[Diamond (diamondburned)]

Summary

UnmountAllUnder parsed /proc/self/mountinfo on every actor restore and teardown, scanning all cached overlay layer mounts on the node under the kernel mount-namespace lock.

• Walks the target directory with dirfd-relative statx and STATX_ATTR_MOUNT_ROOT across bounded passes instead, skipping overlay upper/work scratch trees and unmounted bundle rootfs/volume directories.
• Fails loudly if STATX_ATTR_MOUNT_ROOT is unsupported on the backing filesystem, and detaches broken or disconnected mounts that fail statx/open/readdir with ENOTCONN, ESTALE, or EIO.
• Deletes the now-unused mountinfo parser and its unit test, and adds BenchmarkUnmountAllUnder comparing bundle unmount under ambient mount-table noise.

Benchmark (benchstat)

Reproducible on Cloudtop via unshare -Urm go test -run='^$' -bench='^BenchmarkUnmountAllUnder$' -benchmem -count=10 ./internal/imagecache:

goos: linux
goarch: amd64
pkg: go.ate.dev/substrate/internal/imagecache
cpu: AMD EPYC 7B13
                   │  before.txt  │              after.txt               │
                   │    sec/op    │    sec/op     vs base                │
UnmountAllUnder-64   228.5µ ± 3%   168.0µ ± 2%  -26.45% (p=0.000 n=10)

                   │  before.txt  │              after.txt               │
                   │     B/op     │     B/op      vs base                │
UnmountAllUnder-64   4.125Ki ± 0%   2.318Ki ± 0%  -43.80% (p=0.000 n=10)

                   │ before.txt │               after.txt               │
                   │ allocs/op  │  allocs/op   vs base                  │
UnmountAllUnder-64   4.000 ± 0%   64.000 ± 0%  +1500.00% (p=0.000 n=10)

Verification

• go test -race -count=3 -shuffle=on ./internal/imagecache/...
• unshare -Urm go test -count=1 -v -run Unmount ./internal/imagecache/...
• ./hack/verify/boilerplate.sh && ./hack/verify/gofmt.sh && ./hack/verify/package-deps.sh

🤖 PR was made with the use of generative AI.