text: /*
    drbd_int.h
  
    This file is part of DRBD by Philipp Reisner and Lars Ellenberg.
  
    Copyright (C) 2001-2008, LINBIT Information Technologies GmbH.
    Copyright (C) 1999-2008, Philipp Reisner <philipp.reisner@linbit.com>.
    Copyright (C) 2002-2008, Lars Ellenberg <lars.ellenberg@linbit.com>.
  
    drbd 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.
  
    drbd 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 drbd; see the file COPYING.  If not, write to
    the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
  
  */
  
  #ifndef _DRBD_INT_H
  #define _DRBD_INT_H
  
  #include <linux/compiler.h>
  #include <linux/types.h>
  #include <linux/version.h>
  #include <linux/list.h>
  #include <linux/sched.h>
  #include <linux/bitops.h>
  #include <linux/slab.h>
  #include <linux/crypto.h>
  #include <linux/ratelimit.h>
  #include <linux/tcp.h>
  #include <linux/mutex.h>
  #include <linux/major.h>
  #include <linux/blkdev.h>
  #include <linux/genhd.h>
  #include <net/tcp.h>
  #include <linux/lru_cache.h>
  
  #ifdef __CHECKER__
  # define __protected_by(x)       __attribute__((require_context(x,1,999,"rdwr")))
  # define __protected_read_by(x)  __attribute__((require_context(x,1,999,"read")))
  # define __protected_write_by(x) __attribute__((require_context(x,1,999,"write")))
  # define __must_hold(x)       __attribute__((context(x,1,1), require_context(x,1,999,"call")))
  #else
  # define __protected_by(x)
  # define __protected_read_by(x)
  # define __protected_write_by(x)
  # define __must_hold(x)
  #endif
  
  #define __no_warn(lock, stmt) do { __acquire(lock); stmt; __release(lock); } while (0)
  
  /* module parameter, defined in drbd_main.c */
  extern unsigned int minor_count;
  extern int disable_sendpage;
  extern int allow_oos;
  extern unsigned int cn_idx;
  
  #ifdef CONFIG_DRBD_FAULT_INJECTION
  extern int enable_faults;
  extern int fault_rate;
  extern int fault_devs;
  #endif
  
  extern char usermode_helper[];
  
  
  #ifndef TRUE
  #define TRUE 1
  #endif
  #ifndef FALSE
  #define FALSE 0
  #endif
  
  /* I don't remember why XCPU ...
   * This is used to wake the asender,
   * and to interrupt sending the sending task
   * on disconnect.
   */
  #define DRBD_SIG SIGXCPU
  
  /* This is used to stop/restart our threads.
   * Cannot use SIGTERM nor SIGKILL, since these
   * are sent out by init on runlevel changes
   * I choose SIGHUP for now.
   */
  #define DRBD_SIGKILL SIGHUP
  
  /* All EEs on the free list should have ID_VACANT (== 0)
   * freshly allocated EEs get !ID_VACANT (== 1)
   * so if it says "cannot dereference null pointer at address 0x00000001",
   * it is most likely one of these :( */
  
  #define ID_IN_SYNC      (4711ULL)
  #define ID_OUT_OF_SYNC  (4712ULL)
  
  #define ID_SYNCER (-1ULL)
  #define ID_VACANT 0
  #define is_syncer_block_id(id) ((id) == ID_SYNCER)
  
  struct drbd_conf;
  
  
  /* to shorten dev_warn(DEV, "msg"); and relatives statements */
  #define DEV (disk_to_dev(mdev->vdisk))
  
  #define D_ASSERT(exp)	if (!(exp)) \
  	 dev_err(DEV, "ASSERT( " #exp " ) in %s:%d\n", __FILE__, __LINE__)
  
  #define ERR_IF(exp) if (({				\
  	int _b = (exp) != 0;				\
  	if (_b) dev_err(DEV, "%s: (%s) in %s:%d\n",	\
  		__func__, #exp, __FILE__, __LINE__);	\
  	 _b;						\
  	}))
  
  /* Defines to control fault insertion */
  enum {
  	DRBD_FAULT_MD_WR = 0,	/* meta data write */
  	DRBD_FAULT_MD_RD = 1,	/*           read  */
  	DRBD_FAULT_RS_WR = 2,	/* resync          */
  	DRBD_FAULT_RS_RD = 3,
  	DRBD_FAULT_DT_WR = 4,	/* data            */
  	DRBD_FAULT_DT_RD = 5,
  	DRBD_FAULT_DT_RA = 6,	/* data read ahead */
  	DRBD_FAULT_BM_ALLOC = 7,	/* bitmap allocation */
  	DRBD_FAULT_AL_EE = 8,	/* alloc ee */
  	DRBD_FAULT_RECEIVE = 9, /* Changes some bytes upon receiving a [rs]data block */
  
  	DRBD_FAULT_MAX,
  };
  
  #ifdef CONFIG_DRBD_FAULT_INJECTION
  extern unsigned int
  _drbd_insert_fault(struct drbd_conf *mdev, unsigned int type);
  static inline int
  drbd_insert_fault(struct drbd_conf *mdev, unsigned int type) {
  	return fault_rate &&
  		(enable_faults & (1<<type)) &&
  		_drbd_insert_fault(mdev, type);
  }
  #define FAULT_ACTIVE(_m, _t) (drbd_insert_fault((_m), (_t)))
  
  #else
  #define FAULT_ACTIVE(_m, _t) (0)
  #endif
  
  /* integer division, round _UP_ to the next integer */
  #define div_ceil(A, B) ((A)/(B) + ((A)%(B) ? 1 : 0))
  /* usual integer division */
  #define div_floor(A, B) ((A)/(B))
  
  /* drbd_meta-data.c (still in drbd_main.c) */
  /* 4th incarnation of the disk layout. */
  #define DRBD_MD_MAGIC (DRBD_MAGIC+4)
  
  extern struct drbd_conf **minor_table;
  extern struct ratelimit_state drbd_ratelimit_state;
  
  /* on the wire */
  enum drbd_packets {
  	/* receiver (data socket) */
  	P_DATA		      = 0x00,
  	P_DATA_REPLY	      = 0x01, /* Response to P_DATA_REQUEST */
  	P_RS_DATA_REPLY	      = 0x02, /* Response to P_RS_DATA_REQUEST */
  	P_BARRIER	      = 0x03,
  	P_BITMAP	      = 0x04,
  	P_BECOME_SYNC_TARGET  = 0x05,
  	P_BECOME_SYNC_SOURCE  = 0x06,
  	P_UNPLUG_REMOTE	      = 0x07, /* Used at various times to hint the peer */
  	P_DATA_REQUEST	      = 0x08, /* Used to ask for a data block */
  	P_RS_DATA_REQUEST     = 0x09, /* Used to ask for a data block for resync */
  	P_SYNC_PARAM	      = 0x0a,
  	P_PROTOCOL	      = 0x0b,
  	P_UUIDS		      = 0x0c,
  	P_SIZES		      = 0x0d,
  	P_STATE		      = 0x0e,
  	P_SYNC_UUID	      = 0x0f,
  	P_AUTH_CHALLENGE      = 0x10,
  	P_AUTH_RESPONSE	      = 0x11,
  	P_STATE_CHG_REQ	      = 0x12,
  
  	/* asender (meta socket */
  	P_PING		      = 0x13,
  	P_PING_ACK	      = 0x14,
  	P_RECV_ACK	      = 0x15, /* Used in protocol B */
  	P_WRITE_ACK	      = 0x16, /* Used in protocol C */
  	P_RS_WRITE_ACK	      = 0x17, /* Is a P_WRITE_ACK, additionally call set_in_sync(). */
  	P_DISCARD_ACK	      = 0x18, /* Used in proto C, two-primaries conflict detection */
  	P_NEG_ACK	      = 0x19, /* Sent if local disk is unusable */
  	P_NEG_DREPLY	      = 0x1a, /* Local disk is broken... */
  	P_NEG_RS_DREPLY	      = 0x1b, /* Local disk is broken... */
  	P_BARRIER_ACK	      = 0x1c,
  	P_STATE_CHG_REPLY     = 0x1d,
  
  	/* "new" commands, no longer fitting into the ordering scheme above */
  
  	P_OV_REQUEST	      = 0x1e, /* data socket */
  	P_OV_REPLY	      = 0x1f,
  	P_OV_RESULT	      = 0x20, /* meta socket */
  	P_CSUM_RS_REQUEST     = 0x21, /* data socket */
  	P_RS_IS_IN_SYNC	      = 0x22, /* meta socket */
  	P_SYNC_PARAM89	      = 0x23, /* data socket, protocol version 89 replacement for P_SYNC_PARAM */
  	P_COMPRESSED_BITMAP   = 0x24, /* compressed or otherwise encoded bitmap transfer */
  	/* P_CKPT_FENCE_REQ      = 0x25, * currently reserved for protocol D */
  	/* P_CKPT_DISABLE_REQ    = 0x26, * currently reserved for protocol D */
  	P_DELAY_PROBE         = 0x27, /* is used on BOTH sockets */
  
  	P_MAX_CMD	      = 0x28,
  	P_MAY_IGNORE	      = 0x100, /* Flag to test if (cmd > P_MAY_IGNORE) ... */
  	P_MAX_OPT_CMD	      = 0x101,
  
  	/* special command ids for handshake */
  
  	P_HAND_SHAKE_M	      = 0xfff1, /* First Packet on the MetaSock */
  	P_HAND_SHAKE_S	      = 0xfff2, /* First Packet on the Socket */
  
  	P_HAND_SHAKE	      = 0xfffe	/* FIXED for the next century! */
  };
  
  static inline const char *cmdname(enum drbd_packets cmd)
  {
  	/* THINK may need to become several global tables
  	 * when we want to support more than
  	 * one PRO_VERSION */
  	static const char *cmdnames[] = {
  		[P_DATA]	        = "Data",
  		[P_DATA_REPLY]	        = "DataReply",
  		[P_RS_DATA_REPLY]	= "RSDataReply",
  		[P_BARRIER]	        = "Barrier",
  		[P_BITMAP]	        = "ReportBitMap",
  		[P_BECOME_SYNC_TARGET]  = "BecomeSyncTarget",
  		[P_BECOME_SYNC_SOURCE]  = "BecomeSyncSource",
  		[P_UNPLUG_REMOTE]	= "UnplugRemote",
  		[P_DATA_REQUEST]	= "DataRequest",
  		[P_RS_DATA_REQUEST]     = "RSDataRequest",
  		[P_SYNC_PARAM]	        = "SyncParam",
  		[P_SYNC_PARAM89]	= "SyncParam89",
  		[P_PROTOCOL]            = "ReportProtocol",
  		[P_UUIDS]	        = "ReportUUIDs",
  		[P_SIZES]	        = "ReportSizes",
  		[P_STATE]	        = "ReportState",
  		[P_SYNC_UUID]           = "ReportSyncUUID",
  		[P_AUTH_CHALLENGE]      = "AuthChallenge",
  		[P_AUTH_RESPONSE]	= "AuthResponse",
  		[P_PING]		= "Ping",
  		[P_PING_ACK]	        = "PingAck",
  		[P_RECV_ACK]	        = "RecvAck",
  		[P_WRITE_ACK]	        = "WriteAck",
  		[P_RS_WRITE_ACK]	= "RSWriteAck",
  		[P_DISCARD_ACK]	        = "DiscardAck",
  		[P_NEG_ACK]	        = "NegAck",
  		[P_NEG_DREPLY]	        = "NegDReply",
  		[P_NEG_RS_DREPLY]	= "NegRSDReply",
  		[P_BARRIER_ACK]	        = "BarrierAck",
  		[P_STATE_CHG_REQ]       = "StateChgRequest",
  		[P_STATE_CHG_REPLY]     = "StateChgReply",
  		[P_OV_REQUEST]          = "OVRequest",
  		[P_OV_REPLY]            = "OVReply",
  		[P_OV_RESULT]           = "OVResult",
  		[P_CSUM_RS_REQUEST]     = "CsumRSRequest",
  		[P_RS_IS_IN_SYNC]	= "CsumRSIsInSync",
  		[P_COMPRESSED_BITMAP]   = "CBitmap",
  		[P_DELAY_PROBE]         = "DelayProbe",
  		[P_MAX_CMD]	        = NULL,
  	};
  
  	if (cmd == P_HAND_SHAKE_M)
  		return "HandShakeM";
  	if (cmd == P_HAND_SHAKE_S)
  		return "HandShakeS";
  	if (cmd == P_HAND_SHAKE)
  		return "HandShake";
  	if (cmd >= P_MAX_CMD)
  		return "Unknown";
  	return cmdnames[cmd];
  }
  
