mount: refresh and evict hot dir cache (#8174)

* mount: refresh and evict hot dir cache

* mount: guard dir update window and extend TTL

* mount: reuse timestamp for cache mark

* Apply suggestion from @gemini-code-assist[bot]

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

* mount: make dir cache tuning configurable

* mount: dedupe dir update notices

* mount: restore invalidate-all cache helper

* mount: keep hot dir tuning constants

* mount: centralize cache state reset

* mount: mark refresh completion time

* mount: allow disabling idle eviction

---------

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

weed/command/mount.go

@@ -48,6 +48,8 @@ type MountOptions struct {
 	rdmaMaxConcurrent *int
 	rdmaTimeoutMs     *int
 
+	dirIdleEvictSec *int
+
 	// FUSE performance options
 	writebackCache *bool
 	asyncDio       *bool
@@ -107,6 +109,8 @@ func init() {
 	mountOptions.rdmaMaxConcurrent = cmdMount.Flag.Int("rdma.maxConcurrent", 64, "max concurrent RDMA operations")
 	mountOptions.rdmaTimeoutMs = cmdMount.Flag.Int("rdma.timeoutMs", 5000, "RDMA operation timeout in milliseconds")
 
+	mountOptions.dirIdleEvictSec = cmdMount.Flag.Int("dirIdleEvictSec", 600, "seconds to evict idle cached directories (0 to disable)")
+
 	mountCpuProfile = cmdMount.Flag.String("cpuprofile", "", "cpu profile output file")
 	mountMemProfile = cmdMount.Flag.String("memprofile", "", "memory profile output file")
 	mountReadRetryTime = cmdMount.Flag.Duration("readRetryTime", 6*time.Second, "maximum read retry wait time")