Add support for custom backend metadatabackend_metadata_adder

A backend may have the need to add custom metadata to the
encoded data/parity fragments, in addition to the
liberasurecode "fragment metadata headers".  This patch
gives the ability to a EC backend writer to specify a
"metadata adder" that is taken into account when allocating
output data/parity fragment buffers.

Signed-off-by: Tushar Gohad <tushar.gohad@intel.com>

11 files changed, 32 insertions, 12 deletions

diff --git a/include/erasurecode/erasurecode_backend.h b/include/erasurecode/erasurecode_backend.h
index a6e4440..956b2f1 100644
--- a/include/erasurecode/erasurecode_backend.h
+++ b/include/erasurecode/erasurecode_backend.h
@@ -106,6 +106,10 @@ struct ec_backend_common {
     char                        soversion[MAX_LEN]; /* EC backend shared library version */
 
     struct ec_backend_op_stubs  *ops;               /* EC backend stubs */
+    int                         metadata_adder;     /* EC backend custom metadata adder -
+                                                     * metadata_adder bytes are added to
+                                                     * the fragment size when allocating
+                                                     * data/parity fragment buffers */
 };
 
 /* EC backend definition */
diff --git a/include/erasurecode/erasurecode_helpers.h b/include/erasurecode/erasurecode_helpers.h
index e8fddaa..46dc669 100644
--- a/include/erasurecode/erasurecode_helpers.h
+++ b/include/erasurecode/erasurecode_helpers.h
@@ -118,7 +118,7 @@ void init_fragment_header(char *buf)
 void *alloc_zeroed_buffer(int size);
 void *alloc_and_set_buffer(int size, int value);
 void *check_and_free_buffer(void *buf);
-char *alloc_fragment_buffer(int size);
+char *alloc_fragment_buffer(ec_backend_t instance, int size);
 int free_fragment_buffer(char *buf);
 void *get_aligned_buffer16(int size);
 int get_aligned_data_size(ec_backend_t instance, int data_len);
diff --git a/include/erasurecode/erasurecode_preprocessing.h b/include/erasurecode/erasurecode_preprocessing.h
index 7ca891d..0b479c6 100644
--- a/include/erasurecode/erasurecode_preprocessing.h
+++ b/include/erasurecode/erasurecode_preprocessing.h
@@ -37,6 +37,7 @@ int prepare_fragments_for_encode(
         int *blocksize);
 
 int prepare_fragments_for_decode(
+        ec_backend_t instance,
         int k, int m,
         char **data, char **parity,
         int *missing_idxs,
diff --git a/src/backends/isa-l/isa_l_vand.c b/src/backends/isa-l/isa_l_vand.c
index fe11696..e7a575e 100644
--- a/src/backends/isa-l/isa_l_vand.c
+++ b/src/backends/isa-l/isa_l_vand.c
@@ -588,4 +588,5 @@ struct ec_backend_common backend_isa_l_rs_vand = {
 #endif
     .soversion                  = "2.0",
     .ops                        = &isa_l_rs_vand_op_stubs,
+    .metadata_adder             = 0,
 };
diff --git a/src/backends/jerasure/jerasure_rs_cauchy.c b/src/backends/jerasure/jerasure_rs_cauchy.c
index 1c8b528..9d8466a 100644
--- a/src/backends/jerasure/jerasure_rs_cauchy.c
+++ b/src/backends/jerasure/jerasure_rs_cauchy.c
@@ -384,4 +384,5 @@ struct ec_backend_common backend_jerasure_rs_cauchy = {
 #endif
     .soversion                  = "2.0",
     .ops                        = &jerasure_rs_cauchy_op_stubs,
+    .metadata_adder             = 0,
 };
diff --git a/src/backends/jerasure/jerasure_rs_vand.c b/src/backends/jerasure/jerasure_rs_vand.c
index 5866cd5..a8a8257 100644
--- a/src/backends/jerasure/jerasure_rs_vand.c
+++ b/src/backends/jerasure/jerasure_rs_vand.c
@@ -325,4 +325,5 @@ struct ec_backend_common backend_jerasure_rs_vand = {
 #endif
     .soversion                  = "2.0",
     .ops                        = &jerasure_rs_vand_op_stubs,
+    .metadata_adder             = 0,
 };
diff --git a/src/backends/null/null.c b/src/backends/null/null.c
index f71312c..6ca5c98 100644
--- a/src/backends/null/null.c
+++ b/src/backends/null/null.c
@@ -223,5 +223,6 @@ struct ec_backend_common backend_null = {
 #endif
     .soversion                  = "1.0",
     .ops                        = &null_op_stubs,
+    .metadata_adder             = 0,
 };
 
diff --git a/src/backends/xor/flat_xor_hd.c b/src/backends/xor/flat_xor_hd.c
index 289f36e..0979b30 100644
--- a/src/backends/xor/flat_xor_hd.c
+++ b/src/backends/xor/flat_xor_hd.c
@@ -170,5 +170,6 @@ struct ec_backend_common backend_flat_xor_hd = {
 #endif
     .soversion                  = "1.0",
     .ops                        = &flat_xor_hd_op_stubs,
+    .metadata_adder             = 0,
 };
 
