From: Turkijan <turkijan083@gmail.com>
To: Proxmox Backup Server development discussion
<pbs-devel@lists.proxmox.com>
Subject: Re: [pbs-devel] [PATCH proxmox v2] sys: file: use renameat2() from `nix` crate
Date: Fri, 12 Jul 2024 04:16:29 -0400 [thread overview]
Message-ID: <CAFtnzVcO0_quQ91Ft8ELWAx-Dsp0sDNsCdO-nYMt4Qwk9YuKLw@mail.gmail.com> (raw)
In-Reply-To: <20240712075449.238010-1-c.heiss@proxmox.com>
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how to update this for my test proxmox backup server?
On Fri, Jul 12, 2024 at 3:55 AM Christoph Heiss <c.heiss@proxmox.com> wrote:
> Saves us from converting the paths to raw C strings ourselves, thus
> simplifying it quite a bit.
>
> Since the `nix` crate does not provide link() directly, only linkat(),
> that is used instead - which behaves exactly the same as link() when
> using AT_FDCWD and an empty flag set.
>
> No functional changes.
>
> Signed-off-by: Christoph Heiss <c.heiss@proxmox.com>
> ---
> Changes v1 -> v2:
> * use `AtFlags` instead of deprecated `LinkatFlags` (thanks Christian!)
> * use an empty flag set, as AT_SYMLINK_NOFOLLOW is the default anyway
> for linkat()
> * adjust accompanying comment to mention `linkat` instead of `link`
>
> proxmox-sys/src/fs/file.rs | 53 +++++++++++++++++---------------------
> 1 file changed, 23 insertions(+), 30 deletions(-)
>
> diff --git a/proxmox-sys/src/fs/file.rs b/proxmox-sys/src/fs/file.rs
> index ac513891..b2d6ddf6 100644
> --- a/proxmox-sys/src/fs/file.rs
> +++ b/proxmox-sys/src/fs/file.rs
> @@ -10,7 +10,6 @@ use nix::errno::Errno;
> use nix::fcntl::OFlag;
> use nix::sys::stat;
> use nix::unistd;
> -use nix::NixPath;
> use serde_json::Value;
>
> use proxmox_lang::try_block;
> @@ -266,30 +265,32 @@ pub fn atomic_open_or_create_file<P: AsRef<Path>>(
>
> // rotate the file into place, but use `RENAME_NOREPLACE`, so in case
> 2 processes race against
> // 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 {
> - // 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,
> - )) {
> - Err(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());
> + let rename_result = match nix::fcntl::renameat2(
> + None, // AT_FDCWD
> + &temp_file_name,
> + None, // AT_FDCWD
> + path,
> + nix::fcntl::RenameFlags::RENAME_NOREPLACE,
> + ) {
> + Err(Errno::EINVAL) => {
> + // some file systems don't support `RENAME_NOREPLACE`
> + // so we just use `linkat` + `unlink` instead
> + let result = nix::unistd::linkat(
> + None,
> + &temp_file_name,
> + None,
> + &path.to_path_buf(),
> + nix::unistd::AtFlags::empty(),
> + );
> + let _ = nix::unistd::unlink(&temp_file_name);
> result
> - })
> - });
> + }
> + other => other,
> + };
>
> match rename_result {
> - Ok(Ok(Ok(_))) => Ok(file),
> - Ok(Ok(Err(err))) => {
> + Ok(_) => Ok(file),
> + Err(err) => {
> // if another process has already raced ahead and created
> // the file, let's just open theirs instead:
> let _ = nix::unistd::unlink(&temp_file_name);
> @@ -308,14 +309,6 @@ pub fn atomic_open_or_create_file<P: AsRef<Path>>(
> );
> }
> }
> - Ok(Err(err)) => {
> - let _ = nix::unistd::unlink(&temp_file_name);
> - bail!("with_nix_path {:?} failed - {}", path, err);
> - }
> - Err(err) => {
> - let _ = nix::unistd::unlink(&temp_file_name);
> - bail!("with_nix_path {:?} failed - {}", temp_file_name, err);
> - }
> }
> }
>
> --
> 2.45.1
>
>
>
> _______________________________________________
> pbs-devel mailing list
> pbs-devel@lists.proxmox.com
> https://lists.proxmox.com/cgi-bin/mailman/listinfo/pbs-devel
>
>
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next prev parent reply other threads:[~2024-07-12 8:15 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-07-12 7:54 Christoph Heiss
2024-07-12 8:16 ` Turkijan [this message]
2024-07-12 9:39 ` Christian Ebner
2024-07-18 10:29 ` Thomas Lamprecht
2024-07-18 11:19 ` Christian Ebner
2024-07-18 12:03 ` Thomas Lamprecht
2024-07-18 12:13 ` Christian Ebner
2024-07-18 12:19 ` Thomas Lamprecht
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