\begindata{text, 268919564} \textdsversion{12} \define{italic menu:[Font,Italic] attr:[FontFace Italic Int Set]} \define{bold menu:[Font,Bold] attr:[FontFace Bold Int Set]} \define{chapter menu:[Title,Chapter] attr:[Justification Centered Point 0] attr:[FontSize PreviousFontSize Point 4]} \define{section menu:[Title,Section] attr:[Justification Centered Point 0] attr:[FontSize PreviousFontSize Point 4]} \define{subsection menu:[Title,Subsection] attr:[Justification LeftJustified Point 0] attr:[FontSize PreviousFontSize Point 4]} \define{paragraph menu:[Title,Paragraph] attr:[Justification LeftJustified Point 0] attr:[FontSize PreviousFontSize Point 4]} \define{bigger menu:[Font,Bigger] attr:[FontSize PreviousFontSize Point 2]} \define{indent menu:[Region,Indent] attr:[LeftMargin LeftMargin Inch 32768] attr:[RightMargin RightMargin Inch 32768]} \define{typewriter menu:[Font,Typewriter] attr:[FontFace FixedFace Int Set] attr:[FontFamily AndyType Int 0]} \define{display menu:[Region,Display] attr:[LeftMargin LeftMargin Inch 32768] attr:[RightMargin RightMargin Inch 32768] attr:[Justification LeftJustified Point 0]} \define{example menu:[Region,Example] attr:[LeftMargin LeftMargin Inch 32768] attr:[Justification LeftJustified Point 0] attr:[FontFace FixedFace Int Set] attr:[FontFamily AndyType Int 0]} \define{description menu:[Region,Description] attr:[LeftMargin LeftMargin Inch 32768] attr:[Indent LeftEdge Inch -32768]} \define{quotation menu:[Region,Quotation] attr:[LeftMargin LeftMargin Inch 32768] attr:[RightMargin RightMargin Inch 32768] attr:[FontFace Italic Int Set]} \define{subscript menu:[Font,Subscript] attr:[Script PreviousScriptMovement Point 131072] attr:[FontSize PreviousFontSize Point -2]} \define{superscript menu:[Font,Superscript] attr:[Script PreviousScriptMovement Point -393216] attr:[FontSize PreviousFontSize Point -2]} \define{smaller menu:[Font,Smaller] attr:[FontSize PreviousFontSize Point -2]} \define{heading menu:[Title,Heading] attr:[LeftMargin LeftMargin Inch -13107] attr:[Justification LeftJustified Point 0] attr:[FontFace Bold Int Set]} \define{majorheading menu:[Title,MajorHeading] attr:[Justification Centered Point 0] attr:[FontSize PreviousFontSize Point 4]} \define{formatnote menu:[Region,FormatNote] attr:[Flags PassThru Int Set]} \define{subheading menu:[Title,Subheading] attr:[Justification LeftJustified Point 0] attr:[FontFace Bold Int Set]} \define{center menu:[Justify,Center] attr:[Justification Centered Point 0]} \define{flushleft menu:[Justify,FlushLeft] attr:[Justification LeftJustified Point 0]} \define{flushright menu:[Justify,FlushRight] attr:[Justification RightJustified Point 0]} \define{leftindent menu:[Region,LeftIndent] attr:[LeftMargin LeftMargin Inch 32768]} \define{article menu:[Title,Article] attr:[Justification Centered Point 0] attr:[FontSize ConstantFontSize Point 24]} \define{subpara menu:[Title,Subpara] attr:[Justification LeftJustified Point 0] attr:[FontFace Bold Int Set]} \define{subsubpara menu:[Title,Subsubpara] attr:[Justification LeftJustified Point 0] attr:[FontFace Italic Int Set]} \define{struct menu:[Region,struct] attr:[Justification LeftJustified Point 0] attr:[FontFace FixedFace Int Set] attr:[FontFamily AndyType Int 0] attr:[FontSize PreviousFontSize Point -4]} \define{boldtype menu:[Font,BoldType] attr:[FontFace Bold Int Set] attr:[FontFace FixedFace Int Set] attr:[FontFamily AndyType Int 0]} \subsection{ Kernel Support } \paragraph{Overview} The primary components of the Andrew File System, the Andrew File Manager and the Andrew Cache Manager are both written as user level code on top of BSD UNIX. Several kernel modifications were required to support this code. The modifications can be divided into two groups: the inode access facilities allow both the cache and file managers to directly access inodes on a UNIX file system partition, without having to go through an expensive UNIX pathname lookup, and the system call interface "hooks" allow the cache manager to trap requests directed to the Andrew File System, while retaining object compatibility of executable programs. \paragraph{Inode Access Facilities} The inode access facilities, which are restricted to programs running with an effective userid of root, comprise the new system calls \italic{icreate(2v), iopen(2v), iread(2v), iwrite(2v),} and \italic{iinc/idec(2v)}, together with a modified version of the file system consistency check program, \italic{vfsck(8v)}. These system calls allow UNIX inodes to be accessed independently of the UNIX file name space, resulting in very fast access to files. The complete specifications for each call are found with the appropriate manual entry. The \italic{icreate} call is used to allocate an inode on a specified disk partition. Any inode so allocated will be subject to deletion by the standard file system consistency check program. If \italic{icreate} is used, therefore, it is mandatory that \italic{vfsck} be used instead of the standard program. Each inode is stamped with four user supplied parameters, which are used by the \italic{vol-salvage(8v)} program to verify the integrity of a file system built with inodes allocated in this manner. Inodes allocated by icreate may be accessed by the system calls \italic{iopen, iread, iinc,} and \italic{idec.} The \italic{iopen} call may be used to open an inode for reading or writing. The inode must either have been allocated with \italic{icreate} or have a group id of -2. The latter approach is used by the cache manager, the workstation component of the file system, to access files in its cache. Each file exists in the file system with a known name but this name is not normally used for routine cache accesses. \italic{Iopen} is the only call in this group that the Andrew Cache Manager uses. \italic{Iread} and \italic{iwrite} may be used to read and write to inodes created by \italic{icreate} without having to maintain a file descriptor for the inodes. In addition, this call is protected somewhat because the kernel requires one of the parameters in the inode to be supplied by the caller. This is used by the file manager to prevent accidental inode writes to the wrong volume (the first parameter stamped in the inode is the Andrew File System volume number). \italic{Iinc} and \italic{idec} allow the link count of an inode allocated by icreate to be raised or lowered. This is used by the Andrew File Manager to implement cloned volumes--an inode that is used by two volumes will have a link count of two. If the inode link counted is decremented to 0, the inode will be deallocated. \italic{Vfsck} is the modified version of the standard file system consistency check program. It is only necessary if icreate is used and the inodes allocated by icreate are expected to remain in the UNIX partition. It is not needed on workstations, since the Andrew Cache Manager does not use icreate. If \italic{vfsck} is used on an Andrew File System partition, then \italic{vol-salvage(8v)} should also be run. \paragraph{System Call Intercept} This section is obsolete. The cache manager now uses the Sun VNODE interface.\ \enddata{text,268919564}