Adding upstream version 16.2.11+ds.upstream/16.2.11+dsupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 815 insertions, 0 deletions

diff --git a/src/erasure-code/shec/ErasureCodeShec.cc b/src/erasure-code/shec/ErasureCodeShec.cc
new file mode 100644
index 000000000..3634be2fb
--- /dev/null
+++ b/src/erasure-code/shec/ErasureCodeShec.cc
@@ -0,0 +1,815 @@
+// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
+// vim: ts=8 sw=2 smarttab
+/*
+ * Ceph - scalable distributed file system
+ *
+ * Copyright (C) 2014 FUJITSU LIMITED
+ * Copyright (C) 2013,2014 Cloudwatt <libre.licensing@cloudwatt.com>
+ * Copyright (C) 2014 Red Hat <contact@redhat.com>
+ *
+ * Author: Takanori Nakao <nakao.takanori@jp.fujitsu.com>
+ * Author: Takeshi Miyamae <miyamae.takeshi@jp.fujitsu.com>
+ * Author: Loic Dachary <loic@dachary.org>
+ *
+ *  This library is free software; you can redistribute it and/or
+ *  modify it under the terms of the GNU Lesser General Public
+ *  License as published by the Free Software Foundation; either
+ *  version 2.1 of the License, or (at your option) any later version.
+ *
+ */
+
+#include <cstdio>
+#include <cstdlib>
+#include <cstring>
+#include <cerrno>
+#include <algorithm>
+#include "common/debug.h"
+#include "ErasureCodeShec.h"
+extern "C" {
+#include "jerasure/include/jerasure.h"
+#include "jerasure/include/galois.h"
+
+extern int calc_determinant(int *matrix, int dim);
+extern int* reed_sol_vandermonde_coding_matrix(int k, int m, int w);
+}
+
+#define dout_context g_ceph_context
+#define dout_subsys ceph_subsys_osd
+#undef dout_prefix
+#define dout_prefix _prefix(_dout)
+
+using namespace std;
+using namespace ceph;
+
+
+static ostream& _prefix(std::ostream* _dout)
+{
+  return *_dout << "ErasureCodeShec: ";
+}
+
+int ErasureCodeShec::init(ErasureCodeProfile &profile,
+			  ostream *ss)
+{
+  int err = 0;
+  err |= parse(profile);
+  if (err)
+    return err;
+  prepare();
+  return ErasureCode::init(profile, ss);
+}
+
+unsigned int ErasureCodeShec::get_chunk_size(unsigned int object_size) const
+{
+  unsigned alignment = get_alignment();
+  unsigned tail = object_size % alignment;
+  unsigned padded_length = object_size + ( tail ?  ( alignment - tail ) : 0 );
+
+  ceph_assert(padded_length % k == 0);
+  return padded_length / k;
+}
+
+int ErasureCodeShec::_minimum_to_decode(const set<int> &want_to_read,
+				       const set<int> &available_chunks,
+				       set<int> *minimum_chunks)
+{
+  if (!minimum_chunks) return -EINVAL;
+
+  for (set<int>::iterator it = available_chunks.begin(); it != available_chunks.end(); ++it){
+    if (*it < 0 || k+m <= *it) return -EINVAL;
+  }
+
+  for (set<int>::iterator it = want_to_read.begin(); it != want_to_read.end(); ++it){
+    if (*it < 0 || k+m <= *it) return -EINVAL;
+  }
+
+  int want[k + m];
+  int avails[k + m];
+  int minimum[k + m];
+
+  memset(want, 0, sizeof(want));
+  memset(avails, 0, sizeof(avails));
+  memset(minimum, 0, sizeof(minimum));
+  (*minimum_chunks).clear();
+
+  for (set<int>::const_iterator i = want_to_read.begin();
+       i != want_to_read.end();
