File: [local] / sys / dev / raidframe / rf_dagutils.c (download)
Revision 1.1.1.1 (vendor branch), Tue Mar 4 16:09:46 2008 UTC (16 years, 4 months ago) by nbrk
Branch: OPENBSD_4_2_BASE, MAIN
CVS Tags: jornada-partial-support-wip, HEAD Changes since 1.1: +0 -0 lines
Import of OpenBSD 4.2 release kernel tree with initial code to support
Jornada 720/728, StrongARM 1110-based handheld PC.
At this point kernel roots on NFS and boots into vfs_mountroot() and traps.
What is supported:
- glass console, Jornada framebuffer (jfb) works in 16bpp direct color mode
(needs some palette tweaks for non black/white/blue colors, i think)
- saic, SA11x0 interrupt controller (needs cleanup)
- sacom, SA11x0 UART (supported only as boot console for now)
- SA11x0 GPIO controller fully supported (but can't handle multiple interrupt
handlers on one gpio pin)
- sassp, SSP port on SA11x0 that attaches spibus
- Jornada microcontroller (jmcu) to control kbd, battery, etc throught
the SPI bus (wskbd attaches on jmcu, but not tested)
- tod functions seem work
- initial code for SA-1111 (chip companion) : this is TODO
Next important steps, i think:
- gpio and intc on sa1111
- pcmcia support for sa11x0 (and sa1111 help logic)
- REAL root on nfs when we have PCMCIA support (we may use any of supported pccard NICs)
- root on wd0! (using already supported PCMCIA-ATA)
|
/* $OpenBSD: rf_dagutils.c,v 1.4 2002/12/16 07:01:03 tdeval Exp $ */
/* $NetBSD: rf_dagutils.c,v 1.6 1999/12/09 02:26:09 oster Exp $ */
/*
* Copyright (c) 1995 Carnegie-Mellon University.
* All rights reserved.
*
* Authors: Mark Holland, William V. Courtright II, Jim Zelenka
*
* 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_dagutils.c -- Utility routines for manipulating dags.
*
*****************************************************************************/
#include "rf_archs.h"
#include "rf_types.h"
#include "rf_threadstuff.h"
#include "rf_raid.h"
#include "rf_dag.h"
#include "rf_dagutils.h"
#include "rf_dagfuncs.h"
#include "rf_general.h"
#include "rf_freelist.h"
#include "rf_map.h"
#include "rf_shutdown.h"
#define SNUM_DIFF(_a_,_b_) (((_a_)>(_b_))?((_a_)-(_b_)):((_b_)-(_a_)))
RF_RedFuncs_t rf_xorFuncs = {
rf_RegularXorFunc, "Reg Xr", rf_SimpleXorFunc, "Simple Xr"
};
RF_RedFuncs_t rf_xorRecoveryFuncs = {
rf_RecoveryXorFunc, "Recovery Xr", rf_RecoveryXorFunc, "Recovery Xr"
};
void rf_RecurPrintDAG(RF_DagNode_t *, int, int);
void rf_PrintDAG(RF_DagHeader_t *);
int rf_ValidateBranch(RF_DagNode_t *, int *, int *, RF_DagNode_t **, int);
void rf_ValidateBranchVisitedBits(RF_DagNode_t *, int, int);
void rf_ValidateVisitedBits(RF_DagHeader_t *);
/*****************************************************************************
*
* InitNode - Initialize a dag node.
*
* The size of the propList array is always the same as that of the
* successors array.
*
*****************************************************************************/
void
rf_InitNode(
RF_DagNode_t *node,
RF_NodeStatus_t initstatus,
int commit,
int (*doFunc) (RF_DagNode_t *),
int (*undoFunc) (RF_DagNode_t *node),
int (*wakeFunc) (RF_DagNode_t *node, int),
int nSucc,
int nAnte,
int nParam,
int nResult,
RF_DagHeader_t *hdr,
char *name,
RF_AllocListElem_t *alist
)
{
void **ptrs;
int nptrs;
if (nAnte > RF_MAX_ANTECEDENTS)
RF_PANIC();
node->status = initstatus;
node->commitNode = commit;
node->doFunc = doFunc;
node->undoFunc = undoFunc;
node->wakeFunc = wakeFunc;
node->numParams = nParam;
node->numResults = nResult;
node->numAntecedents = nAnte;
node->numAntDone = 0;
node->next = NULL;
node->numSuccedents = nSucc;
node->name = name;
node->dagHdr = hdr;
node->visited = 0;
/* Allocate all the pointers with one call to malloc. */
nptrs = nSucc + nAnte + nResult + nSucc;
if (nptrs <= RF_DAG_PTRCACHESIZE) {
/*
* The dag_ptrs field of the node is basically some scribble
* space to be used here. We could get rid of it, and always
* allocate the range of pointers, but that's expensive. So,
* we pick a "common case" size for the pointer cache.
* Hopefully, we'll find that:
* (1) Generally, nptrs doesn't exceed RF_DAG_PTRCACHESIZE by
* only a little bit (least efficient case).
* (2) Generally, ntprs isn't a lot less than
* RF_DAG_PTRCACHESIZE (wasted memory).
*/
ptrs = (void **) node->dag_ptrs;
} else {
RF_CallocAndAdd(ptrs, nptrs, sizeof(void *), (void **), alist);
}
node->succedents = (nSucc) ? (RF_DagNode_t **) ptrs : NULL;
node->antecedents = (nAnte) ? (RF_DagNode_t **) (ptrs + nSucc) : NULL;
node->results = (nResult) ? (void **) (ptrs + nSucc + nAnte) : NULL;
node->propList = (nSucc) ? (RF_PropHeader_t **)
(ptrs + nSucc + nAnte + nResult) : NULL;
if (nParam) {
if (nParam <= RF_DAG_PARAMCACHESIZE) {
node->params = (RF_DagParam_t *) node->dag_params;
} else {
RF_CallocAndAdd(node->params, nParam,
sizeof(RF_DagParam_t), (RF_DagParam_t *), alist);
}
} else {
node->params = NULL;
}
}
/*****************************************************************************
*
* Allocation and deallocation routines.
