fix: don't set parent on xattr walk fidRefs - #106
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The txattrwalk handler created fidRefs with parent set to ref.parent but never called addChild or parent.IncRef. This caused two issues: 1. DecRef called parent.pathNode.removeChild on a ref that was never registered, triggering a spurious NOT FOUND. 2. DecRef called parent.DecRef without a matching IncRef, which could prematurely drop the parent's refcount to zero and remove other legitimately registered refs from childRefNames, leading to a panic in nameFor during clone walks. Xattr fids are ephemeral and don't represent filesystem paths, so they should not participate in path tree tracking. Setting parent to nil (the zero value, already omitted) prevents DecRef from touching the path tree or parent ref.
Signed-off-by: Chris Koch <c@chrisko.ch>
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Additional details and impacted files@@ Coverage Diff @@
## main #106 +/- ##
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- Coverage 61.63% 61.62% -0.01%
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Files 37 37
Lines 3871 3870 -1
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- Hits 2386 2385 -1
Misses 1276 1276
Partials 209 209
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I kept on getting "bad address" (EFAULT) errors with a dynamic 9p filesystem I am building. After (a lot of) tracing, I think I've narrowed it down to this -- but I could do with some sanity checking, especially around the xattr calls behaviour which I only discovered thanks to diod.
The txattrwalk handler created fidRefs with parent set to ref.parent but never called addChild or parent.IncRef. This caused two issues:
DecRef called parent.pathNode.removeChild on a ref that was never registered, triggering a spurious NOT FOUND.
DecRef called parent.DecRef without a matching IncRef, which could prematurely drop the parent's refcount to zero and remove other legitimately registered refs from childRefNames, leading to a panic in nameFor during clone walks.
Xattr fids are ephemeral and don't represent filesystem paths, so they should not participate in path tree tracking. Setting parent to nil (the zero value, already omitted) prevents DecRef from touching the path tree or parent ref.