path: root/sys/dev/raidframe/rf_evenodd.c

/*	$OpenBSD: rf_evenodd.c,v 1.1 1999/01/11 14:29:21 niklas Exp $	*/
/*	$NetBSD: rf_evenodd.c,v 1.1 1998/11/13 04:20:29 oster Exp $	*/
/*
 * Copyright (c) 1995 Carnegie-Mellon University.
 * All rights reserved.
 *
 * Author: Chang-Ming Wu
 *
 * 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@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_evenodd.c -- implements EVENODD array architecture
 *
 ****************************************************************************************/

#include "rf_archs.h"

#if RF_INCLUDE_EVENODD > 0

#include "rf_types.h"
#include "rf_raid.h"
#include "rf_dag.h"
#include "rf_dagffrd.h"
#include "rf_dagffwr.h"
#include "rf_dagdegrd.h"
#include "rf_dagdegwr.h"
#include "rf_dagutils.h"
#include "rf_dagfuncs.h"
#include "rf_threadid.h"
#include "rf_etimer.h"
#include "rf_general.h"
#include "rf_evenodd.h"
#include "rf_configure.h"
#include "rf_parityscan.h"
#include "rf_utils.h"
#include "rf_map.h"
#include "rf_pq.h"
#include "rf_mcpair.h"
#include "rf_sys.h"
#include "rf_evenodd.h"
#include "rf_evenodd_dagfuncs.h"
#include "rf_evenodd_dags.h"
#include "rf_engine.h"

typedef struct RF_EvenOddConfigInfo_s {
  RF_RowCol_t **stripeIdentifier;                    /* filled in at config time & used by IdentifyStripe */
} RF_EvenOddConfigInfo_t;

int rf_ConfigureEvenOdd(listp, raidPtr, cfgPtr)
  RF_ShutdownList_t  **listp;
  RF_Raid_t           *raidPtr;
  RF_Config_t         *cfgPtr;
{
  RF_RaidLayout_t *layoutPtr = &raidPtr->Layout;
  RF_EvenOddConfigInfo_t *info;
  RF_RowCol_t i, j, startdisk;
  
  RF_MallocAndAdd(info, sizeof(RF_EvenOddConfigInfo_t), (RF_EvenOddConfigInfo_t *), raidPtr->cleanupList);
  layoutPtr->layoutSpecificInfo = (void *) info;

  RF_ASSERT(raidPtr->numRow == 1);

  info->stripeIdentifier = rf_make_2d_array(raidPtr->numCol, raidPtr->numCol, raidPtr->cleanupList);
  startdisk = 0;
  for (i=0; i<raidPtr->numCol; i++) {
    for (j=0; j<raidPtr->numCol; j++) {
      info->stripeIdentifier[i][j] = (startdisk + j) % raidPtr->numCol;
    }
    if ((startdisk -= 2) < 0) startdisk += raidPtr->numCol; 
  }

  /* fill in the remaining layout parameters */
  layoutPtr->numStripe = layoutPtr->stripeUnitsPerDisk;
  layoutPtr->bytesPerStripeUnit = layoutPtr->sectorsPerStripeUnit << raidPtr->logBytesPerSector;
  layoutPtr->numDataCol = raidPtr->numCol-2; /*  ORIG: layoutPtr->numDataCol = raidPtr->numCol-1;  */
#if RF_EO_MATRIX_DIM > 17
  if (raidPtr->numCol <= 17){
      printf("Number of stripe units in a parity stripe is smaller than 17. Please\n");
      printf("define the macro RF_EO_MATRIX_DIM in file rf_evenodd_dagfuncs.h to \n");
      printf("be 17 to increase performance. \n");
      return(EINVAL); 
  }
#elif RF_EO_MATRIX_DIM == 17
  if (raidPtr->numCol > 17) {
      printf("Number of stripe units in a parity stripe is bigger than 17. Please\n");
      printf("define the macro RF_EO_MATRIX_DIM in file rf_evenodd_dagfuncs.h to \n");
      printf("be 257 for encoding and decoding functions to work. \n");
      return(EINVAL);
  }
#endif
  layoutPtr->dataSectorsPerStripe = layoutPtr->numDataCol * layoutPtr->sectorsPerStripeUnit;
  layoutPtr->numParityCol = 2;
  layoutPtr->dataStripeUnitsPerDisk = layoutPtr->stripeUnitsPerDisk;
  raidPtr->sectorsPerDisk = layoutPtr->stripeUnitsPerDisk * layoutPtr->sectorsPerStripeUnit;