*
*****************************************************************************/
void
rf_FreeDAG(RF_DagHeader_t *dag_h)
{
RF_AccessStripeMapHeader_t *asmap, *t_asmap;
RF_DagHeader_t *nextDag;
int i;
while (dag_h) {
nextDag = dag_h->next;
for (i = 0; dag_h->memChunk[i] && i < RF_MAXCHUNKS; i++) {
/* Release mem chunks. */
rf_ReleaseMemChunk(dag_h->memChunk[i]);
dag_h->memChunk[i] = NULL;
}
RF_ASSERT(i == dag_h->chunkIndex);
if (dag_h->xtraChunkCnt > 0) {
/* Free xtraMemChunks. */
for (i = 0; dag_h->xtraMemChunk[i] &&
i < dag_h->xtraChunkIndex; i++) {
rf_ReleaseMemChunk(dag_h->xtraMemChunk[i]);
dag_h->xtraMemChunk[i] = NULL;
}
RF_ASSERT(i == dag_h->xtraChunkIndex);
/* Free ptrs to xtraMemChunks. */
RF_Free(dag_h->xtraMemChunk, dag_h->xtraChunkCnt *
sizeof(RF_ChunkDesc_t *));
}
rf_FreeAllocList(dag_h->allocList);
for (asmap = dag_h->asmList; asmap;) {
t_asmap = asmap;
asmap = asmap->next;
rf_FreeAccessStripeMap(t_asmap);
}
rf_FreeDAGHeader(dag_h);
dag_h = nextDag;
}
}
RF_PropHeader_t *
rf_MakePropListEntry(RF_DagHeader_t *dag_h, int resultNum, int paramNum,
RF_PropHeader_t *next, RF_AllocListElem_t *allocList)
{
RF_PropHeader_t *p;
RF_CallocAndAdd(p, 1, sizeof(RF_PropHeader_t), (RF_PropHeader_t *),
allocList);
p->resultNum = resultNum;
p->paramNum = paramNum;
p->next = next;
return (p);
}
static RF_FreeList_t *rf_dagh_freelist;
#define RF_MAX_FREE_DAGH 128
#define RF_DAGH_INC 16
#define RF_DAGH_INITIAL 32
void rf_ShutdownDAGs(void *);
void
rf_ShutdownDAGs(void *ignored)
{
RF_FREELIST_DESTROY(rf_dagh_freelist, next, (RF_DagHeader_t *));
}
int
rf_ConfigureDAGs(RF_ShutdownList_t **listp)
{
int rc;
RF_FREELIST_CREATE(rf_dagh_freelist, RF_MAX_FREE_DAGH, RF_DAGH_INC,
sizeof(RF_DagHeader_t));
if (rf_dagh_freelist == NULL)
return (ENOMEM);
rc = rf_ShutdownCreate(listp, rf_ShutdownDAGs, NULL);
if (rc) {
RF_ERRORMSG3("Unable to add to shutdown list file %s line"
" %d rc=%d\n", __FILE__, __LINE__, rc);
rf_ShutdownDAGs(NULL);
return (rc);
}
RF_FREELIST_PRIME(rf_dagh_freelist, RF_DAGH_INITIAL, next,
(RF_DagHeader_t *));
return (0);
}
RF_DagHeader_t *
rf_AllocDAGHeader(void)
{
RF_DagHeader_t *dh;
RF_FREELIST_GET(rf_dagh_freelist, dh, next, (RF_DagHeader_t *));
if (dh) {
bzero((char *) dh, sizeof(RF_DagHeader_t));
}
return (dh);
}
void
rf_FreeDAGHeader(RF_DagHeader_t *dh)
{
RF_FREELIST_FREE(rf_dagh_freelist, dh, next);
}
/* Allocate a buffer big enough to hold the data described by pda. */
void *
rf_AllocBuffer(RF_Raid_t *raidPtr, RF_DagHeader_t *dag_h,
RF_PhysDiskAddr_t *pda, RF_AllocListElem_t *allocList)
{
char *p;
RF_MallocAndAdd(p, pda->numSector << raidPtr->logBytesPerSector,
(char *), allocList);
return ((void *) p);
}
/*****************************************************************************
*
* Debug routines.
*
*****************************************************************************/
char *
rf_NodeStatusString(RF_DagNode_t *node)
{
switch (node->status) {
case rf_wait:
return ("wait");
case rf_fired:
return ("fired");
case rf_good:
return ("good");
case rf_bad:
return ("bad");
default:
return ("?");
}
}
void
rf_PrintNodeInfoString(RF_DagNode_t *node)
{
RF_PhysDiskAddr_t *pda;
int (*df) (RF_DagNode_t *) = node->doFunc;
int i, lk, unlk;
void *bufPtr;
if ((df == rf_DiskReadFunc) || (df == rf_DiskWriteFunc) ||
(df == rf_DiskReadMirrorIdleFunc) ||
(df == rf_DiskReadMirrorPartitionFunc)) {
pda = (RF_PhysDiskAddr_t *) node->params[0].p;
bufPtr = (void *) node->params[1].p;
lk = RF_EXTRACT_LOCK_FLAG(node->params[3].v);
unlk = RF_EXTRACT_UNLOCK_FLAG(node->params[3].v);
RF_ASSERT(!(lk && unlk));
printf("r %d c %d offs %ld nsect %d buf 0x%lx %s\n", pda->row,
pda->col, (long) pda->startSector, (int) pda->numSector,
(long) bufPtr, (lk) ? "LOCK" : ((unlk) ? "UNLK" : " "));
return;
}
if (df == rf_DiskUnlockFunc) {
pda = (RF_PhysDiskAddr_t *) node->params[0].p;
lk = RF_EXTRACT_LOCK_FLAG(node->params[3].v);
unlk = RF_EXTRACT_UNLOCK_FLAG(node->params[3].v);
RF_ASSERT(!(lk && unlk));
printf("r %d c %d %s\n", pda->row, pda->col,
(lk) ? "LOCK" : ((unlk) ? "UNLK" : "nop"));
return;
}
if ((df == rf_SimpleXorFunc) || (df == rf_RegularXorFunc)
|| (df == rf_RecoveryXorFunc)) {
printf("result buf 0x%lx\n", (long) node->results[0]);
for (i = 0; i < node->numParams - 1; i += 2) {
pda = (RF_PhysDiskAddr_t *) node->params[i].p;
bufPtr = (RF_PhysDiskAddr_t *) node->params[i + 1].p;
printf(" buf 0x%lx r%d c%d offs %ld nsect %d\n",
(long) bufPtr, pda->row, pda->col,
(long) pda->startSector, (int) pda->numSector);
}
return;
}
#if RF_INCLUDE_PARITYLOGGING > 0
if (df == rf_ParityLogOverwriteFunc || df == rf_ParityLogUpdateFunc) {
for (i = 0; i < node->numParams - 1; i += 2) {
pda = (RF_PhysDiskAddr_t *) node->params[i].p;
bufPtr = (RF_PhysDiskAddr_t *) node->params[i + 1].p;
printf(" r%d c%d offs %ld nsect %d buf 0x%lx\n",
pda->row, pda->col, (long) pda->startSector,
(int) pda->numSector, (long) bufPtr);
