[PATCH v2] btrfs-progs: device add should check existing FS before adding

[PATCH v2] btrfs-progs: device add should check existing FS before adding

[Anand Jain]

as of now, when 'btrfs device add' adds a device it doesn't
check if the given device contains an existing FS. This
patch will change that to check the same. which when true
add will fail, and ask user to use -f option to overwrite.

further, since now we have test_dev_for_mkfs() function
to check if a disk can be used, so this patch will also
use this function to test the given device before adding.

v2: rebase on 20130920, update man page and review comments

Signed-off-by: Anand Jain <anand.jain@oracle.com>
---
 cmds-device.c  | 36 +++++++++++-------------------------
 man/btrfs.8.in |  6 ++++--
 2 files changed, 15 insertions(+), 27 deletions(-)

diff --git a/cmds-device.c b/cmds-device.c
index 12c802e..7cfc347 100644
--- a/cmds-device.c
+++ b/cmds-device.c
@@ -40,6 +40,7 @@ static const char * const cmd_add_dev_usage[] = {
 	"btrfs device add [options] <device> [<device>...] <path>",
 	"Add a device to a filesystem",
 	"-K|--nodiscard    do not perform whole device TRIM",
+	"-f|--force        force overwrite existing filesystem on the disk",
 	NULL
 };
 
@@ -49,14 +50,17 @@ static int cmd_add_dev(int argc, char **argv)
 	int	i, fdmnt, ret=0, e;
 	DIR	*dirstream = NULL;
 	int discard = 1;
+	int force = 0;
+	char estr[100];
 
 	while (1) {
 		int long_index;
 		static struct option long_options[] = {
 			{ "nodiscard", optional_argument, NULL, 'K'},
+			{ "force", no_argument, NULL, 'f'},
 			{ 0, 0, 0, 0 }
 		};
-		int c = getopt_long(argc, argv, "K", long_options,
+		int c = getopt_long(argc, argv, "Kf", long_options,
 					&long_index);
 		if (c < 0)
 			break;
@@ -64,6 +68,9 @@ static int cmd_add_dev(int argc, char **argv)
 		case 'K':
 			discard = 0;
 			break;
+		case 'f':
+			force = 1;
+			break;
 		default:
 			usage(cmd_add_dev_usage);
 		}
@@ -86,19 +93,11 @@ static int cmd_add_dev(int argc, char **argv)
 		struct btrfs_ioctl_vol_args ioctl_args;
 		int	devfd, res;
 		u64 dev_block_count = 0;
-		struct stat st;
 		int mixed = 0;
 
-		res = check_mounted(argv[i]);
-		if (res < 0) {
-			fprintf(stderr, "error checking %s mount status\n",
-				argv[i]);
-			ret++;
-			continue;
-		}
-		if (res == 1) {
-			fprintf(stderr, "%s is mounted\n", argv[i]);
-			ret++;
+		res = test_dev_for_mkfs(argv[i], force, estr);
+		if (res) {
+			fprintf(stderr, "%s", estr);
 			continue;
 		}
 
@@ -108,19 +107,6 @@ static int cmd_add_dev(int argc, char **argv)
 			ret++;
 			continue;
 		}
-		res = fstat(devfd, &st);
-		if (res) {
-			fprintf(stderr, "ERROR: Unable to stat '%s'\n", argv[i]);
-			close(devfd);
-			ret++;
-			continue;
-		}
-		if (!S_ISBLK(st.st_mode)) {
-			fprintf(stderr, "ERROR: '%s' is not a block device\n", argv[i]);
-			close(devfd);
-			ret++;
-			continue;
-		}
 
 		res = btrfs_prepare_device(devfd, argv[i], 1, &dev_block_count,
 					   0, &mixed, discard);
diff --git a/man/btrfs.8.in b/man/btrfs.8.in
index 60e02bb..a65ed93 100644
--- a/man/btrfs.8.in
+++ b/man/btrfs.8.in
@@ -47,7 +47,7 @@ btrfs \- control a btrfs filesystem
 \fBbtrfs\fP \fB[filesystem] balance status\fP [-v] \fI<path>\fP
 .PP
 .PP
-\fBbtrfs\fP \fBdevice add\fP [-K] \fI<device>\fP [\fI<device>...\fP] \fI<path>\fP
+\fBbtrfs\fP \fBdevice add\fP [-Kf] \fI<device>\fP [\fI<device>...\fP] \fI<path>\fP
 .PP
 \fBbtrfs\fP \fBdevice delete\fP \fI<device>\fP [\fI<device>...\fP] \fI<path>\fP
 .PP
@@ -390,7 +390,7 @@ be verbose
 .RE
 .TP
 
