Skip AllocateTest if fallocate() is not supported in the file system

Summary: To avoid false positive test failures when the file system doesn't support fallocate. In EnvTest.AllocateTest, we first make a simple fallocate call and check the error codes to rule out the possibility that it is not supported. Skip the test if the error code indicates it is not supported.

Test Plan: Run the test and make sure it passes on file systems supporting and not supporting fallocate

Reviewers: yhchiang, ljin, igor

Reviewed By: igor

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D23667

util/env_test.cc

@@ -17,6 +17,11 @@
 #include <unistd.h>
 #endif
 
+#ifdef ROCKSDB_FALLOCATE_PRESENT
+#include <errno.h>
+#include <fcntl.h>
+#endif
+
 #include "rocksdb/env.h"
 #include "port/port.h"
 #include "util/coding.h"
@@ -478,6 +483,31 @@ TEST(EnvPosixTest, RandomAccessUniqueID) {
 #ifdef ROCKSDB_FALLOCATE_PRESENT
 TEST(EnvPosixTest, AllocateTest) {
   std::string fname = GetOnDiskTestDir() + "/preallocate_testfile";
+
+  // Try fallocate in a file to see whether the target file system supports it.
+  // Skip the test if fallocate is not supported.
+  std::string fname_test_fallocate =
+      GetOnDiskTestDir() + "/preallocate_testfile_2";
+  int fd = -1;
+  do {
+    fd = open(fname_test_fallocate.c_str(), O_CREAT | O_RDWR | O_TRUNC, 0644);
+  } while (fd < 0 && errno == EINTR);
+  ASSERT_GT(fd, 0);
+
+  int alloc_status = fallocate(fd, 0, 0, 1);
+
+  int err_number = 0;
+  if (alloc_status != 0) {
+    err_number = errno;
+    fprintf(stderr, "Warning: fallocate() fails, %s\n", strerror(err_number));
+  }
+  close(fd);
+  ASSERT_OK(env_->DeleteFile(fname_test_fallocate));
+  if (alloc_status != 0 && err_number == EOPNOTSUPP) {
+    // The filesystem containing the file does not support fallocate
+    return;
+  }
+
   EnvOptions soptions;
   soptions.use_mmap_writes = false;
   unique_ptr<WritableFile> wfile;