（1）文件系统id结构：16个字符组成
struct ceph_fsid { unsigned char fsid[16];}; 以及对应的比较函数：
static inline int ceph_fsid_compare(const struct ceph_fsid *a, const struct ceph_fsid *b){ return memcmp(a, b, sizeof(*a));} （2）定义保留的snap的id宏
typedef __le64 ceph_snapid_t;#define CEPH_SNAPDIR ((__u64)(-1)) /* reserved for hidden .snap dir */#define CEPH_NOSNAP ((__u64)(-2)) /* "head", "live" revision */#define CEPH_MAXSNAP ((__u64)(-3)) /* largest valid snapid */struct ceph_timespec {//自定义的时间描述结构体 __le32 tv_sec; __le32 tv_nsec;} __attribute__ ((packed)); （3）对象布局宏：对象怎样放到放置组PG里面去（placement group）
#define CEPH_OBJECT_LAYOUT_HASH 1 //哈希#define CEPH_OBJECT_LAYOUT_LINEAR 2 //线性#define CEPH_OBJECT_LAYOUT_HASHINO 3 //哈希inodestruct ceph_object_layout {//对象布局 struct ceph_pg ol_pgid; /* raw pg, with _full_ ps precision. */ __le32 ol_stripe_unit; /* for per-object parity, if any */} __attribute__ ((packed)); （4）PG布局宏：PG怎样放置到存储设备上去
#define CEPH_PG_LAYOUT_CRUSH 0 //CRUSH算法，伪随机hash#define CEPH_PG_LAYOUT_HASH 1 //hash#define CEPH_PG_LAYOUT_LINEAR 2 //线性#define CEPH_PG_LAYOUT_HYBRID 3 #define CEPH_PG_MAX_SIZE 16 /* max # osds in a single pg */
（5）PG编码到一个64位
struct ceph_pg { __le16 preferred; /* preferred primary osd */参考主osd __le16 ps; /* placement seed */放置种子 __le32 pool; /* object pool */对象池} __attribute__ ((packed)); 下面是两种对象池的宏定义：
#define CEPH_PG_TYPE_REP 1 //冗余#define CEPH_PG_TYPE_RAID4 2 //raid
控制PG数量的函数定义：保证b小于bmask并且bmask是2的n次方的最小值
随着时间b的增加产生一个稳定的映射
static inline int ceph_stable_mod(int x, int b, int bmask){ if ((x & bmask) < b) return x & bmask; else return x & (bmask >> 1);} （6）划时代和版本的组合，被用作存储层的序列化突变
struct ceph_eversion { __le32 epoch; __le64 version;} __attribute__ ((packed)); （7）osd（对象存储设备）映射位的宏定义：
#define CEPH_OSD_EXISTS (1<<0) //osd存在#define CEPH_OSD_UP (1<<1) //#define CEPH_OSD_AUTOOUT (1<<2) /* osd was automatically marked out */自动标出#define CEPH_OSD_NEW (1<<3) /* osd is new, never marked in */新的，从未标记extern const char *ceph_osd_state_name(int s);//得到对应的名字，实现如下：const char *ceph_osd_state_name(int s){ switch (s) { case CEPH_OSD_EXISTS: return "exists"; case CEPH_OSD_UP: return "up"; case CEPH_OSD_AUTOOUT: return "autoout"; case CEPH_OSD_NEW: return "new"; default: return "???"; } }/* osd weights. fixed point value: 0x10000 == 1.0 ("in"), 0 == "out" */osd的权重值：最大为0x10000相当于1.0，最小为0#define CEPH_OSD_IN 0x10000#define CEPH_OSD_OUT 0 （8）osd映射标志位定义：
#define CEPH_OSDMAP_NEARFULL (1<<0) /* sync writes (near ENOSPC) */#define CEPH_OSDMAP_FULL (1<<1) /* no data writes (ENOSPC) */#define CEPH_OSDMAP_PAUSERD (1<<2) /* pause all reads */暂停所有读#define CEPH_OSDMAP_PAUSEWR (1<<3) /* pause all writes */#define CEPH_OSDMAP_PAUSEREC (1<<4) /* pause recovery *//* * The error code to return when an OSD can't handle a write * because it is too large. */因为数据太大导致OSD不能处理些时返回的错误代码#define OSD_WRITETOOBIG EMSGSIZE
（9）osd的操作
#define CEPH_OSD_OP_MODE 0xf000 //操作模式#define CEPH_OSD_OP_MODE_RD 0x1000 //读#define CEPH_OSD_OP_MODE_WR 0x2000 //写#define CEPH_OSD_OP_MODE_RMW 0x3000 //读修改写#define CEPH_OSD_OP_MODE_SUB 0x4000 //子操作#define CEPH_OSD_OP_TYPE 0x0f00 //操作类型#define CEPH_OSD_OP_TYPE_LOCK 0x0100 //锁#define CEPH_OSD_OP_TYPE_DATA 0x0200 //数据#define CEPH_OSD_OP_TYPE_ATTR 0x0300 //属性#define CEPH_OSD_OP_TYPE_EXEC 0x0400 //执行#define CEPH_OSD_OP_TYPE_PG 0x0500 //PG#define CEPH_OSD_OP_TYPE_MULTI 0x0600 /* multiobject */多对象
