test/librados_test_stub: reimplement cmpext()

cmpext is a read operation.  As such, it shouldn't be creating objects
or extending them and it should accept snapshots.

The compare code is completely broken, resulting in false positives
(i.e. failures to detect mismatches) in many cases.

Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
(cherry picked from commit 6a2986fcb21af817746034398b26b599c9cd757c)

diff --git a/src/test/librados_test_stub/TestMemIoCtxImpl.cc b/src/test/librados_test_stub/TestMemIoCtxImpl.cc
index cc99b1ee710cc7b002cbf4717395031aee224737..839232a2187504fb4aadbc0a121a5516c56ef74f 100644 (file)
--- a/src/test/librados_test_stub/TestMemIoCtxImpl.cc
+++ b/src/test/librados_test_stub/TestMemIoCtxImpl.cc
@@ -20,6 +20,17 @@ static void to_vector(const interval_set<uint64_t> &set,
   }
 }
 
+// see PrimaryLogPG::finish_extent_cmp()
+static int cmpext_compare(const bufferlist &bl, const bufferlist &read_bl) {
+  for (uint64_t idx = 0; idx < bl.length(); ++idx) {
+    char read_byte = (idx < read_bl.length() ? read_bl[idx] : 0);
+    if (bl[idx] != read_byte) {
+      return -MAX_ERRNO - idx;
+    }
+  }
+  return 0;
+}
+
 namespace librados {
 
 TestMemIoCtxImpl::TestMemIoCtxImpl() {
@@ -620,32 +631,30 @@ int TestMemIoCtxImpl::writesame(const std::string& oid, bufferlist& bl, size_t l
 
 int TestMemIoCtxImpl::cmpext(const std::string& oid, uint64_t off,
                              bufferlist& cmp_bl) {
-  if (get_snap_read() != CEPH_NOSNAP) {
-    return -EROFS;
-  } else if (m_client->is_blacklisted()) {
+  if (m_client->is_blacklisted()) {
     return -EBLACKLISTED;
   }
 
-  if (cmp_bl.length() == 0) {
-    return -EINVAL;
-  }
+  bufferlist read_bl;
+  uint64_t len = cmp_bl.length();
 
   TestMemCluster::SharedFile file;
   {
-    RWLock::WLocker l(m_pool->file_lock);
-    file = get_file(oid, true, get_snap_context());
+    RWLock::RLocker l(m_pool->file_lock);
+    file = get_file(oid, false, get_snap_context());
+    if (file == NULL) {
+      return cmpext_compare(cmp_bl, read_bl);
+    }
   }
 
   RWLock::RLocker l(file->lock);
-  size_t len = cmp_bl.length();
-  ensure_minimum_length(off + len, &file->data);
-  if (len > 0 && off <= len) {
-    for (uint64_t p = off; p < len; p++)  {
-      if (file->data[p] != cmp_bl[p])
-        return -MAX_ERRNO - p;
-    }
+  if (off >= file->data.length()) {
+    len = 0;
+  } else if (off + len > file->data.length()) {
+    len = file->data.length() - off;
   }
-  return 0;
+  read_bl.substr_of(file->data, off, len);
+  return cmpext_compare(cmp_bl, read_bl);
 }
 
 int TestMemIoCtxImpl::xattr_get(const std::string& oid,