[pbs-devel] [PATCH proxmox-backup v7 04/20] datastore: add helper for checking if a removable datastore is available

[Christian Ebner]

On 4/19/24 17:35, Hannes Laimer wrote:
> On Fri Apr 19, 2024 at 11:14 AM CEST, Christian Ebner wrote:
>> On 4/19/24 10:58, Hannes Laimer wrote:
>>> Signed-off-by: Hannes Laimer <h.laimer at proxmox.com>
>>> ---
>>>    pbs-api-types/src/maintenance.rs |  2 +-
>>>    pbs-datastore/src/datastore.rs   | 44 ++++++++++++++++++++++++++++++++
>>>    pbs-datastore/src/lib.rs         |  2 +-
>>>    3 files changed, 46 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/pbs-api-types/src/maintenance.rs b/pbs-api-types/src/maintenance.rs
>>> index fd4d3416..4f653ec7 100644
>>> --- a/pbs-api-types/src/maintenance.rs
>>> +++ b/pbs-api-types/src/maintenance.rs
>>> @@ -81,7 +81,7 @@ impl MaintenanceMode {
>>>        /// Used for deciding whether the datastore is cleared from the internal cache after the last
>>>        /// task finishes, so all open files are closed.
>>>        pub fn is_offline(&self) -> bool {
>>> -        self.ty == MaintenanceType::Offline
>>> +        self.ty == MaintenanceType::Offline || self.ty == MaintenanceType::Unmount
>>>        }
>>>    
>>>        pub fn check(&self, operation: Option<Operation>) -> Result<(), Error> {
>>> diff --git a/pbs-datastore/src/datastore.rs b/pbs-datastore/src/datastore.rs
>>> index f95da761..274f1506 100644
>>> --- a/pbs-datastore/src/datastore.rs
>>> +++ b/pbs-datastore/src/datastore.rs
>>> @@ -14,6 +14,7 @@ use proxmox_schema::ApiType;
>>>    use proxmox_sys::error::SysError;
>>>    use proxmox_sys::fs::{file_read_optional_string, replace_file, CreateOptions};
>>>    use proxmox_sys::fs::{lock_dir_noblock, DirLockGuard};
>>> +use proxmox_sys::linux::procfs::MountInfo;
>>>    use proxmox_sys::process_locker::ProcessLockSharedGuard;
>>>    use proxmox_sys::WorkerTaskContext;
>>>    use proxmox_sys::{task_log, task_warn};
>>> @@ -49,6 +50,39 @@ pub fn check_backup_owner(owner: &Authid, auth_id: &Authid) -> Result<(), Error>
>>>        Ok(())
>>>    }
>>>    
>>> +/// check if a removable datastore is currently available/mounted by using the UUID
>>> +/// to find the `/dev/sdX` path and checking in /proc/self/mountinfo for entries containing it.
>>> +/// If it should mounted, but not in the expected path, so config.path, it is considered not
>>> +/// available.
>>> +pub fn is_datastore_available(config: &DataStoreConfig) -> bool {
>>> +    config.backing_device.as_ref().map_or(true, |uuid| {
>>> +        if let Ok(store_dev_path) = std::fs::read_link(Path::new("/dev/disk/by-uuid").join(uuid))
>>> +            .map(|p| p.to_string_lossy().into_owned())
>>
>> while this probably never happens for this case, the `to_string_lossy`
>> might replace non UTF-8 characters here.
>>
>> So I think this and the next two map calls should be replaced with a
>> `canonicalize` of `PathBuf`, which also resolves the symlink?
>>
>> https://doc.rust-lang.org/std/path/struct.PathBuf.html#method.canonicalize
>>
> 
> doesn't work, I'm not 100% sure, but I think it's beacuse it uses the
> running dir of the binary as a base

True, but we can work around that by adding the base if the symlink is a 
relative path. This should do the trick:

```
     config.backing_device.as_ref().map_or(true, |uuid| {
         let mut target = PathBuf::from("/dev/disk/by-uuid");
         if let Ok(store_dev_path) = std::fs::read_link(target.join(uuid))
             .map(|link_target| {
                 // Replaces current path buffer content if link_target 
is absolute path
                 // 
https://docs.rs/rustc-std-workspace-std/latest/std/path/struct.PathBuf.html#method.push
                 target.push(link_target);
                 target
             })
             .and_then(|target| target.canonicalize())
         {
```