+       ++i) {
+    want[*i] = 1;
+  }
+
+  for (set<int>::const_iterator i = available_chunks.begin();
+       i != available_chunks.end();
+       ++i) {
+    avails[*i] = 1;
+  }
+
+  {
+    int decoding_matrix[k*k];
+    int dm_row[k];
+    int dm_column[k];
+    memset(decoding_matrix, 0, sizeof(decoding_matrix));
+    memset(dm_row, 0, sizeof(dm_row));
+    memset(dm_column, 0, sizeof(dm_column));
+    if (shec_make_decoding_matrix(true, want, avails, decoding_matrix, dm_row, dm_column, minimum) < 0) {
+      return -EIO;
+    }
+  }
+
+  for (int i = 0; i < k + m; i++) {
+    if (minimum[i] == 1) minimum_chunks->insert(i);
+  }
+
+  return 0;
+}
+
+int ErasureCodeShec::minimum_to_decode_with_cost(const set<int> &want_to_read,
+						 const map<int, int> &available,
+						 set<int> *minimum_chunks)
+{
+  set <int> available_chunks;
+
+  for (map<int, int>::const_iterator i = available.begin();
+       i != available.end();
+       ++i)
+    available_chunks.insert(i->first);
+
+  return _minimum_to_decode(want_to_read, available_chunks, minimum_chunks);
+}
+
+int ErasureCodeShec::encode(const set<int> &want_to_encode,
+			    const bufferlist &in,
+			    map<int, bufferlist> *encoded)
+{
+  unsigned int k = get_data_chunk_count();
+  unsigned int m = get_chunk_count() - k;
+  bufferlist out;
+
+  if (!encoded || !encoded->empty()){
+    return -EINVAL;
+  }
+
+  int err = encode_prepare(in, *encoded);
+  if (err)
+    return err;
+  encode_chunks(want_to_encode, encoded);
+  for (unsigned int i = 0; i < k + m; i++) {
+    if (want_to_encode.count(i) == 0)
+      encoded->erase(i);
+  }
+  return 0;
+}
+
+int ErasureCodeShec::encode_chunks(const set<int> &want_to_encode,
+				   map<int, bufferlist> *encoded)
+{
+  char *chunks[k + m];
+  for (int i = 0; i < k + m; i++){
+    chunks[i] = (*encoded)[i].c_str();
+  }
+  shec_encode(&chunks[0], &chunks[k], (*encoded)[0].length());
+  return 0;
+}
+
+int ErasureCodeShec::_decode(const set<int> &want_to_read,
+			    const map<int, bufferlist> &chunks,
+			    map<int, bufferlist> *decoded)
+{
+  vector<int> have;
+
+  if (!decoded || !decoded->empty()){
+    return -EINVAL;
+  }
+  if (!want_to_read.empty() && chunks.empty()) {
+    // i need to get the blocksize from the first element of chunks
+    return -1;
+  }
+
+  have.reserve(chunks.size());
+  for (map<int, bufferlist>::const_iterator i = chunks.begin();
+       i != chunks.end();
+       ++i) {
+    have.push_back(i->first);
+  }
+  if (includes(
+	have.begin(), have.end(), want_to_read.begin(), want_to_read.end())) {
+    for (set<int>::iterator i = want_to_read.begin();
+	 i != want_to_read.end();
+	 ++i) {
+      (*decoded)[*i] = chunks.find(*i)->second;
+    }
+    return 0;
+  }
+  unsigned int k = get_data_chunk_count();
+  unsigned int m = get_chunk_count() - k;
+  unsigned blocksize = (*chunks.begin()).second.length();
+  for (unsigned int i =  0; i < k + m; i++) {
+    if (chunks.find(i) == chunks.end()) {
+      bufferlist tmp;
+      bufferptr ptr(buffer::create_aligned(blocksize, SIMD_ALIGN));
