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libutil: Gracefully fall back from unsupported O_TMPFILE

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Some filesystems, notably most FUSE-based ones and some top-level overlaysfs
ones do not support this and we need a graceful fallback.
This commit is contained in:
Sergei Zimmerman 2025-12-18 22:12:14 +03:00
parent 9254fab407
commit 06f21596a0
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1 changed files with 16 additions and 6 deletions
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18
src/libutil/file-system.cc
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@ -553,17 +553,27 @@ AutoCloseFD createAnonymousTempFile()
{
AutoCloseFD fd;
#ifdef O_TMPFILE
fd = ::open(defaultTempDir().c_str(), O_TMPFILE | O_CLOEXEC | O_RDWR, S_IWUSR | S_IRUSR);
if (!fd)
static std::atomic_flag tmpfileUnsupported{};
if (!tmpfileUnsupported.test()) /* Try with O_TMPFILE first. */ {
/* Use O_EXCL, because the file is never supposed to be linked into filesystem. */
fd = ::open(defaultTempDir().c_str(), O_TMPFILE | O_CLOEXEC | O_RDWR | O_EXCL, S_IWUSR | S_IRUSR);
if (!fd) {
/* Not supported by the filesystem or the kernel. */
if (errno == EOPNOTSUPP || errno == EISDIR)
tmpfileUnsupported.test_and_set(); /* Set flag and fall through to createTempFile. */
else
throw SysError("creating anonymous temporary file");
#else
} else {
return fd; /* Successfully created. */
}
}
#endif
auto [fd2, path] = createTempFile("nix-anonymous");
if (!fd2)
throw SysError("creating temporary file '%s'", path);
fd = std::move(fd2);
#ifndef _WIN32
unlink(requireCString(path)); /* We only care about the file descriptor. */
# endif
#endif
return fd;
}