xref: /src/sys/dev/raidframe/rf_dagdegrd.c

/*	$NetBSD: rf_dagdegrd.c,v 1.1 1998/11/13 04:20:27 oster Exp $	*/
/*
 * Copyright (c) 1995 Carnegie-Mellon University.
 * All rights reserved.
 *
 * Author: Mark Holland, Daniel Stodolsky, William V. Courtright II
 *
 * Permission to use, copy, modify and distribute this software and
 * its documentation is hereby granted, provided that both the copyright
 * notice and this permission notice appear in all copies of the
 * software, derivative works or modified versions, and any portions
 * thereof, and that both notices appear in supporting documentation.
 *
 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
 * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
 * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
 *
 * Carnegie Mellon requests users of this software to return to
 *
 *  Software Distribution Coordinator  or  Software.Distribution (at) CS.CMU.EDU
 *  School of Computer Science
 *  Carnegie Mellon University
 *  Pittsburgh PA 15213-3890
 *
 * any improvements or extensions that they make and grant Carnegie the
 * rights to redistribute these changes.
 */

/*
 * rf_dagdegrd.c
 *
 * code for creating degraded read DAGs
 *
 * :
 * Log: rf_dagdegrd.c,v
 * Revision 1.20  1996/11/05 21:10:40  jimz
 * failed pda generalization
 *
 * Revision 1.19  1996/08/19  23:30:36  jimz
 * fix chained declustered accesses in degraded mode when mirror copy is failed
 * (workload shifting not allowed when there are no duplicate copies extant)
 *
 * Revision 1.18  1996/07/31  16:29:01  jimz
 * asm/asmap re-fix (EO merge)
 *
 * Revision 1.17  1996/07/31  15:34:34  jimz
 * evenodd changes; bugfixes for double-degraded archs, generalize
 * some formerly PQ-only functions
 *
 * Revision 1.16  1996/07/28  20:31:39  jimz
 * i386netbsd port
 * true/false fixup
 *
 * Revision 1.15  1996/07/27  23:36:08  jimz
 * Solaris port of simulator
 *
 * Revision 1.14  1996/07/22  19:52:16  jimz
 * switched node params to RF_DagParam_t, a union of
 * a 64-bit int and a void *, for better portability
 * attempted hpux port, but failed partway through for
 * lack of a single C compiler capable of compiling all
 * source files
 *
 * Revision 1.13  1996/06/09  02:36:46  jimz
 * lots of little crufty cleanup- fixup whitespace
 * issues, comment #ifdefs, improve typing in some
 * places (esp size-related)
 *
 * Revision 1.12  1996/06/07  22:26:27  jimz
 * type-ify which_ru (RF_ReconUnitNum_t)
 *
 * Revision 1.11  1996/06/07  21:33:04  jimz
 * begin using consistent types for sector numbers,
 * stripe numbers, row+col numbers, recon unit numbers
 *
 * Revision 1.10  1996/05/31  22:26:54  jimz
 * fix a lot of mapping problems, memory allocation problems
 * found some weird lock issues, fixed 'em
 * more code cleanup
 *
 * Revision 1.9  1996/05/30  11:29:41  jimz
 * Numerous bug fixes. Stripe lock release code disagreed with the taking code
 * about when stripes should be locked (I made it consistent: no parity, no lock)
 * There was a lot of extra serialization of I/Os which I've removed- a lot of
 * it was to calculate values for the cache code, which is no longer with us.
 * More types, function, macro cleanup. Added code to properly quiesce the array
 * on shutdown. Made a lot of stuff array-specific which was (bogusly) general
 * before. Fixed memory allocation, freeing bugs.
 *
 * Revision 1.8  1996/05/27  18:56:37  jimz
 * more code cleanup
 * better typing
 * compiles in all 3 environments
 *
 * Revision 1.7  1996/05/24  22:17:04  jimz
 * continue code + namespace cleanup
 * typed a bunch of flags
 *
 * Revision 1.6  1996/05/24  04:28:55  jimz
 * release cleanup ckpt
 *
 * Revision 1.5  1996/05/23  21:46:35  jimz
 * checkpoint in code cleanup (release prep)
 * lots of types, function names have been fixed
 *
 * Revision 1.4  1996/05/23  00:33:23  jimz
 * code cleanup: move all debug decls to rf_options.c, all extern
 * debug decls to rf_options.h, all debug vars preceded by rf_
 *
 * Revision 1.3  1996/05/18  19:51:34  jimz
 * major code cleanup- fix syntax, make some types consistent,
 * add prototypes, clean out dead code, et cetera
 *
 * Revision 1.2  1996/05/08  21:01:24  jimz
 * fixed up enum type names that were conflicting with other
 * enums and function names (ie, "panic")
 * future naming trends will be towards RF_ and rf_ for
 * everything raidframe-related
 *
 * Revision 1.1  1996/05/03  19:22:23  wvcii
 * Initial revision
 *
 */

#include "rf_types.h"
#include "rf_raid.h"
#include "rf_dag.h"
#include "rf_dagutils.h"
#include "rf_dagfuncs.h"
#include "rf_threadid.h"
#include "rf_debugMem.h"
#include "rf_memchunk.h"
#include "rf_general.h"
#include "rf_dagdegrd.h"
#include "rf_sys.h"


/******************************************************************************
 *
 * General comments on DAG creation:
 *
 * All DAGs in this file use roll-away error recovery.  Each DAG has a single
 * commit node, usually called "Cmt."  If an error occurs before the Cmt node
 * is reached, the execution engine will halt forward execution and work
 * backward through the graph, executing the undo functions.  Assuming that
 * each node in the graph prior to the Cmt node are undoable and atomic - or -
 * does not make changes to permanent state, the graph will fail atomically.
 * If an error occurs after the Cmt node executes, the engine will roll-forward
 * through the graph, blindly executing nodes until it reaches the end.
 * If a graph reaches the end, it is assumed to have completed successfully.
 *
 * A graph has only 1 Cmt node.
 *
 */


/******************************************************************************
 *
 * The following wrappers map the standard DAG creation interface to the
 * DAG creation routines.  Additionally, these wrappers enable experimentation
 * with new DAG structures by providing an extra level of indirection, allowing
 * the DAG creation routines to be replaced at this single point.
 */

void rf_CreateRaidFiveDegradedReadDAG(
  RF_Raid_t             *raidPtr,
  RF_AccessStripeMap_t  *asmap,
  RF_DagHeader_t        *dag_h,
  void                  *bp,
  RF_RaidAccessFlags_t   flags,
  RF_AllocListElem_t    *allocList)
{
  rf_CreateDegradedReadDAG(raidPtr, asmap, dag_h, bp, flags, allocList,
    &rf_xorRecoveryFuncs);
}


/******************************************************************************
 *
 * DAG creation code begins here
 */


