[PATCH 2/8] Create the man page entry for the command btrfs fi df

[Goffredo Baroncelli <kreijack@libero.it>]

Signed-off-by: Goffredo Baroncelli <kreijack@inwind.it>
---
 man/btrfs.8.in | 52 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 52 insertions(+)

diff --git a/man/btrfs.8.in b/man/btrfs.8.in
index b620348..4acf16d 100644
--- a/man/btrfs.8.in
+++ b/man/btrfs.8.in
@@ -35,6 +35,9 @@ btrfs \- control a btrfs filesystem
 .PP
 \fBbtrfs\fP \fBfilesystem label\fP [\fI<device>\fP|\fI<mount_point>\fP] [\fI<newlabel>\fP]
 .PP
+\fBbtrfs\fP \fBfilesystem df\fP\fI [-b] \fIpath [path..]\fR\fP
+.PP
+\fBbtrfs\fP \fBfilesystem balance\fP\fI <path> \fP
 .PP
 \fBbtrfs\fP \fB[filesystem] balance start\fP [\fIoptions\fP] \fI<path>\fP
 .PP
@@ -370,6 +373,55 @@ force reducing of metadata integrity
 
 \fB[filesystem] balance pause\fR\fI <path>\fR
 Pause running balance.
+
+.RE
+.TP
+
+\fBfilesystem df\fP [-b] \fIpath [path..]\fR
+
+Show space usage information for a mount point.
+
+\fB-b\fP Set byte as unit
+
+The command \fBbtrfs filesystem df\fP is used to query how many space on the 
+disk(s) are used and an estimation of the free
+space of the filesystem.
+The output of the command \fBbtrfs filesystem df\fP shows:
+
+.RS
+.IP \fBDisk\ size\fP
+the total size of the disks which compose the filesystem.
+
+.IP \fBDisk\ allocated\fP
+the size of the area of the disks used by the chunks.
+
+.IP \fBDisk\ unallocated\fP 
+the size of the area of the disks which is free (i.e.
+the differences of the values above).
+
+.IP \fBUsed\fP
+the portion of the logical space used by the file and metadata.
+
+.IP \fBFree\ (estimated)\fP
+the estimated free space available: i.e. how many space can be used
+by the user. The evaluation 
+cannot be rigorous because it depends by the allocation policy (DUP, Single,
+RAID1...) of the metadata and data chunks. If every chunk is stored as
+"Single" the sum of the \fBfree (estimated)\fP space and the \fBused\fP 
+space  is equal to the \fBdisk size\fP.
+Otherwise if all the chunk are mirrored (raid1 or raid10) or duplicated
+the sum of the \fBfree (estimated)\fP space and the \fBused\fP space is
+half of the \fBdisk size\fP. Normally the \fBfree (estimated)\fP is between
+these two limits.
+
+.IP \fBData\ to\ disk\ ratio\fP
+the ratio betwen the \fBlogical size\fP (i.e. the space available by
+the chunks) and the \fBdisk allocated\fP (by the chunks). Normally it is 
+lower than 100% because the metadata is duplicated for security reasons.
+If all the data and metadata are duplicated (or have a profile like RAID1)
+the \fBData\ to\ disk\ ratio\fP could be 50%.
+
+.RE
 .TP
 
 \fB[filesystem] balance cancel\fR\fI <path>\fR
-- 
1.8.5.3



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