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Date: Wed, 29 Nov 2023 16:00:47 +0100 (CET)
From: Christian Ebner <c.ebner@proxmox.com>
To: Proxmox Backup Server development discussion <pbs-devel@lists.proxmox.com>, 
 Lukas Wagner <l.wagner@proxmox.com>, Markus Frank <m.frank@proxmox.com>
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Subject: Re: [pbs-devel] [PATCH proxmox-backup] api: enhance directory
 existence check
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> On 29.11.2023 15:51 CET Lukas Wagner <l.wagner@proxmox.com> wrote:
> 
> 
> 
> But that does not detect if another (empty) filesystem is already 
> mounted at that directory, right?

To add to Lukas response, you could compare the `st_dev` of parent and mountpoint
to check if there already if a different filesystem mounted, something like:

use std::os::linux::fs::MetadataExt;

...

match std::fs::metadata(&default_path) {
     Err(_) => {} // path does not exist
     Ok(stat) => {
         let basedir_dev = std::fs::metadata(BASE_MOUNT_DIR)?.st_dev();
         if stat.st_dev != basedir_dev {
             bail!("path {default_path:?} already exists and is mountpoint");
         }
         ...
    }
}