/******************************************************************************
 * Create a degraded read DAG for RAID level 1
 *
 * Hdr -> Nil -> R(p/s)d -> Commit -> Trm
 *
 * The "Rd" node reads data from the surviving disk in the mirror pair
 *   Rpd - read of primary copy
 *   Rsd - read of secondary copy
 *
 * Parameters:  raidPtr   - description of the physical array
 *              asmap     - logical & physical addresses for this access
 *              bp        - buffer ptr (for holding write data)
 *              flags     - general flags (e.g. disk locking)
 *              allocList - list of memory allocated in DAG creation
 *****************************************************************************/

void rf_CreateRaidOneDegradedReadDAG(
  RF_Raid_t             *raidPtr,
  RF_AccessStripeMap_t  *asmap,
  RF_DagHeader_t        *dag_h,
  void                  *bp,
  RF_RaidAccessFlags_t   flags,
  RF_AllocListElem_t    *allocList)
{
  RF_DagNode_t *nodes, *rdNode, *blockNode, *commitNode, *termNode;
  RF_StripeNum_t parityStripeID;
  RF_ReconUnitNum_t which_ru;
  RF_PhysDiskAddr_t *pda;
  int useMirror, i;

  useMirror = 0;
  parityStripeID = rf_RaidAddressToParityStripeID(&(raidPtr->Layout),
    asmap->raidAddress, &which_ru);
  if (rf_dagDebug) {
    printf("[Creating RAID level 1 degraded read DAG]\n");
  }
  dag_h->creator = "RaidOneDegradedReadDAG";
  /* alloc the Wnd nodes and the Wmir node */
  if (asmap->numDataFailed == 0)
    useMirror = RF_FALSE;
  else
    useMirror = RF_TRUE;

  /* total number of nodes = 1 + (block + commit + terminator) */
  RF_CallocAndAdd(nodes, 4, sizeof(RF_DagNode_t), (RF_DagNode_t *), allocList);
  i = 0;
  rdNode      = &nodes[i]; i++;
  blockNode   = &nodes[i]; i++;
  commitNode = &nodes[i]; i++;
  termNode    = &nodes[i]; i++;

  /* this dag can not commit until the commit node is reached.   errors prior
   * to the commit point imply the dag has failed and must be retried
   */
  dag_h->numCommitNodes = 1;
  dag_h->numCommits = 0;
  dag_h->numSuccedents = 1;

  /* initialize the block, commit, and terminator nodes */
  rf_InitNode(blockNode, rf_wait, RF_FALSE, rf_NullNodeFunc, rf_NullNodeUndoFunc,
    NULL, 1, 0, 0, 0, dag_h, "Nil", allocList);
  rf_InitNode(commitNode, rf_wait, RF_TRUE, rf_NullNodeFunc, rf_NullNodeUndoFunc,
    NULL, 1, 1, 0, 0, dag_h, "Cmt", allocList);
  rf_InitNode(termNode, rf_wait, RF_FALSE, rf_TerminateFunc, rf_TerminateUndoFunc,
    NULL, 0, 1, 0, 0, dag_h, "Trm", allocList);

  pda = asmap->physInfo;
  RF_ASSERT(pda != NULL);
  /* parityInfo must describe entire parity unit */
  RF_ASSERT(asmap->parityInfo->next == NULL);

  /* initialize the data node */
  if (!useMirror) {
    /* read primary copy of data */
    rf_InitNode(rdNode, rf_wait, RF_FALSE, rf_DiskReadFunc, rf_DiskReadUndoFunc,
      rf_GenericWakeupFunc, 1, 1, 4, 0, dag_h, "Rpd", allocList);
    rdNode->params[0].p = pda;
    rdNode->params[1].p = pda->bufPtr;
    rdNode->params[2].v = parityStripeID;
    rdNode->params[3].v = RF_CREATE_PARAM3(RF_IO_NORMAL_PRIORITY, 0, 0, which_ru);
  }
  else {
    /* read secondary copy of data */
    rf_InitNode(rdNode, rf_wait, RF_FALSE, rf_DiskReadFunc, rf_DiskReadUndoFunc,
      rf_GenericWakeupFunc, 1, 1, 4, 0, dag_h, "Rsd", allocList);
    rdNode->params[0].p = asmap->parityInfo;
    rdNode->params[1].p = pda->bufPtr;
    rdNode->params[2].v = parityStripeID;
    rdNode->params[3].v = RF_CREATE_PARAM3(RF_IO_NORMAL_PRIORITY, 0, 0, which_ru);
  }

  /* connect header to block node */
  RF_ASSERT(dag_h->numSuccedents == 1);
  RF_ASSERT(blockNode->numAntecedents == 0);
  dag_h->succedents[0] = blockNode;

  /* connect block node to rdnode */
  RF_ASSERT(blockNode->numSuccedents == 1);
  RF_ASSERT(rdNode->numAntecedents == 1);
  blockNode->succedents[0] = rdNode;
  rdNode->antecedents[0] = blockNode;
  rdNode->antType[0] = rf_control;

  /* connect rdnode to commit node */
  RF_ASSERT(rdNode->numSuccedents == 1);
  RF_ASSERT(commitNode->numAntecedents == 1);
  rdNode->succedents[0] = commitNode;
  commitNode->antecedents[0] = rdNode;
  commitNode->antType[0] = rf_control;

  /* connect commit node to terminator */
  RF_ASSERT(commitNode->numSuccedents == 1);
  RF_ASSERT(termNode->numAntecedents == 1);
  RF_ASSERT(termNode->numSuccedents == 0);
  commitNode->succedents[0] = termNode;
  termNode->antecedents[0] = commitNode;
  termNode->antType[0] = rf_control;
}



/******************************************************************************
 *
 * creates a DAG to perform a degraded-mode read of data within one stripe.
 * This DAG is as follows:
 *
 * Hdr -> Block -> Rud -> Xor -> Cmt -> T
 *              -> Rrd ->
 *              -> Rp -->
 *
 * Each R node is a successor of the L node
 * One successor arc from each R node goes to C, and the other to X
 * There is one Rud for each chunk of surviving user data requested by the
 * user, and one Rrd for each chunk of surviving user data _not_ being read by
 * the user
 * R = read, ud = user data, rd = recovery (surviving) data, p = parity
 * X = XOR, C = Commit, T = terminate
 *
 * The block node guarantees a single source node.
 *
 * Note:  The target buffer for the XOR node is set to the actual user buffer
 * where the failed data is supposed to end up.  This buffer is zero'd by the
 * code here.  Thus, if you create a degraded read dag, use it, and then
 * re-use, you have to be sure to zero the target buffer prior to the re-use.
 *
 * The recfunc argument at the end specifies the name and function used for
 * the redundancy
 * recovery function.
 *
 *****************************************************************************/

void rf_CreateDegradedReadDAG(
  RF_Raid_t             *raidPtr,
  RF_AccessStripeMap_t  *asmap,
  RF_DagHeader_t        *dag_h,
  void                  *bp,
  RF_RaidAccessFlags_t   flags,
  RF_AllocListElem_t    *allocList,
  RF_RedFuncs_t         *recFunc)
{
  RF_DagNode_t *nodes, *rudNodes, *rrdNodes, *xorNode, *blockNode;
  RF_DagNode_t *commitNode, *rpNode, *termNode;
  int nNodes, nRrdNodes, nRudNodes, nXorBufs, i;
  int j, paramNum;
  RF_SectorCount_t sectorsPerSU;
  RF_ReconUnitNum_t which_ru;
  char *overlappingPDAs; /* a temporary array of flags */
  RF_AccessStripeMapHeader_t *new_asm_h[2];
  RF_PhysDiskAddr_t *pda, *parityPDA;
  RF_StripeNum_t parityStripeID;
  RF_PhysDiskAddr_t *failedPDA;
  RF_RaidLayout_t *layoutPtr;
  char *rpBuf;

  layoutPtr = &(raidPtr->Layout);
  /* failedPDA points to the pda within the asm that targets the failed disk */
  failedPDA = asmap->failedPDAs[0];
  parityStripeID = rf_RaidAddressToParityStripeID(layoutPtr,
    asmap->raidAddress, &which_ru);
  sectorsPerSU = layoutPtr->sectorsPerStripeUnit;

  if (rf_dagDebug) {
    printf("[Creating degraded read DAG]\n");
  }

  RF_ASSERT( asmap->numDataFailed == 1 );
  dag_h->creator = "DegradedReadDAG";

