dm snapshot: split out exception store implementations

Move the existing snapshot exception store implementations out into
separate files.  Later patches will place these behind a new
interface in preparation for alternative implementations.

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

1 files changed, 95 insertions, 0 deletions

diff --git a/drivers/md/dm-snap-transient.c b/drivers/md/dm-snap-transient.c
new file mode 100644
index 000000000000..2a781df57fef
--- /dev/null
+++ b/drivers/md/dm-snap-transient.c
@@ -0,0 +1,95 @@
+/*
+ * Copyright (C) 2001-2002 Sistina Software (UK) Limited.
+ * Copyright (C) 2006-2008 Red Hat GmbH
+ *
+ * This file is released under the GPL.
+ */
+
+#include "dm-exception-store.h"
+#include "dm-snap.h"
+
+#include <linux/mm.h>
+#include <linux/pagemap.h>
+#include <linux/vmalloc.h>
+#include <linux/slab.h>
+#include <linux/dm-io.h>
+
+#define DM_MSG_PREFIX "transient snapshot"
+
+/*-----------------------------------------------------------------
+ * Implementation of the store for non-persistent snapshots.
+ *---------------------------------------------------------------*/
+struct transient_c {
+        sector_t next_free;
+};
+
+static void transient_destroy(struct dm_exception_store *store)
+{
+        kfree(store->context);
+}
+
+static int transient_read_metadata(struct dm_exception_store *store)
+{
+        return 0;
+}
+
+static int transient_prepare(struct dm_exception_store *store,
+                             struct dm_snap_exception *e)
+{
+        struct transient_c *tc = (struct transient_c *) store->context;
+        sector_t size = get_dev_size(store->snap->cow->bdev);
+
+        if (size < (tc->next_free + store->snap->chunk_size))
+                return -1;
+
+        e->new_chunk = sector_to_chunk(store->snap, tc->next_free);
+        tc->next_free += store->snap->chunk_size;
+
+        return 0;
+}
+
+static void transient_commit(struct dm_exception_store *store,
+                             struct dm_snap_exception *e,
+                             void (*callback) (void *, int success),
+                             void *callback_context)
+{
+        /* Just succeed */
+        callback(callback_context, 1);
+}
+
+static void transient_fraction_full(struct dm_exception_store *store,
+                                    sector_t *numerator, sector_t *denominator)
+{
+        *numerator = ((struct transient_c *) store->context)->next_free;
+        *denominator = get_dev_size(store->snap->cow->bdev);
+}
+
+int dm_create_transient(struct dm_exception_store *store)
+{
+        struct transient_c *tc;
+
+        store->destroy = transient_destroy;
+        store->read_metadata = transient_read_metadata;
+        store->prepare_exception = transient_prepare;
+        store->commit_exception = transient_commit;
+        store->drop_snapshot = NULL;
+        store->fraction_full = transient_fraction_full;
+
+        tc = kmalloc(sizeof(struct transient_c), GFP_KERNEL);
+        if (!tc)
+                return -ENOMEM;
+
+        tc->next_free = 0;
+        store->context = tc;
+
+        return 0;
+}
+
+int dm_transient_snapshot_init(void)
+{
+        return 0;
+}
+
+void dm_transient_snapshot_exit(void)
+{
+}