1150,58 @@ static int cmd_filesystem_resize(const struct cmd_struct *cmd,
 		return 1;
 	}
 
-	printf("Resize '%s' of '%s'\n", path, amount);
+	ret = get_fs_info(path, &fi_args, &di_args);
+	if (ret)
+		error("unable to retrieve fs info");
+
+	if (!fi_args.num_devices)
+		error("num_devices = 0");
+
+	ret = sscanf(amount, "%d:%255s", &devid, newsize);
+
+	if (ret != 2)
+		error("invalid format");
+
+	dev_idx = -1;
+	for(i = 0; i < fi_args.num_devices; i++) {
+		if (di_args[i].devid == devid) {
+			dev_idx = i;
+			break;
+		}
+	}
+
+	if (dev_idx < 0)
+		error("cannot find devid : %d", devid);
+
+	if (!strcmp(newsize, "max")) {
+		res_str = "max";
+	} else {
+		if (strlen(newsize) < 3)
+			error("invalid format");
+
+		sign = newsize[0];
+		if (sign != '-' && sign != '+')
+			error("invalid format");
+
+		inc_bytes = parse_size(&newsize[1]);
+
+		res_bytes = 0;
+		if (sign == '+')
+			res_bytes = di_args[0].total_bytes + inc_bytes;
+		else if (sign == '-')
+			res_bytes = di_args[0].total_bytes - inc_bytes;
+		else
+			error("invalid format");
+
+		res_str = pretty_size_mode(res_bytes, UNITS_DEFAULT);
+	}
+
+	printf("Resize device id %d (%s) from %s to %s\n", devid, di_args[dev_idx].path,
+		   pretty_size_mode(di_args[dev_idx].total_bytes, UNITS_DEFAULT),
+		   res_str);
+
+	free(di_args);
+
 	memset(&args, 0, sizeof(args));
 	strncpy_null(args.name, amount);
 	res = ioctl(fd, BTRFS_IOC_RESIZE, &args);
-- 
2.25.1