  /*
   * generate two ASMs identifying the surviving data we need
   * in order to recover the lost data
   */

  /* overlappingPDAs array must be zero'd */
  RF_Calloc(overlappingPDAs, asmap->numStripeUnitsAccessed, sizeof(char), (char *));
  rf_GenerateFailedAccessASMs(raidPtr, asmap, failedPDA, dag_h, new_asm_h, &nXorBufs,
    &rpBuf, overlappingPDAs, allocList);

  /*
   * create all the nodes at once
   *
   * -1 because no access is generated for the failed pda
   */
  nRudNodes = asmap->numStripeUnitsAccessed-1;
  nRrdNodes = ((new_asm_h[0]) ? new_asm_h[0]->stripeMap->numStripeUnitsAccessed : 0) +
              ((new_asm_h[1]) ? new_asm_h[1]->stripeMap->numStripeUnitsAccessed : 0);
  nNodes = 5 + nRudNodes + nRrdNodes; /* lock, unlock, xor, Rp, Rud, Rrd */
  RF_CallocAndAdd(nodes, nNodes, sizeof(RF_DagNode_t), (RF_DagNode_t *),
    allocList);
  i = 0;
  blockNode   = &nodes[i]; i++;
  commitNode  = &nodes[i]; i++;
  xorNode     = &nodes[i]; i++;
  rpNode      = &nodes[i]; i++;
  termNode    = &nodes[i]; i++;
  rudNodes    = &nodes[i]; i += nRudNodes;
  rrdNodes    = &nodes[i]; i += nRrdNodes;
  RF_ASSERT(i == nNodes);

  /* initialize nodes */
  dag_h->numCommitNodes = 1;
  dag_h->numCommits = 0;
  /* this dag can not commit until the commit node is reached
   * errors prior to the commit point imply the dag has failed
   */
  dag_h->numSuccedents = 1;

  rf_InitNode(blockNode, rf_wait, RF_FALSE, rf_NullNodeFunc, rf_NullNodeUndoFunc,
    NULL, nRudNodes+nRrdNodes+1, 0, 0, 0, dag_h, "Nil", allocList);
  rf_InitNode(commitNode, rf_wait, RF_TRUE, rf_NullNodeFunc, rf_NullNodeUndoFunc,
    NULL, 1, 1, 0, 0, dag_h, "Cmt", allocList);
  rf_InitNode(termNode, rf_wait, RF_FALSE, rf_TerminateFunc, rf_TerminateUndoFunc,
    NULL, 0, 1, 0, 0, dag_h, "Trm", allocList);
  rf_InitNode(xorNode, rf_wait, RF_FALSE, recFunc->simple, rf_NullNodeUndoFunc,
    NULL, 1, nRudNodes+nRrdNodes+1, 2*nXorBufs+2, 1, dag_h,
	recFunc->SimpleName, allocList);

  /* fill in the Rud nodes */
  for (pda=asmap->physInfo, i=0; i<nRudNodes; i++, pda=pda->next) {
    if (pda == failedPDA) {i--; continue;}
    rf_InitNode(&rudNodes[i], rf_wait, RF_FALSE, rf_DiskReadFunc,
      rf_DiskReadUndoFunc, rf_GenericWakeupFunc, 1, 1, 4, 0, dag_h,
      "Rud", allocList);
    RF_ASSERT(pda);
    rudNodes[i].params[0].p = pda;
    rudNodes[i].params[1].p = pda->bufPtr;
    rudNodes[i].params[2].v = parityStripeID;
    rudNodes[i].params[3].v = RF_CREATE_PARAM3(RF_IO_NORMAL_PRIORITY, 0, 0, which_ru);
  }

  /* fill in the Rrd nodes */
  i = 0;
  if (new_asm_h[0]) {
    for (pda=new_asm_h[0]->stripeMap->physInfo;
         i<new_asm_h[0]->stripeMap->numStripeUnitsAccessed;
         i++, pda=pda->next)
    {
      rf_InitNode(&rrdNodes[i], rf_wait, RF_FALSE, rf_DiskReadFunc,
        rf_DiskReadUndoFunc, rf_GenericWakeupFunc, 1, 1, 4, 0,
        dag_h, "Rrd", allocList);
      RF_ASSERT(pda);
      rrdNodes[i].params[0].p = pda;
      rrdNodes[i].params[1].p = pda->bufPtr;
      rrdNodes[i].params[2].v = parityStripeID;
      rrdNodes[i].params[3].v = RF_CREATE_PARAM3(RF_IO_NORMAL_PRIORITY, 0, 0, which_ru);
    }
  }
  if (new_asm_h[1]) {
    for (j=0,pda=new_asm_h[1]->stripeMap->physInfo;
         j<new_asm_h[1]->stripeMap->numStripeUnitsAccessed;
         j++, pda=pda->next)
    {
      rf_InitNode(&rrdNodes[i+j], rf_wait, RF_FALSE, rf_DiskReadFunc,
        rf_DiskReadUndoFunc, rf_GenericWakeupFunc, 1, 1, 4, 0,
        dag_h, "Rrd", allocList);
      RF_ASSERT(pda);
      rrdNodes[i+j].params[0].p = pda;
      rrdNodes[i+j].params[1].p = pda->bufPtr;
      rrdNodes[i+j].params[2].v = parityStripeID;
      rrdNodes[i+j].params[3].v = RF_CREATE_PARAM3(RF_IO_NORMAL_PRIORITY, 0, 0, which_ru);
    }
  }

  /* make a PDA for the parity unit */
  RF_MallocAndAdd(parityPDA, sizeof(RF_PhysDiskAddr_t), (RF_PhysDiskAddr_t *), allocList);
  parityPDA->row = asmap->parityInfo->row;
  parityPDA->col = asmap->parityInfo->col;
  parityPDA->startSector = ((asmap->parityInfo->startSector / sectorsPerSU)
    * sectorsPerSU) + (failedPDA->startSector % sectorsPerSU);
  parityPDA->numSector = failedPDA->numSector;

  /* initialize the Rp node */
  rf_InitNode(rpNode, rf_wait, RF_FALSE, rf_DiskReadFunc, rf_DiskReadUndoFunc,
    rf_GenericWakeupFunc, 1, 1, 4, 0, dag_h, "Rp ", allocList);
  rpNode->params[0].p = parityPDA;
  rpNode->params[1].p = rpBuf;
  rpNode->params[2].v = parityStripeID;
  rpNode->params[3].v = RF_CREATE_PARAM3(RF_IO_NORMAL_PRIORITY, 0, 0, which_ru);