  /* for sending/receiving the bitmap,
   * possibly in some encoding scheme */
  struct bm_xfer_ctx {
  	/* "const"
  	 * stores total bits and long words
  	 * of the bitmap, so we don't need to
  	 * call the accessor functions over and again. */
  	unsigned long bm_bits;
  	unsigned long bm_words;
  	/* during xfer, current position within the bitmap */
  	unsigned long bit_offset;
  	unsigned long word_offset;
  
  	/* statistics; index: (h->command == P_BITMAP) */
  	unsigned packets[2];
  	unsigned bytes[2];
  };
  
  extern void INFO_bm_xfer_stats(struct drbd_conf *mdev,
  		const char *direction, struct bm_xfer_ctx *c);
  
  static inline void bm_xfer_ctx_bit_to_word_offset(struct bm_xfer_ctx *c)
  {
  	/* word_offset counts "native long words" (32 or 64 bit),
  	 * aligned at 64 bit.
  	 * Encoded packet may end at an unaligned bit offset.
  	 * In case a fallback clear text packet is transmitted in
  	 * between, we adjust this offset back to the last 64bit
  	 * aligned "native long word", which makes coding and decoding
  	 * the plain text bitmap much more convenient.  */
  #if BITS_PER_LONG == 64
  	c->word_offset = c->bit_offset >> 6;
  #elif BITS_PER_LONG == 32
  	c->word_offset = c->bit_offset >> 5;
  	c->word_offset &= ~(1UL);
  #else
  # error "unsupported BITS_PER_LONG"
  #endif
  }
  
  #ifndef __packed
  #define __packed __attribute__((packed))
  #endif
  
  /* This is the layout for a packet on the wire.
   * The byteorder is the network byte order.
   *     (except block_id and barrier fields.
   *	these are pointers to local structs
   *	and have no relevance for the partner,
   *	which just echoes them as received.)
   *
   * NOTE that the payload starts at a long aligned offset,
   * regardless of 32 or 64 bit arch!
   */
  struct p_header {
  	u32	  magic;
  	u16	  command;
  	u16	  length;	/* bytes of data after this header */
  	u8	  payload[0];
  } __packed;
  /* 8 bytes. packet FIXED for the next century! */
  
  /*
   * short commands, packets without payload, plain p_header:
   *   P_PING
   *   P_PING_ACK
   *   P_BECOME_SYNC_TARGET
   *   P_BECOME_SYNC_SOURCE
   *   P_UNPLUG_REMOTE
   */
  
  /*
   * commands with out-of-struct payload:
   *   P_BITMAP    (no additional fields)
   *   P_DATA, P_DATA_REPLY (see p_data)
   *   P_COMPRESSED_BITMAP (see receive_compressed_bitmap)
   */
  
  /* these defines must not be changed without changing the protocol version */
  #define DP_HARDBARRIER	      1
  #define DP_RW_SYNC	      2
  #define DP_MAY_SET_IN_SYNC    4
  
  struct p_data {
  	struct p_header head;
  	u64	    sector;    /* 64 bits sector number */
  	u64	    block_id;  /* to identify the request in protocol B&C */
  	u32	    seq_num;
  	u32	    dp_flags;
  } __packed;
  
  /*
   * commands which share a struct:
   *  p_block_ack:
   *   P_RECV_ACK (proto B), P_WRITE_ACK (proto C),
   *   P_DISCARD_ACK (proto C, two-primaries conflict detection)
   *  p_block_req:
   *   P_DATA_REQUEST, P_RS_DATA_REQUEST
   */
  struct p_block_ack {
  	struct p_header head;
  	u64	    sector;
  	u64	    block_id;
  	u32	    blksize;
  	u32	    seq_num;
  } __packed;
  
  
  struct p_block_req {
  	struct p_header head;
  	u64 sector;
  	u64 block_id;
  	u32 blksize;
  	u32 pad;	/* to multiple of 8 Byte */
  } __packed;
  
  /*
   * commands with their own struct for additional fields:
   *   P_HAND_SHAKE
   *   P_BARRIER
   *   P_BARRIER_ACK
   *   P_SYNC_PARAM
   *   ReportParams
   */
  
  struct p_handshake {
  	struct p_header head;	/* 8 bytes */
  	u32 protocol_min;
  	u32 feature_flags;
  	u32 protocol_max;
  
  	/* should be more than enough for future enhancements
  	 * for now, feature_flags and the reserverd array shall be zero.
  	 */
  
  	u32 _pad;
  	u64 reserverd[7];
  } __packed;
  /* 80 bytes, FIXED for the next century */
  
  struct p_barrier {
  	struct p_header head;
  	u32 barrier;	/* barrier number _handle_ only */
  	u32 pad;	/* to multiple of 8 Byte */
  } __packed;
  
  struct p_barrier_ack {
  	struct p_header head;
  	u32 barrier;
  	u32 set_size;
  } __packed;
  
  struct p_rs_param {
  	struct p_header head;
  	u32 rate;
  
  	      /* Since protocol version 88 and higher. */
  	char verify_alg[0];
  } __packed;
  
  struct p_rs_param_89 {
  	struct p_header head;
  	u32 rate;
          /* protocol version 89: */
  	char verify_alg[SHARED_SECRET_MAX];
  	char csums_alg[SHARED_SECRET_MAX];
  } __packed;
  
  enum drbd_conn_flags {
  	CF_WANT_LOSE = 1,
  	CF_DRY_RUN = 2,
  };
  
  struct p_protocol {
  	struct p_header head;
  	u32 protocol;
  	u32 after_sb_0p;
  	u32 after_sb_1p;
  	u32 after_sb_2p;
  	u32 conn_flags;
  	u32 two_primaries;
  
                /* Since protocol version 87 and higher. */
  	char integrity_alg[0];
  
  } __packed;
  
  struct p_uuids {
  	struct p_header head;
  	u64 uuid[UI_EXTENDED_SIZE];
  } __packed;
  
  struct p_rs_uuid {
  	struct p_header head;
  	u64	    uuid;
  } __packed;
  
  struct p_sizes {
  	struct p_header head;
  	u64	    d_size;  /* size of disk */
  	u64	    u_size;  /* user requested size */
  	u64	    c_size;  /* current exported size */
  	u32	    max_segment_size;  /* Maximal size of a BIO */
  	u16	    queue_order_type;  /* not yet implemented in DRBD*/
  	u16	    dds_flags; /* use enum dds_flags here. */
  } __packed;
  
  struct p_state {
  	struct p_header head;
  	u32	    state;
  } __packed;
  
  struct p_req_state {
  	struct p_header head;
  	u32	    mask;
  	u32	    val;
  } __packed;
  
  struct p_req_state_reply {
  	struct p_header head;
  	u32	    retcode;
  } __packed;
  
  struct p_drbd06_param {
  	u64	  size;
  	u32	  state;
  	u32	  blksize;
  	u32	  protocol;
  	u32	  version;
  	u32	  gen_cnt[5];
  	u32	  bit_map_gen[5];
  } __packed;
  
  struct p_discard {
  	struct p_header head;
  	u64	    block_id;
  	u32	    seq_num;
  	u32	    pad;
  } __packed;
  
  /* Valid values for the encoding field.
   * Bump proto version when changing this. */
  enum drbd_bitmap_code {
  	/* RLE_VLI_Bytes = 0,
  	 * and other bit variants had been defined during
  	 * algorithm evaluation. */
  	RLE_VLI_Bits = 2,
  };
  
  struct p_compressed_bm {
  	struct p_header head;
  	/* (encoding & 0x0f): actual encoding, see enum drbd_bitmap_code
  	 * (encoding & 0x80): polarity (set/unset) of first runlength
  	 * ((encoding >> 4) & 0x07): pad_bits, number of trailing zero bits
  	 * used to pad up to head.length bytes
  	 */
  	u8 encoding;
  
  	u8 code[0];
  } __packed;
  
  struct p_delay_probe {
  	struct p_header head;
  	u32	seq_num; /* sequence number to match the two probe packets */
  	u32	offset;	 /* usecs the probe got sent after the reference time point */
  } __packed;
  
  /* DCBP: Drbd Compressed Bitmap Packet ... */
  static inline enum drbd_bitmap_code
  DCBP_get_code(struct p_compressed_bm *p)
  {
  	return (enum drbd_bitmap_code)(p->encoding & 0x0f);
  }
  
  static inline void
  DCBP_set_code(struct p_compressed_bm *p, enum drbd_bitmap_code code)
  {
  	BUG_ON(code & ~0xf);
  	p->encoding = (p->encoding & ~0xf) | code;
  }
  
  static inline int
  DCBP_get_start(struct p_compressed_bm *p)
  {
  	return (p->encoding & 0x80) != 0;
  }
  
  static inline void
  DCBP_set_start(struct p_compressed_bm *p, int set)
  {
  	p->encoding = (p->encoding & ~0x80) | (set ? 0x80 : 0);
  }
  
  static inline int
  DCBP_get_pad_bits(struct p_compressed_bm *p)
  {
  	return (p->encoding >> 4) & 0x7;
  }
  
  static inline void
  DCBP_set_pad_bits(struct p_compressed_bm *p, int n)
  {
  	BUG_ON(n & ~0x7);
  	p->encoding = (p->encoding & (~0x7 << 4)) | (n << 4);
  }
  
  /* one bitmap packet, including the p_header,
   * should fit within one _architecture independend_ page.
   * so we need to use the fixed size 4KiB page size
   * most architechtures have used for a long time.
   */
  #define BM_PACKET_PAYLOAD_BYTES (4096 - sizeof(struct p_header))
  #define BM_PACKET_WORDS (BM_PACKET_PAYLOAD_BYTES/sizeof(long))
  #define BM_PACKET_VLI_BYTES_MAX (4096 - sizeof(struct p_compressed_bm))
  #if (PAGE_SIZE < 4096)
  /* drbd_send_bitmap / receive_bitmap would break horribly */
  #error "PAGE_SIZE too small"
  #endif
  
  union p_polymorph {
          struct p_header          header;
          struct p_handshake       handshake;
          struct p_data            data;
          struct p_block_ack       block_ack;
          struct p_barrier         barrier;
          struct p_barrier_ack     barrier_ack;
          struct p_rs_param_89     rs_param_89;
          struct p_protocol        protocol;
          struct p_sizes           sizes;
          struct p_uuids           uuids;
          struct p_state           state;
          struct p_req_state       req_state;
          struct p_req_state_reply req_state_reply;
          struct p_block_req       block_req;
  } __packed;
  
  /**********************************************************************/
  enum drbd_thread_state {
  	None,
  	Running,
  	Exiting,
  	Restarting
  };
  
  struct drbd_thread {
  	spinlock_t t_lock;
  	struct task_struct *task;
  	struct completion stop;
  	enum drbd_thread_state t_state;
  	int (*function) (struct drbd_thread *);
  	struct drbd_conf *mdev;
  	int reset_cpu_mask;
  };
  
  static inline enum drbd_thread_state get_t_state(struct drbd_thread *thi)
  {
  	/* THINK testing the t_state seems to be uncritical in all cases
  	 * (but thread_{start,stop}), so we can read it *without* the lock.
  	 *	--lge */
  
  	smp_rmb();
  	return thi->t_state;
  }
  
  
  /*
   * Having this as the first member of a struct provides sort of "inheritance".
   * "derived" structs can be "drbd_queue_work()"ed.
   * The callback should know and cast back to the descendant struct.
   * drbd_request and drbd_epoch_entry are descendants of drbd_work.
   */
  struct drbd_work;
  typedef int (*drbd_work_cb)(struct drbd_conf *, struct drbd_work *, int cancel);
  struct drbd_work {
  	struct list_head list;
  	drbd_work_cb cb;
  };
  
  struct drbd_tl_epoch;
  struct drbd_request {
  	struct drbd_work w;
  	struct drbd_conf *mdev;
  
  	/* if local IO is not allowed, will be NULL.
  	 * if local IO _is_ allowed, holds the locally submitted bio clone,
  	 * or, after local IO completion, the ERR_PTR(error).
  	 * see drbd_endio_pri(). */
  	struct bio *private_bio;
  
  	struct hlist_node colision;
  	sector_t sector;
  	unsigned int size;
  	unsigned int epoch; /* barrier_nr */
  