-\fBdevice add\fR\fI [-K] <dev> \fP[\fI<dev>...\fP] \fI<path>\fR
+\fBdevice add\fR\fI [-Kf] <dev> \fP[\fI<dev>...\fP] \fI<path>\fR
 Add device(s) to the filesystem identified by \fI<path>\fR.
 If applicable, a whole device discard (TRIM) operation is performed.
 .RS
@@ -398,6 +398,8 @@ If applicable, a whole device discard (TRIM) operation is performed.
 \fIOptions\fR
 .IP "\fB-K|--nodiscard\fP" 5
 do not perform discard by default
+.IP "\fB-f|--force\fP" 5
+force overwrite of existing filesystem on the given disk(s)
 .RE
 .TP
 
-- 
1.8.4.rc4.1.g0d8beaa

Re: [PATCH v2] btrfs-progs: device add should check existing FS before adding

[Zach Brown]

> @@ -49,14 +50,17 @@ static int cmd_add_dev(int argc, char **argv)
>  	int	i, fdmnt, ret=0, e;
>  	DIR	*dirstream = NULL;
>  	int discard = 1;
> +	int force = 0;
> +	char estr[100];
>  
> +		res = test_dev_for_mkfs(argv[i], force, estr);
> +		if (res) {
> +			fprintf(stderr, "%s", estr);
>  			continue;
>  		}

This test_dev_for_mkfs() error string interface is bad.  The caller
should not have to magically guess the string size that the function is
going to use.  Especially because users can trivial provide giant paths
that exhaust that tiny buffer.  If an arbitrarily too small buffer in
the caller was needed at all, its length should have been passed in with
the string pointer.  (Or a string struct that all C projects eventually
grow.)

But all the callers just immediately print it anyway.  Get rid of that
string argument entirely and just have test_dev_for_mkfs() print the
strings.

- z

Re: [PATCH v2] btrfs-progs: device add should check existing FS before adding

[Anand Jain]

On 09/28/2013 02:32 AM, Zach Brown wrote:
>> @@ -49,14 +50,17 @@ static int cmd_add_dev(int argc, char **argv)
>>   	int	i, fdmnt, ret=0, e;
>>   	DIR	*dirstream = NULL;
>>   	int discard = 1;
>> +	int force = 0;
>> +	char estr[100];
>>
>> +		res = test_dev_for_mkfs(argv[i], force, estr);
>> +		if (res) {
>> +			fprintf(stderr, "%s", estr);
>>   			continue;
>>   		}
>
> This test_dev_for_mkfs() error string interface is bad.  The caller
> should not have to magically guess the string size that the function is
> going to use.  Especially because users can trivial provide giant paths
> that exhaust that tiny buffer.  If an arbitrarily too small buffer in
> the caller was needed at all, its length should have been passed in with
> the string pointer.  (Or a string struct that all C projects eventually
> grow.)
>
> But all the callers just immediately print it anyway.  Get rid of that
> string argument entirely and just have test_dev_for_mkfs() print the
> strings.

  Right. But this patch didn't introduce test_dev_for_mkfs()
  revamp of it will be good in a separate patch as it touches
  other functions as well.

Thanks, Anand

[PATCH] btrfs-progs: calculate disk space that a subvol could free

[Anand Jain]

It needs a lot more information about the snapshots if
snapshot's life cycle has to be all auto managed by
scripts _some day_.  this patch is a step towards that.

This patch provides the size which would be freed
if the subvol/snapshot is deleted.
preview:
---------------------
btrfs su show /btrfs/sv1
::
	Unshared space: 	89.09MiB
---------------------

v2: rename to 'unshared space' and edit commit text

Signed-off-by: Anand Jain <anand.jain@oracle.com>
---
 cmds-subvolume.c |   5 ++
 utils.c          | 154 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 utils.h          |   1 +
 3 files changed, 160 insertions(+)

diff --git a/cmds-subvolume.c b/cmds-subvolume.c
index de246ab..0f36cde 100644
--- a/cmds-subvolume.c
+++ b/cmds-subvolume.c
@@ -809,6 +809,7 @@ static int cmd_subvol_show(int argc, char **argv)
 	int fd = -1, mntfd = -1;
 	int ret = 1;
 	DIR *dirstream1 = NULL, *dirstream2 = NULL;
+	u64 freeable_bytes;
 
 	if (check_argc_exact(argc, 2))
 		usage(cmd_subvol_show_usage);
@@ -878,6 +879,8 @@ static int cmd_subvol_show(int argc, char **argv)
 		goto out;
 	}
 
