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-rw-r--r--raid5extend.c80
1 files changed, 80 insertions, 0 deletions
diff --git a/raid5extend.c b/raid5extend.c
new file mode 100644
index 0000000..d8e62c2
--- /dev/null
+++ b/raid5extend.c
@@ -0,0 +1,80 @@
+
+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));
+ }
+ }
+}