  raidPtr->totalSectors = layoutPtr->stripeUnitsPerDisk * layoutPtr->numDataCol * layoutPtr->sectorsPerStripeUnit;

  return(0);
}

int rf_GetDefaultNumFloatingReconBuffersEvenOdd(RF_Raid_t *raidPtr)
{
  return(20);
}

RF_HeadSepLimit_t rf_GetDefaultHeadSepLimitEvenOdd(RF_Raid_t *raidPtr)
{
  return(10);
}

void rf_IdentifyStripeEvenOdd(
  RF_Raid_t        *raidPtr,
  RF_RaidAddr_t     addr,
  RF_RowCol_t     **diskids,
  RF_RowCol_t      *outRow)
{
  RF_StripeNum_t stripeID = rf_RaidAddressToStripeID(&raidPtr->Layout, addr);
  RF_EvenOddConfigInfo_t *info = (RF_EvenOddConfigInfo_t *) raidPtr->Layout.layoutSpecificInfo;

  *outRow = 0;
  *diskids = info->stripeIdentifier[ stripeID % raidPtr->numCol ];
}

/* The layout of stripe unit on the disks are:      c0 c1 c2 c3 c4  

 						     0  1  2  E  P
						     5  E  P  3  4
						     P  6  7  8  E
	 					    10 11  E  P  9
						     E  P 12 13 14
						     ....

  We use the MapSectorRAID5 to map data information because the routine can be shown to map exactly 
  the layout of data stripe unit as shown above although we have 2 redundant information now.
  But for E and P, we use rf_MapEEvenOdd and rf_MapParityEvenOdd which are different method from raid-5.
*/


void rf_MapParityEvenOdd(
	RF_Raid_t 	*raidPtr, 
	RF_RaidAddr_t 	 raidSector, 
	RF_RowCol_t 	*row,   
	RF_RowCol_t 	*col, 
	RF_SectorNum_t  *diskSector,  
	int  	  	 remap)
{
  RF_StripeNum_t SUID = raidSector / raidPtr->Layout.sectorsPerStripeUnit;
  RF_StripeNum_t endSUIDofthisStrip = (SUID/raidPtr->Layout.numDataCol + 1)*raidPtr->Layout.numDataCol - 1;

  *row = 0;        
  *col = ( endSUIDofthisStrip + 2)%raidPtr->numCol;
  *diskSector = (SUID / (raidPtr->Layout.numDataCol)) * raidPtr->Layout.sectorsPerStripeUnit +
    (raidSector % raidPtr->Layout.sectorsPerStripeUnit);
}

void rf_MapEEvenOdd(
  RF_Raid_t       *raidPtr,
  RF_RaidAddr_t    raidSector,
  RF_RowCol_t     *row,
  RF_RowCol_t     *col,
  RF_SectorNum_t  *diskSector,
  int              remap)
{
  RF_StripeNum_t SUID = raidSector / raidPtr->Layout.sectorsPerStripeUnit;
  RF_StripeNum_t endSUIDofthisStrip = (SUID/raidPtr->Layout.numDataCol + 1)*raidPtr->Layout.numDataCol - 1;