}
return;
}
#endif /* RF_INCLUDE_PARITYLOGGING > 0 */
if ((df == rf_TerminateFunc) || (df == rf_NullNodeFunc)) {
printf("\n");
return;
}
printf("?\n");
}
void
rf_RecurPrintDAG(RF_DagNode_t *node, int depth, int unvisited)
{
char *anttype;
int i;
node->visited = (unvisited) ? 0 : 1;
printf("(%d) %d C%d %s: %s,s%d %d/%d,a%d/%d,p%d,r%d S{", depth,
node->nodeNum, node->commitNode, node->name,
rf_NodeStatusString(node), node->numSuccedents,
node->numSuccFired, node->numSuccDone,
node->numAntecedents, node->numAntDone,
node->numParams, node->numResults);
for (i = 0; i < node->numSuccedents; i++) {
printf("%d%s", node->succedents[i]->nodeNum,
((i == node->numSuccedents - 1) ? "\0" : " "));
}
printf("} A{");
for (i = 0; i < node->numAntecedents; i++) {
switch (node->antType[i]) {
case rf_trueData:
anttype = "T";
break;
case rf_antiData:
anttype = "A";
break;
case rf_outputData:
anttype = "O";
break;
case rf_control:
anttype = "C";
break;
default:
anttype = "?";
break;
}
printf("%d(%s)%s", node->antecedents[i]->nodeNum, anttype,
(i == node->numAntecedents - 1) ? "\0" : " ");
}
printf("}; ");
rf_PrintNodeInfoString(node);
for (i = 0; i < node->numSuccedents; i++) {
if (node->succedents[i]->visited == unvisited)
rf_RecurPrintDAG(node->succedents[i], depth + 1,
unvisited);
}
}
void
rf_PrintDAG(RF_DagHeader_t *dag_h)
{
int unvisited, i;
char *status;
/* Set dag status. */
switch (dag_h->status) {
case rf_enable:
status = "enable";
break;
case rf_rollForward:
status = "rollForward";
break;
case rf_rollBackward:
status = "rollBackward";
break;
default:
status = "illegal !";
break;
}
/* Find out if visited bits are currently set or cleared. */
unvisited = dag_h->succedents[0]->visited;
printf("DAG type: %s\n", dag_h->creator);
printf("format is (depth) num commit type: status,nSucc nSuccFired/n"
"SuccDone,nAnte/nAnteDone,nParam,nResult S{x} A{x(type)}; info\n");
printf("(0) %d Hdr: %s, s%d, (commit %d/%d) S{", dag_h->nodeNum,
status, dag_h->numSuccedents, dag_h->numCommitNodes,
dag_h->numCommits);
for (i = 0; i < dag_h->numSuccedents; i++) {
printf("%d%s", dag_h->succedents[i]->nodeNum,
((i == dag_h->numSuccedents - 1) ? "\0" : " "));
}
printf("};\n");
for (i = 0; i < dag_h->numSuccedents; i++) {
if (dag_h->succedents[i]->visited == unvisited)
rf_RecurPrintDAG(dag_h->succedents[i], 1, unvisited);
}
}
/* Assign node numbers. */
int
rf_AssignNodeNums(RF_DagHeader_t *dag_h)
{
int unvisited, i, nnum;
RF_DagNode_t *node;
nnum = 0;
unvisited = dag_h->succedents[0]->visited;
dag_h->nodeNum = nnum++;
for (i = 0; i < dag_h->numSuccedents; i++) {
node = dag_h->succedents[i];
if (node->visited == unvisited) {
nnum = rf_RecurAssignNodeNums(dag_h->succedents[i],
nnum, unvisited);
}
}
return (nnum);
}
int
rf_RecurAssignNodeNums(RF_DagNode_t *node, int num, int unvisited)
{
int i;
node->visited = (unvisited) ? 0 : 1;
node->nodeNum = num++;
for (i = 0; i < node->numSuccedents; i++) {
if (node->succedents[i]->visited == unvisited) {
num = rf_RecurAssignNodeNums(node->succedents[i],
num, unvisited);
}
}
return (num);
}
/* Set the header pointers in each node to "newptr". */
void
rf_ResetDAGHeaderPointers(RF_DagHeader_t *dag_h, RF_DagHeader_t *newptr)
{
int i;
for (i = 0; i < dag_h->numSuccedents; i++)
if (dag_h->succedents[i]->dagHdr != newptr)
rf_RecurResetDAGHeaderPointers(dag_h->succedents[i],
newptr);
}
void
rf_RecurResetDAGHeaderPointers(RF_DagNode_t *node, RF_DagHeader_t *newptr)
{
int i;
node->dagHdr = newptr;
for (i = 0; i < node->numSuccedents; i++)
if (node->succedents[i]->dagHdr != newptr)
rf_RecurResetDAGHeaderPointers(node->succedents[i],
newptr);
}
void
rf_PrintDAGList(RF_DagHeader_t *dag_h)
{
int i = 0;
for (; dag_h; dag_h = dag_h->next) {
rf_AssignNodeNums(dag_h);
printf("\n\nDAG %d IN LIST:\n", i++);
rf_PrintDAG(dag_h);
}
}
int
rf_ValidateBranch(RF_DagNode_t *node, int *scount, int *acount,
RF_DagNode_t **nodes, int unvisited)
{
int i, retcode = 0;
/* Construct an array of node pointers indexed by node num. */
node->visited = (unvisited) ? 0 : 1;
nodes[node->nodeNum] = node;
if (node->next != NULL) {
printf("INVALID DAG: next pointer in node is not NULL.\n");
retcode = 1;
}
if (node->status != rf_wait) {
printf("INVALID DAG: Node status is not wait.\n");
retcode = 1;
}
if (node->numAntDone != 0) {
printf("INVALID DAG: numAntDone is not zero.\n");
retcode = 1;
}
if (node->doFunc == rf_TerminateFunc) {
if (node->numSuccedents != 0) {
printf("INVALID DAG: Terminator node has"
" succedents.\n");
retcode = 1;
}
} else {
if (node->numSuccedents == 0) {
printf("INVALID DAG: Non-terminator node has no"
" succedents\n");
retcode = 1;
}
}
for (i = 0; i < node->numSuccedents; i++) {
if (!node->succedents[i]) {
printf("INVALID DAG: succedent %d of node %s"
" is NULL.\n", i, node->name);
retcode = 1;
}
scount[node->succedents[i]->nodeNum]++;
}
for (i = 0; i < node->numAntecedents; i++) {