diff --git a/src/erasurecode.c b/src/erasurecode.c
index b3d1395..61cd269 100644
--- a/src/erasurecode.c
+++ b/src/erasurecode.c
@@ -598,7 +598,7 @@ int liberasurecode_decode(int desc,
      * (realloc_bm).
      *
      */
-    ret = prepare_fragments_for_decode(k, m,
+    ret = prepare_fragments_for_decode(instance, k, m,
                                        data, parity, missing_idxs, 
                                        &orig_data_size, &blocksize,
                                        fragment_len, &realloc_bm);
@@ -765,7 +765,7 @@ int liberasurecode_reconstruct_fragment(int desc,
      * It passes back a bitmap telling us which buffers need to be freed by
      * us (realloc_bm).
      */
-    ret = prepare_fragments_for_decode(k, m, data, parity, missing_idxs,
+    ret = prepare_fragments_for_decode(instance, k, m, data, parity, missing_idxs,
                                        &orig_data_size, &blocksize,
                                        fragment_len, &realloc_bm);
     if (ret < 0) {
diff --git a/src/erasurecode_helpers.c b/src/erasurecode_helpers.c
index 6e4c882..42877eb 100644
--- a/src/erasurecode_helpers.c
+++ b/src/erasurecode_helpers.c
@@ -103,14 +103,20 @@ void * check_and_free_buffer(void * buf)
     return NULL;
 }
 
-char *alloc_fragment_buffer(int size)
+char *alloc_fragment_buffer(ec_backend_t instance, int size)
 {
     char *buf;
     fragment_header_t *header = NULL;
 
+    if (NULL != instance) {
+        /* Account for any custom backend metadata in the fragment size */
+         size += instance->common.metadata_adder;
+    }
+
+    /* liberasurecode metadata */
     size += sizeof(fragment_header_t);
-    buf = get_aligned_buffer16(size);
 
+    buf = get_aligned_buffer16(size);
     if (buf) {
         header = (fragment_header_t *) buf;
         header->magic = LIBERASURECODE_FRAG_HEADER_MAGIC;
diff --git a/src/erasurecode_preprocessing.c b/src/erasurecode_preprocessing.c
index c3e5ed6..ec471fb 100644
--- a/src/erasurecode_preprocessing.c
+++ b/src/erasurecode_preprocessing.c
@@ -49,7 +49,7 @@ int prepare_fragments_for_encode(ec_backend_t instance,
 
     for (i = 0; i < k; i++) {
         int payload_size = data_len > bsize ? bsize : data_len;
-        char *fragment = (char *) alloc_fragment_buffer(bsize);
+        char *fragment = (char *) alloc_fragment_buffer(instance, bsize);
         if (NULL == fragment) {
             ret = -ENOMEM;
             goto out_error;
@@ -67,7 +67,7 @@ int prepare_fragments_for_encode(ec_backend_t instance,
     }
 
     for (i = 0; i < m; i++) {
-        char *fragment = (char *) alloc_fragment_buffer(bsize);
+        char *fragment = (char *) alloc_fragment_buffer(instance, bsize);
         if (NULL == fragment) {
             ret = -ENOMEM;
             goto out_error;
@@ -107,7 +107,7 @@ out_error:
  * case, the caller has to free up in the success case, so it may as well do
  * so in the failure case.
  */
-int prepare_fragments_for_decode(
+int prepare_fragments_for_decode(ec_backend_t instance,
         int k, int m,
         char **data, char **parity,
         int  *missing_idxs,
@@ -135,14 +135,16 @@ int prepare_fragments_for_decode(
          * 'data_list'
          */
         if (NULL == data[i]) {
-            data[i] = alloc_fragment_buffer(fragment_size - sizeof(fragment_header_t));
+            data[i] = alloc_fragment_buffer(instance,
+                    fragment_size - sizeof(fragment_header_t));
             if (NULL == data[i]) {
                 log_error("Could not allocate data buffer!");
                 return -1;
             }
             *realloc_bm = *realloc_bm | (1 << i);
         } else if (!is_addr_aligned((unsigned long)data[i], 16)) {
-            char *tmp_buf = alloc_fragment_buffer(fragment_size - sizeof(fragment_header_t));
+            char *tmp_buf = alloc_fragment_buffer(instance,
+                    fragment_size - sizeof(fragment_header_t));
             memcpy(tmp_buf, data[i], fragment_size);
             data[i] = tmp_buf;
             *realloc_bm = *realloc_bm | (1 << i);
@@ -170,14 +172,16 @@ int prepare_fragments_for_decode(
          * DO NOT FREE: the python GC should free the original when cleaning up 'data_list'
          */
         if (NULL == parity[i]) {
-            parity[i] = alloc_fragment_buffer(fragment_size-sizeof(fragment_header_t));
+            parity[i] = alloc_fragment_buffer(instance,
+                    fragment_size - sizeof(fragment_header_t));
             if (NULL == parity[i]) {
                 log_error("Could not allocate parity buffer!");
                 return -1;
             }
             *realloc_bm = *realloc_bm | (1 << (k + i));
         } else if (!is_addr_aligned((unsigned long)parity[i], 16)) {
-            char *tmp_buf = alloc_fragment_buffer(fragment_size-sizeof(fragment_header_t));
+            char *tmp_buf = alloc_fragment_buffer(instance,
+                    fragment_size - sizeof(fragment_header_t));
             memcpy(tmp_buf, parity[i], fragment_size);
             parity[i] = tmp_buf;
             *realloc_bm = *realloc_bm | (1 << (k + i));