  *row = 0;        
  *col = ( endSUIDofthisStrip + 1)%raidPtr->numCol;
  *diskSector = (SUID / (raidPtr->Layout.numDataCol)) * raidPtr->Layout.sectorsPerStripeUnit +
    (raidSector % raidPtr->Layout.sectorsPerStripeUnit);
}

void rf_EODagSelect(
  RF_Raid_t             *raidPtr,
  RF_IoType_t            type,
  RF_AccessStripeMap_t  *asmap,
  RF_VoidFuncPtr *createFunc)
{
  RF_RaidLayout_t *layoutPtr = &(raidPtr->Layout);
  unsigned ndfail = asmap->numDataFailed;
  unsigned npfail = asmap->numParityFailed +asmap->numQFailed;
  unsigned ntfail = npfail + ndfail;

  RF_ASSERT(RF_IO_IS_R_OR_W(type));
  if (ntfail > 2) 
    {
      RF_ERRORMSG("more than two disks failed in a single group!  Aborting I/O operation.\n");
      /* *infoFunc = */ *createFunc = NULL;
      return;
    }

  /* ok, we can do this I/O */
  if (type == RF_IO_TYPE_READ)
    {
      switch (ndfail)
	{
	case 0:
	  /* fault free read */
	  *createFunc = (RF_VoidFuncPtr)rf_CreateFaultFreeReadDAG;   /* same as raid 5 */
	  break;
	case 1:
	  /* lost a single data unit */
	  /* two cases:
	        (1) parity is not lost.
		    do a normal raid 5 reconstruct read.
		(2) parity is lost.
		    do a reconstruct read using "e".
          */
	  if (ntfail == 2) /* also lost redundancy */
	    {
	      if (asmap->failedPDAs[1]->type == RF_PDA_TYPE_PARITY) 
		*createFunc = (RF_VoidFuncPtr)rf_EO_110_CreateReadDAG; 
	      else
		*createFunc = (RF_VoidFuncPtr)rf_EO_101_CreateReadDAG; 
	    }
	  else
	    {
	      /* P and E are ok. But is there a failure
		 in some unaccessed data unit?
              */
	      if (rf_NumFailedDataUnitsInStripe(raidPtr,asmap)==2)
		*createFunc = (RF_VoidFuncPtr)rf_EO_200_CreateReadDAG; 
	      else
		  *createFunc = (RF_VoidFuncPtr)rf_EO_100_CreateReadDAG; 
	    }
	  break;
	case 2:
	  /* *createFunc = rf_EO_200_CreateReadDAG; */
	  *createFunc = NULL;
	  break;
	}
      return;
    }

  /* a write */
  switch (ntfail)
    {
    case 0: /* fault free */
      if (rf_suppressLocksAndLargeWrites ||
	  (((asmap->numStripeUnitsAccessed <= (layoutPtr->numDataCol / 2)) && (layoutPtr->numDataCol != 1)) ||
	   (asmap->parityInfo->next != NULL) || (asmap->qInfo->next != NULL) || rf_CheckStripeForFailures(raidPtr, asmap))) {
	
	*createFunc = (RF_VoidFuncPtr)rf_EOCreateSmallWriteDAG;
      }
      else {
	*createFunc = (RF_VoidFuncPtr)rf_EOCreateLargeWriteDAG;
      }
      break;