if (!node->antecedents[i]) {
printf("INVALID DAG: antecedent %d of node %s is"
" NULL.\n", i, node->name);
retcode = 1;
}
acount[node->antecedents[i]->nodeNum]++;
}
for (i = 0; i < node->numSuccedents; i++) {
if (node->succedents[i]->visited == unvisited) {
if (rf_ValidateBranch(node->succedents[i], scount,
acount, nodes, unvisited)) {
retcode = 1;
}
}
}
return (retcode);
}
void
rf_ValidateBranchVisitedBits(RF_DagNode_t *node, int unvisited, int rl)
{
int i;
RF_ASSERT(node->visited == unvisited);
for (i = 0; i < node->numSuccedents; i++) {
if (node->succedents[i] == NULL) {
printf("node=%lx node->succedents[%d] is NULL.\n",
(long) node, i);
RF_ASSERT(0);
}
rf_ValidateBranchVisitedBits(node->succedents[i],
unvisited, rl + 1);
}
}
/*
* NOTE: Never call this on a big dag, because it is exponential
* in execution time.
*/
void
rf_ValidateVisitedBits(RF_DagHeader_t *dag)
{
int i, unvisited;
unvisited = dag->succedents[0]->visited;
for (i = 0; i < dag->numSuccedents; i++) {
if (dag->succedents[i] == NULL) {
printf("dag=%lx dag->succedents[%d] is NULL.\n",
(long) dag, i);
RF_ASSERT(0);
}
rf_ValidateBranchVisitedBits(dag->succedents[i], unvisited, 0);
}
}
/*
* Validate a DAG. _at entry_ verify that:
* -- numNodesCompleted is zero
* -- node queue is null
* -- dag status is rf_enable
* -- next pointer is null on every node
* -- all nodes have status wait
* -- numAntDone is zero in all nodes
* -- terminator node has zero successors
* -- no other node besides terminator has zero successors
* -- no successor or antecedent pointer in a node is NULL
* -- number of times that each node appears as a successor of another node
* is equal to the antecedent count on that node
* -- number of times that each node appears as an antecedent of another node
* is equal to the succedent count on that node
* -- what else ?
*/
int
rf_ValidateDAG(RF_DagHeader_t *dag_h)
{
int i, nodecount;
int *scount, *acount; /* Per-node successor and antecedent counts. */
RF_DagNode_t **nodes; /* Array of ptrs to nodes in dag. */
int retcode = 0;
int unvisited;
int commitNodeCount = 0;
if (rf_validateVisitedDebug)
rf_ValidateVisitedBits(dag_h);
if (dag_h->numNodesCompleted != 0) {
printf("INVALID DAG: num nodes completed is %d, should be 0.\n",
dag_h->numNodesCompleted);
retcode = 1;
goto validate_dag_bad;
}
if (dag_h->status != rf_enable) {
printf("INVALID DAG: not enabled.\n");
retcode = 1;
goto validate_dag_bad;
}
if (dag_h->numCommits != 0) {
printf("INVALID DAG: numCommits != 0 (%d)\n",
dag_h->numCommits);
retcode = 1;
goto validate_dag_bad;
}
if (dag_h->numSuccedents != 1) {
/* Currently, all dags must have only one succedent. */
printf("INVALID DAG: numSuccedents != 1 (%d).\n",
dag_h->numSuccedents);
retcode = 1;
goto validate_dag_bad;
}
nodecount = rf_AssignNodeNums(dag_h);
unvisited = dag_h->succedents[0]->visited;
RF_Calloc(scount, nodecount, sizeof(int), (int *));
RF_Calloc(acount, nodecount, sizeof(int), (int *));
RF_Calloc(nodes, nodecount, sizeof(RF_DagNode_t *), (RF_DagNode_t **));
for (i = 0; i < dag_h->numSuccedents; i++) {
if ((dag_h->succedents[i]->visited == unvisited)
&& rf_ValidateBranch(dag_h->succedents[i], scount,
acount, nodes, unvisited)) {
retcode = 1;
}
}
/* Start at 1 to skip the header node. */
for (i = 1; i < nodecount; i++) {
if (nodes[i]->commitNode)
commitNodeCount++;
if (nodes[i]->doFunc == NULL) {
printf("INVALID DAG: node %s has an undefined"
" doFunc.\n", nodes[i]->name);
retcode = 1;
goto validate_dag_out;
}
if (nodes[i]->undoFunc == NULL) {
printf("INVALID DAG: node %s has an undefined"
" doFunc.\n", nodes[i]->name);
retcode = 1;
goto validate_dag_out;
}
if (nodes[i]->numAntecedents != scount[nodes[i]->nodeNum]) {
printf("INVALID DAG: node %s has %d antecedents but"
" appears as a succedent %d times.\n",
nodes[i]->name, nodes[i]->numAntecedents,
scount[nodes[i]->nodeNum]);
retcode = 1;
goto validate_dag_out;
}
if (nodes[i]->numSuccedents != acount[nodes[i]->nodeNum]) {
printf("INVALID DAG: node %s has %d succedents but"
" appears as an antecedent %d times.\n",
nodes[i]->name, nodes[i]->numSuccedents,
acount[nodes[i]->nodeNum]);
retcode = 1;
goto validate_dag_out;
}
}
if (dag_h->numCommitNodes != commitNodeCount) {
printf("INVALID DAG: incorrect commit node count. "
"hdr->numCommitNodes (%d) found (%d) commit nodes"
" in graph.\n",
dag_h->numCommitNodes, commitNodeCount);
retcode = 1;
goto validate_dag_out;
}
validate_dag_out:
RF_Free(scount, nodecount * sizeof(int));
RF_Free(acount, nodecount * sizeof(int));
RF_Free(nodes, nodecount * sizeof(RF_DagNode_t *));
if (retcode)
rf_PrintDAGList(dag_h);
if (rf_validateVisitedDebug)
rf_ValidateVisitedBits(dag_h);
return (retcode);
validate_dag_bad:
rf_PrintDAGList(dag_h);
return (retcode);
}
/*****************************************************************************
*
* Misc construction routines.
