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diff --git a/Documentation/device-mapper/snapshot.txt b/Documentation/device-mapper/snapshot.txt
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+++ b/Documentation/device-mapper/snapshot.txt
@@ -122,3 +122,47 @@ volumeGroup-base: 0 2097152 snapshot-merge 254:11 254:12 P 16
122brw------- 1 root root 254, 11 29 ago 18:15 /dev/mapper/volumeGroup-base-real 122brw------- 1 root root 254, 11 29 ago 18:15 /dev/mapper/volumeGroup-base-real
123brw------- 1 root root 254, 12 29 ago 18:16 /dev/mapper/volumeGroup-base-cow 123brw------- 1 root root 254, 12 29 ago 18:16 /dev/mapper/volumeGroup-base-cow
124brw------- 1 root root 254, 10 29 ago 18:16 /dev/mapper/volumeGroup-base 124brw------- 1 root root 254, 10 29 ago 18:16 /dev/mapper/volumeGroup-base
125
126
127How to determine when a merging is complete
128===========================================
129The snapshot-merge and snapshot status lines end with:
130 <sectors_allocated>/<total_sectors> <metadata_sectors>
131
132Both <sectors_allocated> and <total_sectors> include both data and metadata.
133During merging, the number of sectors allocated gets smaller and
134smaller. Merging has finished when the number of sectors holding data
135is zero, in other words <sectors_allocated> == <metadata_sectors>.
136
137Here is a practical example (using a hybrid of lvm and dmsetup commands):
138
139# lvs
140 LV VG Attr LSize Origin Snap% Move Log Copy% Convert
141 base volumeGroup owi-a- 4.00g
142 snap volumeGroup swi-a- 1.00g base 18.97
143
144# dmsetup status volumeGroup-snap
1450 8388608 snapshot 397896/2097152 1560
146 ^^^^ metadata sectors
147
148# lvconvert --merge -b volumeGroup/snap
149 Merging of volume snap started.
150
151# lvs volumeGroup/snap
152 LV VG Attr LSize Origin Snap% Move Log Copy% Convert
153 base volumeGroup Owi-a- 4.00g 17.23
154
155# dmsetup status volumeGroup-base
1560 8388608 snapshot-merge 281688/2097152 1104
157
158# dmsetup status volumeGroup-base
1590 8388608 snapshot-merge 180480/2097152 712
160
161# dmsetup status volumeGroup-base
1620 8388608 snapshot-merge 16/2097152 16
163
164Merging has finished.
165
166# lvs
167 LV VG Attr LSize Origin Snap% Move Log Copy% Convert
168 base volumeGroup owi-a- 4.00g