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Chris LuandGitHub
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* mount: invalidate hot directory listings by section A cached directory used to be dropped whole when it saw 64 changes in 2s: with a continuous writer the listing cycled through wipe, direct listing and full rebuild for as long as the writer kept going, and every sibling lookup fell through to the filer in between. Split each cached listing into name-range sections of 1024 entries. A burst of foreign changes invalidates just the section it lands in; entries stay served and events keep applying, and the next readdir re-lists only that range from the filer, reconciled through the version gate so it cannot roll back newer applied events. Lookups in an invalidated section read through until then. The mount's own writes no longer invalidate anything: they are ground truth for its cache. * meta_cache: drop the version floor with a deleted or moved directory The other teardown paths already clear both maps; a floor left behind here would fence the listing of a directory re-created at the same path. * mount: harden section refresh An unversioned listing (pre-upgrade filer) now only fills gaps instead of reconciling: without a snapshot to order against, an overwrite or the deletion sweep could roll back an event applied after the listing. The section table can be rebuilt or re-split between the listing and its apply, so the refresh only marks fresh or splits when the section still covers the range it read. Splicing bounds from a stale range into a rebuilt table could leave them unsorted. Bound the wait: a readdir gives a refresh five seconds before serving the maintained-but-unverified cache. Bound the size: a range grown past four sections aborts the refresh and drops the directory cache, re-tiling it with a full rebuild, with that request served direct. Cover the filer-facing path with a listing server: paging with the snapshot pinned across pages, the section cutoff, no calls for a fresh section, and the overgrown-range abort. * meta_cache: make the section table a self-contained state machine Churn counting, freshness, stale-range scanning and the refresh completion with its guard and split now live on dirSections itself, free of the lock, the store and the apply loop, so they test directly with synthetic clocks and tables. MetaCache keeps thin wrappers that hold its mutex and find the directory's table. * meta_cache: keep section internals out of the apply request The request now carries the completed build's table and one refresh as opaque values built by section code, and the boundary-derivation rule moves out of the build loop into a collector next to the rest of the section logic. * mount: fence refreshed sections with a snapshot floor A refresh versioned the entries it fetched and tombstoned the ones it swept, but a name absent from both cache and listing kept the old directory floor, so a delayed event between the two snapshots could resurrect it into a section already marked fresh. The section now carries its own floor, consulted next to the directory floor, covering every name in the range, present or absent — which also retires the refresh's per-entry version stamps and sweep tombstones. An unversioned listing sets no floor and vouches for nothing: it may still fill gaps, but the section stays stale and reads through until a filer that stamps snapshots re-validates it. A listing's reach is unknowable up front — a resumed handle can skip far ahead, and shrunken sections let one batch span many — so a readdir now re-validates every stale section from its start name to the end of the directory instead of the next two. * mount: fence tombstoned names with floors and gate the reconcile A tombstone answered for its name before the floors were consulted, so one at an old position let through events the newer listing floor should have fenced; a build never hit this because it prunes superseded tombstones, which a section refresh does not. The version gate now raises a tombstone to the floors like any other record. With no per-entry versions, only the section floor fences a reconcile's work, so a range the rebuilt or re-split table no longer has must not touch the store either: the range check moves ahead of the mutations, under the same lock the floor install holds. An unversioned refresh no longer retries: the section is remembered as unverifiable and skipped by the stale scan, or every batch of every readdir would re-list the same ranges against a filer that cannot vouch for them. * mount: clear beaten unversioned markers and skip refresh mid-build An unversioned marker outliving the snapshot write that replaced its content bypassed the section floor the same way an old tombstone did, letting a delayed pre-snapshot event roll the entry back. The refresh now clears the marker when its write wins; pinned local-only entries are not replaced at all, keeping their content and marker. A rebuild wipes and repopulates the store off the apply loop, so a refresh reconciling meanwhile could sweep children the build had already inserted and let it publish the directory incomplete. The refresh now skips a building directory, as events (buffered) and purges (skipped) already do; its staleness dies with the build's fresh table. * mount: clear the unversioned marker only after its replacement lands Clearing before the insert meant a failed write left the old local content claiming the listing floors, fencing the very events that were still entitled to correct it. * meta_cache: rename the section state machine to sectionList dirSections named both the type and the map of them. * mount: raise the default cacheDirMaxEntries to 100000 The low ceiling guarded against whole-listing rebuild churn: a big cached directory under writes kept re-streaming everything. Sectioned invalidation ended that — a burst now costs one range listing — so the remaining cost of caching a large directory is its one-time build, comparable to the single direct listing that read-through mode pays on every enumeration instead. * meta_cache: cover section border and edge cases A bound-named entry belongs to the section starting at the bound: the neighboring refresh's sweep stops before it, its own section's covers it. Churn past everything the build saw lands in the tail section, a rename spanning two sections invalidates both, and a listed entry at the section's end name is cut off with the ones beyond it.