btrfs-progs: check for exclusive operation before issuing another

If the exclusive operation is available in sysfs file, check if there's
one already running. The check is done for:

- device add, remove, replace
- balance
- filesystem resize

All commands will validate arguments and check before the ioctl or
before any potentially irreversible operations (like clearing device
before replacing).

Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

cmds/balance.c

@@ -436,11 +436,21 @@ static int do_balance(const char *path, struct btrfs_ioctl_balance_args *args,
 	int fd;
 	int ret;
 	DIR *dirstream = NULL;
+	int exclop;
 
 	fd = btrfs_open_dir(path, &dirstream, 1);
 	if (fd < 0)
 		return 1;
 
+	exclop = get_fs_exclop(fd);
+	if (exclop > 0 ) {
+		error(
+	"unable to start balance, another exclusive operation '%s' in progress",
+			get_fs_exclop_name(exclop));
+		close_file_or_dir(fd, dirstream);
+		return 1;
+	}
+
 	ret = ioctl(fd, BTRFS_IOC_BALANCE_V2, args);
 	if (ret < 0) {
 		/*

cmds/device.c

@@ -61,6 +61,7 @@ static int cmd_device_add(const struct cmd_struct *cmd,
 	int discard = 1;
 	int force = 0;
 	int last_dev;
+	int exclop;
 
 	optind = 0;
 	while (1) {
@@ -96,6 +97,15 @@ static int cmd_device_add(const struct cmd_struct *cmd,
 	if (fdmnt < 0)
 		return 1;
 
+	exclop = get_fs_exclop(fdmnt);
+	if (exclop > 0) {
+		error(
+	"unable to start device add, another exclusive operation '%s' in progress",
+			get_fs_exclop_name(exclop));
+		close_file_or_dir(fdmnt, dirstream);
+		return 1;
+	}
+
 	for (i = optind; i < last_dev; i++){
 		struct btrfs_ioctl_vol_args ioctl_args;
 		int	devfd, res;
@@ -155,6 +165,7 @@ static int _cmd_device_remove(const struct cmd_struct *cmd,
 	char	*mntpnt;
 	int i, fdmnt, ret = 0;
 	DIR	*dirstream = NULL;
+	int exclop;
 
 	clean_args_no_options(cmd, argc, argv);
 
@@ -167,6 +178,15 @@ static int _cmd_device_remove(const struct cmd_struct *cmd,
 	if (fdmnt < 0)
 		return 1;
 
+	exclop = get_fs_exclop(fdmnt);
+	if (exclop > 0 ) {
+		error(
+	"unable to start device remove, another exclusive operation '%s' in progress",
+			get_fs_exclop_name(exclop));
+		close_file_or_dir(fdmnt, dirstream);
+		return 1;
+	}
+
 	for(i = optind; i < argc - 1; i++) {
 		struct	btrfs_ioctl_vol_args arg;
 		struct btrfs_ioctl_vol_args_v2 argv2 = {0};

cmds/filesystem.c

@@ -1079,6 +1079,7 @@ static int cmd_filesystem_resize(const struct cmd_struct *cmd,
 	char	*amount, *path;
 	DIR	*dirstream = NULL;
 	struct stat st;
+	int exclop;
 
 	clean_args_no_options_relaxed(cmd, argc, argv);
 
@@ -1110,6 +1111,15 @@ static int cmd_filesystem_resize(const struct cmd_struct *cmd,
 	if (fd < 0)
 		return 1;
 
+	exclop = get_fs_exclop(fd);
+	if (exclop > 0) {
+		error(
+"unable to start filesystem resize, nother exclusive operation '%s' in progress",
+			get_fs_exclop_name(exclop));
+		close_file_or_dir(fd, dirstream);
+		return 1;
+	}
+
 	printf("Resize '%s' of '%s'\n", path, amount);
 	memset(&args, 0, sizeof(args));
 	strncpy_null(args.name, amount);

cmds/replace.c

@@ -136,6 +136,7 @@ static int cmd_replace_start(const struct cmd_struct *cmd,
 	DIR *dirstream = NULL;
 	u64 srcdev_size;
 	u64 dstdev_size;
+	int exclop;
 
 	optind = 0;
 	while ((c = getopt(argc, argv, "Brf")) != -1) {
@@ -257,6 +258,17 @@ static int cmd_replace_start(const struct cmd_struct *cmd,
 		error("unable to open %s: %m", dstdev);
 		goto leave_with_error;
 	}
+
+	/* Check status before any potentially destructive operation */
+	exclop = get_fs_exclop(fdmnt);
+	if (exclop > 0) {
+		error(
+	"unable to start device replace, another exclusive operation '%s' in progress",
+			get_fs_exclop_name(exclop));
+		close_file_or_dir(fdmnt, dirstream);
+		goto leave_with_error;
+	}
+
 	strncpy((char *)start_args.start.tgtdev_name, dstdev,
 		BTRFS_DEVICE_PATH_NAME_MAX);
 	ret = btrfs_prepare_device(fddstdev, dstdev, &dstdev_block_count, 0,