Sprite 1984 - 1993/Sprite 1984 - 1993.iso/man/lib/misc/Disk.man

Text File | 1992-08-31 | 15.1 KB | 362 lines

'\" Copyright 1989 Regents of the University of California
'\" Permission to use, copy, modify, and distribute this
'\" documentation for any purpose and without fee is hereby
'\" granted, provided that this notice appears in all copies.
'\" The University of California makes no representations about
'\" the suitability of this material for any purpose.  It is
'\" provided "as is" without express or implied warranty.
'\"
'\" $Header: /sprite/src/lib/disk/RCS/Disk.man,v 1.8 92/08/31 12:20:45 voelker Exp $ SPRITE (Berkeley)
'/"
.so \*(]ltmac.sprite
.HS Disk lib
.BS
.SH NAME
.VS
Disk_ReadLabel, Disk_WriteLabel, Disk_EraseLabel, Disk_NewLabel, Disk_ReadDecLabel, Disk_WriteDecLabel, Disk_ReadSunLabel,  Disk_WriteSunLabel, Disk_HasFilesystem, Disk_ReadLfsSuperBlock, Disk_WriteLfsSuperBlock, Disk_ReadLfsCheckpointHdr, Disk_WriteLfsCheckPointHdr, Disk_WriteLfsCheckPointArea, Disk_LfsCheckpointTrailer, Disk_ForEachCheckpointRegion, Disk_ReadDomainHeader, Disk_WriteDomainHeader, Disk_ReadSummaryInfo, Disk_WriteSummaryInfo, Disk_SectorRead, Disk_SectorWrite, Disk_BlockRead, Disk_BlockWrite, Disk_BadBlockRead, Disk_FragRead, Disk_FragWrite, Disk_PrintDomainHeader, Disk_PrintSummaryInfo, Disk_PrintFileDescBitmap, Disk_PrintDataBlockBitmap, Disk_PrintDirEntry, Disk_PrintLabel, Disk_PrintLfsSuperBlock, Disk_PrintLfsSuperBlockHdr, Disk_PrintLfsDescMapParams, Disk_PrintLfsSegUsageParams, Disk_PrintLfsFileLayoutParams, Disk_PrintLfsStableMemParams, Disk_PrintLfsCheckpointHdr, Disk_PrintLfsCheckpointRegion, Disk_PrintLfsCheckpointTrailer
\- Package for accessing OFS and LFS file systems via raw disks
.VE
.SH SYNOPSIS
.nf
.VS
#include <disk.h>
.VE
.VS
Disk_Label *
\fBDisk_ReadLabel\fR(\fIfileID\fR)
int
\fBDisk_WriteLabel\fR(\fIfileID, labelPtr\fR)
Disk_Label *
\fBDisk_NewLabel\fR(\fIlabelType\fR)
int
\fBDisk_EraseLabel\fR(\fIfileID, labelType\fR)
.VE
.VS
Dec_DiskLabel *
\fBDisk_ReadDecLabel\fR(\fIfileID\fR)
int
\fBDisk_WriteDecLabel\fR(\fIfileID, decLabelPtr\fR)
.VE
Sun_DiskLabel *
\fBDisk_ReadSunLabel\fR(\fIfileID\fR)
.VS
int
\fBDisk_WriteSunLabel\fR(\fIfileID, sunLabelPtr\fR)
.VE
.VS
Ofs_DomainHeader *
\fBDisk_ReadDomainHeader\fR(\fIfileID, labelPtr\fR)
int
\fBDisk_WriteDomainHeader\fR(\fIfileID, labelPtr, headerPtr\fR)
.VS
Ofs_SummaryInfo *
\fBDisk_ReadSummaryInfo\fR(\fIfileID, labelPtr\fR)
int
\fBDisk_WriteSummaryInfo\fR(\fIfileID, labelPtr, summaryPtr\fR)
.VE
.VE
int
\fBDisk_SectorRead\fR(\fIfileID, index, count, buffer\fR)
int
\fBDisk_SectorWrite\fR(\fIfileID, index, count, buffer\fR)
int
\fBDisk_BlockRead\fR(\fIfileID, headerPtr, index, count, buffer\fR)
int
\fBDisk_BlockWrite\fR(\fIfileID, headerPtr, index, count, buffer\fR)
int
\fBDisk_BadBlockRead\fR(\fIfileID, headerPtr, index, buffer\fR)
int
\fBDisk_FragRead\fR(\fIfileID, headerPtr, index, count, buffer\fR)
int
\fBDisk_FragWrite\fR(\fIfileID, headerPtr, index, count, buffer\fR)
void
\fBDisk_PrintDomainHeader\fR(\fIheaderPtr\fR)
void
\fBDisk_PrintSummaryInfo\fR(\fIsummaryPtr\fR)
.VS
\fBDisk_PrintLabel\fR(\fIlabelPtr\fR)
