mdctl-0.5mdctl-0.5

1 files changed, 80 insertions, 0 deletions

diff --git a/raid5extend.c b/raid5extend.c
new file mode 100644
index 0000000..98615a6
--- /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));
+	}
+    }
+}