scoutfs-notify

Observer-only file access notifications for ScoutFS. Maintained as a rebasable git format-patch series so it can be layered onto each upstream release with minimal maintenance.

What it adds

• New mount option notify_events=0|1 (default 0) that turns on a per-mount ring buffer of file open and read events.
• New mount option notify_ring_kb=N (4..4096, default 64) sizing that ring.
• New ioctl SCOUTFS_IOC_READ_NOTIFY (nr 25) that lets a single privileged userspace reader drain the ring. Reader is expected to relay events over a Unix socket to a watcher daemon.
• Three percpu counters: notify_emitted, notify_dropped_ring_full, notify_reader_attached.

The notification path is strictly observer-only: if the ring fills, records are dropped but the monotonic seq field still advances so readers see a gap. notify_events=0 reduces the hook to a single predicted-false branch.

Nothing in the data-waiter state machine is touched by this series; a future patch series may add data-waiter observation events (reserved type values 3+).

Base

Currently rebased against:

scoutfs v1.29

See base.txt for the exact tag the patches target.

Applying

On a git checkout of scoutfs at the base tag:

./apply.sh /path/to/scoutfs

The script runs git am --3way against each patches/*.patch. Requires the target to be a git working tree.

For a non-git tarball, apply with:

cd /path/to/scoutfs
for p in /path/to/scoutfs-notify/patches/*.patch; do
    patch -p1 < "$p"
done

Rebasing onto a new upstream release

# In your scoutfs working clone
git fetch --tags
git checkout -B notify v1.30          # new upstream tag
git am --3way patches/*.patch          # from this repo
# ... resolve any conflicts, git am --continue ...
git format-patch v1.30..notify -o patches/
# Update base.txt and commit the refreshed patches

Tagging

Tag releases of the patch set with both the upstream version and a patch revision so consumers can pin precisely:

v1.29-notify-1
v1.29-notify-2
v1.30-notify-1