  	/* barrier_nr: used to check on "completion" whether this req was in
  	 * the current epoch, and we therefore have to close it,
  	 * starting a new epoch...
  	 */
  
  	/* up to here, the struct layout is identical to drbd_epoch_entry;
  	 * we might be able to use that to our advantage...  */
  
  	struct list_head tl_requests; /* ring list in the transfer log */
  	struct bio *master_bio;       /* master bio pointer */
  	unsigned long rq_state; /* see comments above _req_mod() */
  	int seq_num;
  	unsigned long start_time;
  };
  
  struct drbd_tl_epoch {
  	struct drbd_work w;
  	struct list_head requests; /* requests before */
  	struct drbd_tl_epoch *next; /* pointer to the next barrier */
  	unsigned int br_number;  /* the barriers identifier. */
  	int n_req;	/* number of requests attached before this barrier */
  };
  
  struct drbd_request;
  
  /* These Tl_epoch_entries may be in one of 6 lists:
     active_ee .. data packet being written
     sync_ee   .. syncer block being written
     done_ee   .. block written, need to send P_WRITE_ACK
     read_ee   .. [RS]P_DATA_REQUEST being read
  */
  
  struct drbd_epoch {
  	struct list_head list;
  	unsigned int barrier_nr;
  	atomic_t epoch_size; /* increased on every request added. */
  	atomic_t active;     /* increased on every req. added, and dec on every finished. */
  	unsigned long flags;
  };
  
  /* drbd_epoch flag bits */
  enum {
  	DE_BARRIER_IN_NEXT_EPOCH_ISSUED,
  	DE_BARRIER_IN_NEXT_EPOCH_DONE,
  	DE_CONTAINS_A_BARRIER,
  	DE_HAVE_BARRIER_NUMBER,
  	DE_IS_FINISHING,
  };
  
  enum epoch_event {
  	EV_PUT,
  	EV_GOT_BARRIER_NR,
  	EV_BARRIER_DONE,
  	EV_BECAME_LAST,
  	EV_CLEANUP = 32, /* used as flag */
  };
  
  struct drbd_wq_barrier {
  	struct drbd_work w;
  	struct completion done;
  };
  
  struct digest_info {
  	int digest_size;
  	void *digest;
  };
  
  struct drbd_epoch_entry {
  	struct drbd_work w;
  	struct hlist_node colision;
  	struct drbd_epoch *epoch;
  	struct drbd_conf *mdev;
  	struct page *pages;
  	atomic_t pending_bios;
  	unsigned int size;
  	/* see comments on ee flag bits below */
  	unsigned long flags;
  	sector_t sector;
  	u64 block_id;
  };
  
  /* ee flag bits.
   * While corresponding bios are in flight, the only modification will be
   * set_bit WAS_ERROR, which has to be atomic.
   * If no bios are in flight yet, or all have been completed,
   * non-atomic modification to ee->flags is ok.
   */
  enum {
  	__EE_CALL_AL_COMPLETE_IO,
  	__EE_MAY_SET_IN_SYNC,
  
  	/* This epoch entry closes an epoch using a barrier.
  	 * On sucessful completion, the epoch is released,
  	 * and the P_BARRIER_ACK send. */
  	__EE_IS_BARRIER,
  
  	/* In case a barrier failed,
  	 * we need to resubmit without the barrier flag. */
  	__EE_RESUBMITTED,
  
  	/* we may have several bios per epoch entry.
  	 * if any of those fail, we set this flag atomically
  	 * from the endio callback */
  	__EE_WAS_ERROR,
  };
  #define EE_CALL_AL_COMPLETE_IO (1<<__EE_CALL_AL_COMPLETE_IO)
  #define EE_MAY_SET_IN_SYNC     (1<<__EE_MAY_SET_IN_SYNC)
  #define EE_IS_BARRIER          (1<<__EE_IS_BARRIER)
  #define	EE_RESUBMITTED         (1<<__EE_RESUBMITTED)
  #define EE_WAS_ERROR           (1<<__EE_WAS_ERROR)
  
  /* global flag bits */
  enum {
  	CREATE_BARRIER,		/* next P_DATA is preceeded by a P_BARRIER */
  	SIGNAL_ASENDER,		/* whether asender wants to be interrupted */
  	SEND_PING,		/* whether asender should send a ping asap */
  
  	STOP_SYNC_TIMER,	/* tell timer to cancel itself */
  	UNPLUG_QUEUED,		/* only relevant with kernel 2.4 */
  	UNPLUG_REMOTE,		/* sending a "UnplugRemote" could help */
  	MD_DIRTY,		/* current uuids and flags not yet on disk */
  	DISCARD_CONCURRENT,	/* Set on one node, cleared on the peer! */
  	USE_DEGR_WFC_T,		/* degr-wfc-timeout instead of wfc-timeout. */
  	CLUSTER_ST_CHANGE,	/* Cluster wide state change going on... */
  	CL_ST_CHG_SUCCESS,
  	CL_ST_CHG_FAIL,
  	CRASHED_PRIMARY,	/* This node was a crashed primary.
  				 * Gets cleared when the state.conn
  				 * goes into C_CONNECTED state. */
  	WRITE_BM_AFTER_RESYNC,	/* A kmalloc() during resync failed */
  	NO_BARRIER_SUPP,	/* underlying block device doesn't implement barriers */
  	CONSIDER_RESYNC,
  
  	MD_NO_BARRIER,		/* meta data device does not support barriers,
  				   so don't even try */
  	SUSPEND_IO,		/* suspend application io */
  	BITMAP_IO,		/* suspend application io;
  				   once no more io in flight, start bitmap io */
  	BITMAP_IO_QUEUED,       /* Started bitmap IO */
  	RESYNC_AFTER_NEG,       /* Resync after online grow after the attach&negotiate finished. */
  	NET_CONGESTED,		/* The data socket is congested */
  
  	CONFIG_PENDING,		/* serialization of (re)configuration requests.
  				 * if set, also prevents the device from dying */
  	DEVICE_DYING,		/* device became unconfigured,
  				 * but worker thread is still handling the cleanup.
  				 * reconfiguring (nl_disk_conf, nl_net_conf) is dissalowed,
  				 * while this is set. */
  	RESIZE_PENDING,		/* Size change detected locally, waiting for the response from
  				 * the peer, if it changed there as well. */
  	CONN_DRY_RUN,		/* Expect disconnect after resync handshake. */
  	GOT_PING_ACK,		/* set when we receive a ping_ack packet, misc wait gets woken */
  };
  
  struct drbd_bitmap; /* opaque for drbd_conf */
  
  /* TODO sort members for performance
   * MAYBE group them further */
  
  /* THINK maybe we actually want to use the default "event/%s" worker threads
   * or similar in linux 2.6, which uses per cpu data and threads.
   *
   * To be general, this might need a spin_lock member.
   * For now, please use the mdev->req_lock to protect list_head,
   * see drbd_queue_work below.
   */
  struct drbd_work_queue {
  	struct list_head q;
  	struct semaphore s; /* producers up it, worker down()s it */
  	spinlock_t q_lock;  /* to protect the list. */
  };
  
  struct drbd_socket {
  	struct drbd_work_queue work;
  	struct mutex mutex;
  	struct socket    *socket;
  	/* this way we get our
  	 * send/receive buffers off the stack */
  	union p_polymorph sbuf;
  	union p_polymorph rbuf;
  };
  
  struct drbd_md {
  	u64 md_offset;		/* sector offset to 'super' block */
  
  	u64 la_size_sect;	/* last agreed size, unit sectors */
  	u64 uuid[UI_SIZE];
  	u64 device_uuid;
  	u32 flags;
  	u32 md_size_sect;
  
  	s32 al_offset;	/* signed relative sector offset to al area */
  	s32 bm_offset;	/* signed relative sector offset to bitmap */
  
  	/* u32 al_nr_extents;	   important for restoring the AL
  	 * is stored into  sync_conf.al_extents, which in turn
  	 * gets applied to act_log->nr_elements
  	 */
  };
  
  /* for sync_conf and other types... */
  #define NL_PACKET(name, number, fields) struct name { fields };
  #define NL_INTEGER(pn,pr,member) int member;
  #define NL_INT64(pn,pr,member) __u64 member;
  #define NL_BIT(pn,pr,member)   unsigned member:1;
  #define NL_STRING(pn,pr,member,len) unsigned char member[len]; int member ## _len;
  #include "linux/drbd_nl.h"
  
  struct drbd_backing_dev {
  	struct block_device *backing_bdev;
  	struct block_device *md_bdev;
  	struct file *lo_file;
  	struct file *md_file;
  	struct drbd_md md;
  	struct disk_conf dc; /* The user provided config... */
  	sector_t known_size; /* last known size of that backing device */
  };
  
  struct drbd_md_io {
  	struct drbd_conf *mdev;
  	struct completion event;
  	int error;
  };
  
  struct bm_io_work {
  	struct drbd_work w;
  	char *why;
  	int (*io_fn)(struct drbd_conf *mdev);
  	void (*done)(struct drbd_conf *mdev, int rv);
  };
  
  enum write_ordering_e {
  	WO_none,
  	WO_drain_io,
  	WO_bdev_flush,
  	WO_bio_barrier
  };
  
  struct drbd_conf {
  	/* things that are stored as / read from meta data on disk */
  	unsigned long flags;
  
  	/* configured by drbdsetup */
  	struct net_conf *net_conf; /* protected by get_net_conf() and put_net_conf() */
  	struct syncer_conf sync_conf;
  	struct drbd_backing_dev *ldev __protected_by(local);
  
  	sector_t p_size;     /* partner's disk size */
  	struct request_queue *rq_queue;
  	struct block_device *this_bdev;
  	struct gendisk	    *vdisk;
  
  	struct drbd_socket data; /* data/barrier/cstate/parameter packets */
  	struct drbd_socket meta; /* ping/ack (metadata) packets */
  	int agreed_pro_version;  /* actually used protocol version */
  	unsigned long last_received; /* in jiffies, either socket */
  	unsigned int ko_count;
  	struct drbd_work  resync_work,
  			  unplug_work,
  			  md_sync_work;
  	struct timer_list resync_timer;
  	struct timer_list md_sync_timer;
  
  	/* Used after attach while negotiating new disk state. */
  	union drbd_state new_state_tmp;
  
  	union drbd_state state;
  	wait_queue_head_t misc_wait;
  	wait_queue_head_t state_wait;  /* upon each state change. */
  	unsigned int send_cnt;
  	unsigned int recv_cnt;
  	unsigned int read_cnt;
  	unsigned int writ_cnt;
  	unsigned int al_writ_cnt;
  	unsigned int bm_writ_cnt;
  	atomic_t ap_bio_cnt;	 /* Requests we need to complete */
  	atomic_t ap_pending_cnt; /* AP data packets on the wire, ack expected */
  	atomic_t rs_pending_cnt; /* RS request/data packets on the wire */
  	atomic_t unacked_cnt;	 /* Need to send replys for */
  	atomic_t local_cnt;	 /* Waiting for local completion */
  	atomic_t net_cnt;	 /* Users of net_conf */
  	spinlock_t req_lock;
  	struct drbd_tl_epoch *unused_spare_tle; /* for pre-allocation */
  	struct drbd_tl_epoch *newest_tle;
  	struct drbd_tl_epoch *oldest_tle;
  	struct list_head out_of_sequence_requests;
  	struct hlist_head *tl_hash;
  	unsigned int tl_hash_s;
  
  	/* blocks to sync in this run [unit BM_BLOCK_SIZE] */
  	unsigned long rs_total;
  	/* number of sync IOs that failed in this run */
  	unsigned long rs_failed;
  	/* Syncer's start time [unit jiffies] */
  	unsigned long rs_start;
  	/* cumulated time in PausedSyncX state [unit jiffies] */
  	unsigned long rs_paused;
  	/* block not up-to-date at mark [unit BM_BLOCK_SIZE] */
  	unsigned long rs_mark_left;
  	/* marks's time [unit jiffies] */
  	unsigned long rs_mark_time;
  	/* skipped because csum was equeal [unit BM_BLOCK_SIZE] */
  	unsigned long rs_same_csum;
  