*
*****************************************************************************/
void
rf_redirect_asm(RF_Raid_t *raidPtr, RF_AccessStripeMap_t *asmap)
{
int ds = (raidPtr->Layout.map->flags & RF_DISTRIBUTE_SPARE) ? 1 : 0;
int row = asmap->physInfo->row;
int fcol = raidPtr->reconControl[row]->fcol;
int srow = raidPtr->reconControl[row]->spareRow;
int scol = raidPtr->reconControl[row]->spareCol;
RF_PhysDiskAddr_t *pda;
RF_ASSERT(raidPtr->status[row] == rf_rs_reconstructing);
for (pda = asmap->physInfo; pda; pda = pda->next) {
if (pda->col == fcol) {
if (rf_dagDebug) {
if (!rf_CheckRUReconstructed(
raidPtr->reconControl[row]->reconMap,
pda->startSector)) {
RF_PANIC();
}
}
/*printf("Remapped data for large write\n");*/
if (ds) {
raidPtr->Layout.map->MapSector(raidPtr,
pda->raidAddress, &pda->row, &pda->col,
&pda->startSector, RF_REMAP);
} else {
pda->row = srow;
pda->col = scol;
}
}
}
for (pda = asmap->parityInfo; pda; pda = pda->next) {
if (pda->col == fcol) {
if (rf_dagDebug) {
if (!rf_CheckRUReconstructed(
raidPtr->reconControl[row]->reconMap,
pda->startSector)) {
RF_PANIC();
}
}
}
if (ds) {
(raidPtr->Layout.map->MapParity) (raidPtr,
pda->raidAddress, &pda->row, &pda->col,
&pda->startSector, RF_REMAP);
} else {
pda->row = srow;
pda->col = scol;
}
}
}
/*
* This routine allocates read buffers and generates stripe maps for the
* regions of the array from the start of the stripe to the start of the
* access, and from the end of the access to the end of the stripe. It also
* computes and returns the number of DAG nodes needed to read all this data.
* Note that this routine does the wrong thing if the access is fully
* contained within one stripe unit, so we RF_ASSERT against this case at the
* start.
*/
void
rf_MapUnaccessedPortionOfStripe(
RF_Raid_t *raidPtr,
RF_RaidLayout_t *layoutPtr, /* in: layout information */
RF_AccessStripeMap_t *asmap, /* in: access stripe map */
RF_DagHeader_t *dag_h, /* in: header of the dag */
/* to create */
RF_AccessStripeMapHeader_t **new_asm_h, /* in: ptr to array of 2 */
/* headers, to be */
/* filled in */
int *nRodNodes, /* out: num nodes to be */
/* generated to read */
/* unaccessed data */
char **sosBuffer, /* out: pointers to newly */
/* allocated buffer */
char **eosBuffer,
RF_AllocListElem_t *allocList
)
{
RF_RaidAddr_t sosRaidAddress, eosRaidAddress;
RF_SectorNum_t sosNumSector, eosNumSector;
RF_ASSERT(asmap->numStripeUnitsAccessed > (layoutPtr->numDataCol / 2));
/*
* Generate an access map for the region of the array from start of
* stripe to start of access.
*/
new_asm_h[0] = new_asm_h[1] = NULL;
*nRodNodes = 0;
if (!rf_RaidAddressStripeAligned(layoutPtr, asmap->raidAddress)) {
sosRaidAddress = rf_RaidAddressOfPrevStripeBoundary(layoutPtr,
asmap->raidAddress);
sosNumSector = asmap->raidAddress - sosRaidAddress;
RF_MallocAndAdd(*sosBuffer, rf_RaidAddressToByte(raidPtr,
sosNumSector), (char *), allocList);
new_asm_h[0] = rf_MapAccess(raidPtr, sosRaidAddress,
sosNumSector, *sosBuffer, RF_DONT_REMAP);
new_asm_h[0]->next = dag_h->asmList;
dag_h->asmList = new_asm_h[0];
*nRodNodes += new_asm_h[0]->stripeMap->numStripeUnitsAccessed;
RF_ASSERT(new_asm_h[0]->stripeMap->next == NULL);
/* We're totally within one stripe here. */
if (asmap->flags & RF_ASM_REDIR_LARGE_WRITE)
rf_redirect_asm(raidPtr, new_asm_h[0]->stripeMap);
}
/*
* Generate an access map for the region of the array from end of
* access to end of stripe.
*/
if (!rf_RaidAddressStripeAligned(layoutPtr, asmap->endRaidAddress)) {
eosRaidAddress = asmap->endRaidAddress;
eosNumSector = rf_RaidAddressOfNextStripeBoundary(layoutPtr,
eosRaidAddress) - eosRaidAddress;
RF_MallocAndAdd(*eosBuffer, rf_RaidAddressToByte(raidPtr,
eosNumSector), (char *), allocList);
new_asm_h[1] = rf_MapAccess(raidPtr, eosRaidAddress,
eosNumSector, *eosBuffer, RF_DONT_REMAP);
new_asm_h[1]->next = dag_h->asmList;
dag_h->asmList = new_asm_h[1];
*nRodNodes += new_asm_h[1]->stripeMap->numStripeUnitsAccessed;
RF_ASSERT(new_asm_h[1]->stripeMap->next == NULL);
/* We're totally within one stripe here. */
if (asmap->flags & RF_ASM_REDIR_LARGE_WRITE)
rf_redirect_asm(raidPtr, new_asm_h[1]->stripeMap);
}
}
/* Returns non-zero if the indicated ranges of stripe unit offsets overlap. */
int
rf_PDAOverlap(RF_RaidLayout_t *layoutPtr, RF_PhysDiskAddr_t *src,
RF_PhysDiskAddr_t *dest)
{
RF_SectorNum_t soffs =
rf_StripeUnitOffset(layoutPtr, src->startSector);
RF_SectorNum_t doffs =
rf_StripeUnitOffset(layoutPtr, dest->startSector);
/* Use -1 to be sure we stay within SU. */
RF_SectorNum_t send =
rf_StripeUnitOffset(layoutPtr, src->startSector +
src->numSector - 1);
RF_SectorNum_t dend =
rf_StripeUnitOffset(layoutPtr, dest->startSector +
dest->numSector - 1);
return ((RF_MAX(soffs, doffs) <= RF_MIN(send, dend)) ? 1 : 0);
}
/*
* GenerateFailedAccessASMs
*
* This routine figures out what portion of the stripe needs to be read
* to effect the degraded read or write operation. It's primary function
* is to identify everything required to recover the data, and then
* eliminate anything that is already being accessed by the user.
