[pbs-devel] applied-series: [PATCH proxmox-backup v3 0/3] fix #6750: fix possible deadlock for s3 backed datastore backups

[Fabian Grünbichler]

with some follow-ups sent:
https://lore.proxmox.com/pbs-devel/20250929093228.205510-1-f.gruenbichler@proxmox.com/T/#u
https://lore.proxmox.com/pbs-devel/20250929092143.190162-1-f.gruenbichler@proxmox.com/T/#u

AFAICT those are the only other instances that might be problematic..

Quoting Christian Ebner (2025-09-29 10:04:04)
> These patches aim to fix a deadlock which can occur during backup
> jobs to datastores backed by S3 backend. The deadlock most likely is
> caused by the mutex guard for the backup shared state being held
> while entering the tokio::task::block_in_place context and executing
> async code, which however can lead to deadlocks as described in [0].
> 
> Therefore, these patches avoid holding the mutex guard for the shared
> backup state while performing the s3 backend operations, by
> prematurely dropping it. To avoid inconsistencies, introduce flags
> to keep track of the index writers closing state and add a transient
> `Finishing` state to be entered during manifest updates.
> 
> Changes since version 2 (thanks @Fabian):
> - Avoid unneeded mutex guard during backup removal
> 
> Changes since version 1 (thanks @Fabian):
> - Use the shared backup state's writers in addition with a closed flag
>   instead of counting active backend operations.
> - Replace finished flag with BackupState enum to introduce the new,
>   transient `Finishing` state to be entered during manifest updates.
> - Add missing checks and refactor code to the now mutable reference when
>   accessing the shared backup state in the respective close calls.
> 
> 
> [0] https://docs.rs/tokio/latest/tokio/sync/struct.Mutex.html#which-kind-of-mutex-should-you-use
> 
> Link to the bugtracker issue:
> https://bugzilla.proxmox.com/show_bug.cgi?id=6750
> 
> Another report in the community forum:
> https://forum.proxmox.com/threads/171422/
> 
> proxmox-backup:
> 
> Christian Ebner (3):
>   fix #6750: api: avoid possible deadlock on datastores with s3 backend
>   api: backup: never hold mutex guard when doing manifest update
>   api: backup: avoid holding mutex and inline backup cleanup method
> 
>  src/api2/backup/environment.rs | 181 ++++++++++++++++++++++-----------
>  src/api2/backup/mod.rs         |  24 ++++-
>  2 files changed, 140 insertions(+), 65 deletions(-)
> 
> 
> Summary over all repositories:
>   2 files changed, 140 insertions(+), 65 deletions(-)
> 
> -- 
> Generated by git-murpp 0.8.1
> 
> 
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