    case 1: /* single disk fault */
      if (npfail==1) 
	{
	  RF_ASSERT ((asmap->failedPDAs[0]->type == RF_PDA_TYPE_PARITY) ||  (asmap->failedPDAs[0]->type == RF_PDA_TYPE_Q));
	  if (asmap->failedPDAs[0]->type == RF_PDA_TYPE_Q)
	    { /* q died, treat like normal mode raid5 write.*/
	      if (((asmap->numStripeUnitsAccessed <= (layoutPtr->numDataCol / 2)) || (asmap->numStripeUnitsAccessed == 1))
		  || (asmap->parityInfo->next!=NULL) || rf_NumFailedDataUnitsInStripe(raidPtr,asmap))
		*createFunc = (RF_VoidFuncPtr)rf_EO_001_CreateSmallWriteDAG;
	      else
		*createFunc = (RF_VoidFuncPtr)rf_EO_001_CreateLargeWriteDAG;
	    }
	  else
	    { /* parity died, small write only updating Q */
	      if (((asmap->numStripeUnitsAccessed <= (layoutPtr->numDataCol / 2)) || (asmap->numStripeUnitsAccessed == 1))
		  || (asmap->qInfo->next!=NULL) || rf_NumFailedDataUnitsInStripe(raidPtr,asmap))
		*createFunc = (RF_VoidFuncPtr)rf_EO_010_CreateSmallWriteDAG;
	      else
		*createFunc = (RF_VoidFuncPtr)rf_EO_010_CreateLargeWriteDAG;
	    }
	}
      else
	{ /* data missing. 
	     Do a P reconstruct write if only a single data unit
	     is lost in the stripe, otherwise a reconstruct
	     write which employnig both P and E units. */
	  if (rf_NumFailedDataUnitsInStripe(raidPtr,asmap)==2)
	  {  
            if (asmap->numStripeUnitsAccessed == 1)
              *createFunc = (RF_VoidFuncPtr)rf_EO_200_CreateWriteDAG;
            else
              *createFunc = NULL;  /* No direct support for this case now, like that in Raid-5  */
          }
	  else
          {
            if (asmap->numStripeUnitsAccessed != 1 && asmap->failedPDAs[0]->numSector != layoutPtr->sectorsPerStripeUnit)
                   *createFunc = NULL; /* No direct support for this case now, like that in Raid-5  */
            else   *createFunc = (RF_VoidFuncPtr)rf_EO_100_CreateWriteDAG;
          }
	}
      break;

    case 2: /* two disk faults */
      switch (npfail)
	{
	case 2: /* both p and q dead */
	  *createFunc = (RF_VoidFuncPtr)rf_EO_011_CreateWriteDAG;
	  break;
	case 1: /* either p or q and dead data */
	  RF_ASSERT(asmap->failedPDAs[0]->type == RF_PDA_TYPE_DATA);
	  RF_ASSERT ((asmap->failedPDAs[1]->type == RF_PDA_TYPE_PARITY) ||  (asmap->failedPDAs[1]->type == RF_PDA_TYPE_Q));
	  if (asmap->failedPDAs[1]->type == RF_PDA_TYPE_Q)
          {
	    if(asmap->numStripeUnitsAccessed != 1 && asmap->failedPDAs[0]->numSector != layoutPtr->sectorsPerStripeUnit)
                *createFunc = NULL; /* In both PQ and EvenOdd, no direct support for this case now, like that in Raid-5  */
	    else
	        *createFunc = (RF_VoidFuncPtr)rf_EO_101_CreateWriteDAG;
          }
	  else
          {
            if (asmap->numStripeUnitsAccessed != 1 && asmap->failedPDAs[0]->numSector != layoutPtr->sectorsPerStripeUnit)
                *createFunc = NULL; /* No direct support for this case, like that in Raid-5  */
            else
	        *createFunc = (RF_VoidFuncPtr)rf_EO_110_CreateWriteDAG;
	  }
	  break;
	case 0: /* double data loss */
        /*  if(asmap->failedPDAs[0]->numSector + asmap->failedPDAs[1]->numSector == 2 * layoutPtr->sectorsPerStripeUnit )
                *createFunc = rf_EOCreateLargeWriteDAG;
            else    							*/
	        *createFunc = NULL; /* currently, in Evenodd, No support for simultaneous access of both failed SUs */
	  break;
	}
      break;

    default:  /* more than 2 disk faults */
      *createFunc = NULL;
      RF_PANIC();
    }
  return;
}