*
* The main result is two new ASMs, one for the region from the start of the
* stripe to the start of the access, and one for the region from the end of
* the access to the end of the stripe. These ASMs describe everything that
* needs to be read to effect the degraded access. Other results are:
* nXorBufs -- The total number of buffers that need to be XORed together
* to recover the lost data,
* rpBufPtr -- Ptr to a newly-allocated buffer to hold the parity. If NULL
* at entry, not allocated.
* overlappingPDAs --
* Describes which of the non-failed PDAs, in the user access,
* overlap data that needs to be read to effect recovery.
* overlappingPDAs[i]==1 if and only if, neglecting the failed
* PDA, the i'th pda in the input asm overlaps data that needs
* to be read for recovery.
*/
/* in: asmap - ASM for the actual access, one stripe only. */
/* in: faildPDA - Which component of the access has failed. */
/* in: dag_h - Header of the DAG we're going to create. */
/* out: new_asm_h - The two new ASMs. */
/* out: nXorBufs - The total number of xor bufs required. */
/* out: rpBufPtr - A buffer for the parity read. */
void
rf_GenerateFailedAccessASMs(
RF_Raid_t *raidPtr,
RF_AccessStripeMap_t *asmap,
RF_PhysDiskAddr_t *failedPDA,
RF_DagHeader_t *dag_h,
RF_AccessStripeMapHeader_t **new_asm_h,
int *nXorBufs,
char **rpBufPtr,
char *overlappingPDAs,
RF_AllocListElem_t *allocList
)
{
RF_RaidLayout_t *layoutPtr = &(raidPtr->Layout);
/* s=start, e=end, s=stripe, a=access, f=failed, su=stripe unit */
RF_RaidAddr_t sosAddr, sosEndAddr, eosStartAddr, eosAddr;
RF_SectorCount_t numSect[2], numParitySect;
RF_PhysDiskAddr_t *pda;
char *rdBuf, *bufP;
int foundit, i;
bufP = NULL;
foundit = 0;
/*
* First compute the following raid addresses:
* - Start of stripe
* - (sosAddr) MIN(start of access, start of failed SU)
* - (sosEndAddr) MAX(end of access, end of failed SU)
* - (eosStartAddr) end of stripe (i.e. start of next stripe)
* (eosAddr)
*/
sosAddr = rf_RaidAddressOfPrevStripeBoundary(layoutPtr,
asmap->raidAddress);
sosEndAddr = RF_MIN(asmap->raidAddress,
rf_RaidAddressOfPrevStripeUnitBoundary(layoutPtr,
failedPDA->raidAddress));
eosStartAddr = RF_MAX(asmap->endRaidAddress,
rf_RaidAddressOfNextStripeUnitBoundary(layoutPtr,
failedPDA->raidAddress));
eosAddr = rf_RaidAddressOfNextStripeBoundary(layoutPtr,
asmap->raidAddress);
/*
* Now generate access stripe maps for each of the above regions of
* the stripe. Use a dummy (NULL) buf ptr for now.
*/
new_asm_h[0] = (sosAddr != sosEndAddr) ?
rf_MapAccess(raidPtr, sosAddr, sosEndAddr - sosAddr, NULL,
RF_DONT_REMAP) : NULL;
new_asm_h[1] = (eosStartAddr != eosAddr) ?
rf_MapAccess(raidPtr, eosStartAddr, eosAddr - eosStartAddr, NULL,
RF_DONT_REMAP) : NULL;
/*
* Walk through the PDAs and range-restrict each SU to the region of
* the SU touched on the failed PDA. Also compute total data buffer
* space requirements in this step. Ignore the parity for now.
*/
numSect[0] = numSect[1] = 0;
if (new_asm_h[0]) {
new_asm_h[0]->next = dag_h->asmList;
dag_h->asmList = new_asm_h[0];
for (pda = new_asm_h[0]->stripeMap->physInfo; pda;
pda = pda->next) {
rf_RangeRestrictPDA(raidPtr, failedPDA, pda,
RF_RESTRICT_NOBUFFER, 0);
numSect[0] += pda->numSector;
}
}
if (new_asm_h[1]) {
new_asm_h[1]->next = dag_h->asmList;
dag_h->asmList = new_asm_h[1];
for (pda = new_asm_h[1]->stripeMap->physInfo;
pda; pda = pda->next) {
rf_RangeRestrictPDA(raidPtr, failedPDA, pda,
RF_RESTRICT_NOBUFFER, 0);
numSect[1] += pda->numSector;
}
}
numParitySect = failedPDA->numSector;
/*
* Allocate buffer space for the data & parity we have to read to
* recover from the failure.
*/
if (numSect[0] + numSect[1] + ((rpBufPtr) ? numParitySect : 0)) {
/* Don't allocate parity buf if not needed. */
RF_MallocAndAdd(rdBuf, rf_RaidAddressToByte(raidPtr,
numSect[0] + numSect[1] + numParitySect), (char *),
allocList);
bufP = rdBuf;
if (rf_degDagDebug)
printf("Newly allocated buffer (%d bytes) is 0x%lx\n",
(int) rf_RaidAddressToByte(raidPtr,
numSect[0] + numSect[1] + numParitySect),
(unsigned long) bufP);
}
/*
* Now walk through the pdas one last time and assign buffer pointers
* (ugh!). Again, ignore the parity. Also, count nodes to find out
* how many bufs need to be xored together.