+	freeable_bytes = get_subvol_freeable_bytes(fd);
+
 	ret = 0;
 	/* print the info */
 	printf("%s\n", fullpath);
@@ -915,6 +918,8 @@ static int cmd_subvol_show(int argc, char **argv)
 	else
 		printf("\tFlags: \t\t\t-\n");
 
+	printf("\tUnshared space: \t%s\n",
+		pretty_size(freeable_bytes));
 	/* print the snapshots of the given subvol if any*/
 	printf("\tSnapshot(s):\n");
 	filter_set = btrfs_list_alloc_filter_set();
diff --git a/utils.c b/utils.c
index ccb5199..ca30485 100644
--- a/utils.c
+++ b/utils.c
@@ -2062,3 +2062,157 @@ int lookup_ino_rootid(int fd, u64 *rootid)
 
 	return 0;
 }
+
+/* gets the ref count for given extent
+ * 0 = didn't find the item
+ * n = number of references
+*/
+u64 get_extent_refcnt(int fd, u64 disk_blk)
+{
+	int ret = 0, i, e;
+	struct btrfs_ioctl_search_args args;
+	struct btrfs_ioctl_search_key *sk = &args.key;
+	struct btrfs_ioctl_search_header sh;
+	unsigned long off = 0;
+
+	memset(&args, 0, sizeof(args));
+
+	sk->tree_id = BTRFS_EXTENT_TREE_OBJECTID;
+
+	sk->min_type = BTRFS_EXTENT_ITEM_KEY;
+	sk->max_type = BTRFS_EXTENT_ITEM_KEY;
+
+	sk->min_objectid = disk_blk;
+	sk->max_objectid = disk_blk;
+
+	sk->max_offset = (u64)-1;
+	sk->max_transid = (u64)-1;
+
+	while (1) {
+		sk->nr_items = 4096;
+
+		ret = ioctl(fd, BTRFS_IOC_TREE_SEARCH, &args);
+		e = errno;
+		if (ret < 0) {
+			fprintf(stderr, "ERROR: search failed - %s\n",
+				strerror(e));
+			return 0;
+		}
+		if (sk->nr_items == 0)
+			break;
+
+		off = 0;
+		for (i = 0; i < sk->nr_items; i++) {
+			struct btrfs_extent_item *ei;
+			u64 ref;
+
+			memcpy(&sh, args.buf + off, sizeof(sh));
+			off += sizeof(sh);
+
+			if (sh.type != BTRFS_EXTENT_ITEM_KEY) {
+				off += sh.len;
+				continue;
+			}
+
+			ei = (struct btrfs_extent_item *)(args.buf + off);
+			ref = btrfs_stack_extent_refs(ei);
+			return ref;
+		}
+		sk->min_objectid = sh.objectid;
+		sk->min_offset = sh.offset;
+		sk->min_type = sh.type;
+		if (sk->min_offset < (u64)-1)
+			sk->min_offset++;
+		else if (sk->min_objectid < (u64)-1) {
+			sk->min_objectid++;
+			sk->min_offset = 0;
+			sk->min_type = 0;
+		} else
+			break;
+	}
+	return 0;
+}
+
+u64 get_subvol_freeable_bytes(int fd)
+{
+	int ret = 0, i, e;
+	struct btrfs_ioctl_search_args args;
+	struct btrfs_ioctl_search_key *sk = &args.key;
+	struct btrfs_ioctl_search_header sh;
+	unsigned long off = 0;
+	u64 size_bytes = 0;
+
+	memset(&args, 0, sizeof(args));
+
+	sk->tree_id = 0;
+
+	sk->min_type = BTRFS_EXTENT_DATA_KEY;
+	sk->max_type = BTRFS_EXTENT_DATA_KEY;
+
+	sk->max_objectid = (u64) -1;
+	sk->max_offset = (u64)-1;
+	sk->max_transid = (u64)-1;
+
+	while (1) {
+		sk->nr_items = 4096;
+
+		ret = ioctl(fd, BTRFS_IOC_TREE_SEARCH, &args);
+		e = errno;
+		if (ret < 0) {
+			fprintf(stderr, "ERROR: search failed - %s\n",
+				strerror(e));
+			return 0;
+		}
+		if (sk->nr_items == 0)
+			break;
+
+		off = 0;
+		for (i = 0; i < sk->nr_items; i++) {
+			struct btrfs_file_extent_item *efi;
+			u64 disk_bytenr = 0;
+			u64 num_bytes = 0;
+			u64 refcnt;
+			u8 type;
+
+			memcpy(&sh, args.buf + off, sizeof(sh));
+			off += sizeof(sh);
+
+			if (sh.type != BTRFS_EXTENT_DATA_KEY) {
+				off += sh.len;
+				continue;
+			}
+
+			efi = (struct btrfs_file_extent_item *)(args.buf + off);
+			type = btrfs_stack_file_extent_type(efi);
+
+			if (type == BTRFS_FILE_EXTENT_INLINE) {
+				size_bytes +=
+					btrfs_stack_file_extent_ram_bytes(efi);
+				goto skip_extent_data;
+			}
+			disk_bytenr = btrfs_stack_file_extent_disk_bytenr(efi);
+			num_bytes = btrfs_stack_file_extent_num_bytes(efi);
+
+			if (disk_bytenr) {
+				refcnt = get_extent_refcnt(fd, disk_bytenr);
+				if (refcnt == 1)
+					size_bytes += num_bytes;
+			}
+skip_extent_data:
+			off += sh.len;
+		}
+		sk->min_objectid = sh.objectid;
+		sk->min_offset = sh.offset;
+		sk->min_type = sh.type;
+
+		if (sk->min_offset < (u64)-1)
+			sk->min_offset++;
+		else if (sk->min_objectid < (u64)-1) {
+			sk->min_objectid++;
+			sk->min_offset = 0;
+			sk->min_type = 0;
+		} else
+			break;
+	}
+	return size_bytes;
+}
diff --git a/utils.h b/utils.h
index 0f31db7..4ddcf09 100644
--- a/utils.h
+++ b/utils.h
@@ -91,5 +91,6 @@ int csum_tree_block(struct btrfs_root *root, struct extent_buffer *buf,
 int ask_user(char *question);
 int lookup_ino_rootid(int fd, u64 *rootid);
 int btrfs_scan_lblkid(int update_kernel);
+u64 get_subvol_freeable_bytes(int fd);
 
