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The change to only allocate a buffer for the first xattr item with kmalloc instead of the entire logical xattr payload with vmalloc included a regression for getting large xattrs. getxattr used to copy the entire payload into the large vmalloc so it could unlock just after get_next_xattr. The change to only getting the first item buffer added a call to copy from the rest of the items but those copies weren't covered by the locks. This would often work because the lock pointer still pointed to a valid lock. But if the lock was invalidated then the mode would no longer be compatible and _item_lookup would return EINVAL. The fix is to extend xattr_rwsem and cluster lock coverage to the rest fo the function body, which includes the value item copies. This also makes getxattr's lock coverage consistent with setxattr and listxattr which might reduce the risk of similar mistakes in the future. 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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