* feat(mount): set FOPEN_KEEP_CACHE when file mtime is unchanged
On re-open of an unmodified file, signal the kernel to preserve its
existing page cache. This eliminates redundant volume server reads for
workloads that repeatedly open-read-close the same files (build systems,
config readers, etc.).
* fix(mount): use guarded type assertion for openMtimeCache load
Use the two-value form of type assertion when loading from sync.Map
to prevent potential panics if a non-int64 value is ever stored.
* fix(mount): skip redundant mtime store and invalidate on truncation
- Avoid redundant sync.Map Store when cached mtime already matches
the current mtime, reducing contention on the hot open path.
- Invalidate openMtimeCache in SetAttr when file size changes
(truncation), preventing stale kernel page cache after ftruncate.
* fix(mount): use nanosecond mtime precision and bounded cache for FOPEN_KEEP_CACHE
- Compare both Mtime (seconds) and MtimeNs (nanoseconds) to detect
sub-second modifications common in automated workloads.
- Replace unbounded sync.Map with a bounded map + mutex (8192 entries,
random eviction when full), following the existing atimeMap pattern.
- Extract applyKeepCacheFlag and invalidateOpenMtimeCache methods for
clarity and testability.
- Add tests for nanosecond precision and cache eviction.
* fix(mount): invalidate mtime cache in truncateEntry for O_TRUNC consistency
Add invalidateOpenMtimeCache call to truncateEntry so the Create path
with O_TRUNC follows the same explicit invalidation pattern as SetAttr
and Write.
Chris LuandGitHub
9896eade51