+      tmp.push_back(ptr);
+      tmp.claim_append((*decoded)[i]);
+      (*decoded)[i].swap(tmp);
+    } else {
+      (*decoded)[i] = chunks.find(i)->second;
+      (*decoded)[i].rebuild_aligned(SIMD_ALIGN);
+    }
+  }
+  return decode_chunks(want_to_read, chunks, decoded);
+}
+
+int ErasureCodeShec::decode_chunks(const set<int> &want_to_read,
+				   const map<int, bufferlist> &chunks,
+				   map<int, bufferlist> *decoded)
+{
+  unsigned blocksize = (*chunks.begin()).second.length();
+  int erased[k + m];
+  int erased_count = 0;
+  int avails[k + m];
+  char *data[k];
+  char *coding[m];
+
+  for (int i = 0; i < k + m; i++) {
+    erased[i] = 0;
+    if (chunks.find(i) == chunks.end()) {
+      if (want_to_read.count(i) > 0) {
+	erased[i] = 1;
+	erased_count++;
+      }
+      avails[i] = 0;
+    } else {
+      avails[i] = 1;
+    }
+    if (i < k)
+      data[i] = (*decoded)[i].c_str();
+    else
+      coding[i - k] = (*decoded)[i].c_str();
+  }
+
+  if (erased_count > 0) {
+    return shec_decode(erased, avails, data, coding, blocksize);
+  } else {
+    return 0;
+  }
+}
+
+//
+// ErasureCodeShecReedSolomonVandermonde
+//
+
+void ErasureCodeShecReedSolomonVandermonde::shec_encode(char **data,
+					     char **coding,
+					     int blocksize)
+{
+  jerasure_matrix_encode(k, m, w, matrix, data, coding, blocksize);
+}
+
+int ErasureCodeShecReedSolomonVandermonde::shec_decode(int *erased,
+					    int *avails,
+					    char **data,
+					    char **coding,
+					    int blocksize)
+{
+  return shec_matrix_decode(erased, avails, data, coding, blocksize);
+}
+
+unsigned ErasureCodeShecReedSolomonVandermonde::get_alignment() const
+{
+  return k*w*sizeof(int);
+}
+
+int ErasureCodeShecReedSolomonVandermonde::parse(const ErasureCodeProfile &profile)
+{
+  int err = 0;
+  // k, m, c
+  if (profile.find("k") == profile.end() &&
+      profile.find("m") == profile.end() &&
+      profile.find("c") == profile.end()){
+    dout(10) << "(k, m, c) default to " << "(" << DEFAULT_K
+	     << ", " << DEFAULT_M << ", " << DEFAULT_C << ")" << dendl;
+    k = DEFAULT_K; m = DEFAULT_M; c = DEFAULT_C;
+  } else if (profile.find("k") == profile.end() ||
+	     profile.find("m") == profile.end() ||
+	     profile.find("c") == profile.end()){
+    dout(10) << "(k, m, c) must be chosen" << dendl;
+    err = -EINVAL;
+  } else {
+    std::string err_k, err_m, err_c, value_k, value_m, value_c;
+    value_k = profile.find("k")->second;
+    value_m = profile.find("m")->second;
+    value_c = profile.find("c")->second;
+    k = strict_strtol(value_k.c_str(), 10, &err_k);
+    m = strict_strtol(value_m.c_str(), 10, &err_m);
+    c = strict_strtol(value_c.c_str(), 10, &err_c);
+
+    if (!err_k.empty() || !err_m.empty() || !err_c.empty()){
+      if (!err_k.empty()){
+	derr << "could not convert k=" << value_k << "to int" << dendl;
+      } else if (!err_m.empty()){
+	derr << "could not convert m=" << value_m << "to int" << dendl;
+      } else if (!err_c.empty()){
+	derr << "could not convert c=" << value_c << "to int" << dendl;
+      }