  	/* where does the admin want us to start? (sector) */
  	sector_t ov_start_sector;
  	/* where are we now? (sector) */
  	sector_t ov_position;
  	/* Start sector of out of sync range (to merge printk reporting). */
  	sector_t ov_last_oos_start;
  	/* size of out-of-sync range in sectors. */
  	sector_t ov_last_oos_size;
  	unsigned long ov_left; /* in bits */
  	struct crypto_hash *csums_tfm;
  	struct crypto_hash *verify_tfm;
  
  	struct drbd_thread receiver;
  	struct drbd_thread worker;
  	struct drbd_thread asender;
  	struct drbd_bitmap *bitmap;
  	unsigned long bm_resync_fo; /* bit offset for drbd_bm_find_next */
  
  	/* Used to track operations of resync... */
  	struct lru_cache *resync;
  	/* Number of locked elements in resync LRU */
  	unsigned int resync_locked;
  	/* resync extent number waiting for application requests */
  	unsigned int resync_wenr;
  
  	int open_cnt;
  	u64 *p_uuid;
  	struct drbd_epoch *current_epoch;
  	spinlock_t epoch_lock;
  	unsigned int epochs;
  	enum write_ordering_e write_ordering;
  	struct list_head active_ee; /* IO in progress */
  	struct list_head sync_ee;   /* IO in progress */
  	struct list_head done_ee;   /* send ack */
  	struct list_head read_ee;   /* IO in progress */
  	struct list_head net_ee;    /* zero-copy network send in progress */
  	struct hlist_head *ee_hash; /* is proteced by req_lock! */
  	unsigned int ee_hash_s;
  
  	/* this one is protected by ee_lock, single thread */
  	struct drbd_epoch_entry *last_write_w_barrier;
  
  	int next_barrier_nr;
  	struct hlist_head *app_reads_hash; /* is proteced by req_lock */
  	struct list_head resync_reads;
  	atomic_t pp_in_use;
  	wait_queue_head_t ee_wait;
  	struct page *md_io_page;	/* one page buffer for md_io */
  	struct page *md_io_tmpp;	/* for logical_block_size != 512 */
  	struct mutex md_io_mutex;	/* protects the md_io_buffer */
  	spinlock_t al_lock;
  	wait_queue_head_t al_wait;
  	struct lru_cache *act_log;	/* activity log */
  	unsigned int al_tr_number;
  	int al_tr_cycle;
  	int al_tr_pos;   /* position of the next transaction in the journal */
  	struct crypto_hash *cram_hmac_tfm;
  	struct crypto_hash *integrity_w_tfm; /* to be used by the worker thread */
  	struct crypto_hash *integrity_r_tfm; /* to be used by the receiver thread */
  	void *int_dig_out;
  	void *int_dig_in;
  	void *int_dig_vv;
  	wait_queue_head_t seq_wait;
  	atomic_t packet_seq;
  	unsigned int peer_seq;
  	spinlock_t peer_seq_lock;
  	unsigned int minor;
  	unsigned long comm_bm_set; /* communicated number of set bits. */
  	cpumask_var_t cpu_mask;
  	struct bm_io_work bm_io_work;
  	u64 ed_uuid; /* UUID of the exposed data */
  	struct mutex state_mutex;
  	char congestion_reason;  /* Why we where congested... */
  };
  
  static inline struct drbd_conf *minor_to_mdev(unsigned int minor)
  {
  	struct drbd_conf *mdev;
  
  	mdev = minor < minor_count ? minor_table[minor] : NULL;
  
  	return mdev;
  }
  
  static inline unsigned int mdev_to_minor(struct drbd_conf *mdev)
  {
  	return mdev->minor;
  }
  
  /* returns 1 if it was successfull,
   * returns 0 if there was no data socket.
   * so wherever you are going to use the data.socket, e.g. do
   * if (!drbd_get_data_sock(mdev))
   *	return 0;
   *	CODE();
   * drbd_put_data_sock(mdev);
   */
  static inline int drbd_get_data_sock(struct drbd_conf *mdev)
  {
  	mutex_lock(&mdev->data.mutex);
  	/* drbd_disconnect() could have called drbd_free_sock()
  	 * while we were waiting in down()... */
  	if (unlikely(mdev->data.socket == NULL)) {
  		mutex_unlock(&mdev->data.mutex);
  		return 0;
  	}
  	return 1;
  }
  
  static inline void drbd_put_data_sock(struct drbd_conf *mdev)
  {
  	mutex_unlock(&mdev->data.mutex);
  }
  
  /*
   * function declarations
   *************************/
  
  /* drbd_main.c */
  
  enum chg_state_flags {
  	CS_HARD	= 1,
  	CS_VERBOSE = 2,
  	CS_WAIT_COMPLETE = 4,
  	CS_SERIALIZE    = 8,
  	CS_ORDERED      = CS_WAIT_COMPLETE + CS_SERIALIZE,
  };
  
  enum dds_flags {
  	DDSF_FORCED    = 1,
  	DDSF_NO_RESYNC = 2, /* Do not run a resync for the new space */
  };
  
  extern void drbd_init_set_defaults(struct drbd_conf *mdev);
  extern int drbd_change_state(struct drbd_conf *mdev, enum chg_state_flags f,
  			union drbd_state mask, union drbd_state val);
  extern void drbd_force_state(struct drbd_conf *, union drbd_state,
  			union drbd_state);
  extern int _drbd_request_state(struct drbd_conf *, union drbd_state,
  			union drbd_state, enum chg_state_flags);
  extern int __drbd_set_state(struct drbd_conf *, union drbd_state,
  			    enum chg_state_flags, struct completion *done);
  extern void print_st_err(struct drbd_conf *, union drbd_state,
  			union drbd_state, int);
  extern int  drbd_thread_start(struct drbd_thread *thi);
  extern void _drbd_thread_stop(struct drbd_thread *thi, int restart, int wait);
  #ifdef CONFIG_SMP
  extern void drbd_thread_current_set_cpu(struct drbd_conf *mdev);
  extern void drbd_calc_cpu_mask(struct drbd_conf *mdev);
  #else
  #define drbd_thread_current_set_cpu(A) ({})
  #define drbd_calc_cpu_mask(A) ({})
  #endif
  extern void drbd_free_resources(struct drbd_conf *mdev);
  extern void tl_release(struct drbd_conf *mdev, unsigned int barrier_nr,
  		       unsigned int set_size);
  extern void tl_clear(struct drbd_conf *mdev);
  extern void _tl_add_barrier(struct drbd_conf *, struct drbd_tl_epoch *);
  extern void drbd_free_sock(struct drbd_conf *mdev);
  extern int drbd_send(struct drbd_conf *mdev, struct socket *sock,
  			void *buf, size_t size, unsigned msg_flags);
  extern int drbd_send_protocol(struct drbd_conf *mdev);
  extern int drbd_send_uuids(struct drbd_conf *mdev);
  extern int drbd_send_uuids_skip_initial_sync(struct drbd_conf *mdev);
  extern int drbd_send_sync_uuid(struct drbd_conf *mdev, u64 val);
  extern int drbd_send_sizes(struct drbd_conf *mdev, int trigger_reply, enum dds_flags flags);
  extern int _drbd_send_state(struct drbd_conf *mdev);
  extern int drbd_send_state(struct drbd_conf *mdev);
  extern int _drbd_send_cmd(struct drbd_conf *mdev, struct socket *sock,
  			enum drbd_packets cmd, struct p_header *h,
  			size_t size, unsigned msg_flags);
  #define USE_DATA_SOCKET 1
  #define USE_META_SOCKET 0
  extern int drbd_send_cmd(struct drbd_conf *mdev, int use_data_socket,
  			enum drbd_packets cmd, struct p_header *h,
  			size_t size);
  extern int drbd_send_cmd2(struct drbd_conf *mdev, enum drbd_packets cmd,
  			char *data, size_t size);
  extern int drbd_send_sync_param(struct drbd_conf *mdev, struct syncer_conf *sc);
  extern int drbd_send_b_ack(struct drbd_conf *mdev, u32 barrier_nr,
  			u32 set_size);
  extern int drbd_send_ack(struct drbd_conf *mdev, enum drbd_packets cmd,
  			struct drbd_epoch_entry *e);
  extern int drbd_send_ack_rp(struct drbd_conf *mdev, enum drbd_packets cmd,
  			struct p_block_req *rp);
  extern int drbd_send_ack_dp(struct drbd_conf *mdev, enum drbd_packets cmd,
  			struct p_data *dp);
  extern int drbd_send_ack_ex(struct drbd_conf *mdev, enum drbd_packets cmd,
  			    sector_t sector, int blksize, u64 block_id);
  extern int drbd_send_block(struct drbd_conf *mdev, enum drbd_packets cmd,
  			   struct drbd_epoch_entry *e);
  extern int drbd_send_dblock(struct drbd_conf *mdev, struct drbd_request *req);
  extern int _drbd_send_barrier(struct drbd_conf *mdev,
  			struct drbd_tl_epoch *barrier);
  extern int drbd_send_drequest(struct drbd_conf *mdev, int cmd,
  			      sector_t sector, int size, u64 block_id);
  extern int drbd_send_drequest_csum(struct drbd_conf *mdev,
  				   sector_t sector,int size,
  				   void *digest, int digest_size,
  				   enum drbd_packets cmd);
  extern int drbd_send_ov_request(struct drbd_conf *mdev,sector_t sector,int size);
  
  extern int drbd_send_bitmap(struct drbd_conf *mdev);
  extern int _drbd_send_bitmap(struct drbd_conf *mdev);
  extern int drbd_send_sr_reply(struct drbd_conf *mdev, int retcode);
  extern void drbd_free_bc(struct drbd_backing_dev *ldev);
  extern void drbd_mdev_cleanup(struct drbd_conf *mdev);
  
  /* drbd_meta-data.c (still in drbd_main.c) */
  extern void drbd_md_sync(struct drbd_conf *mdev);
  extern int  drbd_md_read(struct drbd_conf *mdev, struct drbd_backing_dev *bdev);
  /* maybe define them below as inline? */
  extern void drbd_uuid_set(struct drbd_conf *mdev, int idx, u64 val) __must_hold(local);
  extern void _drbd_uuid_set(struct drbd_conf *mdev, int idx, u64 val) __must_hold(local);
  extern void drbd_uuid_new_current(struct drbd_conf *mdev) __must_hold(local);
  extern void _drbd_uuid_new_current(struct drbd_conf *mdev) __must_hold(local);
  extern void drbd_uuid_set_bm(struct drbd_conf *mdev, u64 val) __must_hold(local);
  extern void drbd_md_set_flag(struct drbd_conf *mdev, int flags) __must_hold(local);
  extern void drbd_md_clear_flag(struct drbd_conf *mdev, int flags)__must_hold(local);
  extern int drbd_md_test_flag(struct drbd_backing_dev *, int);
  extern void drbd_md_mark_dirty(struct drbd_conf *mdev);
  extern void drbd_queue_bitmap_io(struct drbd_conf *mdev,
  				 int (*io_fn)(struct drbd_conf *),
  				 void (*done)(struct drbd_conf *, int),
  				 char *why);
  extern int drbd_bmio_set_n_write(struct drbd_conf *mdev);
  extern int drbd_bmio_clear_n_write(struct drbd_conf *mdev);
  extern int drbd_bitmap_io(struct drbd_conf *mdev, int (*io_fn)(struct drbd_conf *), char *why);
  
  
  /* Meta data layout
     We reserve a 128MB Block (4k aligned)
     * either at the end of the backing device
     * or on a separate meta data device. */
  
  #define MD_RESERVED_SECT (128LU << 11)  /* 128 MB, unit sectors */
  /* The following numbers are sectors */
  #define MD_AL_OFFSET 8	    /* 8 Sectors after start of meta area */
  #define MD_AL_MAX_SIZE 64   /* = 32 kb LOG  ~ 3776 extents ~ 14 GB Storage */
  /* Allows up to about 3.8TB */
  #define MD_BM_OFFSET (MD_AL_OFFSET + MD_AL_MAX_SIZE)
  
  /* Since the smalles IO unit is usually 512 byte */
  #define MD_SECTOR_SHIFT	 9
  #define MD_SECTOR_SIZE	 (1<<MD_SECTOR_SHIFT)
  
  /* activity log */
  #define AL_EXTENTS_PT ((MD_SECTOR_SIZE-12)/8-1) /* 61 ; Extents per 512B sector */
  #define AL_EXTENT_SHIFT 22		 /* One extent represents 4M Storage */
  #define AL_EXTENT_SIZE (1<<AL_EXTENT_SHIFT)
  
