Add prepare_merge() and commit_merge() methods to the exception store to
allow for snapshot chunks to be removed from the exception store as the
chunks are merged back into the origin.
prepare_merge() retrieves the details of the last exception in the store
in preparation for that chunk to be merged back into the origin.
commit_merge() is then later used to remove that same exception from the
store once the merge has completed.
Signed-off-by: Mark McLoughlin <markmc@xxxxxxxxxx>
---
drivers/md/dm-exception-store.c | 69 +++++++++++++++++++++++++++++++++++++++
drivers/md/dm-snap.h | 12 +++++++
2 files changed, 81 insertions(+), 0 deletions(-)
diff --git a/drivers/md/dm-exception-store.c b/drivers/md/dm-exception-store.c
index 02fd3e9..4fd5381 100644
--- a/drivers/md/dm-exception-store.c
+++ b/drivers/md/dm-exception-store.c
@@ -624,6 +624,71 @@ static void persistent_commit(struct exception_store *store,
}
}
+/* Given an exception index within a certain area, return the
+ * corresponding chunk index.
+ */
+static inline uint32_t exception_to_chunk(uint32_t area,
+ uint32_t exceptions_per_area,
+ uint32_t exception)
+{
+ /* Header followed by sets of (metadata chunk, exceptions_per_area chunks)
+ */
+ return 1 + (area * (1 + exceptions_per_area)) + 1 + exception;
+}
+
+static int persistent_prepare_merge(struct exception_store *store,
+ struct dm_snap_exception *e,
+ int *empty)
+{
+ struct pstore *ps = get_info(store);
+ struct disk_exception de;
+ int r;
+
+ *empty = 0;
+
+ if (ps->current_committed == 0) {
+ if (ps->current_area == 0) {
+ *empty = 1;
+ return 0;
+ }
+
+ r = area_io(ps, ps->current_area - 1, READ);
+ if (r)
+ return r;
+
+ ps->current_committed = ps->exceptions_per_area - 1;
+ } else {
+ ps->current_committed--;
+ }
+
+ read_exception(ps, ps->current_committed, &de);
+
+ e->old_chunk = de.old_chunk;
+ e->new_chunk = de.new_chunk;
+
+ ps->next_free = exception_to_chunk(ps->current_area,
+ ps->exceptions_per_area,
+ ps->current_committed);
+
+ return 0;
+}
+
+static void persistent_commit_merge(struct exception_store *store)
+{
+ struct pstore *ps = get_info(store);
+ struct disk_exception de;
+ int r;
+
+ read_exception(ps, ps->current_committed, &de);
+
+ de.new_chunk = 0;
+ write_exception(ps, ps->current_committed, &de);
+
+ r = area_io(ps, ps->current_area, WRITE);
+ if (r)
+ ps->valid = 0;
+}
+
static void persistent_drop(struct exception_store *store)
{
struct pstore *ps = get_info(store);
@@ -664,6 +729,8 @@ int dm_create_persistent(struct exception_store *store)
store->read_metadata = persistent_read_metadata;
store->prepare_exception = persistent_prepare;
store->commit_exception = persistent_commit;
+ store->prepare_merge = persistent_prepare_merge;
+ store->commit_merge = persistent_commit_merge;
store->drop_snapshot = persistent_drop;
store->fraction_full = persistent_fraction_full;
store->context = ps;
@@ -727,6 +794,8 @@ int dm_create_transient(struct exception_store *store)
store->read_metadata = transient_read_metadata;
store->prepare_exception = transient_prepare;
store->commit_exception = transient_commit;
+ store->prepare_merge = NULL;
+ store->commit_merge = NULL;
store->drop_snapshot = NULL;
store->fraction_full = transient_fraction_full;
diff --git a/drivers/md/dm-snap.h b/drivers/md/dm-snap.h
index 93bce5d..8b02a42 100644
--- a/drivers/md/dm-snap.h
+++ b/drivers/md/dm-snap.h
@@ -115,6 +115,18 @@ struct exception_store {
void *callback_context);
/*
+ * Prepare the next exception for merging.
+ */
+ int (*prepare_merge) (struct exception_store *store,
+ struct dm_snap_exception *e,
+ int *empty);
+
+ /*
+ * Remove the currently merging exception.
+ */
+ void (*commit_merge) (struct exception_store *store);
+
+ /*
* The snapshot is invalid, note this in the metadata.
*/
void (*drop_snapshot) (struct exception_store *store);
--
1.5.4.1
--
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