  /*
   * the last and nastiest step is to assign all
   * the parameters of the Xor node
   */
  paramNum=0;
  for (i=0; i<nRrdNodes; i++) {
    /* all the Rrd nodes need to be xored together */
    xorNode->params[paramNum++] = rrdNodes[i].params[0];
    xorNode->params[paramNum++] = rrdNodes[i].params[1];
  }
  for (i=0; i<nRudNodes; i++) {
    /* any Rud nodes that overlap the failed access need to be xored in */
    if (overlappingPDAs[i]) {
      RF_MallocAndAdd(pda, sizeof(RF_PhysDiskAddr_t), (RF_PhysDiskAddr_t *), allocList);
      bcopy((char *)rudNodes[i].params[0].p, (char *)pda, sizeof(RF_PhysDiskAddr_t));
      rf_RangeRestrictPDA(raidPtr, failedPDA, pda, RF_RESTRICT_DOBUFFER, 0);
      xorNode->params[paramNum++].p = pda;
      xorNode->params[paramNum++].p = pda->bufPtr;
    }
  }
  RF_Free(overlappingPDAs, asmap->numStripeUnitsAccessed * sizeof(char));

  /* install parity pda as last set of params to be xor'd */
  xorNode->params[paramNum++].p = parityPDA;
  xorNode->params[paramNum++].p = rpBuf;

  /*
   * the last 2 params to the recovery xor node are
   * the failed PDA and the raidPtr
   */
  xorNode->params[paramNum++].p = failedPDA;
  xorNode->params[paramNum++].p = raidPtr;
  RF_ASSERT( paramNum == 2*nXorBufs+2 );

  /*
   * The xor node uses results[0] as the target buffer.
   * Set pointer and zero the buffer. In the kernel, this
   * may be a user buffer in which case we have to remap it.
   */
  xorNode->results[0] = failedPDA->bufPtr;
  RF_BZERO(bp, failedPDA->bufPtr, rf_RaidAddressToByte(raidPtr,
    failedPDA->numSector));

  /* connect nodes to form graph */
  /* connect the header to the block node */
  RF_ASSERT(dag_h->numSuccedents == 1);
  RF_ASSERT(blockNode->numAntecedents == 0);
  dag_h->succedents[0] = blockNode;

  /* connect the block node to the read nodes */
  RF_ASSERT(blockNode->numSuccedents == (1 + nRrdNodes + nRudNodes));
  RF_ASSERT(rpNode->numAntecedents == 1);
  blockNode->succedents[0] = rpNode;
  rpNode->antecedents[0] = blockNode;
  rpNode->antType[0] = rf_control;
  for (i = 0; i < nRrdNodes; i++) {
    RF_ASSERT(rrdNodes[i].numSuccedents == 1);
    blockNode->succedents[1 + i] = &rrdNodes[i];
    rrdNodes[i].antecedents[0] = blockNode;
    rrdNodes[i].antType[0] = rf_control;
  }
  for (i = 0; i < nRudNodes; i++) {
    RF_ASSERT(rudNodes[i].numSuccedents == 1);
    blockNode->succedents[1 + nRrdNodes + i] = &rudNodes[i];
    rudNodes[i].antecedents[0] = blockNode;
    rudNodes[i].antType[0] = rf_control;
  }

  /* connect the read nodes to the xor node */
  RF_ASSERT(xorNode->numAntecedents == (1 + nRrdNodes + nRudNodes));
  RF_ASSERT(rpNode->numSuccedents == 1);
  rpNode->succedents[0] = xorNode;
  xorNode->antecedents[0] = rpNode;
  xorNode->antType[0] = rf_trueData;
  for (i = 0; i < nRrdNodes; i++) {
    RF_ASSERT(rrdNodes[i].numSuccedents == 1);
    rrdNodes[i].succedents[0] = xorNode;
    xorNode->antecedents[1 + i] = &rrdNodes[i];
    xorNode->antType[1 + i] = rf_trueData;
  }
  for (i = 0; i < nRudNodes; i++) {
    RF_ASSERT(rudNodes[i].numSuccedents == 1);
    rudNodes[i].succedents[0] = xorNode;
    xorNode->antecedents[1 + nRrdNodes + i] = &rudNodes[i];
    xorNode->antType[1 + nRrdNodes + i] = rf_trueData;
  }

  /* connect the xor node to the commit node */
  RF_ASSERT(xorNode->numSuccedents == 1);
  RF_ASSERT(commitNode->numAntecedents == 1);
  xorNode->succedents[0] = commitNode;
  commitNode->antecedents[0] = xorNode;
  commitNode->antType[0] = rf_control;

  /* connect the termNode to the commit node */
  RF_ASSERT(commitNode->numSuccedents == 1);
  RF_ASSERT(termNode->numAntecedents == 1);
  RF_ASSERT(termNode->numSuccedents == 0);
  commitNode->succedents[0] = termNode;
  termNode->antType[0] = rf_control;
  termNode->antecedents[0]  = commitNode;
}


/******************************************************************************
 * Create a degraded read DAG for Chained Declustering
 *
 * Hdr -> Nil -> R(p/s)d -> Cmt -> Trm
 *
 * The "Rd" node reads data from the surviving disk in the mirror pair
 *   Rpd - read of primary copy
 *   Rsd - read of secondary copy
 *
 * Parameters:  raidPtr   - description of the physical array
 *              asmap     - logical & physical addresses for this access
 *              bp        - buffer ptr (for holding write data)
 *              flags     - general flags (e.g. disk locking)
 *              allocList - list of memory allocated in DAG creation
 *****************************************************************************/

void rf_CreateRaidCDegradedReadDAG(
  RF_Raid_t             *raidPtr,
  RF_AccessStripeMap_t  *asmap,
  RF_DagHeader_t        *dag_h,
  void                  *bp,
  RF_RaidAccessFlags_t   flags,
  RF_AllocListElem_t    *allocList)
{
  RF_DagNode_t *nodes, *rdNode, *blockNode, *commitNode, *termNode;
  RF_StripeNum_t parityStripeID;
  int useMirror, i, shiftable;
  RF_ReconUnitNum_t which_ru;
  RF_PhysDiskAddr_t *pda;

  if ((asmap->numDataFailed + asmap->numParityFailed) == 0) {
    shiftable = RF_TRUE;
  }
  else {
    shiftable = RF_FALSE;
  }
  useMirror = 0;
  parityStripeID = rf_RaidAddressToParityStripeID(&(raidPtr->Layout),
    asmap->raidAddress, &which_ru);

  if (rf_dagDebug) {
    printf("[Creating RAID C degraded read DAG]\n");
  }
  dag_h->creator = "RaidCDegradedReadDAG";
  /* alloc the Wnd nodes and the Wmir node */
  if (asmap->numDataFailed == 0)
    useMirror = RF_FALSE;
  else
    useMirror = RF_TRUE;

