Btrfs-progs: Fix manual of btrfs command

Usage of balancing btrfs is "btrfs filesystem balance",
not "btrfs device balance". And remove unneeded
usage of "btrfs filesystem defrag".
Also fix some typos and over 80 columns.

Signed-off-by: Akira Fujita <a-fujita@rs.jp.nec.com>

man/btrfs.8.in

@@ -17,20 +17,20 @@ btrfs \- control a btrfs filesystem
 .PP
 \fBbtrfs\fP \fBsubvolume get-default\fP\fI <path>\fP
 .PP
+\fBbtrfs\fP \fBfilesystem defragment\fP -c[zlib|lzo] [-l \fIlen\fR] \
+[-s \fIstart\fR] [-t \fIsize\fR] -[vf] <\fIfile\fR>|<\fIdir\fR> \
+[<\fIfile\fR>|<\fIdir\fR>...]
+.PP
 \fBbtrfs\fP \fBfilesystem sync\fP\fI <path> \fP
 .PP
 \fBbtrfs\fP \fBfilesystem resize\fP\fI [devid:][+/\-]<size>[gkm]|[devid:]max <filesystem>\fP
 .PP
 \fBbtrfs\fP \fBfilesystem label\fP\fI <dev> [newlabel]\fP
 .PP
-\fBbtrfs\fP \fBfilesystem defrag\fP\fI [options] <file>|<dir> [<file>|<dir>...]\fP
-.PP
 \fBbtrfs\fP \fBsubvolume find-new\fP\fI <subvolume> <last_gen>\fP
 .PP
 \fBbtrfs\fP \fBfilesystem balance\fP\fI <path> \fP
 .PP
-\fBbtrfs\fP \fBfilesystem defragment\fP\fI <file>|<dir> [<file>|<dir>...]\fP
-.PP
 \fBbtrfs\fP \fBdevice scan\fP\fI [--all-devices|<device> [<device>...]]\fP
 .PP
 \fBbtrfs\fP \fBdevice show\fP\fI [--all-devices|<uuid>|<label>]\fP
@@ -132,12 +132,17 @@ Get the default subvolume of the filesystem \fI<path>\fR. The output format
 is similar to \fBsubvolume list\fR command.
 .TP
 
-\fBfilesystem defragment\fP -c[zlib|lzo] [-l \fIlen\fR] [-s \fIstart\fR] [-t \fIsize\fR] -[vf] <\fIfile\fR>|<\fIdir\fR> [<\fIfile\fR>|<\fIdir\fR>...]
+\fBfilesystem defragment\fP -c[zlib|lzo] [-l \fIlen\fR] [-s \fIstart\fR] \
+[-t \fIsize\fR] -[vf] <\fIfile\fR>|<\fIdir\fR> [<\fIfile\fR>|<\fIdir\fR>...]
 
 Defragment file data and/or directory metadata. To defragment all files in a
 directory you have to specify each one on its own or use your shell wildcards.
 
-The start position and the number of bytes to deframention can be specified by \fIstart\fR and \fIlen\fR. Any extent bigger than \fIthresh\fR will be considered already defragged. Use 0 to take the kernel default, and use 1 to say eveery single extent must be rewritten. You can also turn on compression in defragment operations.
+The start position and the number of bytes to defragment can be specified by
+\fIstart\fR and \fIlen\fR. Any extent bigger than threshold will be
+considered already defragged. Use 0 to take the kernel default, and use 1 to
+say every single extent must be rewritten. You can also turn on compression in
+defragment operations.
 
 \fB-v\fP be verbose
 
@@ -151,9 +156,9 @@ The start position and the number of bytes to deframention can be specified by \
 
 \fB-t size\fP defragment only files at least \fIsize\fR bytes big
 
-NOTE: defragmenting with kernels up to 2.6.37 will unlink COW-ed copies of data, don't 
+NOTE: defragmenting with kernels up to 2.6.37 will unlink COW-ed copies of data,
-use it if you use snapshots, have de-duplicated your data or made copies with 
+don't use it if you use snapshots, have de-duplicated your data or made
-\fBcp --reflink\fP.
+copies with \fBcp --reflink\fP.
 .TP
 
 \fBsubvolume find-new\fR\fI <subvolume> <last_gen>\fR
@@ -177,7 +182,7 @@ If the prefix \fI+\fR or \fI\-\fR is present the size is increased or decreased
 by the quantity \fI<size>\fR.
 If no units are specified, the unit of the \fI<size>\fR parameter defaults to
 bytes. Optionally, the size parameter may be suffixed by one of the following
-the unit designators: 'K', 'M', or 'G', kilobytes, megabytes, or gigabytes,
+units designators: 'K', 'M', or 'G', kilobytes, megabytes, or gigabytes,
 respectively.
 
 If 'max' is passed, the filesystem will occupy all available space on the
@@ -192,13 +197,13 @@ it with the new desired size.  When recreating the partition make sure to use
 the same starting disk cylinder as before.
 .TP
 
-\fBbtrfs\fP \fBfilesystem label\fP\fI <dev> [newlabel]\fP
+\fBfilesystem label\fP\fI <dev> [newlabel]\fP
 Show or update the label of a filesystem. \fI<dev>\fR is used to identify the
 filesystem. 
 If a \fInewlabel\fR optional argument is passed, the label is changed. The
-following costraints exist for a label:
+following constraints exist for a label:
 .IP
-- the maximum allowable lenght shall be less or equal than 256 chars
+- the maximum allowable length shall be less or equal than 256 chars
 .IP
 - the label shall not  contain the '/' or '\\' characters.
 
@@ -216,7 +221,7 @@ If \fB--all-devices\fP is passed, all the devices under /dev are scanned;
 otherwise the devices list is extracted from the /proc/partitions file.
 .TP
 
-\fBdevice balance\fR \fI<path>\fR
+\fBfilesystem balance\fR \fI<path>\fR
 Balance the chunks of the filesystem identified by \fI<path>\fR
 across the devices.
 .TP