+      err = -EINVAL;
+    } else if (k <= 0){
+      derr << "k=" << k
+	   << " must be a positive number" << dendl;
+      err = -EINVAL;
+    } else if (m <= 0){
+      derr << "m=" << m
+	   << " must be a positive number" << dendl;
+      err = -EINVAL;
+    } else if (c <= 0){
+      derr << "c=" << c
+	   << " must be a positive number" << dendl;
+      err = -EINVAL;
+    } else if (m < c){
+      derr << "c=" << c
+	   << " must be less than or equal to m=" << m << dendl;
+      err = -EINVAL;
+    } else if (k > 12){
+      derr << "k=" << k
+	   << " must be less than or equal to 12" << dendl;
+      err = -EINVAL;
+    } else if (k+m > 20){
+      derr << "k+m=" << k+m
+	   << " must be less than or equal to 20" << dendl;
+      err = -EINVAL;
+    } else if (k<m){
+      derr << "m=" << m
+	   << " must be less than or equal to k=" << k << dendl;
+      err = -EINVAL;
+    }
+  }
+
+  if (err) {
+    derr << "(k, m, c)=(" << k << ", " << m << ", " << c
+	 << ") is not a valid parameter." << dendl;
+    return err;
+  }
+
+  dout(10) << "(k, m, c) set to " << "(" << k << ", " << m << ", "
+	   << c << ")"<< dendl;
+
+  // w
+  if (profile.find("w") == profile.end()){
+    dout(10) << "w default to " << DEFAULT_W << dendl;
+    w = DEFAULT_W;
+  } else {
+    std::string err_w, value_w;
+    value_w = profile.find("w")->second;
+    w = strict_strtol(value_w.c_str(), 10, &err_w);
+
+    if (!err_w.empty()){
+      derr << "could not convert w=" << value_w << "to int" << dendl;
+      dout(10) << "w default to " << DEFAULT_W << dendl;
+      w = DEFAULT_W;
+
+    } else if (w != 8 && w != 16 && w != 32) {
+      derr << "w=" << w
+	   << " must be one of {8, 16, 32}" << dendl;
+      dout(10) << "w default to " << DEFAULT_W << dendl;
+      w = DEFAULT_W;
+
+    } else {
+      dout(10) << "w set to " << w << dendl;
+    }
+  }
+  return 0;
+}
+
+void ErasureCodeShecReedSolomonVandermonde::prepare()
+{
+  // setup shared encoding table
+  int** p_enc_table =
+    tcache.getEncodingTable(technique, k, m, c, w);
+
+  if (!*p_enc_table) {
+    dout(10) << "[ cache tables ] creating coeff for k=" <<
+      k << " m=" << m << " c=" << c << " w=" << w << dendl;
+
+    matrix = shec_reedsolomon_coding_matrix(technique);
+
+    // either our new created table is stored or if it has been
+    // created in the meanwhile the locally allocated table will be
+    // freed by setEncodingTable
+    matrix = tcache.setEncodingTable(technique, k, m, c, w, matrix);
+
+    dout(10) << "matrix = " << dendl;
+    for (int i=0; i<m; i++) {
+      char mat[k+1];
+      for (int j=0; j<k; j++) {
+        if (matrix[i*k+j] > 0) {
+          mat[j] = '1';
+        } else {
+          mat[j] = '0';
+        }
+      }
+      mat[k] = '\0';
+      dout(10) << mat << dendl;
+    }
+  } else {
+    matrix = *p_enc_table;
+  }
+
+  dout(10) << " [ technique ] = " <<
+    ((technique == MULTIPLE) ? "multiple" : "single") << dendl;
+
+  ceph_assert((technique == SINGLE) || (technique == MULTIPLE));
+
+}
+
+// ErasureCodeShec::
+// Mearged from shec.cc.
