--- /dev/null
+/*
+ * Copyright (C) 2015 Andrea Mazzoleni
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ */
+
+#include "internal.h"
+#include "combo.h"
+#include "gf.h"
+
+/**
+ * Validate the provided failed blocks.
+ *
+ * This function checks if the specified failed blocks satisfy the redundancy
+ * information using the data from the known valid parity blocks.
+ *
+ * It's similar at raid_check(), just with a different format for arguments.
+ *
+ * The number of failed blocks @nr must be strictly less than the number of
+ * parities @nv, because you need one more parity to validate the recovering.
+ *
+ * No data or parity blocks are modified.
+ *
+ * @nr Number of failed data blocks.
+ * @id[] Vector of @nr indexes of the failed data blocks.
+ * The indexes start from 0. They must be in order.
+ * @nv Number of valid parity blocks.
+ * @ip[] Vector of @nv indexes of the valid parity blocks.
+ * The indexes start from 0. They must be in order.
+ * @nd Number of data blocks.
+ * @size Size of the blocks pointed by @v. It must be a multipler of 64.
+ * @v Vector of pointers to the blocks of data and parity.
+ * It has (@nd + @ip[@nv - 1] + 1) elements. The starting elements are the
+ * blocks for data, following with the parity blocks.
+ * Each block has @size bytes.
+ * @return 0 if the check is satisfied. -1 otherwise.
+ */
+static int raid_validate(int nr, int *id, int nv, int *ip, int nd, size_t size, void **vv)
+{
+ uint8_t **v = (uint8_t **)vv;
+ const uint8_t *T[RAID_PARITY_MAX][RAID_PARITY_MAX];
+ uint8_t G[RAID_PARITY_MAX * RAID_PARITY_MAX];
+ uint8_t V[RAID_PARITY_MAX * RAID_PARITY_MAX];
+ size_t i;
+ int j, k, l;
+
+ BUG_ON(nr >= nv);
+
+ /* setup the coefficients matrix */
+ for (j = 0; j < nr; ++j)
+ for (k = 0; k < nr; ++k)
+ G[j * nr + k] = A(ip[j], id[k]);
+
+ /* invert it to solve the system of linear equations */
+ raid_invert(G, V, nr);
+
+ /* get multiplication tables */
+ for (j = 0; j < nr; ++j)
+ for (k = 0; k < nr; ++k)
+ T[j][k] = table(V[j * nr + k]);
+
+ /* check all positions */
+ for (i = 0; i < size; ++i) {
+ uint8_t p[RAID_PARITY_MAX];
+
+ /* get parity */
+ for (j = 0; j < nv; ++j)
+ p[j] = v[nd + ip[j]][i];
+
+ /* compute delta parity, skipping broken disks */
+ for (j = 0, k = 0; j < nd; ++j) {
+ uint8_t b;
+
+ /* skip broken disks */
+ if (k < nr && id[k] == j) {
+ ++k;
+ continue;
+ }
+
+ b = v[j][i];
+ for (l = 0; l < nv; ++l)
+ p[l] ^= gfmul[b][gfgen[ip[l]][j]];
+ }
+
+ /* reconstruct data */
+ for (j = 0; j < nr; ++j) {
+ uint8_t b = 0;
+ int idj = id[j];
+
+ /* recompute the data */
+ for (k = 0; k < nr; ++k)
+ b ^= T[j][k][p[k]];
+
+ /* add the parity contribution of the reconstructed data */
+ for (l = nr; l < nv; ++l)
+ p[l] ^= gfmul[b][gfgen[ip[l]][idj]];
+ }
+
+ /* check that the final parity is 0 */
+ for (l = nr; l < nv; ++l)
+ if (p[l] != 0)
+ return -1;
+ }
+
+ return 0;
+}
+
+int raid_check(int nr, int *ir, int nd, int np, size_t size, void **v)
+{
+ /* valid parity index */
+ int ip[RAID_PARITY_MAX];
+ int vp;
+ int rd;
+ int i, j;
+
+ /* enforce limit on size */
+ BUG_ON(size % 64 != 0);
+
+ /* enforce limit on number of failures */
+ BUG_ON(nr >= np); /* >= because we check with extra parity */
+ BUG_ON(np > RAID_PARITY_MAX);
+
+ /* enforce order in index vector */
+ BUG_ON(nr >= 2 && ir[0] >= ir[1]);
+ BUG_ON(nr >= 3 && ir[1] >= ir[2]);
+ BUG_ON(nr >= 4 && ir[2] >= ir[3]);
+ BUG_ON(nr >= 5 && ir[3] >= ir[4]);
+ BUG_ON(nr >= 6 && ir[4] >= ir[5]);
+
+ /* enforce limit on index vector */
+ BUG_ON(nr > 0 && ir[nr-1] >= nd + np);
+
+ /* count failed data disk */
+ rd = 0;
+ while (rd < nr && ir[rd] < nd)
+ ++rd;
+
+ /* put valid parities into ip[] */
+ vp = 0;
+ for (i = rd, j = 0; j < np; ++j) {
+ /* if parity is failed */
+ if (i < nr && ir[i] == nd + j) {
+ /* skip broken parity */
+ ++i;
+ } else {
+ /* store valid parity */
+ ip[vp] = j;
+ ++vp;
+ }
+ }
+
+ return raid_validate(rd, ir, vp, ip, nd, size, v);
+}
+
+int raid_scan(int *ir, int nd, int np, size_t size, void **v)
+{
+ int r;
+
+ /* check the special case of no failure */
+ if (np != 0 && raid_check(0, 0, nd, np, size, v) == 0)
+ return 0;
+
+ /* for each number of possible failures */
+ for (r = 1; r < np; ++r) {
+ /* try all combinations of r failures on n disks */
+ combination_first(r, nd + np, ir);
+ do {
+ /* verify if the combination is a valid one */
+ if (raid_check(r, ir, nd, np, size, v) == 0)
+ return r;
+ } while (combination_next(r, nd + np, ir));
+ }
+
+ /* no solution found */
+ return -1;
+}
+
projects / bcachefs-tools-debian / blobdiff