dm cache: update Documentation for invalidate_cblocks's range syntax
The cache target's invalidate_cblocks message allows cache block
(cblock) ranges to be expressed with: <cblock start>-<cblock end>
The range's <cblock end> value is "one past the end", so the range
includes <cblock start> through <cblock end>-1.
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Acked-by: Joe Thornber <ejt@redhat.com>
diff --git a/Documentation/device-mapper/cache.txt b/Documentation/device-mapper/cache.txt
index 274752f..719320b 100644
--- a/Documentation/device-mapper/cache.txt
+++ b/Documentation/device-mapper/cache.txt
@@ -266,10 +266,12 @@
Invalidation is removing an entry from the cache without writing it
back. Cache blocks can be invalidated via the invalidate_cblocks
message, which takes an arbitrary number of cblock ranges. Each cblock
-must be expressed as a decimal value, in the future a variant message
-that takes cblock ranges expressed in hexidecimal may be needed to
-better support efficient invalidation of larger caches. The cache must
-be in passthrough mode when invalidate_cblocks is used.
+range's end value is "one past the end", meaning 5-10 expresses a range
+of values from 5 to 9. Each cblock must be expressed as a decimal
+value, in the future a variant message that takes cblock ranges
+expressed in hexidecimal may be needed to better support efficient
+invalidation of larger caches. The cache must be in passthrough mode
+when invalidate_cblocks is used.
invalidate_cblocks [<cblock>|<cblock begin>-<cblock end>]*
