Re: bug in file raid5.c, line 659

[David van der Spoel]

On Thu, 9 Sep 1999 [EMAIL PROTECTED] wrote:

>David,
>
>It looks like your system and syslog are very similar to mine.
>Are you using two aic7xxx controllers for 8 * 9Gb disks?
>And is it SMP?
I have an SMP system (Dual PII 350 on Supermicro motherboard) with tho
Qlogic controllers, one with four internal disks, one with four external
disks (all 9Gb). I am runing 2.2.12+RAID patches (990824) + knfsd 1.4.6

>Mine is PII-500 2CPU, with 9 * 18GB on two aic7xxx U2W.
>I've got very same scsi errors with you.
It is very easy to get SCSI error due to termination problems, or cable
length (should be less than 1.5 m). 

I actually wrote a tiny program that fires up a few threads and creates
some large files, which are then read and written more or less randomly.
It succeeds locking up my computer almost. It might be worth a try (see
below)

Groeten, David.
________________________________________________________________________
Dr. David van der Spoel         Biomedical center, Dept. of Biochemistry
s-mail: Husargatan 3, Box 576,  75123 Uppsala, Sweden
e-mail: [EMAIL PROTECTED]    www: http://zorn.bmc.uu.se/~spoel
phone:  46 18 471 4205          fax: 46 18 511 755
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

#include <stdio.h>
#include <unistd.h>

#define MAXOPEN 32
#define BUFS    2048

#define max(a,b) ((a) > (b)) ? (a) : (b) 
#define min(a,b) ((a) < (b)) ? (a) : (b) 

FILE *mk_file(int n)
{
  char buf[32];
  
  if ((n < 0) || (n > MAXOPEN)) {
    return NULL;
  }
  sprintf(buf,"de-junk%d.bin",n);
  if (fopen(buf,"r") == NULL)
    /* File does not exist */
    return fopen(buf,"w+");
  else
    return NULL;
}

void seekit(FILE *fp,int length,int nseek)
{
  int  i,j,step,step0=17,size;
  char buf[BUFS];
  
  step = length - 137;
  while (step < 0)
    step += length;
  rewind(fp);
  for(i=0; (i<nseek); i++) {
    /* Even iterations reading */
    if ((j % 2) == 0) {
      step0 = (step0 + step) % length;
      fseek(fp,step0,SEEK_SET);
      size = min(BUFS,length-step0);
      fread(buf,size,1,fp);
    }
    else {
      /* Odd iterations writing */
      fseek(fp,step0,SEEK_SET);
      size = min(BUFS,length-step0);
      for(j=0; (j<BUFS); j++)
        buf[j] = !buf[j];
      fwrite(buf,min(BUFS,length-step0),1,fp);
    }
  }
}

void justdoit(int i,int bufs,int nblocks,int nseek)
{
  FILE *fp;
  int  j,k;
  char *buf;
  
  /* Open a file */
  fprintf(stderr,"Just do it %d\n",i);
  if ((fp = mk_file(i)) != NULL) {
    /* Create a buffer */
    if ((buf = (char *)malloc(bufs)) == NULL) {
      fclose(fp);
      return;
    }
      
    /* Write the buffer to file a couple of times */
    for(k=0; (k<nblocks); k++)
      fwrite(buf,bufs,1,fp);
    
    seekit(fp,bufs*nblocks,nseek);
    
    /* Clean up */
    free(buf);
    fclose(fp);
  }
  else
    fprintf(stderr,"Can't create file\n");
}

void doit(int n,int bufs,int nblocks,int nseek)
{
  if ((n > 0) && (fork() == 0))
    doit(n-1,bufs,nblocks,nseek);
  else if (n > 0)
    justdoit(n,bufs,nblocks,nseek);
}

void main(int argc,char *argv[])
{
  int nproc  = 4;
  int bufs   = 20435;
  int nblock = 1379;
  int nseek  = 8795;
  
  fprintf(stderr,"%s\n",argv[0]);
  if (argc >= 2)
    nproc = atoi(argv[1]);
  
  if (nproc >= MAXOPEN) {
    fprintf(stderr,"Usage: %s nprocess [ less than %d ]\n",argv[0],MAXOPEN);
    exit(1);
  }
  fprintf(stderr,"Starting %s with nproc=%d, bufs=%d, nblocks=%d, nseek=%d\n",
          argv[0],nproc,bufs,nblock,nseek);
  
  doit(nproc,bufs,nblock,nseek);
}