[dm-devel] [PATCH v2 for-3.14] dm cache: add block sizes and total cache blocks to status output

[Mike Snitzer]

Improve cache_status to emit:
<metadata block size> <#used metadata blocks>/<#total metadata blocks>
<cache block size> <#used cache blocks>/<#total cache blocks>
...

Adding the block sizes allows for easier calculation of the overall size
of both the metadata and cache devices.  Adding <#total cache blocks>
provides useful context for how much of the cache is used.

While updating the status documentation in cache.txt spaces were
tabify'd.

Requested-by: Jonathan Brassow <jbrassow at redhat.com>
Signed-off-by: Mike Snitzer <snitzer at redhat.com>
---
 Documentation/device-mapper/cache.txt |   48 ++++++++++++++++++---------------
 drivers/md/dm-cache-target.c          |   14 ++++++---
 2 files changed, 35 insertions(+), 27 deletions(-)

diff --git a/Documentation/device-mapper/cache.txt b/Documentation/device-mapper/cache.txt
index 719320b..742c4eb 100644
--- a/Documentation/device-mapper/cache.txt
+++ b/Documentation/device-mapper/cache.txt
@@ -217,36 +217,40 @@ the characteristics of a specific policy, always request it by name.
 Status
 ------
 
-<#used metadata blocks>/<#total metadata blocks> <#read hits> <#read misses>
-<#write hits> <#write misses> <#demotions> <#promotions> <#blocks in cache>
-<#dirty> <#features> <features>* <#core args> <core args>* <#policy args>
-<policy args>*
-
-#used metadata blocks    : Number of metadata blocks used
-#total metadata blocks   : Total number of metadata blocks
-#read hits               : Number of times a READ bio has been mapped
+<metadata block size> <#used metadata blocks>/<#total metadata blocks>
+<cache block size> <#used cache blocks>/<#total cache blocks>
+<#read hits> <#read misses> <#write hits> <#write misses>
+<#demotions> <#promotions> <#dirty> <#features> <features>*
+<#core args> <core args>* <#policy args> <policy args>*
+
+metadata block size	 : Fixed block size for each metadata block
+#used metadata blocks	 : Number of metadata blocks used
+#total metadata blocks	 : Total number of metadata blocks
+cache block size	 : Configurable block size for the cache device
+#used cache blocks	 : Number of blocks resident in the cache
+#total cache blocks	 : Total number of cache blocks
+#read hits		 : Number of times a READ bio has been mapped
 			     to the cache
-#read misses             : Number of times a READ bio has been mapped
+#read misses		 : Number of times a READ bio has been mapped
 			     to the origin
-#write hits              : Number of times a WRITE bio has been mapped
+#write hits		 : Number of times a WRITE bio has been mapped
 			     to the cache
-#write misses            : Number of times a WRITE bio has been
+#write misses		 : Number of times a WRITE bio has been
 			     mapped to the origin
-#demotions               : Number of times a block has been removed
+#demotions		 : Number of times a block has been removed
 			     from the cache
-#promotions              : Number of times a block has been moved to
+#promotions		 : Number of times a block has been moved to
 			     the cache
-#blocks in cache         : Number of blocks resident in the cache
-#dirty                   : Number of blocks in the cache that differ
+#dirty			 : Number of blocks in the cache that differ
 			     from the origin
-#feature args            : Number of feature args to follow
-feature args             : 'writethrough' (optional)
-#core args               : Number of core arguments (must be even)
-core args                : Key/value pairs for tuning the core
+#feature args		 : Number of feature args to follow
+feature args		 : 'writethrough' (optional)
+#core args		 : Number of core arguments (must be even)
+core args		 : Key/value pairs for tuning the core
 			     e.g. migration_threshold
-#policy args             : Number of policy arguments to follow (must be even)
-policy args              : Key/value pairs
-			     e.g. 'sequential_threshold 1024
+#policy args		 : Number of policy arguments to follow (must be even)
+policy args		 : Key/value pairs
+			     e.g. sequential_threshold
 
 Messages
 --------
diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c
index 1b1469e..9ad7a2f 100644
--- a/drivers/md/dm-cache-target.c
+++ b/drivers/md/dm-cache-target.c
@@ -2826,9 +2826,10 @@ static void cache_resume(struct dm_target *ti)
 /*
  * Status format:
  *
- * <#used metadata blocks>/<#total metadata blocks>
+ * <metadata block size> <#used metadata blocks>/<#total metadata blocks>
+ * <cache block size> <#used cache blocks>/<#total cache blocks>
  * <#read hits> <#read misses> <#write hits> <#write misses>
- * <#demotions> <#promotions> <#blocks in cache> <#dirty>
+ * <#demotions> <#promotions> <#dirty>
  * <#features> <features>*
  * <#core args> <core args>
  * <#policy args> <policy args>*
@@ -2869,17 +2870,20 @@ static void cache_status(struct dm_target *ti, status_type_t type,
 
 		residency = policy_residency(cache->policy);
 
-		DMEMIT("%llu/%llu %u %u %u %u %u %u %llu %u ",
+		DMEMIT("%u %llu/%llu %u %llu/%llu %u %u %u %u %u %u %llu ",
+		       (unsigned)(DM_CACHE_METADATA_BLOCK_SIZE >> SECTOR_SHIFT),
 		       (unsigned long long)(nr_blocks_metadata - nr_free_blocks_metadata),
 		       (unsigned long long)nr_blocks_metadata,
+		       cache->sectors_per_block,
+		       (unsigned long long) from_cblock(residency),
+		       (unsigned long long) from_cblock(cache->cache_size),
 		       (unsigned) atomic_read(&cache->stats.read_hit),
 		       (unsigned) atomic_read(&cache->stats.read_miss),
 		       (unsigned) atomic_read(&cache->stats.write_hit),
 		       (unsigned) atomic_read(&cache->stats.write_miss),
 		       (unsigned) atomic_read(&cache->stats.demotion),
 		       (unsigned) atomic_read(&cache->stats.promotion),
-		       (unsigned long long) from_cblock(residency),
-		       cache->nr_dirty);
+		       (unsigned long long) from_cblock(cache->nr_dirty));
 
 		if (writethrough_mode(&cache->features))
 			DMEMIT("1 writethrough ");
-- 
1.7.4.4