1 files changed, 230 insertions, 0 deletions
diff --git a/drivers/md/dm-snap.h b/drivers/md/dm-snap.h
new file mode 100644
index 0000000..99c0106
--- /dev/null
+++ b/drivers/md/dm-snap.h
@@ -0,0 +1,230 @@
+/*
+ * dm-snapshot.c
+ *
+ * Copyright (C) 2001-2002 Sistina Software (UK) Limited.
+ *
+ * This file is released under the GPL.
+ */
+
+#ifndef DM_SNAPSHOT_H
+#define DM_SNAPSHOT_H
+
+#include <linux/device-mapper.h>
+#include "dm-bio-list.h"
+#include <linux/blkdev.h>
+#include <linux/workqueue.h>
+
+struct exception_table {
+	uint32_t hash_mask;
+	unsigned hash_shift;
+	struct list_head *table;
+};
+
+/*
+ * The snapshot code deals with largish chunks of the disk at a
+ * time. Typically 32k - 512k.
+ */
+typedef sector_t chunk_t;
+
+/*
+ * An exception is used where an old chunk of data has been
+ * replaced by a new one.
+ * If chunk_t is 64 bits in size, the top 8 bits of new_chunk hold the number
+ * of chunks that follow contiguously.  Remaining bits hold the number of the
+ * chunk within the device.
+ */
+struct dm_snap_exception {
+	struct list_head hash_list;
+
+	chunk_t old_chunk;
+	chunk_t new_chunk;
+};
+
+/*
+ * Funtions to manipulate consecutive chunks
+ */
+#  if defined(CONFIG_LBD) || (BITS_PER_LONG == 64)
+#    define DM_CHUNK_CONSECUTIVE_BITS 8
+#    define DM_CHUNK_NUMBER_BITS 56
+
+static inline chunk_t dm_chunk_number(chunk_t chunk)
+{
+	return chunk & (chunk_t)((1ULL << DM_CHUNK_NUMBER_BITS) - 1ULL);
+}
+
+static inline unsigned dm_consecutive_chunk_count(struct dm_snap_exception *e)
+{
+	return e->new_chunk >> DM_CHUNK_NUMBER_BITS;
+}
+
+static inline void dm_consecutive_chunk_count_inc(struct dm_snap_exception *e)
+{
+	e->new_chunk += (1ULL << DM_CHUNK_NUMBER_BITS);
+
+	BUG_ON(!dm_consecutive_chunk_count(e));
+}
+
+#  else
+#    define DM_CHUNK_CONSECUTIVE_BITS 0
+
+static inline chunk_t dm_chunk_number(chunk_t chunk)
+{
+	return chunk;
+}
+
+static inline unsigned dm_consecutive_chunk_count(struct dm_snap_exception *e)
+{
+	return 0;
+}
+
+static inline void dm_consecutive_chunk_count_inc(struct dm_snap_exception *e)
+{
+}
+
+#  endif
+
+/*
+ * Abstraction to handle the meta/layout of exception stores (the
+ * COW device).
+ */
+struct exception_store {
+
+	/*
+	 * Destroys this object when you've finished with it.
+	 */
+	void (*destroy) (struct exception_store *store);
+
+	/*
+	 * The target shouldn't read the COW device until this is
+	 * called.
+	 */
+	int (*read_metadata) (struct exception_store *store);
+
+	/*
+	 * Find somewhere to store the next exception.
+	 */
+	int (*prepare_exception) (struct exception_store *store,
+				  struct dm_snap_exception *e);
+
+	/*
+	 * Update the metadata with this exception.
+	 */
+	void (*commit_exception) (struct exception_store *store,
+				  struct dm_snap_exception *e,
+				  void (*callback) (void *, int success),
+				  void *callback_context);
+
+	/*
+	 * The snapshot is invalid, note this in the metadata.
+	 */
+	void (*drop_snapshot) (struct exception_store *store);
+
+	/*
+	 * Return how full the snapshot is.
+	 */
+	void (*fraction_full) (struct exception_store *store,
+			       sector_t *numerator,
+			       sector_t *denominator);
+
+	struct dm_snapshot *snap;
+	void *context;
+};
+
+#define DM_TRACKED_CHUNK_HASH_SIZE	16
+#define DM_TRACKED_CHUNK_HASH(x)	((unsigned long)(x) & \
+					 (DM_TRACKED_CHUNK_HASH_SIZE - 1))
+
+struct dm_snapshot {
+	struct rw_semaphore lock;
+	struct dm_target *ti;
+
+	struct dm_dev *origin;
+	struct dm_dev *cow;
+
+	/* List of snapshots per Origin */
+	struct list_head list;
+
+	/* Size of data blocks saved - must be a power of 2 */
+	chunk_t chunk_size;
+	chunk_t chunk_mask;
+	chunk_t chunk_shift;
+
+	/* You can't use a snapshot if this is 0 (e.g. if full) */
+	int valid;
+
+	/* Origin writes don't trigger exceptions until this is set */
+	int active;
+
+	/* Used for display of table */
+	char type;
+
+	mempool_t *pending_pool;
+
+	atomic_t pending_exceptions_count;
+
+	struct exception_table pending;
+	struct exception_table complete;
+
+	/*
+	 * pe_lock protects all pending_exception operations and access
+	 * as well as the snapshot_bios list.
+	 */
+	spinlock_t pe_lock;
+
+	/* The on disk metadata handler */
+	struct exception_store store;
+
+	struct dm_kcopyd_client *kcopyd_client;
+
+	/* Queue of snapshot writes for ksnapd to flush */
+	struct bio_list queued_bios;
+	struct work_struct queued_bios_work;
+
+	/* Chunks with outstanding reads */
+	mempool_t *tracked_chunk_pool;
+	spinlock_t tracked_chunk_lock;
+	struct hlist_head tracked_chunk_hash[DM_TRACKED_CHUNK_HASH_SIZE];
+};
+
+/*
+ * Used by the exception stores to load exceptions hen
+ * initialising.
+ */
+int dm_add_exception(struct dm_snapshot *s, chunk_t old, chunk_t new);
+
+/*
+ * Constructor and destructor for the default persistent
+ * store.
+ */
+int dm_create_persistent(struct exception_store *store);
+
+int dm_create_transient(struct exception_store *store);
+
+/*
+ * Return the number of sectors in the device.
+ */
+static inline sector_t get_dev_size(struct block_device *bdev)
+{
+	return bdev->bd_inode->i_size >> SECTOR_SHIFT;
+}
+
+static inline chunk_t sector_to_chunk(struct dm_snapshot *s, sector_t sector)
+{
+	return (sector & ~s->chunk_mask) >> s->chunk_shift;
+}
+
+static inline sector_t chunk_to_sector(struct dm_snapshot *s, chunk_t chunk)
+{
+	return chunk << s->chunk_shift;
+}
+
+static inline int bdev_equal(struct block_device *lhs, struct block_device *rhs)
+{
+	/*
+	 * There is only ever one instance of a particular block
+	 * device so we can compare pointers safely.
+	 */
+	return lhs == rhs;
+}
+
+#endif