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7eacc7139c
scoutfs_quota_mod_rule calls scoutfs_item_create/delete which use the transaction allocator but it never held it. Without the hold, a concurrent transaction commit can call scoutfs_alloc_init to reinitialize the allocator while dirty_alloc_blocks is in the middle of setting up the freed list block. This overwrites alloc->freed with the server's fresh (empty) state, causing a blkno mismatch BUG_ON in list_block_add. Reproduced by stressing concurrent quota add/del operations across mounts. Crashdump analysis confirms dirty_list_block COW'd a freed block (fr_old=9842, new blkno=9852) but by the time list_block_add ran, freed.ref.blkno was 0 with first_nr=0 and total_nr=0: the freed list head had been zeroed by a concurrent alloc_init. Fix by adding scoutfs_hold_trans/scoutfs_release_trans around the item modification in scoutfs_quota_mod_rule, preventing transaction commit from racing with the allocator use. Rename the 'unlock' label to 'release' since 'out' now directly does the unlock. The unlock safely handles a NULL lock. Signed-off-by: Auke Kok <auke.kok@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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