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The RCU hash table uses deferred work to resize the hash table. There's a time during resize when hash table iteration will return EAGAIN until resize makes more progress. During this time resize can perform GFP_KERNEL allocations. Our shrinker tries to iterate over its RCU hash table to find blocks to reclaim. It tries to restart iteration if it gets EAGAIN on the assumption that it will be usable again soon. Combine the two and our shrinker can get stuck retrying iteration indefinitely because it's shrinking on behalf of the hash table resizing that is trying to allocate the next table before making iteration work again. We have to stop shrinking in this case so that the resizing caller can proceed. Signed-off-by: Zach Brown <zab@versity.com>
Introduction
scoutfs is a clustered in-kernel Linux filesystem designed to support large archival systems. It features additional interfaces and metadata so that archive agents can perform their maintenance workflows without walking all the files in the namespace. Its cluster support lets deployments add nodes to satisfy archival tier bandwidth targets.
The design goal is to reach file populations in the trillions, with the archival bandwidth to match, while remaining operational and responsive.
Highlights of the design and implementation include:
- Fully consistent POSIX semantics between nodes
- Atomic transactions to maintain consistent persistent structures
- Integrated archival metadata replaces syncing to external databases
- Dynamic seperation of resources lets nodes write in parallel
- 64bit throughout; no limits on file or directory sizes or counts
- Open GPLv2 implementation
Community Mailing List
Please join us on the open scoutfs-devel@scoutfs.org mailing list hosted on Google Groups