+
+double ErasureCodeShec::shec_calc_recovery_efficiency1(int k, int m1, int m2, int c1, int c2){
+  int r_eff_k[k];
+  double r_e1;
+  int i, rr, cc, start, end;
+  int first_flag;
+
+  if (m1 < c1 || m2 < c2) return -1;
+  if ((m1 == 0 && c1 != 0) || (m2 == 0 && c2 != 0)) return -1;
+
+  for (i=0; i<k; i++) r_eff_k[i] = 100000000;
+  r_e1 = 0;
+
+  for (rr=0; rr<m1; rr++){
+    start = ((rr*k)/m1) % k;
+    end = (((rr+c1)*k)/m1) % k;
+    for (cc=start, first_flag=1; first_flag || cc!=end; cc=(cc+1)%k){
+      first_flag = 0;
+      r_eff_k[cc] = std::min(r_eff_k[cc], ((rr+c1)*k)/m1 - (rr*k)/m1);
+    }
+    r_e1 += ((rr+c1)*k)/m1 - (rr*k)/m1;
+  }
+
+  for (rr=0; rr<m2; rr++){
+    start = ((rr*k)/m2) % k;
+    end = (((rr+c2)*k)/m2) % k;
+    for (cc=start, first_flag=1; first_flag || cc!=end; cc=(cc+1)%k){
+      first_flag = 0;
+      r_eff_k[cc] = std::min(r_eff_k[cc], ((rr+c2)*k)/m2 - (rr*k)/m2);
+    }
+    r_e1 += ((rr+c2)*k)/m2 - (rr*k)/m2;
+  }
+
+  for (i=0; i<k; i++){
+    r_e1 += r_eff_k[i];
+  }
+
+  r_e1 /= (k+m1+m2);
+
+  return r_e1;
+}
+
+int* ErasureCodeShec::shec_reedsolomon_coding_matrix(int is_single)
+{
+  int *matrix;
+  int rr, cc, start, end;
+  int m1, m2, c1, c2;
+
+  if (w != 8 && w != 16 && w != 32) return NULL;
+
+  if (!is_single){
+    int c1_best = -1, m1_best = -1;
+    double min_r_e1 = 100.0;
+
+    // create all multiple shec pattern and choose best.
+
+    for (c1=0; c1 <= c/2; c1++){
+      for (m1=0; m1 <= m; m1++){
+        c2 = c-c1;
+        m2 = m-m1;
+
+        if (m1 < c1 || m2 < c2) continue;
+        if ((m1 == 0 && c1 != 0) || (m2 == 0 && c2 != 0)) continue;
+        if ((m1 != 0 && c1 == 0) || (m2 != 0 && c2 == 0)) continue;
+
+        // minimize r_e1
+
+        if (true) {
+          double r_e1;
+          r_e1 = shec_calc_recovery_efficiency1(k, m1, m2, c1, c2);
+          if (min_r_e1 - r_e1 > std::numeric_limits<double>::epsilon() &&
+	      r_e1 < min_r_e1) {
+            min_r_e1 = r_e1;
+            c1_best = c1;
+            m1_best = m1;
+          }
+        }
+      }
+    }
+    m1 = m1_best;
+    c1 = c1_best;
+    m2 = m - m1_best;
+    c2 = c - c1_best;
+  } else {
+    m1 = 0;
+    c1 = 0;
+    m2 = m;
+    c2 = c;
+  }
+
+  // create matrix
+  matrix = reed_sol_vandermonde_coding_matrix(k, m, w);
+
+  for (rr=0; rr<m1; rr++){
+    end = ((rr*k)/m1) % k;
+    start = (((rr+c1)*k)/m1) % k;
+    for (cc=start; cc!=end; cc=(cc+1)%k){
+      matrix[cc + rr*k] = 0;
+    }
+  }
+
+  for (rr=0; rr<m2; rr++){
+    end = ((rr*k)/m2) % k;
+    start = (((rr+c2)*k)/m2) % k;
+    for (cc=start; cc!=end; cc=(cc+1)%k){
+      matrix[cc + (rr+m1)*k] = 0;
+    }
+  }
+
+  return matrix;
+}
+
+int ErasureCodeShec::shec_make_decoding_matrix(bool prepare, int *want_, int *avails,
+                                               int *decoding_matrix, int *dm_row, int *dm_column,
+                                               int *minimum)
+{
+  int mindup = k+1, minp = k+1;
+  int want[k + m];
+
+  memset(want, 0, sizeof(want));
+
+  for (int i = 0; i < k + m; ++i) {
+    want[i] = want_[i];
+  }
+
+  for (int i = 0; i < m; ++i) {
+    if (want[i + k] && !avails[i + k]) {
+      for (int j=0; j < k; ++j) {
+        if (matrix[i * k + j] > 0) {
+          want[j] = 1;
+        }
+      }
+    }
+  }
+
+  if (tcache.getDecodingTableFromCache(decoding_matrix,
+                                       dm_row, dm_column, minimum,
+                                       technique,
+                                       k, m, c, w,
+                                       want, avails)) {
+    return 0;
+  }
+
+  for (unsigned long long pp = 0; pp < (1ull << m); ++pp) {
+
+    // select parity chunks
+    int ek = 0;
+    int p[m];
+    for (int i=0; i < m; ++i) {
+      if (pp & (1ull << i)) {
+        p[ek++] = i;
+      }
+    }
+    if (ek > minp) {
+      continue;
+    }
+
+    // Are selected parity chunks avail?