  /* total number of nodes = 1 + (block + commit + terminator) */
  RF_CallocAndAdd(nodes, 4, sizeof(RF_DagNode_t), (RF_DagNode_t *), allocList);
  i = 0;
  rdNode      = &nodes[i]; i++;
  blockNode   = &nodes[i]; i++;
  commitNode = &nodes[i]; i++;
  termNode    = &nodes[i]; i++;

  /*
   * This dag can not commit until the commit node is reached.
   * Errors prior to the commit point imply the dag has failed
   * and must be retried.
   */
  dag_h->numCommitNodes = 1;
  dag_h->numCommits = 0;
  dag_h->numSuccedents = 1;

  /* initialize the block, commit, and terminator nodes */
  rf_InitNode(blockNode, rf_wait, RF_FALSE, rf_NullNodeFunc, rf_NullNodeUndoFunc,
    NULL, 1, 0, 0, 0, dag_h, "Nil", allocList);
  rf_InitNode(commitNode, rf_wait, RF_TRUE, rf_NullNodeFunc, rf_NullNodeUndoFunc,
    NULL, 1, 1, 0, 0, dag_h, "Cmt", allocList);
  rf_InitNode(termNode, rf_wait, RF_FALSE, rf_TerminateFunc, rf_TerminateUndoFunc,
    NULL, 0, 1, 0, 0, dag_h, "Trm", allocList);

  pda = asmap->physInfo;
  RF_ASSERT(pda != NULL);
  /* parityInfo must describe entire parity unit */
  RF_ASSERT(asmap->parityInfo->next == NULL);

  /* initialize the data node */
  if (!useMirror) {
    rf_InitNode(rdNode, rf_wait, RF_FALSE, rf_DiskReadFunc, rf_DiskReadUndoFunc,
      rf_GenericWakeupFunc, 1, 1, 4, 0, dag_h, "Rpd", allocList);
    if (shiftable && rf_compute_workload_shift(raidPtr, pda)) {
     /* shift this read to the next disk in line */
  	 rdNode->params[0].p = asmap->parityInfo;
   	 rdNode->params[1].p = pda->bufPtr;
	 rdNode->params[2].v = parityStripeID;
	 rdNode->params[3].v = RF_CREATE_PARAM3(RF_IO_NORMAL_PRIORITY, 0, 0, which_ru);
	}
    else {
      /* read primary copy */
      rdNode->params[0].p = pda;
      rdNode->params[1].p = pda->bufPtr;
      rdNode->params[2].v = parityStripeID;
      rdNode->params[3].v = RF_CREATE_PARAM3(RF_IO_NORMAL_PRIORITY, 0, 0, which_ru);
    }
  }
  else {
    /* read secondary copy of data */
    rf_InitNode(rdNode, rf_wait, RF_FALSE, rf_DiskReadFunc, rf_DiskReadUndoFunc,
      rf_GenericWakeupFunc, 1, 1, 4, 0, dag_h, "Rsd", allocList);
    rdNode->params[0].p = asmap->parityInfo;
    rdNode->params[1].p = pda->bufPtr;
    rdNode->params[2].v = parityStripeID;
    rdNode->params[3].v = RF_CREATE_PARAM3(RF_IO_NORMAL_PRIORITY, 0, 0, which_ru);
  }

  /* connect header to block node */
  RF_ASSERT(dag_h->numSuccedents == 1);
  RF_ASSERT(blockNode->numAntecedents == 0);
  dag_h->succedents[0] = blockNode;

  /* connect block node to rdnode */
  RF_ASSERT(blockNode->numSuccedents == 1);
  RF_ASSERT(rdNode->numAntecedents == 1);
  blockNode->succedents[0] = rdNode;
  rdNode->antecedents[0] = blockNode;
  rdNode->antType[0] = rf_control;

  /* connect rdnode to commit node */
  RF_ASSERT(rdNode->numSuccedents == 1);
  RF_ASSERT(commitNode->numAntecedents == 1);
  rdNode->succedents[0] = commitNode;
  commitNode->antecedents[0] = rdNode;
  commitNode->antType[0] = rf_control;

  /* connect commit node to terminator */
  RF_ASSERT(commitNode->numSuccedents == 1);
  RF_ASSERT(termNode->numAntecedents == 1);
  RF_ASSERT(termNode->numSuccedents == 0);
  commitNode->succedents[0] = termNode;
  termNode->antecedents[0] = commitNode;
  termNode->antType[0] = rf_control;
}

/*
 * XXX move this elsewhere?
 */
void rf_DD_GenerateFailedAccessASMs(
  RF_Raid_t              *raidPtr,
  RF_AccessStripeMap_t   *asmap,
  RF_PhysDiskAddr_t     **pdap,
  int                    *nNodep,
  RF_PhysDiskAddr_t     **pqpdap,
  int                    *nPQNodep,
  RF_AllocListElem_t     *allocList)
{
  RF_RaidLayout_t *layoutPtr = &(raidPtr->Layout);
  int PDAPerDisk,i;
  RF_SectorCount_t secPerSU = layoutPtr->sectorsPerStripeUnit;
  int numDataCol = layoutPtr->numDataCol;
  int state;
  RF_SectorNum_t suoff, suend;
  unsigned firstDataCol, napdas, count;
  RF_SectorNum_t fone_start, fone_end, ftwo_start = 0, ftwo_end = 0;
  RF_PhysDiskAddr_t *fone = asmap->failedPDAs[0], *ftwo = asmap->failedPDAs[1];
  RF_PhysDiskAddr_t *pda_p;
  RF_PhysDiskAddr_t *phys_p;
  RF_RaidAddr_t sosAddr;

  /* determine how many pda's we will have to generate per unaccess stripe.
     If there is only one failed data unit, it is one; if two, possibly two,
     depending wether they overlap. */

  fone_start = rf_StripeUnitOffset(layoutPtr,fone->startSector);
  fone_end = fone_start + fone->numSector;

#define CONS_PDA(if,start,num) \
  pda_p->row = asmap->if->row;    pda_p->col = asmap->if->col; \
  pda_p->startSector = ((asmap->if->startSector / secPerSU) * secPerSU) + start; \
  pda_p->numSector = num; \
  pda_p->next = NULL; \
  RF_MallocAndAdd(pda_p->bufPtr,rf_RaidAddressToByte(raidPtr,num),(char *), allocList)

