Merge pull request #2905 from realm/js/posix_fallocate-failures

Make posix_fallocate robust against interruption, report right errors

CHANGELOG.md

@@ -2,7 +2,9 @@
 
 ### Bugfixes
 
-* Lorem ipsum.
+* Make calls to posix_fallocate() robust against interruption and report
+ the correct error on failure.
+ PR [#2905](https://github.com/realm/realm-core/pull/2905).
 
 ### Breaking changes
 

src/realm/util/file.cpp

@@ -714,11 +714,19 @@ void File::prealloc_if_supported(SizeType offset, size_t size)
  if (int_cast_with_overflow_detect(size, size2))
  throw std::runtime_error("File size overflow");
 
- if (::posix_fallocate(m_fd, offset, size2) == 0)
+ // posix_fallocate() does not set errno, it returns the error (if any) or zero.
+ // It is also possible for it to be interrupted by EINTR according to some man pages (ex fedora 24)
+ int status;
+ do {
+ status = ::posix_fallocate(m_fd, offset, size2);
+ } while (status == EINTR);
+
+ if (REALM_LIKELY(status == 0)) {
  return;
- int err = errno; // Eliminate any risk of clobbering
- std::string msg = get_errno_msg("posix_fallocate() failed: ", err);
- if (err == ENOSPC || err == EDQUOT) {
+ }
+
+ std::string msg = get_errno_msg("posix_fallocate() failed: ", status);
+ if (status == ENOSPC || status == EDQUOT) {
  throw OutOfDiskSpace(msg);
  }
  throw std::runtime_error(msg);