Re: [pbs-devel] [PATCH proxmox-backup 12/17] datastore: get per-chunk file lock for chunk rename on s3 backend

["Fabian Grünbichler" <f.gruenbichler@proxmox.com>]

On November 3, 2025 12:31 pm, Christian Ebner wrote:
> To guarantee exclusive access during s3 object store and cache
> operations, acquire the per-chunk file before renaming a chunk when
> the datastore is backed by s3.
> 
> This does not yet cover locking for the GC and chunk insert, part
> of subsequent changes.
> 
> Signed-off-by: Christian Ebner <c.ebner@proxmox.com>
> ---
>  pbs-datastore/src/datastore.rs | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/pbs-datastore/src/datastore.rs b/pbs-datastore/src/datastore.rs
> index e7ec87a7f..e65f3a60c 100644
> --- a/pbs-datastore/src/datastore.rs
> +++ b/pbs-datastore/src/datastore.rs
> @@ -2586,6 +2586,7 @@ impl DataStore {
>          let (path, digest_str) = self.chunk_path(digest);
>  
>          let _lock = self.inner.chunk_store.mutex().lock().unwrap();
> +        let _chunk_guard = self.lock_chunk_for_backend(digest)?;

lock inversion?

when inserting into S3, the chunk lock is obtained first, and then the
mutex is obtained for all insertions in chunk_store.insert_chunk while
the chunk lock is held.. while we do have a long timeout here, that
would still be quite bad..

>  
>          let mut counter = 0;
>          let mut new_path = path.clone();
> -- 
> 2.47.3
> 
> 
> 
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> 
> 
> 


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