 #endif
-- 
1.8.4.rc4.1.g0d8beaa

[PATCH V2] btrfs-progs: device add should check existing FS before adding

[Anand Jain]

as of now, when 'btrfs device add' adds a device it doesn't
check if the given device contains an existing FS. This
patch will change that to check the same. which when true
add will fail, and ask user to use -f option to overwrite.

further, since now we have test_dev_for_mkfs() function
to check if a disk can be used, so this patch will also
use this function to test the given device before adding.

v2: worked on review comment
    rebase on 20130920, update man page and review comments

Signed-off-by: Anand Jain <anand.jain@oracle.com>
---
 cmds-device.c  | 36 +++++++++++-------------------------
 man/btrfs.8.in |  6 ++++--
 2 files changed, 15 insertions(+), 27 deletions(-)

diff --git a/cmds-device.c b/cmds-device.c
index 12c802e..7cfc347 100644
--- a/cmds-device.c
+++ b/cmds-device.c
@@ -40,6 +40,7 @@ static const char * const cmd_add_dev_usage[] = {
 	"btrfs device add [options] <device> [<device>...] <path>",
 	"Add a device to a filesystem",
 	"-K|--nodiscard    do not perform whole device TRIM",
+	"-f|--force        force overwrite existing filesystem on the disk",
 	NULL
 };
 
@@ -49,14 +50,17 @@ static int cmd_add_dev(int argc, char **argv)
 	int	i, fdmnt, ret=0, e;
 	DIR	*dirstream = NULL;
 	int discard = 1;
+	int force = 0;
+	char estr[100];
 
 	while (1) {
 		int long_index;
 		static struct option long_options[] = {
 			{ "nodiscard", optional_argument, NULL, 'K'},
+			{ "force", no_argument, NULL, 'f'},
 			{ 0, 0, 0, 0 }
 		};
-		int c = getopt_long(argc, argv, "K", long_options,
+		int c = getopt_long(argc, argv, "Kf", long_options,
 					&long_index);
 		if (c < 0)
 			break;
@@ -64,6 +68,9 @@ static int cmd_add_dev(int argc, char **argv)
 		case 'K':
 			discard = 0;
 			break;
+		case 'f':
+			force = 1;
+			break;
 		default:
 			usage(cmd_add_dev_usage);
 		}
@@ -86,19 +93,11 @@ static int cmd_add_dev(int argc, char **argv)
 		struct btrfs_ioctl_vol_args ioctl_args;
 		int	devfd, res;
 		u64 dev_block_count = 0;
-		struct stat st;
 		int mixed = 0;
 