int rf_VerifyParityEvenOdd(raidPtr, raidAddr, parityPDA, correct_it, flags)
  RF_Raid_t             *raidPtr;
  RF_RaidAddr_t          raidAddr;
  RF_PhysDiskAddr_t     *parityPDA;
  int                    correct_it;
  RF_RaidAccessFlags_t   flags;
{
  RF_RaidLayout_t *layoutPtr = &(raidPtr->Layout);
  RF_RaidAddr_t startAddr = rf_RaidAddressOfPrevStripeBoundary(layoutPtr, raidAddr);
  RF_SectorCount_t numsector = parityPDA->numSector;
  int numbytes  = rf_RaidAddressToByte(raidPtr, numsector);
  int bytesPerStripe = numbytes * layoutPtr->numDataCol;
  RF_DagHeader_t *rd_dag_h, *wr_dag_h;          /* read, write dag */
  RF_DagNode_t *blockNode, *unblockNode, *wrBlock, *wrUnblock;
  RF_AccessStripeMapHeader_t *asm_h;
  RF_AccessStripeMap_t *asmap;
  RF_AllocListElem_t *alloclist;
  RF_PhysDiskAddr_t *pda;
  char *pbuf, *buf, *end_p, *p;
  char *redundantbuf2;
  int redundantTwoErr = 0,  redundantOneErr = 0; 
  int parity_cant_correct = RF_FALSE, red2_cant_correct = RF_FALSE, parity_corrected = RF_FALSE, red2_corrected = RF_FALSE;
  int i, retcode;
  RF_ReconUnitNum_t which_ru;
  RF_StripeNum_t psID = rf_RaidAddressToParityStripeID(layoutPtr, raidAddr, &which_ru);
  int stripeWidth = layoutPtr->numDataCol + layoutPtr->numParityCol;
  RF_AccTraceEntry_t tracerec;
  RF_MCPair_t *mcpair;

  retcode = RF_PARITY_OKAY;

  mcpair = rf_AllocMCPair();
  rf_MakeAllocList(alloclist);
  RF_MallocAndAdd(buf, numbytes * (layoutPtr->numDataCol + layoutPtr->numParityCol), (char *), alloclist);
  RF_CallocAndAdd(pbuf, 1, numbytes, (char *), alloclist);     /* use calloc to make sure buffer is zeroed */
  end_p = buf + bytesPerStripe;
  RF_CallocAndAdd(redundantbuf2, 1, numbytes, (char *), alloclist);  /* use calloc to make sure buffer is zeroed */

  rd_dag_h = rf_MakeSimpleDAG(raidPtr, stripeWidth, numbytes, buf, rf_DiskReadFunc, rf_DiskReadUndoFunc,
			   "Rod", alloclist, flags, RF_IO_NORMAL_PRIORITY);
  blockNode = rd_dag_h->succedents[0];
  unblockNode = blockNode->succedents[0]->succedents[0];

  /* map the stripe and fill in the PDAs in the dag */
  asm_h = rf_MapAccess(raidPtr, startAddr, layoutPtr->dataSectorsPerStripe, buf, RF_DONT_REMAP);
  asmap = asm_h->stripeMap;
  
  for (pda=asmap->physInfo,i=0; i<layoutPtr->numDataCol; i++,pda=pda->next) {
    RF_ASSERT(pda);
    rf_RangeRestrictPDA(raidPtr, parityPDA, pda, 0, 1);
    RF_ASSERT(pda->numSector != 0);
    if (rf_TryToRedirectPDA(raidPtr, pda, 0)) goto out;   /* no way to verify parity if disk is dead.  return w/ good status */
    blockNode->succedents[i]->params[0].p = pda;
    blockNode->succedents[i]->params[2].v = psID;
    blockNode->succedents[i]->params[3].v = RF_CREATE_PARAM3(RF_IO_NORMAL_PRIORITY, 0, 0, which_ru);
  }

