dm snapshot: add allocated metadata to snapshot status

Add number of sectors used by metadata to the end of the snapshot's status
line.

Renamed dm_exception_store_type's 'fraction_full' to 'usage'.  Renamed
arguments to be clearer about what is being returned.  Also added
'metadata_sectors'.

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

1 files changed, 17 insertions, 6 deletions

diff --git a/drivers/md/dm-snap-persistent.c b/drivers/md/dm-snap-persistent.c
index 24b8acd1be83..767065f6c5f3 100644
--- a/drivers/md/dm-snap-persistent.c
+++ b/drivers/md/dm-snap-persistent.c
@@ -489,11 +489,22 @@ static struct pstore *get_info(struct dm_exception_store *store)
         return (struct pstore *) store->context;
 }
 
-static void persistent_fraction_full(struct dm_exception_store *store,
-                                     sector_t *numerator, sector_t *denominator)
+static void persistent_usage(struct dm_exception_store *store,
+                             sector_t *total_sectors,
+                             sector_t *sectors_allocated,
+                             sector_t *metadata_sectors)
 {
-        *numerator = get_info(store)->next_free * store->chunk_size;
-        *denominator = get_dev_size(store->cow->bdev);
+        struct pstore *ps = get_info(store);
+
+        *sectors_allocated = ps->next_free * store->chunk_size;
+        *total_sectors = get_dev_size(store->cow->bdev);
+
+        /*
+         * First chunk is the fixed header.
+         * Then there are (ps->current_area + 1) metadata chunks, each one
+         * separated from the next by ps->exceptions_per_area data chunks.
+         */
+        *metadata_sectors = (ps->current_area + 2) * store->chunk_size;
 }
 
 static void persistent_dtr(struct dm_exception_store *store)
@@ -738,7 +749,7 @@ static struct dm_exception_store_type _persistent_type = {
         .prepare_exception = persistent_prepare_exception,
         .commit_exception = persistent_commit_exception,
         .drop_snapshot = persistent_drop_snapshot,
-        .fraction_full = persistent_fraction_full,
+        .usage = persistent_usage,
         .status = persistent_status,
 };
 
@@ -751,7 +762,7 @@ static struct dm_exception_store_type _persistent_compat_type = {
         .prepare_exception = persistent_prepare_exception,
         .commit_exception = persistent_commit_exception,
         .drop_snapshot = persistent_drop_snapshot,
-        .fraction_full = persistent_fraction_full,
+        .usage = persistent_usage,
         .status = persistent_status,
 };