  if (asmap->numDataFailed==1)
    {
      PDAPerDisk = 1;
      state = 1;
      RF_MallocAndAdd(*pqpdap,2*sizeof(RF_PhysDiskAddr_t),(RF_PhysDiskAddr_t *), allocList);
      pda_p = *pqpdap;
      /* build p */
      CONS_PDA(parityInfo,fone_start,fone->numSector);
      pda_p->type = RF_PDA_TYPE_PARITY;
      pda_p++;
      /* build q */
      CONS_PDA(qInfo,fone_start,fone->numSector);
      pda_p->type = RF_PDA_TYPE_Q;
    }
  else
    {
      ftwo_start = rf_StripeUnitOffset(layoutPtr,ftwo->startSector);
      ftwo_end = ftwo_start + ftwo->numSector;
      if (fone->numSector + ftwo->numSector > secPerSU)
	{
	  PDAPerDisk = 1;
	  state = 2;
	  RF_MallocAndAdd(*pqpdap,2*sizeof(RF_PhysDiskAddr_t),(RF_PhysDiskAddr_t *), allocList);
	  pda_p = *pqpdap;
	  CONS_PDA(parityInfo,0,secPerSU);
	  pda_p->type = RF_PDA_TYPE_PARITY;
	  pda_p++;
	  CONS_PDA(qInfo,0,secPerSU);
	  pda_p->type = RF_PDA_TYPE_Q;
	}
      else
	{
	  PDAPerDisk = 2;
	  state = 3;
	  /* four of them, fone, then ftwo */
	  RF_MallocAndAdd(*pqpdap,4*sizeof(RF_PhysDiskAddr_t),(RF_PhysDiskAddr_t *), allocList);
	  pda_p = *pqpdap;
	  CONS_PDA(parityInfo,fone_start,fone->numSector);
	  pda_p->type = RF_PDA_TYPE_PARITY;
	  pda_p++;
	  CONS_PDA(qInfo,fone_start,fone->numSector);
	  pda_p->type = RF_PDA_TYPE_Q;
	  pda_p++;
	  CONS_PDA(parityInfo,ftwo_start,ftwo->numSector);
	  pda_p->type = RF_PDA_TYPE_PARITY;
	  pda_p++;
	  CONS_PDA(qInfo,ftwo_start,ftwo->numSector);
	  pda_p->type = RF_PDA_TYPE_Q;
	}
    }
  /* figure out number of nonaccessed pda */
  napdas = PDAPerDisk * (numDataCol - asmap->numStripeUnitsAccessed - (ftwo==NULL ? 1 : 0));
  *nPQNodep = PDAPerDisk;

  /* sweep over the over accessed pda's, figuring out the number of
     additional pda's to generate. Of course, skip the failed ones */

  count = 0;
  for ( pda_p=asmap->physInfo; pda_p; pda_p= pda_p->next)
    {
      if ((pda_p == fone) || (pda_p == ftwo))
	continue;
      suoff = rf_StripeUnitOffset(layoutPtr,pda_p->startSector);
      suend = suoff + pda_p->numSector;
      switch (state)
	{
	case 1: /* one failed PDA to overlap */
	  /* if a PDA doesn't contain the failed unit, it can
	     only miss the start or end, not both */
	  if ((suoff > fone_start) || (suend <fone_end))
	    count++;
	  break;
	case 2: /* whole stripe */
	  if (suoff) /* leak at begining */
	    count++;
	  if (suend < numDataCol) /* leak at end */
	    count++;
	  break;
	case 3: /* two disjoint units */
	  if ((suoff > fone_start) || (suend <fone_end))
	    count++;
	  if ((suoff > ftwo_start) || (suend <ftwo_end))
	    count++;
	  break;
	default:
	  RF_PANIC();
	}
    }

  napdas += count;
  *nNodep = napdas;
  if (napdas == 0) return; /* short circuit */

  /* allocate up our list of pda's */

  RF_CallocAndAdd(pda_p, napdas, sizeof(RF_PhysDiskAddr_t), (RF_PhysDiskAddr_t *), allocList);
  *pdap = pda_p;

  /* linkem together */
  for (i=0; i < (napdas-1); i++)
    pda_p[i].next = pda_p+(i+1);

  /* march through the one's up to the first accessed disk */
  firstDataCol = rf_RaidAddressToStripeUnitID(&(raidPtr->Layout),asmap->physInfo->raidAddress) % numDataCol;
  sosAddr      = rf_RaidAddressOfPrevStripeBoundary(layoutPtr, asmap->raidAddress);
  for (i=0; i < firstDataCol; i++)
    {
      if ((pda_p - (*pdap)) == napdas)
	continue;
      pda_p->type = RF_PDA_TYPE_DATA;
      pda_p->raidAddress = sosAddr + (i * secPerSU);
      (raidPtr->Layout.map->MapSector)(raidPtr,pda_p->raidAddress, &(pda_p->row), &(pda_p->col), &(pda_p->startSector), 0);
      /* skip over dead disks */
      if (RF_DEAD_DISK(raidPtr->Disks[pda_p->row][pda_p->col].status))
	continue;
      switch (state)
	{
	case 1: /* fone */
	  pda_p->numSector = fone->numSector;
	  pda_p->raidAddress += fone_start;
	  pda_p->startSector += fone_start;
	  RF_MallocAndAdd(pda_p->bufPtr, rf_RaidAddressToByte(raidPtr,pda_p->numSector), (char *), allocList);
	  break;
	case 2: /* full stripe */
	  pda_p->numSector = secPerSU;
	  RF_MallocAndAdd(pda_p->bufPtr, rf_RaidAddressToByte(raidPtr,secPerSU), (char *), allocList);
	  break;
	case 3: /* two slabs */
	  pda_p->numSector = fone->numSector;
	  pda_p->raidAddress += fone_start;
	  pda_p->startSector += fone_start;
	  RF_MallocAndAdd(pda_p->bufPtr, rf_RaidAddressToByte(raidPtr,pda_p->numSector), (char *), allocList);
	  pda_p++;
          pda_p->type = RF_PDA_TYPE_DATA;
          pda_p->raidAddress = sosAddr + (i * secPerSU);
          (raidPtr->Layout.map->MapSector)(raidPtr,pda_p->raidAddress, &(pda_p->row), &(pda_p->col), &(pda_p->startSector), 0);
	  pda_p->numSector = ftwo->numSector;
	  pda_p->raidAddress += ftwo_start;
	  pda_p->startSector += ftwo_start;
	  RF_MallocAndAdd(pda_p->bufPtr, rf_RaidAddressToByte(raidPtr,pda_p->numSector), (char *), allocList);
	  break;
	default:
	  RF_PANIC();
	}
      pda_p++;
    }