-		res = check_mounted(argv[i]);
-		if (res < 0) {
-			fprintf(stderr, "error checking %s mount status\n",
-				argv[i]);
-			ret++;
-			continue;
-		}
-		if (res == 1) {
-			fprintf(stderr, "%s is mounted\n", argv[i]);
-			ret++;
+		res = test_dev_for_mkfs(argv[i], force, estr);
+		if (res) {
+			fprintf(stderr, "%s", estr);
 			continue;
 		}
 
@@ -108,19 +107,6 @@ static int cmd_add_dev(int argc, char **argv)
 			ret++;
 			continue;
 		}
-		res = fstat(devfd, &st);
-		if (res) {
-			fprintf(stderr, "ERROR: Unable to stat '%s'\n", argv[i]);
-			close(devfd);
-			ret++;
-			continue;
-		}
-		if (!S_ISBLK(st.st_mode)) {
-			fprintf(stderr, "ERROR: '%s' is not a block device\n", argv[i]);
-			close(devfd);
-			ret++;
-			continue;
-		}
 
 		res = btrfs_prepare_device(devfd, argv[i], 1, &dev_block_count,
 					   0, &mixed, discard);
diff --git a/man/btrfs.8.in b/man/btrfs.8.in
index 60e02bb..a65ed93 100644
--- a/man/btrfs.8.in
+++ b/man/btrfs.8.in
@@ -47,7 +47,7 @@ btrfs \- control a btrfs filesystem
 \fBbtrfs\fP \fB[filesystem] balance status\fP [-v] \fI<path>\fP
 .PP
 .PP
-\fBbtrfs\fP \fBdevice add\fP [-K] \fI<device>\fP [\fI<device>...\fP] \fI<path>\fP
+\fBbtrfs\fP \fBdevice add\fP [-Kf] \fI<device>\fP [\fI<device>...\fP] \fI<path>\fP
 .PP
 \fBbtrfs\fP \fBdevice delete\fP \fI<device>\fP [\fI<device>...\fP] \fI<path>\fP
 .PP
@@ -390,7 +390,7 @@ be verbose
 .RE
 .TP
 
-\fBdevice add\fR\fI [-K] <dev> \fP[\fI<dev>...\fP] \fI<path>\fR
+\fBdevice add\fR\fI [-Kf] <dev> \fP[\fI<dev>...\fP] \fI<path>\fR
 Add device(s) to the filesystem identified by \fI<path>\fR.
 If applicable, a whole device discard (TRIM) operation is performed.
 .RS
@@ -398,6 +398,8 @@ If applicable, a whole device discard (TRIM) operation is performed.
 \fIOptions\fR
 .IP "\fB-K|--nodiscard\fP" 5
 do not perform discard by default
+.IP "\fB-f|--force\fP" 5
+force overwrite of existing filesystem on the given disk(s)
 .RE
 .TP
 
-- 
1.8.4.rc4.1.g0d8beaa

Re: [PATCH V2] btrfs-progs: device add should check existing FS before adding

[Anand Jain]

  wrong patch sent. Please ignore this. sorry.


