Fix nasty rebuild bug where partiy would be reconstructed incorrectly

when both data and parity was missing.  The fix is to just call decode
when reconstructing parity, since it will have to do extra work anyway
when data is missing.  We did a little extra work in ISA-L to do better,
but can save that for later, since 99% of the time decode will perform just
fine.

1 files changed, 24 insertions, 4 deletions

diff --git a/test/liberasurecode_test.c b/test/liberasurecode_test.c
index d1ad516..dc112f9 100644
--- a/test/liberasurecode_test.c
+++ b/test/liberasurecode_test.c
@@ -768,6 +768,17 @@ static void encode_decode_test_impl(const ec_backend_id_t be_id,
     free(avail_frags);
 }
 
+/**
+ * Note: this test will attempt to reconstruct a single fragment when
+ * one or more other fragments are missing (specified by skip).  
+ *
+ * For example, if skip is [0, 0, 0, 1, 0, 0] and we are reconstructing
+ * fragment 5, then it will test the reconstruction of fragment 5 when 3
+ * and 5 are assumed unavailable.
+ *
+ * We only mark at most 2 as unavailable, as we cannot guarantee every situation
+ * will be able to habndle 3 failures.
+ */
 static void reconstruct_test_impl(const ec_backend_id_t be_id,
                                  struct ec_args *args,
                                  int *skip)
@@ -796,15 +807,24 @@ static void reconstruct_test_impl(const ec_backend_id_t be_id,
     rc = liberasurecode_encode(desc, orig_data, orig_data_size,
             &encoded_data, &encoded_parity, &encoded_fragment_len);
     assert(rc == 0);
-    num_avail_frags = create_frags_array(&avail_frags, encoded_data,
-                                             encoded_parity, args, skip);
     out = malloc(encoded_fragment_len);
     assert(out != NULL);
     for (i = 0; i < num_fragments; i++) {
+        char *cmp = NULL;
+        // If the current fragment was not chosen as fragments to skip,
+        // remove it and the chosen fragments to skip from the available list
+        // and reset its state
         if (skip[i] == 0) {
-            continue;
+            skip[i] = 1;
+            num_avail_frags = create_frags_array(&avail_frags, encoded_data,
+                                             encoded_parity, args, skip);
+            skip[i] = 0;
+        // Do not reset the skip state if the fragment was chosen as a fragment
+        // to skip for this invocation of the test
+        } else {
+            num_avail_frags = create_frags_array(&avail_frags, encoded_data,
+                                             encoded_parity, args, skip);
         }
-        char *cmp = NULL;
         if (i < args->k) {
             cmp = encoded_data[i];
         }