md_p.h

unxi下共享内存的使用

/*
   md_p.h : physical layout of Linux RAID devices
          Copyright (C) 1996-98 Ingo Molnar, Gadi Oxman
	  
   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, or (at your option)
   any later version.
   
   You should have received a copy of the GNU General Public License
   (for example /usr/src/linux/COPYING); if not, write to the Free
   Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.  
*/

#ifndef _MD_P_H
#define _MD_P_H

/*
 * RAID superblock.
 *
 * The RAID superblock maintains some statistics on each RAID configuration.
 * Each real device in the RAID set contains it near the end of the device.
 * Some of the ideas are copied from the ext2fs implementation.
 *
 * We currently use 4096 bytes as follows:
 *
 *	word offset	function
 *
 *	   0  -    31	Constant generic RAID device information.
 *        32  -    63   Generic state information.
 *	  64  -   127	Personality specific information.
 *	 128  -   511	12 32-words descriptors of the disks in the raid set.
 *	 512  -   911	Reserved.
 *	 912  -  1023	Disk specific descriptor.
 */

/*
 * If x is the real device size in bytes, we return an apparent size of:
 *
 *	y = (x & ~(MD_RESERVED_BYTES - 1)) - MD_RESERVED_BYTES
 *
 * and place the 4kB superblock at offset y.
 */
#define MD_RESERVED_BYTES		(64 * 1024)
#define MD_RESERVED_SECTORS		(MD_RESERVED_BYTES / 512)
#define MD_RESERVED_BLOCKS		(MD_RESERVED_BYTES / BLOCK_SIZE)

#define MD_NEW_SIZE_SECTORS(x)		((x & ~(MD_RESERVED_SECTORS - 1)) - MD_RESERVED_SECTORS)
#define MD_NEW_SIZE_BLOCKS(x)		((x & ~(MD_RESERVED_BLOCKS - 1)) - MD_RESERVED_BLOCKS)

#define MD_SB_BYTES			4096
#define MD_SB_WORDS			(MD_SB_BYTES / 4)
#define MD_SB_BLOCKS			(MD_SB_BYTES / BLOCK_SIZE)
#define MD_SB_SECTORS			(MD_SB_BYTES / 512)

/*
 * The following are counted in 32-bit words
 */
#define	MD_SB_GENERIC_OFFSET		0
#define MD_SB_PERSONALITY_OFFSET	64
#define MD_SB_DISKS_OFFSET		128
#define MD_SB_DESCRIPTOR_OFFSET		992

#define MD_SB_GENERIC_CONSTANT_WORDS	32
#define MD_SB_GENERIC_STATE_WORDS	32
#define MD_SB_GENERIC_WORDS		(MD_SB_GENERIC_CONSTANT_WORDS + MD_SB_GENERIC_STATE_WORDS)
#define MD_SB_PERSONALITY_WORDS		64
#define MD_SB_DESCRIPTOR_WORDS		32
#define MD_SB_DISKS			27
#define MD_SB_DISKS_WORDS		(MD_SB_DISKS*MD_SB_DESCRIPTOR_WORDS)
#define MD_SB_RESERVED_WORDS		(1024 - MD_SB_GENERIC_WORDS - MD_SB_PERSONALITY_WORDS - MD_SB_DISKS_WORDS - MD_SB_DESCRIPTOR_WORDS)
#define MD_SB_EQUAL_WORDS		(MD_SB_GENERIC_WORDS + MD_SB_PERSONALITY_WORDS + MD_SB_DISKS_WORDS)

/*
 * Device "operational" state bits
 */
#define MD_DISK_FAULTY		0 /* disk is faulty / operational */
#define MD_DISK_ACTIVE		1 /* disk is running or spare disk */
#define MD_DISK_SYNC		2 /* disk is in sync with the raid set */
#define MD_DISK_REMOVED		3 /* disk is in sync with the raid set */

typedef struct mdp_device_descriptor_s {
	__u32 number;		/* 0 Device number in the entire set	      */
	__u32 major;		/* 1 Device major number		      */
	__u32 minor;		/* 2 Device minor number		      */
	__u32 raid_disk;	/* 3 The role of the device in the raid set   */
	__u32 state;		/* 4 Operational state			      */
	__u32 reserved[MD_SB_DESCRIPTOR_WORDS - 5];
} mdp_disk_t;

#define MD_SB_MAGIC		0xa92b4efc

/*
 * Superblock state bits
 */
#define MD_SB_CLEAN		0
#define MD_SB_ERRORS		1

typedef struct mdp_superblock_s {
	/*
	 * Constant generic information
	 */
	__u32 md_magic;		/*  0 MD identifier 			      */
	__u32 major_version;	/*  1 major version to which the set conforms */
	__u32 minor_version;	/*  2 minor version ...			      */
	__u32 patch_version;	/*  3 patchlevel version ...		      */
	__u32 gvalid_words;	/*  4 Number of used words in this section    */
	__u32 set_uuid0;	/*  5 Raid set identifier		      */
	__u32 ctime;		/*  6 Creation time			      */
	__u32 level;		/*  7 Raid personality			      */
	__u32 size;		/*  8 Apparent size of each individual disk   */
	__u32 nr_disks;		/*  9 total disks in the raid set	      */
	__u32 raid_disks;	/* 10 disks in a fully functional raid set    */
	__u32 md_minor;		/* 11 preferred MD minor device number	      */
	__u32 not_persistent;	/* 12 does it have a persistent superblock    */
	__u32 set_uuid1;	/* 13 Raid set identifier #2		      */
	__u32 set_uuid2;	/* 14 Raid set identifier #3		      */
	__u32 set_uuid3;	/* 15 Raid set identifier #4		      */
	__u32 gstate_creserved[MD_SB_GENERIC_CONSTANT_WORDS - 16];

	/*
	 * Generic state information
	 */
	__u32 utime;		/*  0 Superblock update time		      */
	__u32 state;		/*  1 State bits (clean, ...)		      */
	__u32 active_disks;	/*  2 Number of currently active disks	      */
	__u32 working_disks;	/*  3 Number of working disks		      */
	__u32 failed_disks;	/*  4 Number of failed disks		      */
	__u32 spare_disks;	/*  5 Number of spare disks		      */
	__u32 sb_csum;		/*  6 checksum of the whole superblock        */
#ifdef __BIG_ENDIAN
	__u32 events_hi;	/*  7 high-order of superblock update count   */
	__u32 events_lo;	/*  8 low-order of superblock update count    */
#else
	__u32 events_lo;	/*  7 low-order of superblock update count    */
	__u32 events_hi;	/*  8 high-order of superblock update count   */
#endif
	__u32 gstate_sreserved[MD_SB_GENERIC_STATE_WORDS - 9];

	/*
	 * Personality information
	 */
	__u32 layout;		/*  0 the array's physical layout	      */
	__u32 chunk_size;	/*  1 chunk size in bytes		      */
	__u32 root_pv;		/*  2 LV root PV */
	__u32 root_block;	/*  3 LV root block */
	__u32 pstate_reserved[MD_SB_PERSONALITY_WORDS - 4];

	/*
	 * Disks information
	 */
	mdp_disk_t disks[MD_SB_DISKS];

	/*
	 * Reserved
	 */
	__u32 reserved[MD_SB_RESERVED_WORDS];

	/*
	 * Active descriptor
	 */
	mdp_disk_t this_disk;

} mdp_super_t;

static inline __u64 md_event(mdp_super_t *sb) {
	__u64 ev = sb->events_hi;
	return (ev<<32)| sb->events_lo;
}

#endif