Fix fully-degraded EC writes destroying bitmaps

src/osd/osd_rmw.cpp

@@ -669,16 +669,17 @@ void* calc_rmw(void *request_buf, osd_rmw_stripe_t *stripes, uint64_t *read_osd_
             stripes[role].write_end = end;
         }
     }
-    if (write_parity)
+    for (int role = 0; role < pg_minsize; role++)
     {
-        for (int role = 0; role < pg_minsize; role++)
+        if (write_parity)
         {
             cover_read(start, end, stripes[role]);
-            if (!stripes[role].read_end && (stripes[role].req_start != 0 || stripes[role].req_end != chunk_size))
-            {
-                // Read bitmaps even if we don't need data but it's not fully overwritten
-                stripes[role].read_end = UINT32_MAX;
-            }
+        }
+        if (!stripes[role].read_end && (stripes[role].req_start != 0 || stripes[role].req_end > 0 && stripes[role].req_end != chunk_size))
+        {
+            // Read bitmaps even if we don't need data but it's not fully overwritten
+            // And even if we don't write parity - we need to modify the bitmap and write it back
+            stripes[role].read_end = UINT32_MAX;
         }
     }
     if (write_osd_set != read_osd_set)

src/osd/osd_rmw_test.cpp

@@ -34,6 +34,7 @@ void test_recover_53_d5();
 void test_recover_22();
 void test_ec_find_good_multi_chunks();
 void test_ec_find_good_42_no_good();
+void test_ec_partial_write_no_parity_preserves_bitmap();
 
 int main(int narg, char *args[])
 {
@@ -80,6 +81,8 @@ int main(int narg, char *args[])
     test_recover_53_d5();
     // Test 20
     test_recover_22();
+    // Test 21
+    test_ec_partial_write_no_parity_preserves_bitmap();
     // End
     printf("all ok\n");
     return 0;
@@ -1507,3 +1510,31 @@ void test_ec_find_good_multi_chunks()
     free(write_buf);
     use_ec(7, 4, false);
 }
+
+/***
+
+21. EC partial write with all parity OSDs missing — modified bitmaps should be read
+
+***/
+
+void test_ec_partial_write_no_parity_preserves_bitmap()
+{
+    const int bmp = 4;
+    osd_num_t osd_set[5] = { 1, 2, 3, 0, 0 };
+    osd_rmw_stripe_t stripes[5] = {};
+    // Partial write to role 0, offset 0, len 4K
+    void *write_buf = malloc_or_die(4096);
+    split_stripes(2, 128*1024, 0, 4096, stripes);
+    assert(stripes[0].req_start == 0 && stripes[0].req_end == 4096);
+    assert(stripes[1].req_start == 0 && stripes[1].req_end == 0);
+    assert(stripes[2].req_start == 0 && stripes[2].req_end == 0);
+    void *rmw_buf = calc_rmw(write_buf, stripes, osd_set, 5, 3, 3, osd_set, 128*1024, bmp);
+    // stripes[0] now requires a bitmap-only read
+    assert(stripes[0].read_end == UINT32_MAX);
+    assert(stripes[1].read_end == 0);
+    assert(stripes[2].read_end == 0);
+    assert(stripes[3].read_end == 0);
+    assert(stripes[4].read_end == 0);
+    free(rmw_buf);
+    free(write_buf);
+}