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T

Auke Kok a87c317931 Account for the pending freed-head rotation in the commit room gates

The server commit deadlocks when its freed allocator list head block
fills to near capacity. Both gates that decide whether a transaction has
room measure it as free slots in the clean freed head block:

  - hold_commit() admits a holder only if scoutfs_alloc_meta_remaining()
    reports enough freed room (2 * COMMIT_HOLD_ALLOC_BUDGET slots).
  - empty_list()/fill_list()'s list_has_blocks() proceed only if the head
    has extent_mod_blocks() slots.

The clean head is not what a transaction gets: the first dirtying
allocation runs dirty_alloc_blocks(), which rotates in a fresh head block
when the current head is under EMPTY_FREED_THRESH. A clean, nearly-full
head has a full block's worth of room as soon as it's touched. With the
gates refusing on the clean full head, no holder is admitted and the
drains never start, so the rotation in dirty_alloc_blocks() is never
reached. The server spins applying empty commits and the filesystem can't
mount or recover (observed at ~11k empty commits/sec; freed head first_nr
8148 of an 8184 capacity).

Fix the accounting in scoutfs_alloc_meta_remaining(): when the freed list
isn't dirtied yet and the clean head is under EMPTY_FREED_THRESH, report
the room the pending rotation will give, SCOUTFS_ALLOC_LIST_MAX_BLOCKS - 2
(a fresh block, less the old avail and freed head blocks the rotation
frees into it). list_has_blocks() routes through the same function so
fill_list()/empty_list() use identical accounting; otherwise an
avail-low, freed-full commit could still wedge because fill_list()
couldn't refill avail past the clean full freed head.

hold_commit() then admits a holder (or a drain starts) and the first
allocation rotates the full head. The avail gate and the meta_low()
loop-stop are left conservative, so genuine ENOSPC still fails and freeing
loops still commit before overflowing a head.

Signed-off-by: Auke Kok <auke.kok@versity.com>

2026-07-23 09:17:39 -07:00

kmod

Account for the pending freed-head rotation in the commit room gates

2026-07-23 09:17:39 -07:00

tests

Remove format-version 1 test.

2026-06-05 09:49:45 -07:00

utils

Guard log_merge, srch_root, and mounted_client item printers

2026-07-23 09:14:31 -07:00

.gitignore

Initial commit

2020-12-07 09:47:12 -08:00

Makefile

Add simple top-level Makefile

2020-12-07 10:39:20 -08:00

README.md

Update README.md

2021-11-05 11:16:57 -07:00

ReleaseNotes.md

v1.32 Release

2026-06-03 11:34:21 -07:00

README.md

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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