  /* march through the touched stripe units */
  for (phys_p = asmap->physInfo; phys_p; phys_p = phys_p->next, i++)
    {
      if ((phys_p == asmap->failedPDAs[0]) || (phys_p == asmap->failedPDAs[1]))
	continue;
      suoff = rf_StripeUnitOffset(layoutPtr,phys_p->startSector);
      suend = suoff + phys_p->numSector;
      switch(state)
	{
	case 1: /* single buffer */
	  if (suoff > fone_start)
	    {
	      RF_ASSERT( suend >= fone_end );
	      /* The data read starts after the mapped access,
		 snip off the begining */
	      pda_p->numSector = suoff - fone_start;
	      pda_p->raidAddress = sosAddr + (i*secPerSU) + fone_start;
	      (raidPtr->Layout.map->MapSector)(raidPtr,pda_p->raidAddress, &(pda_p->row), &(pda_p->col), &(pda_p->startSector), 0);
	      RF_MallocAndAdd(pda_p->bufPtr, rf_RaidAddressToByte(raidPtr,pda_p->numSector), (char *), allocList);
	      pda_p++;
	    }
	  if (suend < fone_end)
	    {
	      RF_ASSERT ( suoff <= fone_start);
	      /* The data read stops before the end of the failed access, extend */
	      pda_p->numSector = fone_end - suend;
	      pda_p->raidAddress = sosAddr + (i*secPerSU) + suend; /* off by one? */
	      (raidPtr->Layout.map->MapSector)(raidPtr,pda_p->raidAddress, &(pda_p->row), &(pda_p->col), &(pda_p->startSector), 0);
	      RF_MallocAndAdd(pda_p->bufPtr, rf_RaidAddressToByte(raidPtr,pda_p->numSector), (char *), allocList);
	      pda_p++;
	    }
	  break;
	case 2: /* whole stripe unit */
	  RF_ASSERT( (suoff == 0) || (suend == secPerSU));
	  if (suend < secPerSU)
	    { /* short read, snip from end on */
	      pda_p->numSector = secPerSU - suend;
	      pda_p->raidAddress = sosAddr + (i*secPerSU) + suend; /* off by one? */
	      (raidPtr->Layout.map->MapSector)(raidPtr,pda_p->raidAddress, &(pda_p->row), &(pda_p->col), &(pda_p->startSector), 0);
	      RF_MallocAndAdd(pda_p->bufPtr, rf_RaidAddressToByte(raidPtr,pda_p->numSector), (char *), allocList);
	      pda_p++;
	    }
	  else
	    if (suoff > 0)
	      { /* short at front */
		pda_p->numSector = suoff;
		pda_p->raidAddress = sosAddr + (i*secPerSU);
		(raidPtr->Layout.map->MapSector)(raidPtr,pda_p->raidAddress, &(pda_p->row), &(pda_p->col), &(pda_p->startSector), 0);
		RF_MallocAndAdd(pda_p->bufPtr, rf_RaidAddressToByte(raidPtr,pda_p->numSector), (char *), allocList);
		pda_p++;
	      }
	  break;
	case 3: /* two nonoverlapping failures */
	  if ((suoff > fone_start) || (suend <fone_end))
	    {
	      if (suoff > fone_start)
		{
		  RF_ASSERT( suend >= fone_end );
		  /* The data read starts after the mapped access,
		     snip off the begining */
		  pda_p->numSector = suoff - fone_start;
		  pda_p->raidAddress = sosAddr + (i*secPerSU) + fone_start;
		  (raidPtr->Layout.map->MapSector)(raidPtr,pda_p->raidAddress, &(pda_p->row), &(pda_p->col), &(pda_p->startSector), 0);
		  RF_MallocAndAdd(pda_p->bufPtr, rf_RaidAddressToByte(raidPtr,pda_p->numSector), (char *), allocList);
		  pda_p++;
		}
	      if (suend < fone_end)
		{
		  RF_ASSERT ( suoff <= fone_start);
		  /* The data read stops before the end of the failed access, extend */
		  pda_p->numSector = fone_end - suend;
		  pda_p->raidAddress = sosAddr + (i*secPerSU) + suend; /* off by one? */
		  (raidPtr->Layout.map->MapSector)(raidPtr,pda_p->raidAddress, &(pda_p->row), &(pda_p->col), &(pda_p->startSector), 0);
		  RF_MallocAndAdd(pda_p->bufPtr, rf_RaidAddressToByte(raidPtr,pda_p->numSector), (char *), allocList);
		  pda_p++;
		}
	    }
	  if ((suoff > ftwo_start) || (suend <ftwo_end))
	    {
	      if (suoff > ftwo_start)
		{
		  RF_ASSERT( suend >= ftwo_end );
		  /* The data read starts after the mapped access,
		     snip off the begining */
		  pda_p->numSector = suoff - ftwo_start;
		  pda_p->raidAddress = sosAddr + (i*secPerSU) + ftwo_start;
		  (raidPtr->Layout.map->MapSector)(raidPtr,pda_p->raidAddress, &(pda_p->row), &(pda_p->col), &(pda_p->startSector), 0);
		  RF_MallocAndAdd(pda_p->bufPtr, rf_RaidAddressToByte(raidPtr,pda_p->numSector), (char *), allocList);
		  pda_p++;
		}
	      if (suend < ftwo_end)
		{
		  RF_ASSERT ( suoff <= ftwo_start);
		  /* The data read stops before the end of the failed access, extend */
		  pda_p->numSector = ftwo_end - suend;
		  pda_p->raidAddress = sosAddr + (i*secPerSU) + suend; /* off by one? */
		  (raidPtr->Layout.map->MapSector)(raidPtr,pda_p->raidAddress, &(pda_p->row), &(pda_p->col), &(pda_p->startSector), 0);
		  RF_MallocAndAdd(pda_p->bufPtr, rf_RaidAddressToByte(raidPtr,pda_p->numSector), (char *), allocList);
		  pda_p++;
		}
	    }
	  break;
	default:
	  RF_PANIC();
        }
    }

  /* after the last accessed disk */
  for (; i < numDataCol; i++ )
    {
      if ((pda_p - (*pdap)) == napdas)
	continue;
      pda_p->type = RF_PDA_TYPE_DATA;
      pda_p->raidAddress = sosAddr + (i * secPerSU);
      (raidPtr->Layout.map->MapSector)(raidPtr,pda_p->raidAddress, &(pda_p->row), &(pda_p->col), &(pda_p->startSector), 0);
      /* skip over dead disks */
      if (RF_DEAD_DISK(raidPtr->Disks[pda_p->row][pda_p->col].status))
	continue;
      switch (state)
	{
	case 1: /* fone */
	  pda_p->numSector = fone->numSector;
	  pda_p->raidAddress += fone_start;
	  pda_p->startSector += fone_start;
	  RF_MallocAndAdd(pda_p->bufPtr, rf_RaidAddressToByte(raidPtr,pda_p->numSector), (char *), allocList);
	  break;
	case 2: /* full stripe */
	  pda_p->numSector = secPerSU;
	  RF_MallocAndAdd(pda_p->bufPtr, rf_RaidAddressToByte(raidPtr,secPerSU), (char *), allocList);
	  break;
	case 3: /* two slabs */
	  pda_p->numSector = fone->numSector;
	  pda_p->raidAddress += fone_start;
	  pda_p->startSector += fone_start;
	  RF_MallocAndAdd(pda_p->bufPtr, rf_RaidAddressToByte(raidPtr,pda_p->numSector), (char *), allocList);
	  pda_p++;
          pda_p->type = RF_PDA_TYPE_DATA;
          pda_p->raidAddress = sosAddr + (i * secPerSU);
          (raidPtr->Layout.map->MapSector)(raidPtr,pda_p->raidAddress, &(pda_p->row), &(pda_p->col), &(pda_p->startSector), 0);
	  pda_p->numSector = ftwo->numSector;
	  pda_p->raidAddress += ftwo_start;
	  pda_p->startSector += ftwo_start;
	  RF_MallocAndAdd(pda_p->bufPtr, rf_RaidAddressToByte(raidPtr,pda_p->numSector), (char *), allocList);
	  break;
	default:
	  RF_PANIC();
	}
      pda_p++;
    }

  RF_ASSERT  (pda_p - *pdap == napdas);
  return;
}

#define INIT_DISK_NODE(node,name) \
rf_InitNode(node, rf_wait, RF_FALSE, rf_DiskReadFunc, rf_DiskReadUndoFunc, rf_GenericWakeupFunc, 2,1,4,0, dag_h, name, allocList); \
(node)->succedents[0] = unblockNode; \
(node)->succedents[1] = recoveryNode; \
(node)->antecedents[0] = blockNode; \
(node)->antType[0] = rf_control

