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int phys2log(int phys, int stripe, int n, int layout)
{
/* In an 'n' disk array using 'layout',
* in stripe 'stripe', the physical disc 'phys'
* stores what logical chunk?
* -1 mean parity.
*
*/
switch(layout) {
case ALGORITHM_LEFT_ASYMMETRIC:
pd = (n-1) - (stripe % n);
if (phys < pd)
return phys;
else if (phys == pd)
return -1;
else return phys-1;
case ALGORITHM_RIGHT_ASYMMETRIC:
pd = stripe % n;
if (phys < pd)
return phys;
else if (phys == pd)
return -1;
else return phys-1;
case ALGORITHM_LEFT_SYMMETRIC:
pd = (n-1) - (stripe %n);
if (phys < pd)
return phys+ n-1-pd;
else if (phys == pd)
return -1;
else return phys-pd-1;
case ALGORITHM_RIGHT_SYMMETRIC:
pd = stripe % n;
if (phys < pd)
return phys+ n-1-pd;
else if (phys == pd)
return -1;
else return phys-pd-1;
}
return -2;
}
raid5_extend(unsigned long len, int chunksize, int layout, int n, int m, int rfds[], int wfds[])
{
static char buf[4096];
unsigned long blocks = len/4;
unsigned int blocksperchunk= chunksize/4096;
unsigned long b;
for (b=0; b<blocks; b++) {
unsigned long stripe = b / blocksperchunk;
unsigned int offset = b - (stripe*blocksperchunk);
unsigned long chunk = stripe * (n-1);
int src;
for (src=0; src<n; src++) {
int dnum, snum;
if (read(rfds[src], buf, sizeof(buf)) != sizeof(buf)) {
error();
return 0;
}
snum = phys2log(src, stripe, n, layout);
if (snum == -1)
continue;
chunk = stripe*(n-1)+snum;
dstripe = chunk/(m-1);
dnum = log2phys(chunk-(stripe*(m-1)), dstripe, m, layout);
llseek(wfds[dnum], dstripe*chunksize+(offset*4096), 0);
write(wfds[dnum], buf, sizeof(buf));
}
}
}
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