overlayfs: unmount before cleanup on build exception#215
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mtelvers merged 1 commit intoJul 21, 2026
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The exception path deleted the merged dir without unmounting it first, unlike the success/error paths. rm -rf on a live overlay mountpoint fails with EBUSY, leaking the mount; retries then stack further mounts on the reused id-keyed path.
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The exception path in
Overlayfs.buildranrm -rfon themergeddirectory without unmounting it first, unlike the success and error paths which unmount before deleting.When the build function raises, the overlay is still mounted, so
rm -rf mergedfails withDevice or resource busy(EBUSY) and the mount leaks. Becausemerged/workare keyed only by the content-hashidand reused, each retry mounts on top of the leaked mount, stacking overlays (observed up to 6 deep) so even the success path's singleumountcan no longer clean up. This fills the store and permanently poisons thatid.Fix: unmount
mergedin the exception handler before deleting, mirroring the success/error paths.