操作系统教程11.ppt

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1、Chapter11:FileSystemImplementationFile-SystemStructureFile-SystemImplementationDirectoryImplementationAllocationMethodsFree-SpaceManagementEfficiencyandPerformanceRecoveryLog-StructuredFileSystemsNFSExample:WAFLFileSystemFile-SystemStructureFilesystemsallowt

2、hedata2bestored,located,retrievedeasilyDesignproblems:Howisitlook2theuserCreatingalgorithms&datastructure2mapthelogicalFSontothesecondary-storageI/OtransfersmemorydisksinunitsofblocksFilesystemorganizedintolayersFilecontrolblockstructureconsistingofinformati

3、onaboutafileOwnership,permissions,locationetc.LayeredFileSystemDevicedriversinterrupthandlersIssuesgeneralcommands:rd,wrtorganizesfiles,logical&physicalblocksTranslation,freespaceMetadataFCBATypicalFileControlBlockOn-DiskStructuresBootcontrolblock(/volume)Con

4、taininfoneeded4bootinganOSfromitbootblockinUFS,partitionbootsectorinNTFSVolumecontrolblock(/volume)Containsvolumedetails,includes:no.&sizeofblocksfree-blockcount&pointerfreeFCBcount&FCBpointerSuperblockinUFS,masterfiletableinNTFSOn-DiskStructuresDirectorystru

5、cture(/FS)ToorganizefilesIncludesfilenames&associateinodeno.inUFSstoredinmasterfiletableinNTFSFilecontrolblock(/file)inodeinUFSstoredinmasterfiletableinNTFSUsesarelationaldatabasestructure,row/fileIn-MemoryFileSystemStructuresMounttableInfoabouteachmountedvol

6、umeIn-memorydirectorystructurecacheInfoofrecentlyaccesseddirectoriesSystem-wideopen-filetableCopiesoftheFCBforallopenfile,etc.Per-processopen-filetableApointertotheappropriateentryinthesystem-wideopen-filetableIn-MemoryFileSystemStructuresVirtualFileSystemsPr

7、ovidesanO-OwayofimplementingFS2functions:Separatesthefile-system-genericoperationsfromtheirimplementationbydefiningacleanVFSinterfaceProvidesamechanismforuniquelyrepresent-ingafilethroughoutanetwork(byvnode)Allowsthesamesystemcallinterface(theAPI)tobeusedford

8、ifferenttypesofFSTheFSAPIistotheVFSinterface.SchematicViewofVirtualFileSystemVirtualFileSystemonLinuxObjectsInode-representsanindividualfileFile-representsanopenfileSuperblock-representsa