On 09/29/2013 11:15 PM, Anand Jain wrote:
> as of now, when 'btrfs device add' adds a device it doesn't
> check if the given device contains an existing FS. This
> patch will change that to check the same. which when true
> add will fail, and ask user to use -f option to overwrite.
>
> further, since now we have test_dev_for_mkfs() function
> to check if a disk can be used, so this patch will also
> use this function to test the given device before adding.
>
> v2: worked on review comment
>      rebase on 20130920, update man page and review comments
>
> Signed-off-by: Anand Jain <anand.jain@oracle.com>
> ---
>   cmds-device.c  | 36 +++++++++++-------------------------
>   man/btrfs.8.in |  6 ++++--
>   2 files changed, 15 insertions(+), 27 deletions(-)
>
> diff --git a/cmds-device.c b/cmds-device.c
> index 12c802e..7cfc347 100644
> --- a/cmds-device.c
> +++ b/cmds-device.c
> @@ -40,6 +40,7 @@ static const char * const cmd_add_dev_usage[] = {
>   	"btrfs device add [options] <device> [<device>...] <path>",
>   	"Add a device to a filesystem",
>   	"-K|--nodiscard    do not perform whole device TRIM",
> +	"-f|--force        force overwrite existing filesystem on the disk",
>   	NULL
>   };
>
> @@ -49,14 +50,17 @@ static int cmd_add_dev(int argc, char **argv)
>   	int	i, fdmnt, ret=0, e;
>   	DIR	*dirstream = NULL;
>   	int discard = 1;
> +	int force = 0;
> +	char estr[100];
>
>   	while (1) {
>   		int long_index;
>   		static struct option long_options[] = {
>   			{ "nodiscard", optional_argument, NULL, 'K'},
> +			{ "force", no_argument, NULL, 'f'},
>   			{ 0, 0, 0, 0 }
>   		};
> -		int c = getopt_long(argc, argv, "K", long_options,
> +		int c = getopt_long(argc, argv, "Kf", long_options,
>   					&long_index);
>   		if (c < 0)
>   			break;
> @@ -64,6 +68,9 @@ static int cmd_add_dev(int argc, char **argv)
>   		case 'K':
>   			discard = 0;
>   			break;
> +		case 'f':
> +			force = 1;
> +			break;
>   		default:
>   			usage(cmd_add_dev_usage);
>   		}
> @@ -86,19 +93,11 @@ static int cmd_add_dev(int argc, char **argv)
>   		struct btrfs_ioctl_vol_args ioctl_args;
>   		int	devfd, res;
>   		u64 dev_block_count = 0;
> -		struct stat st;
>   		int mixed = 0;
>
> -		res = check_mounted(argv[i]);
> -		if (res < 0) {
> -			fprintf(stderr, "error checking %s mount status\n",
> -				argv[i]);
> -			ret++;
> -			continue;
> -		}
> -		if (res == 1) {
> -			fprintf(stderr, "%s is mounted\n", argv[i]);
> -			ret++;
> +		res = test_dev_for_mkfs(argv[i], force, estr);
> +		if (res) {
> +			fprintf(stderr, "%s", estr);
>   			continue;
>   		}
>
> @@ -108,19 +107,6 @@ static int cmd_add_dev(int argc, char **argv)
>   			ret++;
>   			continue;
>   		}
> -		res = fstat(devfd, &st);
> -		if (res) {
> -			fprintf(stderr, "ERROR: Unable to stat '%s'\n", argv[i]);
> -			close(devfd);
> -			ret++;
> -			continue;
> -		}
> -		if (!S_ISBLK(st.st_mode)) {
> -			fprintf(stderr, "ERROR: '%s' is not a block device\n", argv[i]);
> -			close(devfd);
> -			ret++;
> -			continue;
> -		}
>
>   		res = btrfs_prepare_device(devfd, argv[i], 1, &dev_block_count,
>   					   0, &mixed, discard);
> diff --git a/man/btrfs.8.in b/man/btrfs.8.in
> index 60e02bb..a65ed93 100644
> --- a/man/btrfs.8.in
> +++ b/man/btrfs.8.in
> @@ -47,7 +47,7 @@ btrfs \- control a btrfs filesystem
>   \fBbtrfs\fP \fB[filesystem] balance status\fP [-v] \fI<path>\fP
>   .PP
>   .PP
> -\fBbtrfs\fP \fBdevice add\fP [-K] \fI<device>\fP [\fI<device>...\fP] \fI<path>\fP
> +\fBbtrfs\fP \fBdevice add\fP [-Kf] \fI<device>\fP [\fI<device>...\fP] \fI<path>\fP
>   .PP
>   \fBbtrfs\fP \fBdevice delete\fP \fI<device>\fP [\fI<device>...\fP] \fI<path>\fP
>   .PP
> @@ -390,7 +390,7 @@ be verbose
>   .RE
>   .TP
>
> -\fBdevice add\fR\fI [-K] <dev> \fP[\fI<dev>...\fP] \fI<path>\fR
> +\fBdevice add\fR\fI [-Kf] <dev> \fP[\fI<dev>...\fP] \fI<path>\fR
>   Add device(s) to the filesystem identified by \fI<path>\fR.
>   If applicable, a whole device discard (TRIM) operation is performed.
>   .RS
> @@ -398,6 +398,8 @@ If applicable, a whole device discard (TRIM) operation is performed.
>   \fIOptions\fR
>   .IP "\fB-K|--nodiscard\fP" 5
>   do not perform discard by default
> +.IP "\fB-f|--force\fP" 5
> +force overwrite of existing filesystem on the given disk(s)
>   .RE
>   .TP
>
>