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Data preallocation attempts to allocate large aligned regions of extents. It tried to fill the hole around a write offset that didn't contain an extent. It missed the case where there can be multiple extents between the start of the region and the hole. It could try to overwrite these additional existing extents and writes could return EINVAL. We fix this by trimming the preallocation to start at the write offset if there are any extents in the region before the write offset. The data preallocation test output has to be updated now that allocation extents won't grow towards the start of the region when there are existing extents. 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
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