  #if BITS_PER_LONG == 32
  #define LN2_BPL 5
  #define cpu_to_lel(A) cpu_to_le32(A)
  #define lel_to_cpu(A) le32_to_cpu(A)
  #elif BITS_PER_LONG == 64
  #define LN2_BPL 6
  #define cpu_to_lel(A) cpu_to_le64(A)
  #define lel_to_cpu(A) le64_to_cpu(A)
  #else
  #error "LN2 of BITS_PER_LONG unknown!"
  #endif
  
  /* resync bitmap */
  /* 16MB sized 'bitmap extent' to track syncer usage */
  struct bm_extent {
  	int rs_left; /* number of bits set (out of sync) in this extent. */
  	int rs_failed; /* number of failed resync requests in this extent. */
  	unsigned long flags;
  	struct lc_element lce;
  };
  
  #define BME_NO_WRITES  0  /* bm_extent.flags: no more requests on this one! */
  #define BME_LOCKED     1  /* bm_extent.flags: syncer active on this one. */
  
  /* drbd_bitmap.c */
  /*
   * We need to store one bit for a block.
   * Example: 1GB disk @ 4096 byte blocks ==> we need 32 KB bitmap.
   * Bit 0 ==> local node thinks this block is binary identical on both nodes
   * Bit 1 ==> local node thinks this block needs to be synced.
   */
  
  #define BM_BLOCK_SHIFT  12			 /* 4k per bit */
  #define BM_BLOCK_SIZE	 (1<<BM_BLOCK_SHIFT)
  /* (9+3) : 512 bytes @ 8 bits; representing 16M storage
   * per sector of on disk bitmap */
  #define BM_EXT_SHIFT	 (BM_BLOCK_SHIFT + MD_SECTOR_SHIFT + 3)  /* = 24 */
  #define BM_EXT_SIZE	 (1<<BM_EXT_SHIFT)
  
  #if (BM_EXT_SHIFT != 24) || (BM_BLOCK_SHIFT != 12)
  #error "HAVE YOU FIXED drbdmeta AS WELL??"
  #endif
  
  /* thus many _storage_ sectors are described by one bit */
  #define BM_SECT_TO_BIT(x)   ((x)>>(BM_BLOCK_SHIFT-9))
  #define BM_BIT_TO_SECT(x)   ((sector_t)(x)<<(BM_BLOCK_SHIFT-9))
  #define BM_SECT_PER_BIT     BM_BIT_TO_SECT(1)
  
  /* bit to represented kilo byte conversion */
  #define Bit2KB(bits) ((bits)<<(BM_BLOCK_SHIFT-10))
  
  /* in which _bitmap_ extent (resp. sector) the bit for a certain
   * _storage_ sector is located in */
  #define BM_SECT_TO_EXT(x)   ((x)>>(BM_EXT_SHIFT-9))
  
  /* how much _storage_ sectors we have per bitmap sector */
  #define BM_EXT_TO_SECT(x)   ((sector_t)(x) << (BM_EXT_SHIFT-9))
  #define BM_SECT_PER_EXT     BM_EXT_TO_SECT(1)
  
  /* in one sector of the bitmap, we have this many activity_log extents. */
  #define AL_EXT_PER_BM_SECT  (1 << (BM_EXT_SHIFT - AL_EXTENT_SHIFT))
  #define BM_WORDS_PER_AL_EXT (1 << (AL_EXTENT_SHIFT-BM_BLOCK_SHIFT-LN2_BPL))
  
  #define BM_BLOCKS_PER_BM_EXT_B (BM_EXT_SHIFT - BM_BLOCK_SHIFT)
  #define BM_BLOCKS_PER_BM_EXT_MASK  ((1<<BM_BLOCKS_PER_BM_EXT_B) - 1)
  
  /* the extent in "PER_EXTENT" below is an activity log extent
   * we need that many (long words/bytes) to store the bitmap
   *		     of one AL_EXTENT_SIZE chunk of storage.
   * we can store the bitmap for that many AL_EXTENTS within
   * one sector of the _on_disk_ bitmap:
   * bit	 0	  bit 37   bit 38	     bit (512*8)-1
   *	     ...|........|........|.. // ..|........|
   * sect. 0	 `296	  `304			   ^(512*8*8)-1
   *
  #define BM_WORDS_PER_EXT    ( (AL_EXT_SIZE/BM_BLOCK_SIZE) / BITS_PER_LONG )
  #define BM_BYTES_PER_EXT    ( (AL_EXT_SIZE/BM_BLOCK_SIZE) / 8 )  // 128
  #define BM_EXT_PER_SECT	    ( 512 / BM_BYTES_PER_EXTENT )	 //   4
   */
  
  #define DRBD_MAX_SECTORS_32 (0xffffffffLU)
  #define DRBD_MAX_SECTORS_BM \
  	  ((MD_RESERVED_SECT - MD_BM_OFFSET) * (1LL<<(BM_EXT_SHIFT-9)))
  #if DRBD_MAX_SECTORS_BM < DRBD_MAX_SECTORS_32
  #define DRBD_MAX_SECTORS      DRBD_MAX_SECTORS_BM
  #define DRBD_MAX_SECTORS_FLEX DRBD_MAX_SECTORS_BM
  #elif !defined(CONFIG_LBDAF) && BITS_PER_LONG == 32
  #define DRBD_MAX_SECTORS      DRBD_MAX_SECTORS_32
  #define DRBD_MAX_SECTORS_FLEX DRBD_MAX_SECTORS_32
  #else
  #define DRBD_MAX_SECTORS      DRBD_MAX_SECTORS_BM
  /* 16 TB in units of sectors */
  #if BITS_PER_LONG == 32
  /* adjust by one page worth of bitmap,
   * so we won't wrap around in drbd_bm_find_next_bit.
   * you should use 64bit OS for that much storage, anyways. */
  #define DRBD_MAX_SECTORS_FLEX BM_BIT_TO_SECT(0xffff7fff)
  #else
  #define DRBD_MAX_SECTORS_FLEX BM_BIT_TO_SECT(0x1LU << 32)
  #endif
  #endif
  
  /* Sector shift value for the "hash" functions of tl_hash and ee_hash tables.
   * With a value of 6 all IO in one 32K block make it to the same slot of the
   * hash table. */
  #define HT_SHIFT 6
  #define DRBD_MAX_SEGMENT_SIZE (1U<<(9+HT_SHIFT))
  
  /* Number of elements in the app_reads_hash */
  #define APP_R_HSIZE 15
  
  extern int  drbd_bm_init(struct drbd_conf *mdev);
  extern int  drbd_bm_resize(struct drbd_conf *mdev, sector_t sectors, int set_new_bits);
  extern void drbd_bm_cleanup(struct drbd_conf *mdev);
  extern void drbd_bm_set_all(struct drbd_conf *mdev);
  extern void drbd_bm_clear_all(struct drbd_conf *mdev);
  extern int  drbd_bm_set_bits(
  		struct drbd_conf *mdev, unsigned long s, unsigned long e);
  extern int  drbd_bm_clear_bits(
  		struct drbd_conf *mdev, unsigned long s, unsigned long e);
  /* bm_set_bits variant for use while holding drbd_bm_lock */
  extern void _drbd_bm_set_bits(struct drbd_conf *mdev,
  		const unsigned long s, const unsigned long e);
  extern int  drbd_bm_test_bit(struct drbd_conf *mdev, unsigned long bitnr);
  extern int  drbd_bm_e_weight(struct drbd_conf *mdev, unsigned long enr);
  extern int  drbd_bm_write_sect(struct drbd_conf *mdev, unsigned long enr) __must_hold(local);
  extern int  drbd_bm_read(struct drbd_conf *mdev) __must_hold(local);
  extern int  drbd_bm_write(struct drbd_conf *mdev) __must_hold(local);
  extern unsigned long drbd_bm_ALe_set_all(struct drbd_conf *mdev,
  		unsigned long al_enr);
  extern size_t	     drbd_bm_words(struct drbd_conf *mdev);
  extern unsigned long drbd_bm_bits(struct drbd_conf *mdev);
  extern sector_t      drbd_bm_capacity(struct drbd_conf *mdev);
  extern unsigned long drbd_bm_find_next(struct drbd_conf *mdev, unsigned long bm_fo);
  /* bm_find_next variants for use while you hold drbd_bm_lock() */
  extern unsigned long _drbd_bm_find_next(struct drbd_conf *mdev, unsigned long bm_fo);
  extern unsigned long _drbd_bm_find_next_zero(struct drbd_conf *mdev, unsigned long bm_fo);
  extern unsigned long drbd_bm_total_weight(struct drbd_conf *mdev);
  extern int drbd_bm_rs_done(struct drbd_conf *mdev);
  /* for receive_bitmap */
  extern void drbd_bm_merge_lel(struct drbd_conf *mdev, size_t offset,
  		size_t number, unsigned long *buffer);
  /* for _drbd_send_bitmap and drbd_bm_write_sect */
  extern void drbd_bm_get_lel(struct drbd_conf *mdev, size_t offset,
  		size_t number, unsigned long *buffer);
  
  extern void drbd_bm_lock(struct drbd_conf *mdev, char *why);
  extern void drbd_bm_unlock(struct drbd_conf *mdev);
  
  extern int drbd_bm_count_bits(struct drbd_conf *mdev, const unsigned long s, const unsigned long e);
  /* drbd_main.c */
  
  extern struct kmem_cache *drbd_request_cache;
  extern struct kmem_cache *drbd_ee_cache;	/* epoch entries */
  extern struct kmem_cache *drbd_bm_ext_cache;	/* bitmap extents */
  extern struct kmem_cache *drbd_al_ext_cache;	/* activity log extents */
  extern mempool_t *drbd_request_mempool;
  extern mempool_t *drbd_ee_mempool;
  
  extern struct page *drbd_pp_pool; /* drbd's page pool */
  extern spinlock_t   drbd_pp_lock;
  extern int	    drbd_pp_vacant;
  extern wait_queue_head_t drbd_pp_wait;
  
  extern rwlock_t global_state_lock;
  
  extern struct drbd_conf *drbd_new_device(unsigned int minor);
  extern void drbd_free_mdev(struct drbd_conf *mdev);
  
  extern int proc_details;
  
  /* drbd_req */
  extern int drbd_make_request_26(struct request_queue *q, struct bio *bio);
  extern int drbd_read_remote(struct drbd_conf *mdev, struct drbd_request *req);
  extern int drbd_merge_bvec(struct request_queue *q, struct bvec_merge_data *bvm, struct bio_vec *bvec);
  extern int is_valid_ar_handle(struct drbd_request *, sector_t);
  
  
  /* drbd_nl.c */
  extern void drbd_suspend_io(struct drbd_conf *mdev);
  extern void drbd_resume_io(struct drbd_conf *mdev);
  extern char *ppsize(char *buf, unsigned long long size);
  extern sector_t drbd_new_dev_size(struct drbd_conf *, struct drbd_backing_dev *, int);
  enum determine_dev_size { dev_size_error = -1, unchanged = 0, shrunk = 1, grew = 2 };
  extern enum determine_dev_size drbd_determin_dev_size(struct drbd_conf *, enum dds_flags) __must_hold(local);
  extern void resync_after_online_grow(struct drbd_conf *);
  extern void drbd_setup_queue_param(struct drbd_conf *mdev, unsigned int) __must_hold(local);
  extern int drbd_set_role(struct drbd_conf *mdev, enum drbd_role new_role,
  		int force);
  enum drbd_disk_state drbd_try_outdate_peer(struct drbd_conf *mdev);
  extern int drbd_khelper(struct drbd_conf *mdev, char *cmd);
  