+    bool ok = true;
+    for (int i = 0; i < ek && ok; i++) {
+      if (!avails[k+p[i]]) {
+        ok = false;
+        break;
+      }
+    }
+
+    if (!ok) {
+      continue;
+    }
+
+    int tmprow[k + m];
+    int tmpcolumn[k];
+    for (int i = 0; i < k + m; i++) {
+      tmprow[i] = 0;
+    }
+    for (int i = 0; i < k; i++) {
+      tmpcolumn[i] = 0;
+    }
+
+    for (int i=0; i < k; i++) {
+      if (want[i] && !avails[i]) {
+        tmpcolumn[i] = 1;
+      }
+    }
+
+    // Parity chunks which are used to recovery erased data chunks, are added to tmprow.
+    for (int i = 0; i < ek; i++) {
+      tmprow[k + p[i]] = 1;
+      for (int j = 0; j < k; j++) {
+        int element = matrix[(p[i]) * k + j];
+        if (element != 0) {
+          tmpcolumn[j] = 1;
+        }
+        if (element != 0 && avails[j] == 1) {
+          tmprow[j] = 1;
+        }
+      }
+    }
+
+    int dup_row = 0, dup_column = 0, dup = 0;
+    for (int i = 0; i < k + m; i++) {
+      if (tmprow[i]) {
+        dup_row++;
+      }
+    }
+
+    for (int i = 0; i < k; i++) {
+      if (tmpcolumn[i]) {
+        dup_column++;
+      }
+    }
+
+    if (dup_row != dup_column) {
+      continue;
+    }
+    dup = dup_row;
+    if (dup == 0) {
+      mindup = dup;
+      for (int i = 0; i < k; i++) {
+        dm_row[i] = -1;
+      }
+      for (int i = 0; i < k; i++) {
+        dm_column[i] = -1;
+      }
+      break;
+    }
+
+    // minimum is updated.
+    if (dup < mindup) {
+      int tmpmat[dup * dup];
+      {
+        for (int i = 0, row = 0; i < k + m; i++) {
+          if (tmprow[i]) {
+            for (int j = 0, column = 0; j < k; j++) {
+              if (tmpcolumn[j]) {
+                if (i < k) {
+                  tmpmat[row * dup + column] = (i == j ? 1 : 0);
+                } else {
+                  tmpmat[row * dup + column] = matrix[(i - k) * k + j];
+                }
+                column++;
+              }
+            }
+            row++;
+          }
+        }
+      }
+      int det = calc_determinant(tmpmat, dup);
+
+      if (det != 0) {
+        int row_id = 0;
+        int column_id = 0;
+        for (int i = 0; i < k; i++) {
+          dm_row[i] = -1;
+        }
+        for (int i = 0; i < k; i++) {
+          dm_column[i] = -1;
+        }
+
+        mindup = dup;
+        for (int i=0; i < k + m; i++) {
+          if (tmprow[i]) {
+            dm_row[row_id++] = i;
+          }
+        }
+        for (int i=0; i < k; i++) {
+          if (tmpcolumn[i]) {
+            dm_column[column_id++] = i;
+          }
+        }
+        minp = ek;
+      }
+    }
+  }
+
+
+  if (mindup == k+1) {
+    dout(10) << __func__ << ": can't find recover matrix." << dendl;
+    return -1;
+  }
+
+  for (int i = 0; i < k + m; i++) {
