Disable "uncache" behavior in DB shutdown #12751
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Summary: Crash test showed a potential use-after-free where a file marked as obsolete and eligible for uncache on destruction is destroyed in the VersionSet destructor, which only happens as part of DB shutdown. At that point, the in-memory column families have already been destroyed, so attempting to uncache could use-after-free on stuff like getting the `user_comparator()` from the `internal_comparator()`. I attempted to make it smarter, but wasn't able to untangle the destruction dependencies in a way that was safe, understandable, and maintainable. Test Plan: Reproduced by adding uncache_aggressiveness to an existing (but otherwise unrelated) test. This makes it a fair regression test. Also added testing to ensure that trivial moves and DB close & reopen are well behaved with uncache_aggressiveness. Specifically, this issue doesn't seem to be because things are uncached inappropriately in those cases.
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@pdillinger has imported this pull request. If you are a Meta employee, you can view this diff on Phabricator. |
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@pdillinger has updated the pull request. You must reimport the pull request before landing. |
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@pdillinger has imported this pull request. If you are a Meta employee, you can view this diff on Phabricator. |
ltamasi
approved these changes
Jun 11, 2024
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@pdillinger merged this pull request in 21eb82e. |
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Summary: Crash test showed a potential use-after-free where a file marked as obsolete and eligible for uncache on destruction is destroyed in the VersionSet destructor, which only happens as part of DB shutdown. At that point, the in-memory column families have already been destroyed, so attempting to uncache could use-after-free on stuff like getting the
user_comparator()from theinternal_comparator().I attempted to make it smarter, but wasn't able to untangle the destruction dependencies in a way that was safe, understandable, and maintainable.
Test Plan: Reproduced by adding uncache_aggressiveness to an existing (but otherwise unrelated) test. This makes it a fair regression test.
Also added testing to ensure that trivial moves and DB close & reopen are well behaved with uncache_aggressiveness. Specifically, this issue doesn't seem to be because things are uncached inappropriately in those cases.