[pbs-devel] [PATCH 1/2] add tempfile helper without O_TMPFILE or memfd_create

[Fabian Grünbichler]

On July 23, 2020 11:38 am, Mira Limbeck wrote:
> As WSL does not support O_TMPFILE nor memfd_create, we need a different
> way to create tempfiles if we want to support windows host backups
> through WSL (without ADS).
> The workaround is to use mkstemp in /tmp and unlinking the file
> right after creation.
> 
> Add FIXME comment to change it back to O_TMPFILE once we no longer require
> the mkstemp workaround for windows support.
> 
> Signed-off-by: Mira Limbeck <m.limbeck at proxmox.com>
> ---
>  src/tools.rs          |  1 +
>  src/tools/tempfile.rs | 13 +++++++++++++
>  2 files changed, 14 insertions(+)
>  create mode 100644 src/tools/tempfile.rs
> 
> diff --git a/src/tools.rs b/src/tools.rs
> index 44db796d..5e892d41 100644
> --- a/src/tools.rs
> +++ b/src/tools.rs
> @@ -30,6 +30,7 @@ pub mod fs;
>  pub mod format;
>  pub mod lru_cache;
>  pub mod runtime;
> +pub mod tempfile;
>  pub mod ticket;
>  pub mod timer;
>  pub mod statistics;
> diff --git a/src/tools/tempfile.rs b/src/tools/tempfile.rs
> new file mode 100644
> index 00000000..a91ce806
> --- /dev/null
> +++ b/src/tools/tempfile.rs
> @@ -0,0 +1,13 @@
> +use nix::unistd::{mkstemp, unlink};
> +use std::fs::File;
> +use std::os::unix::io::FromRawFd;
> +use anyhow;
> +
> +// FIXME change to O_TMPFILE once a native windows backup client exists

shouldn't we try O_TMPFILE first, and only if it fails fall back to 
mkstemp? or guard this with a feature ("wsl")? also not sure whether all 
current (and future) callers are okay with the different semantics (with 
mkstemp the file is briefly available via a path even if you unlink it 
directly afterwards..).

it also might be better off in proxmox instead of proxmox-backup, it's a 
very generic function after all..

> +pub fn tempfile() -> anyhow::Result<File> {
> +    let (fd, path) = mkstemp("/tmp/proxmox-backup-client_XXXXXX")?;
> +    unlink(path.as_path())?;
> +    let file = unsafe { File::from_raw_fd(fd) };
> +
> +    Ok(file)
> +}
> -- 
> 2.20.1
> 
> 
> 
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