  RF_ASSERT(!asmap->parityInfo->next);
  rf_RangeRestrictPDA(raidPtr, parityPDA, asmap->parityInfo, 0, 1);
  RF_ASSERT(asmap->parityInfo->numSector != 0);
  if (rf_TryToRedirectPDA(raidPtr, asmap->parityInfo, 1))
    goto out;
  blockNode->succedents[ layoutPtr->numDataCol ]->params[0].p = asmap->parityInfo;

  RF_ASSERT(!asmap->qInfo->next);
  rf_RangeRestrictPDA(raidPtr, parityPDA, asmap->qInfo, 0, 1);
  RF_ASSERT(asmap->qInfo->numSector != 0);
  if (rf_TryToRedirectPDA(raidPtr, asmap->qInfo, 1)) goto out; 
  /* 
   * if disk is dead, b/c no reconstruction is implemented right now,
   * the function "rf_TryToRedirectPDA" always return one, which cause
   * go to out and return w/ good status   
   */
  blockNode->succedents[ layoutPtr->numDataCol +1  ]->params[0].p = asmap->qInfo;

  /* fire off the DAG */
  bzero((char *)&tracerec,sizeof(tracerec));
  rd_dag_h->tracerec = &tracerec;

  if (rf_verifyParityDebug) {
    printf("Parity verify read dag:\n");
    rf_PrintDAGList(rd_dag_h);
  }

  RF_LOCK_MUTEX(mcpair->mutex);
  mcpair->flag = 0;
  rf_DispatchDAG(rd_dag_h, (void (*)(void *))rf_MCPairWakeupFunc, 
		 (void *) mcpair);
  while (!mcpair->flag) RF_WAIT_COND(mcpair->cond, mcpair->mutex);
  RF_UNLOCK_MUTEX(mcpair->mutex);
  if (rd_dag_h->status != rf_enable) {
    RF_ERRORMSG("Unable to verify parity:  can't read the stripe\n");
    retcode = RF_PARITY_COULD_NOT_VERIFY;
    goto out;
  }

  for (p=buf, i=0; p<end_p; p+=numbytes, i++) {
    rf_e_encToBuf(raidPtr, i, p, RF_EO_MATRIX_DIM - 2, redundantbuf2, numsector);
    /* 
     * the corresponding columes in EvenOdd encoding Matrix for these p pointers which point 
     * to the databuffer in a full stripe are sequentially from 0 to layoutPtr->numDataCol-1 
     */
    rf_bxor(p, pbuf, numbytes, NULL);
  }
  RF_ASSERT(i==layoutPtr->numDataCol);

  for (i=0; i<numbytes; i++) {
    if (pbuf[i] != buf[bytesPerStripe+i]) {
      if (!correct_it) {
        RF_ERRORMSG3("Parity verify error: byte %d of parity is 0x%x should be 0x%x\n",
            i,(u_char) buf[bytesPerStripe+i],(u_char) pbuf[i]);
      }
    }
    redundantOneErr = 1;
    break;
  }

  for (i=0; i<numbytes; i++) {
    if (redundantbuf2[i] != buf[bytesPerStripe+numbytes+i]) {
      if (!correct_it) {
        RF_ERRORMSG3("Parity verify error: byte %d of second redundant information is 0x%x should be 0x%x\n",
            i,(u_char) buf[bytesPerStripe+numbytes+i],(u_char) redundantbuf2[i]);
      }
      redundantTwoErr = 1;
      break;
    }
  }
  if (redundantOneErr || redundantTwoErr )
    retcode = RF_PARITY_BAD;

