[pbs-devel] [PATCH proxmox] fs: link fallback for atomic create
Wolfgang Bumiller
w.bumiller at proxmox.com
Thu Jul 22 09:33:19 CEST 2021
Some file systems don't support renameat2's RENAME_NOREPLACE
flag (eg. ZFS), at the some time, some other file systems
don't support hardlinks via link (eg. vfat, cifs), so we now
try both: first the rename (since it's more efficient), then
link+unlink for the rest.
If both fail, the file system is simply not supported for
our purposes anyway...
Signed-off-by: Wolfgang Bumiller <w.bumiller at proxmox.com>
---
proxmox/src/tools/fs.rs | 14 +++++++++++---
1 file changed, 11 insertions(+), 3 deletions(-)
diff --git a/proxmox/src/tools/fs.rs b/proxmox/src/tools/fs.rs
index 8087cc8..1a2a51f 100644
--- a/proxmox/src/tools/fs.rs
+++ b/proxmox/src/tools/fs.rs
@@ -236,14 +236,22 @@ pub fn atomic_open_or_create_file<P: AsRef<Path>>(
// the initialization, the first one wins!
let rename_result = temp_file_name.with_nix_path(|c_file_name| {
path.with_nix_path(|new_path| unsafe {
- let rc = libc::renameat2(
+ // This also works on file systems which don't support hardlinks (eg. vfat)
+ match Errno::result(libc::renameat2(
libc::AT_FDCWD,
c_file_name.as_ptr(),
libc::AT_FDCWD,
new_path.as_ptr(),
libc::RENAME_NOREPLACE,
- );
- nix::errno::Errno::result(rc)
+ )) {
+ Err(nix::Error::Sys(Errno::EINVAL)) => (), // dumb file system, try `link`+`unlink`
+ other => return other,
+ };
+ // but some file systems don't support `RENAME_NOREPLACE`
+ // so we just use `link` + `unlink` instead
+ let result = Errno::result(libc::link(c_file_name.as_ptr(), new_path.as_ptr()));
+ let _ = libc::unlink(c_file_name.as_ptr());
+ result
})
});
--
2.30.2
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