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refer #5208 ## Problem See https://neondb.slack.com/archives/C03H1K0PGKH/p1693938336062439?thread_ts=1693928260.704799&cid=C03H1K0PGKH #5208 disable LFC forever in case of error. It is not good because the problem causing this error (for example ENOSPC) can be resolved anti will be nice to reenable it after fixing. Also #5208 disables LFC locally in one backend. But other backends may still see corrupted data. It should not cause problems right now with "permission denied" error because there should be no backend which is able to normally open LFC. But in case of out-of-disk-space error, other backend can read corrupted data. ## Summary of changes 1. Cleanup hash table after error to prevent access to stale or corrupted data 2. Perform disk write under exclusive lock (hoping it will not affect performance because usually write just copy data from user to system space) 3. Use generations to prevent access to stale data in lfc_read ## Checklist before requesting a review - [ ] I have performed a self-review of my code. - [ ] If it is a core feature, I have added thorough tests. - [ ] Do we need to implement analytics? if so did you add the relevant metrics to the dashboard? - [ ] If this PR requires public announcement, mark it with /release-notes label and add several sentences in this section. ## Checklist before merging - [ ] Do not forget to reformat commit message to not include the above checklist --------- Co-authored-by: Konstantin Knizhnik <knizhnik@neon.tech>