  /*  correct the first redundant disk, ie parity if it is error    */
  if (redundantOneErr && correct_it) {    
    wr_dag_h = rf_MakeSimpleDAG(raidPtr, 1, numbytes, pbuf, rf_DiskWriteFunc, rf_DiskWriteUndoFunc,
			     "Wnp", alloclist, flags, RF_IO_NORMAL_PRIORITY);
    wrBlock = wr_dag_h->succedents[0]; wrUnblock = wrBlock->succedents[0]->succedents[0];
    wrBlock->succedents[0]->params[0].p = asmap->parityInfo;
    wrBlock->succedents[0]->params[2].v = psID;
    wrBlock->succedents[0]->params[3].v = RF_CREATE_PARAM3(RF_IO_NORMAL_PRIORITY, 0, 0, which_ru);
    bzero((char *)&tracerec,sizeof(tracerec));
    wr_dag_h->tracerec = &tracerec;
    if (rf_verifyParityDebug) {
      printf("Parity verify write dag:\n");
      rf_PrintDAGList(wr_dag_h);
    }
    RF_LOCK_MUTEX(mcpair->mutex);
    mcpair->flag = 0;
    rf_DispatchDAG(wr_dag_h, (void (*)(void *))rf_MCPairWakeupFunc, 
		   (void *) mcpair);
    while (!mcpair->flag)
      RF_WAIT_COND(mcpair->cond, mcpair->mutex);
    RF_UNLOCK_MUTEX(mcpair->mutex);
    if (wr_dag_h->status != rf_enable) {
      RF_ERRORMSG("Unable to correct parity in VerifyParity:  can't write the stripe\n");
      parity_cant_correct = RF_TRUE;
    } else {
      parity_corrected = RF_TRUE;
    }
    rf_FreeDAG(wr_dag_h);
  }

  if (redundantTwoErr && correct_it) {
    wr_dag_h = rf_MakeSimpleDAG(raidPtr, 1, numbytes, redundantbuf2, rf_DiskWriteFunc, rf_DiskWriteUndoFunc,
                             "Wnred2", alloclist, flags, RF_IO_NORMAL_PRIORITY);
    wrBlock = wr_dag_h->succedents[0]; wrUnblock = wrBlock->succedents[0]->succedents[0];
    wrBlock->succedents[0]->params[0].p = asmap->qInfo;
    wrBlock->succedents[0]->params[2].v = psID;
    wrBlock->succedents[0]->params[3].v = RF_CREATE_PARAM3(RF_IO_NORMAL_PRIORITY, 0, 0, which_ru);
    bzero((char *)&tracerec,sizeof(tracerec));
    wr_dag_h->tracerec = &tracerec;
    if (rf_verifyParityDebug) {
      printf("Dag of write new second redundant information in parity verify :\n");
      rf_PrintDAGList(wr_dag_h);
    }
    RF_LOCK_MUTEX(mcpair->mutex);
    mcpair->flag = 0;
    rf_DispatchDAG(wr_dag_h, (void (*)(void *))rf_MCPairWakeupFunc, 
		   (void *) mcpair);
    while (!mcpair->flag)
      RF_WAIT_COND(mcpair->cond, mcpair->mutex);
    RF_UNLOCK_MUTEX(mcpair->mutex);
    if (wr_dag_h->status != rf_enable) {
      RF_ERRORMSG("Unable to correct second redundant information in VerifyParity:  can't write the stripe\n");
      red2_cant_correct = RF_TRUE;
    } else {
      red2_corrected = RF_TRUE;
    }
    rf_FreeDAG(wr_dag_h);
  }
  if ( (redundantOneErr && parity_cant_correct) || 
       (redundantTwoErr && red2_cant_correct ))
      retcode = RF_PARITY_COULD_NOT_CORRECT;
  if ( (retcode = RF_PARITY_BAD) && parity_corrected && red2_corrected )
      retcode = RF_PARITY_CORRECTED;


out:
  rf_FreeAccessStripeMap(asm_h);
  rf_FreeAllocList(alloclist);
  rf_FreeDAG(rd_dag_h);
  rf_FreeMCPair(mcpair);
  return(retcode);
}

#endif /* RF_INCLUDE_EVENODD > 0 */