LocalFileSystem: Reuse FileStore instance for FsStat

[kohlschuetter]

Currently, we are calling Files.getFileStore for every request to VirtualFileSystem.getFileStat.

On some systems, such as macOS, this may introduce extremely long wait times for NFS operations, effectively hanging the entire NFS client. Delays as high as 14 seconds (!) have been observed.

Move the FileStore access to LocalFileSystem's constructor, such that it can be reused.

Stack trace for observed hang:

	at [email protected]/sun.nio.fs.BsdNativeDispatcher.getfsstat(Native Method)
	at [email protected]/sun.nio.fs.BsdFileSystem.getMountEntries(BsdFileSystem.java:169)
	at [email protected]/sun.nio.fs.BsdFileStore.findMountEntry(BsdFileStore.java:75)
	at [email protected]/sun.nio.fs.UnixFileStore.<init>(UnixFileStore.java:69)
	at [email protected]/sun.nio.fs.BsdFileStore.<init>(BsdFileStore.java:42)
	at [email protected]/sun.nio.fs.BsdFileSystemProvider.getFileStore(BsdFileSystemProvider.java:48)
	at [email protected]/sun.nio.fs.BsdFileSystemProvider.getFileStore(BsdFileSystemProvider.java:36)
	at [email protected]/sun.nio.fs.UnixFileSystemProvider.getFileStore(UnixFileSystemProvider.java:422)
	at [email protected]/java.nio.file.Files.getFileStore(Files.java:1496)
	at app//org.dcache.nfs4j.server.LocalFileSystem.getFsStat(LocalFileSystem.java:209)
	at app//org.dcache.nfs.vfs.ForwardingFileSystem.getFsStat(ForwardingFileSystem.java:57)
	at app//org.dcache.nfs.v4.OperationGETATTR.getFsStat(OperationGETATTR.java:176)
	at app//org.dcache.nfs.v4.OperationGETATTR.fattr2xdr(OperationGETATTR.java:262)
	at app//org.dcache.nfs.v4.OperationGETATTR.getAttributes(OperationGETATTR.java:145)
	at app//org.dcache.nfs.v4.OperationGETATTR.getAttributes(OperationGETATTR.java:169)
	at app//org.dcache.nfs.v4.OperationGETATTR.process(OperationGETATTR.java:124)
	at app//org.dcache.nfs.v4.AbstractOperationExecutor.execute(AbstractOperationExecutor.java:85)
	at app//org.dcache.nfs.v4.NFSServerV41.NFSPROC4_COMPOUND_4(NFSServerV41.java:201)
	at app//org.dcache.nfs.v4.xdr.nfs4_prot_NFS4_PROGRAM_ServerStub.dispatchOncRpcCall(nfs4_prot_NFS4_PROGRAM_ServerStub.java:48)
	at app//org.dcache.oncrpc4j.rpc.RpcDispatcher$1.run(RpcDispatcher.java:122)
	at [email protected]/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1144)
	at [email protected]/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:642)
	at [email protected]/java.lang.Thread.runWith(Thread.java:1583)
	at [email protected]/java.lang.Thread.run(Thread.java:1570)

[kofemann]

@kohlschuetter Thanks for your contribution.