  /* drbd_worker.c */
  extern int drbd_worker(struct drbd_thread *thi);
  extern int drbd_alter_sa(struct drbd_conf *mdev, int na);
  extern void drbd_start_resync(struct drbd_conf *mdev, enum drbd_conns side);
  extern void resume_next_sg(struct drbd_conf *mdev);
  extern void suspend_other_sg(struct drbd_conf *mdev);
  extern int drbd_resync_finished(struct drbd_conf *mdev);
  /* maybe rather drbd_main.c ? */
  extern int drbd_md_sync_page_io(struct drbd_conf *mdev,
  		struct drbd_backing_dev *bdev, sector_t sector, int rw);
  extern void drbd_ov_oos_found(struct drbd_conf*, sector_t, int);
  
  static inline void ov_oos_print(struct drbd_conf *mdev)
  {
  	if (mdev->ov_last_oos_size) {
  		dev_err(DEV, "Out of sync: start=%llu, size=%lu (sectors)\n",
  		     (unsigned long long)mdev->ov_last_oos_start,
  		     (unsigned long)mdev->ov_last_oos_size);
  	}
  	mdev->ov_last_oos_size=0;
  }
  
  
  extern void drbd_csum_bio(struct drbd_conf *, struct crypto_hash *, struct bio *, void *);
  extern void drbd_csum_ee(struct drbd_conf *, struct crypto_hash *, struct drbd_epoch_entry *, void *);
  /* worker callbacks */
  extern int w_req_cancel_conflict(struct drbd_conf *, struct drbd_work *, int);
  extern int w_read_retry_remote(struct drbd_conf *, struct drbd_work *, int);
  extern int w_e_end_data_req(struct drbd_conf *, struct drbd_work *, int);
  extern int w_e_end_rsdata_req(struct drbd_conf *, struct drbd_work *, int);
  extern int w_e_end_csum_rs_req(struct drbd_conf *, struct drbd_work *, int);
  extern int w_e_end_ov_reply(struct drbd_conf *, struct drbd_work *, int);
  extern int w_e_end_ov_req(struct drbd_conf *, struct drbd_work *, int);
  extern int w_ov_finished(struct drbd_conf *, struct drbd_work *, int);
  extern int w_resync_inactive(struct drbd_conf *, struct drbd_work *, int);
  extern int w_resume_next_sg(struct drbd_conf *, struct drbd_work *, int);
  extern int w_send_write_hint(struct drbd_conf *, struct drbd_work *, int);
  extern int w_make_resync_request(struct drbd_conf *, struct drbd_work *, int);
  extern int w_send_dblock(struct drbd_conf *, struct drbd_work *, int);
  extern int w_send_barrier(struct drbd_conf *, struct drbd_work *, int);
  extern int w_send_read_req(struct drbd_conf *, struct drbd_work *, int);
  extern int w_prev_work_done(struct drbd_conf *, struct drbd_work *, int);
  extern int w_e_reissue(struct drbd_conf *, struct drbd_work *, int);
  
  extern void resync_timer_fn(unsigned long data);
  
  /* drbd_receiver.c */
  extern int drbd_submit_ee(struct drbd_conf *mdev, struct drbd_epoch_entry *e,
  		const unsigned rw, const int fault_type);
  extern int drbd_release_ee(struct drbd_conf *mdev, struct list_head *list);
  extern struct drbd_epoch_entry *drbd_alloc_ee(struct drbd_conf *mdev,
  					    u64 id,
  					    sector_t sector,
  					    unsigned int data_size,
  					    gfp_t gfp_mask) __must_hold(local);
  extern void drbd_free_ee(struct drbd_conf *mdev, struct drbd_epoch_entry *e);
  extern void drbd_wait_ee_list_empty(struct drbd_conf *mdev,
  		struct list_head *head);
  extern void _drbd_wait_ee_list_empty(struct drbd_conf *mdev,
  		struct list_head *head);
  extern void drbd_set_recv_tcq(struct drbd_conf *mdev, int tcq_enabled);
  extern void _drbd_clear_done_ee(struct drbd_conf *mdev, struct list_head *to_be_freed);
  extern void drbd_flush_workqueue(struct drbd_conf *mdev);
  
  /* yes, there is kernel_setsockopt, but only since 2.6.18. we don't need to
   * mess with get_fs/set_fs, we know we are KERNEL_DS always. */
  static inline int drbd_setsockopt(struct socket *sock, int level, int optname,
  			char __user *optval, int optlen)
  {
  	int err;
  	if (level == SOL_SOCKET)
  		err = sock_setsockopt(sock, level, optname, optval, optlen);
  	else
  		err = sock->ops->setsockopt(sock, level, optname, optval,
  					    optlen);
  	return err;
  }
  
  static inline void drbd_tcp_cork(struct socket *sock)
  {
  	int __user val = 1;
  	(void) drbd_setsockopt(sock, SOL_TCP, TCP_CORK,
  			(char __user *)&val, sizeof(val));
  }
  
  static inline void drbd_tcp_uncork(struct socket *sock)
  {
  	int __user val = 0;
  	(void) drbd_setsockopt(sock, SOL_TCP, TCP_CORK,
  			(char __user *)&val, sizeof(val));
  }
  
  static inline void drbd_tcp_nodelay(struct socket *sock)
  {
  	int __user val = 1;
  	(void) drbd_setsockopt(sock, SOL_TCP, TCP_NODELAY,
  			(char __user *)&val, sizeof(val));
  }
  
  static inline void drbd_tcp_quickack(struct socket *sock)
  {
  	int __user val = 2;
  	(void) drbd_setsockopt(sock, SOL_TCP, TCP_QUICKACK,
  			(char __user *)&val, sizeof(val));
  }
  
  void drbd_bump_write_ordering(struct drbd_conf *mdev, enum write_ordering_e wo);
  
  /* drbd_proc.c */
  extern struct proc_dir_entry *drbd_proc;
  extern const struct file_operations drbd_proc_fops;
  extern const char *drbd_conn_str(enum drbd_conns s);
  extern const char *drbd_role_str(enum drbd_role s);
  
  /* drbd_actlog.c */
  extern void drbd_al_begin_io(struct drbd_conf *mdev, sector_t sector);
  extern void drbd_al_complete_io(struct drbd_conf *mdev, sector_t sector);
  extern void drbd_rs_complete_io(struct drbd_conf *mdev, sector_t sector);
  extern int drbd_rs_begin_io(struct drbd_conf *mdev, sector_t sector);
  extern int drbd_try_rs_begin_io(struct drbd_conf *mdev, sector_t sector);
  extern void drbd_rs_cancel_all(struct drbd_conf *mdev);
  extern int drbd_rs_del_all(struct drbd_conf *mdev);
  extern void drbd_rs_failed_io(struct drbd_conf *mdev,
  		sector_t sector, int size);
  extern int drbd_al_read_log(struct drbd_conf *mdev, struct drbd_backing_dev *);
  extern void __drbd_set_in_sync(struct drbd_conf *mdev, sector_t sector,
  		int size, const char *file, const unsigned int line);
  #define drbd_set_in_sync(mdev, sector, size) \
  	__drbd_set_in_sync(mdev, sector, size, __FILE__, __LINE__)
  extern void __drbd_set_out_of_sync(struct drbd_conf *mdev, sector_t sector,
  		int size, const char *file, const unsigned int line);
  #define drbd_set_out_of_sync(mdev, sector, size) \
  	__drbd_set_out_of_sync(mdev, sector, size, __FILE__, __LINE__)
  extern void drbd_al_apply_to_bm(struct drbd_conf *mdev);
  extern void drbd_al_to_on_disk_bm(struct drbd_conf *mdev);
  extern void drbd_al_shrink(struct drbd_conf *mdev);
  
  
  /* drbd_nl.c */
  
  void drbd_nl_cleanup(void);
  int __init drbd_nl_init(void);
  void drbd_bcast_state(struct drbd_conf *mdev, union drbd_state);
  void drbd_bcast_sync_progress(struct drbd_conf *mdev);
  void drbd_bcast_ee(struct drbd_conf *mdev,
  		const char *reason, const int dgs,
  		const char* seen_hash, const char* calc_hash,
  		const struct drbd_epoch_entry* e);
  
  
  /**
   * DOC: DRBD State macros
   *
   * These macros are used to express state changes in easily readable form.
   *
   * The NS macros expand to a mask and a value, that can be bit ored onto the
   * current state as soon as the spinlock (req_lock) was taken.
   *
   * The _NS macros are used for state functions that get called with the
   * spinlock. These macros expand directly to the new state value.
   *
   * Besides the basic forms NS() and _NS() additional _?NS[23] are defined
   * to express state changes that affect more than one aspect of the state.
   *
   * E.g. NS2(conn, C_CONNECTED, peer, R_SECONDARY)
   * Means that the network connection was established and that the peer
   * is in secondary role.
   */
  #define role_MASK R_MASK
  #define peer_MASK R_MASK
  #define disk_MASK D_MASK
  #define pdsk_MASK D_MASK
  #define conn_MASK C_MASK
  #define susp_MASK 1
  #define user_isp_MASK 1
  #define aftr_isp_MASK 1
  
  #define NS(T, S) \
  	({ union drbd_state mask; mask.i = 0; mask.T = T##_MASK; mask; }), \
  	({ union drbd_state val; val.i = 0; val.T = (S); val; })
  #define NS2(T1, S1, T2, S2) \
  	({ union drbd_state mask; mask.i = 0; mask.T1 = T1##_MASK; \
  	  mask.T2 = T2##_MASK; mask; }), \
  	({ union drbd_state val; val.i = 0; val.T1 = (S1); \
  	  val.T2 = (S2); val; })
  #define NS3(T1, S1, T2, S2, T3, S3) \
  	({ union drbd_state mask; mask.i = 0; mask.T1 = T1##_MASK; \
  	  mask.T2 = T2##_MASK; mask.T3 = T3##_MASK; mask; }), \
  	({ union drbd_state val;  val.i = 0; val.T1 = (S1); \
  	  val.T2 = (S2); val.T3 = (S3); val; })
  
  #define _NS(D, T, S) \
  	D, ({ union drbd_state __ns; __ns.i = D->state.i; __ns.T = (S); __ns; })
  #define _NS2(D, T1, S1, T2, S2) \
  	D, ({ union drbd_state __ns; __ns.i = D->state.i; __ns.T1 = (S1); \
  	__ns.T2 = (S2); __ns; })
  #define _NS3(D, T1, S1, T2, S2, T3, S3) \
  	D, ({ union drbd_state __ns; __ns.i = D->state.i; __ns.T1 = (S1); \
  	__ns.T2 = (S2); __ns.T3 = (S3); __ns; })
  
  /*
   * inline helper functions
   *************************/
  
  /* see also page_chain_add and friends in drbd_receiver.c */
  static inline struct page *page_chain_next(struct page *page)
  {
  	return (struct page *)page_private(page);
  }
  #define page_chain_for_each(page) \
  	for (; page && ({ prefetch(page_chain_next(page)); 1; }); \
  			page = page_chain_next(page))
  #define page_chain_for_each_safe(page, n) \
  	for (; page && ({ n = page_chain_next(page); 1; }); page = n)
  
  static inline int drbd_bio_has_active_page(struct bio *bio)
  {
  	struct bio_vec *bvec;
  	int i;
  
  	__bio_for_each_segment(bvec, bio, i, 0) {
  		if (page_count(bvec->bv_page) > 1)
  			return 1;
  	}
  
  	return 0;
  }
  
  static inline int drbd_ee_has_active_page(struct drbd_epoch_entry *e)
  {
  	struct page *page = e->pages;
  	page_chain_for_each(page) {
  		if (page_count(page) > 1)
  			return 1;
  	}
  	return 0;
  }
  
  
  static inline void drbd_state_lock(struct drbd_conf *mdev)
  {
  	wait_event(mdev->misc_wait,
  		   !test_and_set_bit(CLUSTER_ST_CHANGE, &mdev->flags));
  }
  
  static inline void drbd_state_unlock(struct drbd_conf *mdev)
  {
  	clear_bit(CLUSTER_ST_CHANGE, &mdev->flags);
  	wake_up(&mdev->misc_wait);
  }
  
  static inline int _drbd_set_state(struct drbd_conf *mdev,
  				   union drbd_state ns, enum chg_state_flags flags,
  				   struct completion *done)
  {
  	int rv;
  
  	read_lock(&global_state_lock);
  	rv = __drbd_set_state(mdev, ns, flags, done);
  	read_unlock(&global_state_lock);
  
  	return rv;
  }
  
  /**
   * drbd_request_state() - Reqest a state change
   * @mdev:	DRBD device.
   * @mask:	mask of state bits to change.
   * @val:	value of new state bits.
   *
   * This is the most graceful way of requesting a state change. It is verbose
   * quite verbose in case the state change is not possible, and all those
   * state changes are globally serialized.
   */
  static inline int drbd_request_state(struct drbd_conf *mdev,
  				     union drbd_state mask,
  				     union drbd_state val)
  {
  	return _drbd_request_state(mdev, mask, val, CS_VERBOSE + CS_ORDERED);
  }
  