*/
(*nXorBufs) = 1; /* In read case, 1 is for parity. */
/* In write case, 1 is for failed data. */
if (new_asm_h[0]) {
for (pda = new_asm_h[0]->stripeMap->physInfo; pda;
pda = pda->next) {
pda->bufPtr = bufP;
bufP += rf_RaidAddressToByte(raidPtr, pda->numSector);
}
*nXorBufs += new_asm_h[0]->stripeMap->numStripeUnitsAccessed;
}
if (new_asm_h[1]) {
for (pda = new_asm_h[1]->stripeMap->physInfo; pda;
pda = pda->next) {
pda->bufPtr = bufP;
bufP += rf_RaidAddressToByte(raidPtr, pda->numSector);
}
(*nXorBufs) += new_asm_h[1]->stripeMap->numStripeUnitsAccessed;
}
if (rpBufPtr)
/* The rest of the buffer is for parity. */
*rpBufPtr = bufP;
/*
* The last step is to figure out how many more distinct buffers need
* to get xor'd to produce the missing unit. there's one for each
* user-data read node that overlaps the portion of the failed unit
* being accessed.
*/
for (foundit = i = 0, pda = asmap->physInfo;
pda; i++, pda = pda->next) {
if (pda == failedPDA) {
i--;
foundit = 1;
continue;
}
if (rf_PDAOverlap(layoutPtr, pda, failedPDA)) {
overlappingPDAs[i] = 1;
(*nXorBufs)++;
}
}
if (!foundit) {
RF_ERRORMSG("GenerateFailedAccessASMs: did not find failedPDA"
" in asm list.\n");
RF_ASSERT(0);
}
if (rf_degDagDebug) {
if (new_asm_h[0]) {
printf("First asm:\n");
rf_PrintFullAccessStripeMap(new_asm_h[0], 1);
}
if (new_asm_h[1]) {
printf("Second asm:\n");
rf_PrintFullAccessStripeMap(new_asm_h[1], 1);
}
}
}
/*
* Adjust the offset and number of sectors in the destination pda so that
* it covers at most the region of the SU covered by the source PDA. This
* is exclusively a restriction: the number of sectors indicated by the
* target PDA can only shrink.
*
* For example: s = sectors within SU indicated by source PDA
* d = sectors within SU indicated by dest PDA
* r = results, stored in dest PDA
*
* |--------------- one stripe unit ---------------------|
* | sssssssssssssssssssssssssssssssss |
* | ddddddddddddddddddddddddddddddddddddddddddddd |
* | rrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr |
*
* Another example:
*
* |--------------- one stripe unit ---------------------|
* | sssssssssssssssssssssssssssssssss |
* | ddddddddddddddddddddddd |
* | rrrrrrrrrrrrrrrr |
*
*/
void
rf_RangeRestrictPDA(RF_Raid_t *raidPtr, RF_PhysDiskAddr_t *src,
RF_PhysDiskAddr_t *dest, int dobuffer, int doraidaddr)
{
RF_RaidLayout_t *layoutPtr = &raidPtr->Layout;
RF_SectorNum_t soffs =
rf_StripeUnitOffset(layoutPtr, src->startSector);
RF_SectorNum_t doffs =
rf_StripeUnitOffset(layoutPtr, dest->startSector);
RF_SectorNum_t send =
rf_StripeUnitOffset(layoutPtr, src->startSector +
src->numSector - 1); /* Use -1 to be sure we stay within SU. */
RF_SectorNum_t dend =
rf_StripeUnitOffset(layoutPtr, dest->startSector +
dest->numSector - 1);
RF_SectorNum_t subAddr =
rf_RaidAddressOfPrevStripeUnitBoundary(layoutPtr,
dest->startSector); /* Stripe unit boundary. */
dest->startSector = subAddr + RF_MAX(soffs, doffs);
dest->numSector = subAddr + RF_MIN(send, dend) + 1 - dest->startSector;
if (dobuffer)
dest->bufPtr += (soffs > doffs) ?
rf_RaidAddressToByte(raidPtr, soffs - doffs) : 0;
if (doraidaddr) {
dest->raidAddress =
rf_RaidAddressOfPrevStripeUnitBoundary(layoutPtr,
dest->raidAddress) +
rf_StripeUnitOffset(layoutPtr, dest->startSector);
}
}
/*
* Want the highest of these primes to be the largest one
* less than the max expected number of columns (won't hurt
* to be too small or too large, but won't be optimal, either)
* --jimz
*/
#define NLOWPRIMES 8
static int lowprimes[NLOWPRIMES] = {2, 3, 5, 7, 11, 13, 17, 19};
/*****************************************************************************
* Compute the workload shift factor. (chained declustering)
*
* Return nonzero if access should shift to secondary, otherwise,
* access is to primary.
*****************************************************************************/
int
rf_compute_workload_shift(RF_Raid_t *raidPtr, RF_PhysDiskAddr_t *pda)
{
/*
* Variables:
* d = Column of disk containing primary.
* f = Column of failed disk.
* n = Number of disks in array.
* sd = "shift distance"
* (number of columns that d is to the right of f).
* row = Row of array the access is in.
* v = Numerator of redirection ratio.
* k = Denominator of redirection ratio.
*/
RF_RowCol_t d, f, sd, row, n;
int k, v, ret, i;
row = pda->row;
n = raidPtr->numCol;
/* Assign column of primary copy to d. */
d = pda->col;
/* Assign column of dead disk to f. */
for (f = 0; ((!RF_DEAD_DISK(raidPtr->Disks[row][f].status)) &&
(f < n)); f++);
RF_ASSERT(f < n);
RF_ASSERT(f != d);
sd = (f > d) ? (n + d - f) : (d - f);
RF_ASSERT(sd < n);
/*
* v of every k accesses should be redirected.
*
* v/k := (n-1-sd)/(n-1)
*/
v = (n - 1 - sd);
k = (n - 1);
#if 1
/*
* XXX
* Is this worth it ?
*
* Now reduce the fraction, by repeatedly factoring
* out primes (just like they teach in elementary school !).
