[PATCH v4 04/13] dm exception store: snapshot-merge usage accounting

Mike Snitzer
2009-11-20T20:27:53Z

Conditionally adjust snapshot usage accounting if snapshot-merge is in
progress. Care is taken to preserve the established kernel<->userspace
interface.

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: Mikulas Patocka <mpatocka@redhat.com>
---
drivers/md/dm-snap-persistent.c | 21 ++++++++++++++++++++-
1 files changed, 20 insertions(+), 1 deletions(-)

diff --git a/drivers/md/dm-snap-persistent.c b/drivers/md/dm-snap-persistent.c
index 1f5752e..3cb609b 100644
--- a/drivers/md/dm-snap-persistent.c
+++ b/drivers/md/dm-snap-persistent.c
@@ -91,6 +91,7 @@ struct pstore {
struct dm_exception_store *store;
int version;
int valid;
+ int merging; /* 1 if there is merging going on */
uint32_t exceptions_per_area;

/*
@@ -506,7 +507,20 @@ static void persistent_usage(struct dm_exception_store *store,
{
struct pstore *ps = get_info(store);

- *sectors_allocated = ps->next_free * store->chunk_size;
+ /*
+ * Must maintain the fact that DM reports all metadata chunks
+ * in 'sectors_allocated'
+ * - preserves the established kernel<->userspace interface
+ * - snapshot-merge must account for the first two metadata
+ * chunks in its 'sectors_allocated'
+ */
+ if (!ps->merging) {
+ *sectors_allocated = ps->next_free * store->chunk_size;
+ } else {
+ *sectors_allocated =
+ (area_location(ps, ps->current_area) - 1 +
+ ps->current_committed + 2) * store->chunk_size;
+ }
*total_sectors = get_dev_size(dm_snap_cow(store->snap)->bdev);

/*
@@ -608,6 +622,8 @@ static int persistent_prepare_exception(struct dm_exception_store *store,
chunk_t next_free;
sector_t size = get_dev_size(dm_snap_cow(store->snap)->bdev);

+ ps->merging = 0;
+
/* Is there enough room ? */
if (size < ((ps->next_free + 1) * store->chunk_size))
return -ENOSPC;
@@ -696,6 +712,8 @@ static int persistent_prepare_merge(struct dm_exception_store *store,
struct pstore *ps = get_info(store);
struct disk_exception de;

+ ps->merging = 1;
+
if (!ps->current_committed) {
if (!ps->current_area)
return 0;
@@ -767,6 +785,7 @@ static int persistent_ctr(struct dm_exception_store *store,

ps->store = store;
ps->valid = 1;
+ ps->merging = 0;
ps->version = SNAPSHOT_DISK_VERSION;
ps->area = NULL;
ps->zero_area = NULL;
--
1.6.5.2