+    minimum[i] = 0;
+  }
+
+  for (int i=0; i < k && dm_row[i] != -1; i++) {
+    minimum[dm_row[i]] = 1;
+  }
+
+  for (int i = 0; i < k; ++i) {
+    if (want[i] && avails[i]) {
+      minimum[i] = 1;
+    }
+  }
+
+  for (int i = 0; i < m; ++i) {
+    if (want[k + i] && avails[k + i] && !minimum[k + i]) {
+      for (int j = 0; j < k; ++j) {
+        if (matrix[i * k + j] > 0 && !want[j]) {
+          minimum[k + i] = 1;
+          break;
+        }
+      }
+    }
+  }
+
+  if (mindup == 0) {
+    return 0;
+  }
+
+  int tmpmat[mindup * mindup];
+  for (int i=0; i < mindup; i++) {
+    for (int j=0; j < mindup; j++) {
+      if (dm_row[i] < k) {
+        tmpmat[i * mindup + j] = (dm_row[i] == dm_column[j] ? 1 : 0);
+      } else {
+        tmpmat[i * mindup + j] = matrix[(dm_row[i] - k) * k + dm_column[j]];
+      }
+    }
+    if (dm_row[i] < k) {
+      for (int j = 0; j < mindup; j++) {
+        if (dm_row[i] == dm_column[j]) {
+          dm_row[i] = j;
+        }
+      }
+    } else {
+      dm_row[i] -= (k - mindup);
+    }
+  }
+
+  if (prepare) {
+    return 0;
+  }
+
+  int ret = jerasure_invert_matrix(tmpmat, decoding_matrix, mindup, w);
+
+  tcache.putDecodingTableToCache(decoding_matrix, dm_row, dm_column, minimum, technique,
+                                 k, m, c, w, want, avails);
+
+  return ret;
+}
+
+int ErasureCodeShec::shec_matrix_decode(int *want, int *avails, char **data_ptrs,
+                                        char **coding_ptrs, int size)
+{
+  int decoding_matrix[k*k];
+  int dm_row[k], dm_column[k];
+  int minimum[k + m];
+
+  memset(decoding_matrix, 0, sizeof(decoding_matrix));
+  memset(dm_row, -1, sizeof(dm_row));
+  memset(dm_column, -1, sizeof(dm_column));
+  memset(minimum, -1, sizeof(minimum));
+
+  if (w != 8 && w != 16 && w != 32) return -1;
+
+  if (shec_make_decoding_matrix(false, want, avails, decoding_matrix,
+                                dm_row, dm_column, minimum) < 0) {
+    return -1;
+  }
+
+  // Get decoding matrix size
+  int dm_size = 0;
+  for (int i = 0; i < k; i++) {
+    if (dm_row[i] == -1) {
+      break;
+    }
+    dm_size++;
+  }
+
+  char *dm_data_ptrs[dm_size];
+  for (int i = 0; i < dm_size; i++) {
+    dm_data_ptrs[i] = data_ptrs[dm_column[i]];
+  }
+
+  // Decode the data drives
+  for (int i = 0; i < dm_size; i++) {
+    if (!avails[dm_column[i]]) {
+      jerasure_matrix_dotprod(dm_size, w, decoding_matrix + (i * dm_size),
+                              dm_row, i, dm_data_ptrs, coding_ptrs, size);
+    }
+  }
+
+  // Re-encode any erased coding devices
+  for (int i = 0; i < m; i++) {
+    if (want[k+i] && !avails[k+i]) {
+      jerasure_matrix_dotprod(k, w, matrix + (i * k), NULL, i+k,
+                              data_ptrs, coding_ptrs, size);
+    }
+  }
+
+  return 0;
+}