Btrfs-progs: introduce -g -c --sort options into btrfs subvol list command

This patch introduces '-g' '-c' '--sort' options

The option '-g' can help you filter the subvolumes by the generation, you may
use it just like:

	btrfs subvol list -g +/-value <path>

'+' means the generation of the subvolumes should >= the value you specified.
'-' means the generation should <= the value
If you don't input either '+' nor '-', this command will list the subvolumes
that their generation equals to the value.

However if you want to find gengeration between value1 and value2
you may use the above like:

        btrfs sub list -g -value1 -g +value2 <path>

The option '-c' can help you filter the subvolumes by the ogeneration, you may
use it just like:

	btrfs subvol list -c +/-value <path>

The usage is the same to '-g'

You might want to list subvolumes in order of some items, such as root id, gen
and so on, you can use '--sort'. Now you can sort the subvolumes by root id,
gen, ogen and path.

For example:
If you want to list subvolumes in order of rootid, you can use the option like
that:

	btrfs sub list --sort=+/-rooid <path>

Here, '+' means the result is sorted by ascending order. '-' is by descending
order. If you don't specify either '+' nor '-', the result is sorted by
default - ascending order.

If you want to combine sort items, you do it like that:

	btrfs sub list --sort=-rootid,+path,ogen,gen <path>

Signed-off-by: Wang Shilong <wangsl-fnst@cn.fujitsu.com>
Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>

1 files changed, 26 insertions, 3 deletions

diff --git a/man/btrfs.8.in b/man/btrfs.8.in
index 0845b4dc..5c95ccc6 100644
--- a/man/btrfs.8.in
+++ b/man/btrfs.8.in
@@ -11,7 +11,7 @@ btrfs \- control a btrfs filesystem
 .PP
 \fBbtrfs\fP \fBsubvolume create\fP\fI [<dest>/]<name>\fP
 .PP
-\fBbtrfs\fP \fBsubvolume list\fP\fI [-pr] <path>\fP
+\fBbtrfs\fP \fBsubvolume list\fP\fI [-pr] [-s 0|1] [-g [+|-]value] [-c [+|-]value] [--rootid=rootid,gen,ogen,path] <path>\fP
 .PP
 \fBbtrfs\fP \fBsubvolume set-default\fP\fI <id> <path>\fP
 .PP
@@ -108,18 +108,41 @@ Create a subvolume in \fI<dest>\fR (or in the current directory if
 \fI<dest>\fR is omitted).
 .TP
 
-\fBsubvolume list\fR\fI [-pr] <path>\fR
+\fBsubvolume list\fR\fI [-pr][-s 0|1] [-g [+|-]value] [-c [+|-]value] [--sort=gen,ogen,rootid,path] <path>\fR
+.RS
 List the subvolumes present in the filesystem \fI<path>\fR. For every
 subvolume the following information is shown by default.
 ID <ID> top level <ID> path <path>
 where path is the relative path of the subvolume to the \fItop level\fR
 subvolume.
+
 The subvolume's ID may be used by the \fBsubvolume set-default\fR command, or
 at mount time via the \fIsubvol=\fR option.
 If \fI-p\fR is given, then \fIparent <ID>\fR is added to the output between ID
 and top level. The parent's ID may be used at mount time via the
 \fIsubvolrootid=\fR option.
-If \fI-r\fR is given, only readonly subvolumes in the filesystem will be listed.
+
+\fB-r\fP only readonly subvolumes in the filesystem wille be listed.
+
+\fB-s\fP only snapshot subvolumes in the filesystem will  be listed.
+
+\fB-g [+|-]value\fP
+list subvolumes in the filesystem that its generation is
+>=, <= or = value. '+' means >= value, '-' means <= value, If there is
+neither '+' nor '-', it means = value.
+
+\fB-c [+|-]value\fP
+list subvolumes in the filesystem that its ogeneration is
+>=, <= or = value. The usage is the same to '-g' option.
+
+\fB--sort=gen,ogen,path,rootid\fP
+list subvolumes in order by specified items.
+you can add '+' or '-' in front of each items, '+' means ascending,'-'
+means descending. The default is ascending.
+
+for \fB--sort\fP you can combine some items together by ',', just like
+\f--sort=+ogen,-gen,path,rootid\fR.
+.RE
 .TP
 
 \fBsubvolume set-default\fR\fI <id> <path>\fR