  #define __drbd_chk_io_error(m,f) __drbd_chk_io_error_(m,f, __func__)
  static inline void __drbd_chk_io_error_(struct drbd_conf *mdev, int forcedetach, const char *where)
  {
  	switch (mdev->ldev->dc.on_io_error) {
  	case EP_PASS_ON:
  		if (!forcedetach) {
  			if (__ratelimit(&drbd_ratelimit_state))
  				dev_err(DEV, "Local IO failed in %s."
  					     "Passing error on...\n", where);
  			break;
  		}
  		/* NOTE fall through to detach case if forcedetach set */
  	case EP_DETACH:
  	case EP_CALL_HELPER:
  		if (mdev->state.disk > D_FAILED) {
  			_drbd_set_state(_NS(mdev, disk, D_FAILED), CS_HARD, NULL);
  			dev_err(DEV, "Local IO failed in %s."
  				     "Detaching...\n", where);
  		}
  		break;
  	}
  }
  
  /**
   * drbd_chk_io_error: Handle the on_io_error setting, should be called from all io completion handlers
   * @mdev:	 DRBD device.
   * @error:	 Error code passed to the IO completion callback
   * @forcedetach: Force detach. I.e. the error happened while accessing the meta data
   *
   * See also drbd_main.c:after_state_ch() if (os.disk > D_FAILED && ns.disk == D_FAILED)
   */
  #define drbd_chk_io_error(m,e,f) drbd_chk_io_error_(m,e,f, __func__)
  static inline void drbd_chk_io_error_(struct drbd_conf *mdev,
  	int error, int forcedetach, const char *where)
  {
  	if (error) {
  		unsigned long flags;
  		spin_lock_irqsave(&mdev->req_lock, flags);
  		__drbd_chk_io_error_(mdev, forcedetach, where);
  		spin_unlock_irqrestore(&mdev->req_lock, flags);
  	}
  }
  
  
  /**
   * drbd_md_first_sector() - Returns the first sector number of the meta data area
   * @bdev:	Meta data block device.
   *
   * BTW, for internal meta data, this happens to be the maximum capacity
   * we could agree upon with our peer node.
   */
  static inline sector_t drbd_md_first_sector(struct drbd_backing_dev *bdev)
  {
  	switch (bdev->dc.meta_dev_idx) {
  	case DRBD_MD_INDEX_INTERNAL:
  	case DRBD_MD_INDEX_FLEX_INT:
  		return bdev->md.md_offset + bdev->md.bm_offset;
  	case DRBD_MD_INDEX_FLEX_EXT:
  	default:
  		return bdev->md.md_offset;
  	}
  }
  
  /**
   * drbd_md_last_sector() - Return the last sector number of the meta data area
   * @bdev:	Meta data block device.
   */
  static inline sector_t drbd_md_last_sector(struct drbd_backing_dev *bdev)
  {
  	switch (bdev->dc.meta_dev_idx) {
  	case DRBD_MD_INDEX_INTERNAL:
  	case DRBD_MD_INDEX_FLEX_INT:
  		return bdev->md.md_offset + MD_AL_OFFSET - 1;
  	case DRBD_MD_INDEX_FLEX_EXT:
  	default:
  		return bdev->md.md_offset + bdev->md.md_size_sect;
  	}
  }
  
  /* Returns the number of 512 byte sectors of the device */
  static inline sector_t drbd_get_capacity(struct block_device *bdev)
  {
  	/* return bdev ? get_capacity(bdev->bd_disk) : 0; */
  	return bdev ? bdev->bd_inode->i_size >> 9 : 0;
  }
  
  /**
   * drbd_get_max_capacity() - Returns the capacity we announce to out peer
   * @bdev:	Meta data block device.
   *
   * returns the capacity we announce to out peer.  we clip ourselves at the
   * various MAX_SECTORS, because if we don't, current implementation will
   * oops sooner or later
   */
  static inline sector_t drbd_get_max_capacity(struct drbd_backing_dev *bdev)
  {
  	sector_t s;
  	switch (bdev->dc.meta_dev_idx) {
  	case DRBD_MD_INDEX_INTERNAL:
  	case DRBD_MD_INDEX_FLEX_INT:
  		s = drbd_get_capacity(bdev->backing_bdev)
  			? min_t(sector_t, DRBD_MAX_SECTORS_FLEX,
  					drbd_md_first_sector(bdev))
  			: 0;
  		break;
  	case DRBD_MD_INDEX_FLEX_EXT:
  		s = min_t(sector_t, DRBD_MAX_SECTORS_FLEX,
  				drbd_get_capacity(bdev->backing_bdev));
  		/* clip at maximum size the meta device can support */
  		s = min_t(sector_t, s,
  			BM_EXT_TO_SECT(bdev->md.md_size_sect
  				     - bdev->md.bm_offset));
  		break;
  	default:
  		s = min_t(sector_t, DRBD_MAX_SECTORS,
  				drbd_get_capacity(bdev->backing_bdev));
  	}
  	return s;
  }
  
  /**
   * drbd_md_ss__() - Return the sector number of our meta data super block
   * @mdev:	DRBD device.
   * @bdev:	Meta data block device.
   */
  static inline sector_t drbd_md_ss__(struct drbd_conf *mdev,
  				    struct drbd_backing_dev *bdev)
  {
  	switch (bdev->dc.meta_dev_idx) {
  	default: /* external, some index */
  		return MD_RESERVED_SECT * bdev->dc.meta_dev_idx;
  	case DRBD_MD_INDEX_INTERNAL:
  		/* with drbd08, internal meta data is always "flexible" */
  	case DRBD_MD_INDEX_FLEX_INT:
  		/* sizeof(struct md_on_disk_07) == 4k
  		 * position: last 4k aligned block of 4k size */
  		if (!bdev->backing_bdev) {
  			if (__ratelimit(&drbd_ratelimit_state)) {
  				dev_err(DEV, "bdev->backing_bdev==NULL\n");
  				dump_stack();
  			}
  			return 0;
  		}
  		return (drbd_get_capacity(bdev->backing_bdev) & ~7ULL)
  			- MD_AL_OFFSET;
  	case DRBD_MD_INDEX_FLEX_EXT:
  		return 0;
  	}
  }
  
  static inline void
  _drbd_queue_work(struct drbd_work_queue *q, struct drbd_work *w)
  {
  	list_add_tail(&w->list, &q->q);
  	up(&q->s);
  }
  
  static inline void
  drbd_queue_work_front(struct drbd_work_queue *q, struct drbd_work *w)
  {
  	unsigned long flags;
  	spin_lock_irqsave(&q->q_lock, flags);
  	list_add(&w->list, &q->q);
  	up(&q->s); /* within the spinlock,
  		      see comment near end of drbd_worker() */
  	spin_unlock_irqrestore(&q->q_lock, flags);
  }
  
  static inline void
  drbd_queue_work(struct drbd_work_queue *q, struct drbd_work *w)
  {
  	unsigned long flags;
  	spin_lock_irqsave(&q->q_lock, flags);
  	list_add_tail(&w->list, &q->q);
  	up(&q->s); /* within the spinlock,
  		      see comment near end of drbd_worker() */
  	spin_unlock_irqrestore(&q->q_lock, flags);
  }
  
  static inline void wake_asender(struct drbd_conf *mdev)
  {
  	if (test_bit(SIGNAL_ASENDER, &mdev->flags))
  		force_sig(DRBD_SIG, mdev->asender.task);
  }
  
  static inline void request_ping(struct drbd_conf *mdev)
  {
  	set_bit(SEND_PING, &mdev->flags);
  	wake_asender(mdev);
  }
  
  static inline int drbd_send_short_cmd(struct drbd_conf *mdev,
  	enum drbd_packets cmd)
  {
  	struct p_header h;
  	return drbd_send_cmd(mdev, USE_DATA_SOCKET, cmd, &h, sizeof(h));
  }
  
  static inline int drbd_send_ping(struct drbd_conf *mdev)
  {
  	struct p_header h;
  	return drbd_send_cmd(mdev, USE_META_SOCKET, P_PING, &h, sizeof(h));
  }
  
  static inline int drbd_send_ping_ack(struct drbd_conf *mdev)
  {
  	struct p_header h;
  	return drbd_send_cmd(mdev, USE_META_SOCKET, P_PING_ACK, &h, sizeof(h));
  }
  
  static inline void drbd_thread_stop(struct drbd_thread *thi)
  {
  	_drbd_thread_stop(thi, FALSE, TRUE);
  }
  
  static inline void drbd_thread_stop_nowait(struct drbd_thread *thi)
  {
  	_drbd_thread_stop(thi, FALSE, FALSE);
  }
  
  static inline void drbd_thread_restart_nowait(struct drbd_thread *thi)
  {
  	_drbd_thread_stop(thi, TRUE, FALSE);
  }
  
  /* counts how many answer packets packets we expect from our peer,
   * for either explicit application requests,
   * or implicit barrier packets as necessary.
   * increased:
   *  w_send_barrier
   *  _req_mod(req, queue_for_net_write or queue_for_net_read);
   *    it is much easier and equally valid to count what we queue for the
   *    worker, even before it actually was queued or send.
   *    (drbd_make_request_common; recovery path on read io-error)
   * decreased:
   *  got_BarrierAck (respective tl_clear, tl_clear_barrier)
   *  _req_mod(req, data_received)
   *     [from receive_DataReply]
   *  _req_mod(req, write_acked_by_peer or recv_acked_by_peer or neg_acked)
   *     [from got_BlockAck (P_WRITE_ACK, P_RECV_ACK)]
   *     for some reason it is NOT decreased in got_NegAck,
   *     but in the resulting cleanup code from report_params.
   *     we should try to remember the reason for that...
   *  _req_mod(req, send_failed or send_canceled)
   *  _req_mod(req, connection_lost_while_pending)
   *     [from tl_clear_barrier]
   */
  static inline void inc_ap_pending(struct drbd_conf *mdev)
  {
  	atomic_inc(&mdev->ap_pending_cnt);
  }
  
  #define ERR_IF_CNT_IS_NEGATIVE(which)				\
  	if (atomic_read(&mdev->which) < 0)			\
  		dev_err(DEV, "in %s:%d: " #which " = %d < 0 !\n",	\
  		    __func__ , __LINE__ ,			\
  		    atomic_read(&mdev->which))
  
  #define dec_ap_pending(mdev)	do {				\
  	typecheck(struct drbd_conf *, mdev);			\
  	if (atomic_dec_and_test(&mdev->ap_pending_cnt))		\
  		wake_up(&mdev->misc_wait);			\
  	ERR_IF_CNT_IS_NEGATIVE(ap_pending_cnt); } while (0)
  
  /* counts how many resync-related answers we still expect from the peer
   *		     increase			decrease
   * C_SYNC_TARGET sends P_RS_DATA_REQUEST (and expects P_RS_DATA_REPLY)
   * C_SYNC_SOURCE sends P_RS_DATA_REPLY   (and expects P_WRITE_ACK whith ID_SYNCER)
   *					   (or P_NEG_ACK with ID_SYNCER)
   */
  static inline void inc_rs_pending(struct drbd_conf *mdev)
  {
  	atomic_inc(&mdev->rs_pending_cnt);
  }
  
  #define dec_rs_pending(mdev)	do {				\
  	typecheck(struct drbd_conf *, mdev);			\
  	atomic_dec(&mdev->rs_pending_cnt);			\
  	ERR_IF_CNT_IS_NEGATIVE(rs_pending_cnt); } while (0)
  
  /* counts how many answers we still need to send to the peer.
   * increased on
   *  receive_Data	unless protocol A;
   *			we need to send a P_RECV_ACK (proto B)
   *			or P_WRITE_ACK (proto C)
   *  receive_RSDataReply (recv_resync_read) we need to send a P_WRITE_ACK
   *  receive_DataRequest (receive_RSDataRequest) we need to send back P_DATA
   *  receive_Barrier_*	we need to send a P_BARRIER_ACK
   */
  static inline void inc_unacked(struct drbd_conf *mdev)
  {
  	atomic_inc(&mdev->unacked_cnt);
  }
  
  #define dec_unacked(mdev)	do {				\
  	typecheck(struct drbd_conf *, mdev);			\
  	atomic_dec(&mdev->unacked_cnt);				\
  	ERR_IF_CNT_IS_NEGATIVE(unacked_cnt); } while (0)
  