#define DISK_NODE_PARAMS(_node_,_p_) \
  (_node_).params[0].p = _p_ ; \
  (_node_).params[1].p = (_p_)->bufPtr; \
  (_node_).params[2].v = parityStripeID; \
  (_node_).params[3].v = RF_CREATE_PARAM3(RF_IO_NORMAL_PRIORITY, 0, 0, which_ru)

void rf_DoubleDegRead(
  RF_Raid_t              *raidPtr,
  RF_AccessStripeMap_t   *asmap,
  RF_DagHeader_t         *dag_h,
  void                   *bp,
  RF_RaidAccessFlags_t    flags,
  RF_AllocListElem_t     *allocList,
  char                   *redundantReadNodeName,
  char                   *recoveryNodeName,
  int                   (*recovFunc)(RF_DagNode_t *))
{
  RF_RaidLayout_t *layoutPtr = &(raidPtr->Layout);
  RF_DagNode_t *nodes, *rudNodes, *rrdNodes, *recoveryNode, *blockNode, *unblockNode, *rpNodes, *rqNodes, *termNode;
  RF_PhysDiskAddr_t *pda, *pqPDAs;
  RF_PhysDiskAddr_t *npdas;
  int nNodes, nRrdNodes, nRudNodes, i;
  RF_ReconUnitNum_t which_ru;
  int nReadNodes, nPQNodes;
  RF_PhysDiskAddr_t *failedPDA = asmap->failedPDAs[0];
  RF_PhysDiskAddr_t *failedPDAtwo = asmap->failedPDAs[1];
  RF_StripeNum_t parityStripeID = rf_RaidAddressToParityStripeID(layoutPtr, asmap->raidAddress, &which_ru);

  if (rf_dagDebug) printf("[Creating Double Degraded Read DAG]\n");
  rf_DD_GenerateFailedAccessASMs(raidPtr, asmap, &npdas, &nRrdNodes, &pqPDAs, &nPQNodes,allocList);

  nRudNodes = asmap->numStripeUnitsAccessed - (asmap->numDataFailed);
  nReadNodes = nRrdNodes + nRudNodes + 2*nPQNodes;
  nNodes = 4 /* block, unblock, recovery, term */ + nReadNodes;

  RF_CallocAndAdd(nodes, nNodes, sizeof(RF_DagNode_t), (RF_DagNode_t *), allocList);
  i = 0;
  blockNode    = &nodes[i]; i += 1;
  unblockNode  = &nodes[i]; i += 1;
  recoveryNode = &nodes[i]; i += 1;
  termNode     = &nodes[i]; i += 1;
  rudNodes     = &nodes[i]; i += nRudNodes;
  rrdNodes     = &nodes[i]; i += nRrdNodes;
  rpNodes      = &nodes[i]; i += nPQNodes;
  rqNodes      = &nodes[i]; i += nPQNodes;
  RF_ASSERT(i == nNodes);

  dag_h->numSuccedents = 1;
  dag_h->succedents[0] = blockNode;
  dag_h->creator = "DoubleDegRead";
  dag_h->numCommits = 0;
  dag_h->numCommitNodes = 1; /*unblock */

  rf_InitNode(termNode, rf_wait, RF_FALSE, rf_TerminateFunc, rf_TerminateUndoFunc, NULL, 0, 2, 0, 0, dag_h, "Trm", allocList);
  termNode->antecedents[0]  = unblockNode;
  termNode->antType[0] = rf_control;
  termNode->antecedents[1]  = recoveryNode;
  termNode->antType[1] = rf_control;

  /* init the block and unblock nodes */
  /* The block node has all nodes except itself, unblock and recovery as successors. Similarly for
     predecessors of the unblock. */
  rf_InitNode(blockNode, rf_wait, RF_FALSE, rf_NullNodeFunc, rf_NullNodeUndoFunc, NULL, nReadNodes, 0, 0, 0, dag_h, "Nil", allocList);
  rf_InitNode(unblockNode, rf_wait, RF_TRUE, rf_NullNodeFunc, rf_NullNodeUndoFunc, NULL, 1, nReadNodes, 0, 0, dag_h, "Nil", allocList);

  for (i=0; i < nReadNodes; i++)
    {
      blockNode->succedents[i] = rudNodes+i;
      unblockNode->antecedents[i] = rudNodes+i;
      unblockNode->antType[i] = rf_control;
    }
  unblockNode->succedents[0] = termNode;

  /* The recovery node has all the reads as predecessors, and the term node as successors. It gets a pda as a param
     from each of the read nodes plus the raidPtr.
     For each failed unit is has a result pda. */
  rf_InitNode(recoveryNode, rf_wait, RF_FALSE, recovFunc, rf_NullNodeUndoFunc, NULL,
	   1, /* succesors */
	   nReadNodes, /* preds */
	   nReadNodes+2, /* params */
	   asmap->numDataFailed, /* results */
	   dag_h, recoveryNodeName, allocList);

  recoveryNode->succedents[0] = termNode;
  for (i=0; i < nReadNodes; i++) {
    recoveryNode->antecedents[i] = rudNodes+i;
    recoveryNode->antType[i] = rf_trueData;
  }

  /* build the read nodes, then come back and fill in recovery params and results */
  pda = asmap->physInfo;
  for (i=0; i < nRudNodes; pda = pda->next)
    {
      if ((pda == failedPDA) || (pda == failedPDAtwo))
	continue;
      INIT_DISK_NODE(rudNodes+i,"Rud");
      RF_ASSERT(pda);
      DISK_NODE_PARAMS(rudNodes[i],pda);
      i++;
    }

  pda = npdas;
  for (i=0; i < nRrdNodes; i++, pda = pda->next)
    {
      INIT_DISK_NODE(rrdNodes+i,"Rrd");
      RF_ASSERT(pda);
      DISK_NODE_PARAMS(rrdNodes[i],pda);
    }

  /* redundancy pdas */
  pda = pqPDAs;
  INIT_DISK_NODE(rpNodes,"Rp");
  RF_ASSERT(pda);
  DISK_NODE_PARAMS(rpNodes[0],pda);
  pda++;
  INIT_DISK_NODE(rqNodes,redundantReadNodeName );
  RF_ASSERT(pda);
  DISK_NODE_PARAMS(rqNodes[0],pda);
  if (nPQNodes==2)
    {
      pda++;
      INIT_DISK_NODE(rpNodes+1,"Rp");
      RF_ASSERT(pda);
      DISK_NODE_PARAMS(rpNodes[1],pda);
      pda++;
      INIT_DISK_NODE( rqNodes+1,redundantReadNodeName );
      RF_ASSERT(pda);
      DISK_NODE_PARAMS(rqNodes[1],pda);
    }

  /* fill in recovery node params */
  for (i=0; i < nReadNodes; i++)
    recoveryNode->params[i] = rudNodes[i].params[0]; /* pda */
  recoveryNode->params[i++].p = (void *) raidPtr;
  recoveryNode->params[i++].p = (void *) asmap;
  recoveryNode->results[0] = failedPDA;
  if (asmap->numDataFailed ==2 )
    recoveryNode->results[1] = failedPDAtwo;

  /* zero fill the target data buffers? */
}