下面是定义操作模式与类型组合的枚举：
enum { CEPH_OSD_OP_READ = CEPH_OSD_OP_MODE_RD | CEPH_OSD_OP_TYPE_DATA | 1,中间省略很多... CEPH_OSD_OP_PGLS_FILTER = CEPH_OSD_OP_MODE_RD | CEPH_OSD_OP_TYPE_PG | 2,}; 以及定义了判断操作是否为每一种类型或模式的操作，如判断是否为锁操作类型的函数如下：
static inline int ceph_osd_op_type_lock(int op){ return (op & CEPH_OSD_OP_TYPE) == CEPH_OSD_OP_TYPE_LOCK;} 返回操作名称的函数：
extern const char *ceph_osd_op_name(int op);
（10）osd操作标志定义：有详细的英文注释了
enum { CEPH_OSD_FLAG_ACK = 0x0001, /* want (or is) "ack" ack */ CEPH_OSD_FLAG_ONNVRAM = 0x0002, /* want (or is) "onnvram" ack */ CEPH_OSD_FLAG_ONDISK = 0x0004, /* want (or is) "ondisk" ack */ CEPH_OSD_FLAG_RETRY = 0x0008, /* resend attempt */ CEPH_OSD_FLAG_READ = 0x0010, /* op may read */ CEPH_OSD_FLAG_WRITE = 0x0020, /* op may write */ CEPH_OSD_FLAG_ORDERSNAP = 0x0040, /* EOLDSNAP if snapc is out of order */ CEPH_OSD_FLAG_PEERSTAT_OLD = 0x0080, /* DEPRECATED msg includes osd_peer_stat */ CEPH_OSD_FLAG_BALANCE_READS = 0x0100, CEPH_OSD_FLAG_PARALLELEXEC = 0x0200, /* execute op in parallel */ CEPH_OSD_FLAG_PGOP = 0x0400, /* pg op, no object */ CEPH_OSD_FLAG_EXEC = 0x0800, /* op may exec */ CEPH_OSD_FLAG_EXEC_PUBLIC = 0x1000, /* op may exec (public) */ CEPH_OSD_FLAG_LOCALIZE_READS = 0x2000, /* read from nearby replica, if any */ CEPH_OSD_FLAG_RWORDERED = 0x4000, /* order wrt concurrent reads */};enum { CEPH_OSD_OP_FLAG_EXCL = 1, /* EXCL object create */ CEPH_OSD_OP_FLAG_FAILOK = 2, /* continue despite failure */};#define EOLDSNAPC 85 /* ORDERSNAP flag set; writer has old snapc*/#define EBLACKLISTED 108 /* blacklisted */ （11）扩展属性比较操作枚举定义：
enum { CEPH_OSD_CMPXATTR_OP_NOP = 0, CEPH_OSD_CMPXATTR_OP_EQ = 1, CEPH_OSD_CMPXATTR_OP_NE = 2, CEPH_OSD_CMPXATTR_OP_GT = 3, CEPH_OSD_CMPXATTR_OP_GTE = 4, CEPH_OSD_CMPXATTR_OP_LT = 5, CEPH_OSD_CMPXATTR_OP_LTE = 6};enum { CEPH_OSD_CMPXATTR_MODE_STRING = 1, CEPH_OSD_CMPXATTR_MODE_U64 = 2}; （12）osd操作结构体封装定义，可能是来至数据有效负载：
struct ceph_osd_op { __le16 op; /* CEPH_OSD_OP_* */ __le32 flags; /* CEPH_OSD_FLAG_* */ union {//各种数据包格式定义 struct { __le64 offset, length;//偏移量和长度 __le64 truncate_size; __le32 truncate_seq; } __attribute__ ((packed)) extent; struct { __le32 name_len; __le32 value_len; __u8 cmp_op; /* CEPH_OSD_CMPXATTR_OP_* */ __u8 cmp_mode; /* CEPH_OSD_CMPXATTR_MODE_* */ } __attribute__ ((packed)) xattr; struct { __u8 class_len; __u8 method_len; __u8 argc; __le32 indata_len; } __attribute__ ((packed)) cls; struct { __le64 count; __le32 start_epoch; /* for the pgls sequence */ } __attribute__ ((packed)) pgls; struct { __le64 snapid; } __attribute__ ((packed)) snap; struct { __le64 cookie; __le64 ver; __u8 flag; /* 0 = unwatch, 1 = watch */ } __attribute__ ((packed)) watch; struct { __le64 offset, length; __le64 src_offset; } __attribute__ ((packed)) clonerange; }; __le32 payload_len;//数据长度} __attribute__ ((packed));struct ceph_osd_reply_head {//回复头部 __le32 client_inc; /* client incarnation */ __le32 flags; struct ceph_object_layout layout; __le32 osdmap_epoch; struct ceph_eversion reassert_version; /* for replaying uncommitted */ __le32 result; /* result code */ __le32 object_len; /* length of object name */ __le32 num_ops; //操作数量 struct ceph_osd_op ops[0]; /* ops[], object */存放所有操作} __attribute__ ((packed));