*/
for (i = 0; i < NLOWPRIMES; i++) {
if (lowprimes[i] > v)
break;
while (((v % lowprimes[i]) == 0) && ((k % lowprimes[i]) == 0)) {
v /= lowprimes[i];
k /= lowprimes[i];
}
}
#endif
raidPtr->hist_diskreq[row][d]++;
if (raidPtr->hist_diskreq[row][d] > v) {
ret = 0; /* Do not redirect. */
} else {
ret = 1; /* Redirect. */
}
#if 0
printf("d=%d f=%d sd=%d v=%d k=%d ret=%d h=%d\n", d, f, sd, v, k, ret,
raidPtr->hist_diskreq[row][d]);
#endif
if (raidPtr->hist_diskreq[row][d] >= k) {
/* Reset counter. */
raidPtr->hist_diskreq[row][d] = 0;
}
return (ret);
}
/*
* Disk selection routines.
*/
/*
* Select the disk with the shortest queue from a mirror pair.
* Both the disk I/Os queued in RAIDframe as well as those at the physical
* disk are counted as members of the "queue".
*/
void
rf_SelectMirrorDiskIdle(RF_DagNode_t *node)
{
RF_Raid_t *raidPtr = (RF_Raid_t *) node->dagHdr->raidPtr;
RF_RowCol_t rowData, colData, rowMirror, colMirror;
int dataQueueLength, mirrorQueueLength, usemirror;
RF_PhysDiskAddr_t *data_pda = (RF_PhysDiskAddr_t *) node->params[0].p;
RF_PhysDiskAddr_t *mirror_pda = (RF_PhysDiskAddr_t *) node->params[4].p;
RF_PhysDiskAddr_t *tmp_pda;
RF_RaidDisk_t **disks = raidPtr->Disks;
RF_DiskQueue_t **dqs = raidPtr->Queues, *dataQueue, *mirrorQueue;
/* Return the [row col] of the disk with the shortest queue. */
rowData = data_pda->row;
colData = data_pda->col;
rowMirror = mirror_pda->row;
colMirror = mirror_pda->col;
dataQueue = &(dqs[rowData][colData]);
mirrorQueue = &(dqs[rowMirror][colMirror]);
#ifdef RF_LOCK_QUEUES_TO_READ_LEN
RF_LOCK_QUEUE_MUTEX(dataQueue, "SelectMirrorDiskIdle");
#endif /* RF_LOCK_QUEUES_TO_READ_LEN */
dataQueueLength = dataQueue->queueLength + dataQueue->numOutstanding;
#ifdef RF_LOCK_QUEUES_TO_READ_LEN
RF_UNLOCK_QUEUE_MUTEX(dataQueue, "SelectMirrorDiskIdle");
RF_LOCK_QUEUE_MUTEX(mirrorQueue, "SelectMirrorDiskIdle");
#endif /* RF_LOCK_QUEUES_TO_READ_LEN */
mirrorQueueLength = mirrorQueue->queueLength +
mirrorQueue->numOutstanding;
#ifdef RF_LOCK_QUEUES_TO_READ_LEN
RF_UNLOCK_QUEUE_MUTEX(mirrorQueue, "SelectMirrorDiskIdle");
#endif /* RF_LOCK_QUEUES_TO_READ_LEN */
usemirror = 0;
if (RF_DEAD_DISK(disks[rowMirror][colMirror].status)) {
usemirror = 0;
} else
if (RF_DEAD_DISK(disks[rowData][colData].status)) {
usemirror = 1;
} else
if (raidPtr->parity_good == RF_RAID_DIRTY) {
/* Trust only the main disk. */
usemirror = 0;
} else
if (dataQueueLength < mirrorQueueLength) {
usemirror = 0;
} else
if (mirrorQueueLength < dataQueueLength) {
usemirror = 1;
} else {
/* Queues are equal length. */
/* Attempt cleverness. */
if (SNUM_DIFF(dataQueue
->last_deq_sector, data_pda
->startSector) <=
SNUM_DIFF(mirrorQueue
->last_deq_sector, mirror_pda
->startSector)) {
usemirror = 0;
} else {
usemirror = 1;
}
}
if (usemirror) {
/* Use mirror (parity) disk, swap params 0 & 4. */
tmp_pda = data_pda;
node->params[0].p = mirror_pda;
node->params[4].p = tmp_pda;
} else {
/* Use data disk, leave param 0 unchanged. */
}
/*printf("dataQueueLength %d, mirrorQueueLength %d\n", dataQueueLength,
mirrorQueueLength);*/
}
/*
* Do simple partitioning. This assumes that
* the data and parity disks are laid out identically.
*/
void
rf_SelectMirrorDiskPartition(RF_DagNode_t *node)
{
RF_Raid_t *raidPtr = (RF_Raid_t *) node->dagHdr->raidPtr;
RF_RowCol_t rowData, colData, rowMirror, colMirror;
RF_PhysDiskAddr_t *data_pda = (RF_PhysDiskAddr_t *) node->params[0].p;
RF_PhysDiskAddr_t *mirror_pda = (RF_PhysDiskAddr_t *) node->params[4].p;
RF_PhysDiskAddr_t *tmp_pda;
RF_RaidDisk_t **disks = raidPtr->Disks;
RF_DiskQueue_t **dqs = raidPtr->Queues, *dataQueue, *mirrorQueue;
int usemirror;
/* Return the [row col] of the disk with the shortest queue. */
rowData = data_pda->row;
colData = data_pda->col;
rowMirror = mirror_pda->row;
colMirror = mirror_pda->col;
dataQueue = &(dqs[rowData][colData]);
mirrorQueue = &(dqs[rowMirror][colMirror]);
usemirror = 0;
if (RF_DEAD_DISK(disks[rowMirror][colMirror].status)) {
usemirror = 0;
} else
if (RF_DEAD_DISK(disks[rowData][colData].status)) {
usemirror = 1;
} else
if (raidPtr->parity_good == RF_RAID_DIRTY) {
/* Trust only the main disk. */
usemirror = 0;
} else
if (data_pda->startSector <
(disks[rowData][colData].numBlocks / 2)) {
usemirror = 0;
} else {
usemirror = 1;
}
if (usemirror) {
/* Use mirror (parity) disk, swap params 0 & 4. */
tmp_pda = data_pda;
node->params[0].p = mirror_pda;
node->params[4].p = tmp_pda;
} else {
/* Use data disk, leave param 0 unchanged. */
}
}