  #define sub_unacked(mdev, n)	do {				\
  	typecheck(struct drbd_conf *, mdev);			\
  	atomic_sub(n, &mdev->unacked_cnt);			\
  	ERR_IF_CNT_IS_NEGATIVE(unacked_cnt); } while (0)
  
  
  static inline void put_net_conf(struct drbd_conf *mdev)
  {
  	if (atomic_dec_and_test(&mdev->net_cnt))
  		wake_up(&mdev->misc_wait);
  }
  
  /**
   * get_net_conf() - Increase ref count on mdev->net_conf; Returns 0 if nothing there
   * @mdev:	DRBD device.
   *
   * You have to call put_net_conf() when finished working with mdev->net_conf.
   */
  static inline int get_net_conf(struct drbd_conf *mdev)
  {
  	int have_net_conf;
  
  	atomic_inc(&mdev->net_cnt);
  	have_net_conf = mdev->state.conn >= C_UNCONNECTED;
  	if (!have_net_conf)
  		put_net_conf(mdev);
  	return have_net_conf;
  }
  
  /**
   * get_ldev() - Increase the ref count on mdev->ldev. Returns 0 if there is no ldev
   * @M:		DRBD device.
   *
   * You have to call put_ldev() when finished working with mdev->ldev.
   */
  #define get_ldev(M) __cond_lock(local, _get_ldev_if_state(M,D_INCONSISTENT))
  #define get_ldev_if_state(M,MINS) __cond_lock(local, _get_ldev_if_state(M,MINS))
  
  static inline void put_ldev(struct drbd_conf *mdev)
  {
  	__release(local);
  	if (atomic_dec_and_test(&mdev->local_cnt))
  		wake_up(&mdev->misc_wait);
  	D_ASSERT(atomic_read(&mdev->local_cnt) >= 0);
  }
  
  #ifndef __CHECKER__
  static inline int _get_ldev_if_state(struct drbd_conf *mdev, enum drbd_disk_state mins)
  {
  	int io_allowed;
  
  	atomic_inc(&mdev->local_cnt);
  	io_allowed = (mdev->state.disk >= mins);
  	if (!io_allowed)
  		put_ldev(mdev);
  	return io_allowed;
  }
  #else
  extern int _get_ldev_if_state(struct drbd_conf *mdev, enum drbd_disk_state mins);
  #endif
  
  /* you must have an "get_ldev" reference */
  static inline void drbd_get_syncer_progress(struct drbd_conf *mdev,
  		unsigned long *bits_left, unsigned int *per_mil_done)
  {
  	/*
  	 * this is to break it at compile time when we change that
  	 * (we may feel 4TB maximum storage per drbd is not enough)
  	 */
  	typecheck(unsigned long, mdev->rs_total);
  
  	/* note: both rs_total and rs_left are in bits, i.e. in
  	 * units of BM_BLOCK_SIZE.
  	 * for the percentage, we don't care. */
  
  	*bits_left = drbd_bm_total_weight(mdev) - mdev->rs_failed;
  	/* >> 10 to prevent overflow,
  	 * +1 to prevent division by zero */
  	if (*bits_left > mdev->rs_total) {
  		/* doh. maybe a logic bug somewhere.
  		 * may also be just a race condition
  		 * between this and a disconnect during sync.
  		 * for now, just prevent in-kernel buffer overflow.
  		 */
  		smp_rmb();
  		dev_warn(DEV, "cs:%s rs_left=%lu > rs_total=%lu (rs_failed %lu)\n",
  				drbd_conn_str(mdev->state.conn),
  				*bits_left, mdev->rs_total, mdev->rs_failed);
  		*per_mil_done = 0;
  	} else {
  		/* make sure the calculation happens in long context */
  		unsigned long tmp = 1000UL -
  				(*bits_left >> 10)*1000UL
  				/ ((mdev->rs_total >> 10) + 1UL);
  		*per_mil_done = tmp;
  	}
  }
  
  
  /* this throttles on-the-fly application requests
   * according to max_buffers settings;
   * maybe re-implement using semaphores? */
  static inline int drbd_get_max_buffers(struct drbd_conf *mdev)
  {
  	int mxb = 1000000; /* arbitrary limit on open requests */
  	if (get_net_conf(mdev)) {
  		mxb = mdev->net_conf->max_buffers;
  		put_net_conf(mdev);
  	}
  	return mxb;
  }
  
  static inline int drbd_state_is_stable(union drbd_state s)
  {
  
  	/* DO NOT add a default clause, we want the compiler to warn us
  	 * for any newly introduced state we may have forgotten to add here */
  
  	switch ((enum drbd_conns)s.conn) {
  	/* new io only accepted when there is no connection, ... */
  	case C_STANDALONE:
  	case C_WF_CONNECTION:
  	/* ... or there is a well established connection. */
  	case C_CONNECTED:
  	case C_SYNC_SOURCE:
  	case C_SYNC_TARGET:
  	case C_VERIFY_S:
  	case C_VERIFY_T:
  	case C_PAUSED_SYNC_S:
  	case C_PAUSED_SYNC_T:
  		/* maybe stable, look at the disk state */
  		break;
  
  	/* no new io accepted during tansitional states
  	 * like handshake or teardown */
  	case C_DISCONNECTING:
  	case C_UNCONNECTED:
  	case C_TIMEOUT:
  	case C_BROKEN_PIPE:
  	case C_NETWORK_FAILURE:
  	case C_PROTOCOL_ERROR:
  	case C_TEAR_DOWN:
  	case C_WF_REPORT_PARAMS:
  	case C_STARTING_SYNC_S:
  	case C_STARTING_SYNC_T:
  	case C_WF_BITMAP_S:
  	case C_WF_BITMAP_T:
  	case C_WF_SYNC_UUID:
  	case C_MASK:
  		/* not "stable" */
  		return 0;
  	}
  
  	switch ((enum drbd_disk_state)s.disk) {
  	case D_DISKLESS:
  	case D_INCONSISTENT:
  	case D_OUTDATED:
  	case D_CONSISTENT:
  	case D_UP_TO_DATE:
  		/* disk state is stable as well. */
  		break;
  
  	/* no new io accepted during tansitional states */
  	case D_ATTACHING:
  	case D_FAILED:
  	case D_NEGOTIATING:
  	case D_UNKNOWN:
  	case D_MASK:
  		/* not "stable" */
  		return 0;
  	}
  
  	return 1;
  }
  
  static inline int __inc_ap_bio_cond(struct drbd_conf *mdev)
  {
  	int mxb = drbd_get_max_buffers(mdev);
  
  	if (mdev->state.susp)
  		return 0;
  	if (test_bit(SUSPEND_IO, &mdev->flags))
  		return 0;
  
  	/* to avoid potential deadlock or bitmap corruption,
  	 * in various places, we only allow new application io
  	 * to start during "stable" states. */
  
  	/* no new io accepted when attaching or detaching the disk */
  	if (!drbd_state_is_stable(mdev->state))
  		return 0;
  
  	/* since some older kernels don't have atomic_add_unless,
  	 * and we are within the spinlock anyways, we have this workaround.  */
  	if (atomic_read(&mdev->ap_bio_cnt) > mxb)
  		return 0;
  	if (test_bit(BITMAP_IO, &mdev->flags))
  		return 0;
  	return 1;
  }
  
  /* I'd like to use wait_event_lock_irq,
   * but I'm not sure when it got introduced,
   * and not sure when it has 3 or 4 arguments */
  static inline void inc_ap_bio(struct drbd_conf *mdev, int count)
  {
  	/* compare with after_state_ch,
  	 * os.conn != C_WF_BITMAP_S && ns.conn == C_WF_BITMAP_S */
  	DEFINE_WAIT(wait);
  
  	/* we wait here
  	 *    as long as the device is suspended
  	 *    until the bitmap is no longer on the fly during connection
  	 *    handshake as long as we would exeed the max_buffer limit.
  	 *
  	 * to avoid races with the reconnect code,
  	 * we need to atomic_inc within the spinlock. */
  
  	spin_lock_irq(&mdev->req_lock);
  	while (!__inc_ap_bio_cond(mdev)) {
  		prepare_to_wait(&mdev->misc_wait, &wait, TASK_UNINTERRUPTIBLE);
  		spin_unlock_irq(&mdev->req_lock);
  		schedule();
  		finish_wait(&mdev->misc_wait, &wait);
  		spin_lock_irq(&mdev->req_lock);
  	}
  	atomic_add(count, &mdev->ap_bio_cnt);
  	spin_unlock_irq(&mdev->req_lock);
  }
  
  static inline void dec_ap_bio(struct drbd_conf *mdev)
  {
  	int mxb = drbd_get_max_buffers(mdev);
  	int ap_bio = atomic_dec_return(&mdev->ap_bio_cnt);
  
  	D_ASSERT(ap_bio >= 0);
  	/* this currently does wake_up for every dec_ap_bio!
  	 * maybe rather introduce some type of hysteresis?
  	 * e.g. (ap_bio == mxb/2 || ap_bio == 0) ? */
  	if (ap_bio < mxb)
  		wake_up(&mdev->misc_wait);
  	if (ap_bio == 0 && test_bit(BITMAP_IO, &mdev->flags)) {
  		if (!test_and_set_bit(BITMAP_IO_QUEUED, &mdev->flags))
  			drbd_queue_work(&mdev->data.work, &mdev->bm_io_work.w);
  	}
  }
  
  static inline void drbd_set_ed_uuid(struct drbd_conf *mdev, u64 val)
  {
  	mdev->ed_uuid = val;
  }
  
  static inline int seq_cmp(u32 a, u32 b)
  {
  	/* we assume wrap around at 32bit.
  	 * for wrap around at 24bit (old atomic_t),
  	 * we'd have to
  	 *  a <<= 8; b <<= 8;
  	 */
  	return (s32)(a) - (s32)(b);
  }
  #define seq_lt(a, b) (seq_cmp((a), (b)) < 0)
  #define seq_gt(a, b) (seq_cmp((a), (b)) > 0)
  #define seq_ge(a, b) (seq_cmp((a), (b)) >= 0)
  #define seq_le(a, b) (seq_cmp((a), (b)) <= 0)
  /* CAUTION: please no side effects in arguments! */
  #define seq_max(a, b) ((u32)(seq_gt((a), (b)) ? (a) : (b)))
  
  static inline void update_peer_seq(struct drbd_conf *mdev, unsigned int new_seq)
  {
  	unsigned int m;
  	spin_lock(&mdev->peer_seq_lock);
  	m = seq_max(mdev->peer_seq, new_seq);
  	mdev->peer_seq = m;
  	spin_unlock(&mdev->peer_seq_lock);
  	if (m == new_seq)
  		wake_up(&mdev->seq_wait);
  }
  
  static inline void drbd_update_congested(struct drbd_conf *mdev)
  {
  	struct sock *sk = mdev->data.socket->sk;
  	if (sk->sk_wmem_queued > sk->sk_sndbuf * 4 / 5)
  		set_bit(NET_CONGESTED, &mdev->flags);
  }
  
  static inline int drbd_queue_order_type(struct drbd_conf *mdev)
  {
  	/* sorry, we currently have no working implementation
  	 * of distributed TCQ stuff */
  #ifndef QUEUE_ORDERED_NONE
  #define QUEUE_ORDERED_NONE 0
  #endif
  	return QUEUE_ORDERED_NONE;
  }
  
  static inline void drbd_blk_run_queue(struct request_queue *q)
  {
  	if (q && q->unplug_fn)
  		q->unplug_fn(q);
  }
  
  static inline void drbd_kick_lo(struct drbd_conf *mdev)
  {
  	if (get_ldev(mdev)) {
  		drbd_blk_run_queue(bdev_get_queue(mdev->ldev->backing_bdev));
  		put_ldev(mdev);
  	}
  }
  
  static inline void drbd_md_flush(struct drbd_conf *mdev)
  {
  	int r;
  
  	if (test_bit(MD_NO_BARRIER, &mdev->flags))
  		return;
  
  	r = blkdev_issue_flush(mdev->ldev->md_bdev, GFP_KERNEL, NULL,
  			BLKDEV_IFL_WAIT);
  	if (r) {
  		set_bit(MD_NO_BARRIER, &mdev->flags);
  		dev_err(DEV, "meta data flush failed with status %d, disabling md-flushes\n", r);
  	}
  }
  
  #endif
  