evms_snapshot.h

unxi下共享内存的使用

/* -*- linux-c -*- */
/*
 *
 *   Copyright (c) International Business Machines  Corp., 2000
 *
 *   This program is free software;  you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation; either version 2 of the License, or 
 *   (at your option) any later version.
 * 
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY;  without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See
 *   the GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program;  if not, write to the Free Software 
 *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */
/*
 * linux/include/linux/evms_snapshot.h
 *
 * EVMS Snapshot Feature kernel header file
 *
 */

#ifndef __EVMS_SNAPSHOT_INCLUDED__
#define __EVMS_SNAPSHOT_INCLUDED__

#define	EVMS_SNAPSHOT_VERSION_MAJOR		2
#define EVMS_SNAPSHOT_VERSION_MINOR		0
#define EVMS_SNAPSHOT_VERSION_PATCHLEVEL	0

#define EVMS_SNAPSHOT_FEATURE_ID		104

#define EVMS_SNAPSHOT_SIGNATURE	0x536e4170	// SnAp
#define MAX_HASH_CHAIN_ENTRIES	10

#define EVMS_SNAPSHOT		0x01		// Status flags
#define EVMS_SNAPSHOT_ORG	0x02
#define EVMS_SNAPSHOT_DISABLED	0x04
#define EVMS_SNAPSHOT_FULL	0x08
#define EVMS_SNAPSHOT_QUIESCED	0x10
#define EVMS_SNAPSHOT_WRITEABLE 0x20

						// option definitions
#define SNAP_OPTION_ORG_VOLUME_NAME     "original"   // original volume   
#define SNAP_OPTION_ORG_VOLUME_INDEX    0            // original volume   
#define SNAP_OPTION_SNAPSHOT_NAME       "snapshot"   // snapshot volume   
#define SNAP_OPTION_SNAPSHOT_INDEX      1            // snapshot volume   
#define SNAP_OPTION_CHUNKSIZE_NAME      "chunksize"  // chunksize   
#define SNAP_OPTION_CHUNKSIZE_INDEX     2            // chunksize  
#define SNAP_OPTION_WRITEABLE_NAME      "writeable"  // writeable snapshot
#define SNAP_OPTION_WRITEABLE_INDEX     3            // writeable snapshot

#define SNAPSHOT_DEFAULT_CHUNK_SIZE 128  	     //sectors
#define SNAPSHOT_MIN_CHUNK_SIZE     16		     // 8k
#define SNAPSHOT_MAX_CHUNK_SIZE     2048	     // = 1Meg
#define SNAPSHOT_CHUNK_BUFFER_SIZE  128  	     // copy buffer

#define SNAPSHOT_QUERY_PERCENT_FULL 1                // ioctl internal command to query percent full

#define SECTOR_SIZE 512

// description of on disk meta data sector for snapshot feature
typedef struct _snapshot_metadata {
/* 0*/	u_int32_t  	            	signature;
/* 4*/	u_int32_t       	        CRC;
/* 8*/	evms_version_t          	version;		/* structure version */
/*12*/	u_int32_t			flags;
/*16*/	char				original_volume[128];
/*144*/	u_int64_t			original_size;
/*152*/	u_int64_t         	    	lba_of_COW_table;
/*160*/	u_int64_t              		lba_of_first_chunk;
/*168*/	u_int32_t			chunk_size;          // in sectors
/*172*/	u_int32_t			total_chunks;        
} snapshot_metadata_t;


#ifdef __KERNEL__

// Entries in the snapshot remapping structure
typedef struct _snapshot_hash_entry {
	unsigned long long		org_chunk;
	unsigned long long		snap_chunk;
	struct _snapshot_hash_entry	* next;
	struct _snapshot_hash_entry	* prev;
} snapshot_hash_entry_t;


typedef struct _snapshot_volume {
	evms_logical_node_t *   logical_node;           // node below us
	unsigned long		chunk_size;		// Sectors
	unsigned long		chunk_shift;		// shift value for chunk size
	unsigned long		num_chunks;		// in this volume
	unsigned long	        next_cow_entry;		// Index into current COW table
	unsigned long long	current_cow_sector;	// LOGICAL sector of current COW table
	unsigned long 		next_free_chunk;	// index of next free chunk (not LBA!)
	u_int64_t		cow_table[64];		// Pointer to one sector's worth of COW tables
	unsigned long		hash_table_size;        // size of the hash table for the remap
	unsigned long		flags;			// status flags
	snapshot_hash_entry_t	** snapshot_map;	// array of remapped chunks
	struct _snapshot_volume * snapshot_next;	// Linked list of volumes snapshotting this original
	struct _snapshot_volume * snapshot_org;		// Pointer to volume being snapshotted
	struct semaphore	snap_semaphore;		// Semaphore for locking of snapshots
	unsigned char		* chunk_data_buffer;	// Buffer for reading data when doing a copy-on-write
} snapshot_volume_t;

#else
typedef struct _snapshot_volume {
	storage_object_t *      object;		        // our exported object
	storage_object_t *      child_object;	        // our child object
	unsigned long		chunk_size;		// Sectors
	unsigned long		num_chunks;		// in this volume
	unsigned long	        next_cow_entry;		// Index into current COW table
	unsigned long long	current_cow_sector;	// LOGICAL sector of current COW table
	unsigned long 		next_free_chunk;	// index of next free chunk (not LBA!)
	u_int64_t		cow_table[64];		// Pointer to one sector's worth of COW tables
	unsigned long		hash_table_size;        // size of the hash table for the remap
	unsigned long		flags;			// status flags
//	snapshot_hash_entry_t	** snapshot_map;	// array of remapped chunks
	struct _snapshot_volume * snapshot_next;	// Linked list of volumes snapshotting this original
	struct _snapshot_volume * snapshot_org;		// Pointer to volume being snapshotted
//	struct semaphore	snap_semaphore;		// Semaphore for locking of snapshots
//	unsigned char		* chunk_data_buffer;	// Buffer for reading data when doing a copy-on-write
	snapshot_metadata_t     meta_data;              // copy of metadata if not original
} snapshot_volume_t;

#endif
#endif