.VE
void
\fBDisk_PrintFileDescBitmap\fR(\fIheaderPtr, bitmap\fR)
void
\fBDisk_PrintDataBlockBitmap\fR(\fIheaderPtr, bitmap\fR)
void
\fBDisk_PrintDirEntry\fR(\fIdirEntryPtr\fR)
.VS
int
\fBDisk_HasFilesystem\fR(\fIfileID, labelptr\fR)
LfsSuperBlock*
\fBDisk_ReadLfsSuperBlock\fR(\fIfileId, labelPtr\fR)
ReturnStatus
\fBDisk_WriteLfsSuperBlock\fR(\fIfileId, lfsSuperPtr\fR)
LfsCheckPointHdr*
\fBDisk_ReadLfsCheckPointHdr\fR(\fIfileId, labelPtr, areaPtr\fR)
ReturnStatus
\fBDisk_WriteLfsCheckPointHdr\fR(\fIfileId, headerPtr, area, labelPtr\fR)
ReturnStatus
\fBDisk_WriteLfsCheckPointArea\fR(\fIfileId, headerPtr, area, labelPtr\fR)
LfsCheckPointTrailer*
\fBDisk_LfsCheckPointTrailer\fR(\fIcheckPointHdrPtr\fR)
ReturnStatus
\fBDisk_ForEachCheckPointRegion\fR(\fIcheckPointHdrPtr, regionProc\fR)
void
\fBDisk_PrintLfsSuperBlockHdr\fR(\fIlfsSuperHdrPtr\fR)
void
\fBDisk_PrintLfsStableMemParams\fR(\fIstableMemPtr\fR)
void
\fBDisk_PrintLfsDescMapParams\fR(\fIdescMapPtr\fR)
void
\fBDisk_PrintLfsSegUsageParams\fR(\fIsegUsagePtr\fR)
void
\fBDisk_PrintLfsFileLayoutParams\fR(\fIfileLayoutPtr\fR)
void
\fBDisk_PrintLfsSuperBlock\fR(\fIlfsSuperPtr\fR)
void
\fBDisk_PrintLfsCheckPointHdr\fR(\fIcheckPointHdr\fR)
void
\fBDisk_PrintLfsCheckPointRegion\fR(\fIregionPtr\fR)
void
\fBDisk_PrintLfsCheckPointTrailer\fR(\fItrailerPtr\fR)
.VE
.SH ARGUMENTS
.AS Ofs_DomainHeader blockNumber
.AP int fileID in
File descriptor from \fBopen\fP of raw disk.
.AP int partition in
Index of partition to access, 0-7.
.VS
.AP Disk_Label *labelPtr in
Basic disk information from \fBDisk_ReadLabel\fP.
.AP Disk_NativeLabelType labelType in
Type of machine-specific (native) disk label on the disk.
.AP Dec_DiskLabel *decLabelPtr
Native disk label for ds3100s.
.AP Sun_DiskLabel *sunLabelPtr
Native disk label for Suns.
.VE
.AP int index in
Index of first (sector/block/fragment) to transfer.
.AP int count in
Number of (sectors/blocks/fragments) to transfer.
.AP char *buffer in
Buffer for data transferred.
.AP Ofs_DomainHeader *headerPtr in
Disk header information from \fBDisk_ReadDiskHeader\fP.
.AP Ofs_SummaryInfo *summaryPtr in
Disk summary information sector.
.AP char *bitmap in
Array of bitmap bytes.
.AP Fslcl_DirEntry *dirEntryPtr in
Directory entry structure.
.AP LfsSuperBlock *lfsSuperPtr in
LFS Super Block structure.
.AP LfsSuperBlockHdr *lfsSuperHdrPtr in
Static parameters describing LFS layout on disk.
.AP LfsCheckPointHdr *checkPointHdrPtr in
Structure describing and heading a LFS checkpoint area.
.AP int areaPtr out
If non-NULL, returns the checkpoint the header is for.
.AP int area in
Flag determining the checkpoint area (0 or 1).
.AP LfsCheckPointTrailer *trailerPtr in
Structure capping a LFS checkpoinit area.
.AP int\ proc(LfsCheckPointRegion*) regionProc in
Procedure used to iterate over the various checkpoint regions
between the lfsCheckPointHdr and the lfsChecpointTrailer.
.AP LfsStableMemParams *stableMemPtr in
Configuration parameters for stable memory data structures.
.AP LfsDescMapParams *descMapPtr in
LFS descriptor map layout on disk.
.AP LfsSegUsageParams *segUsagePtr in
LFS segment usage array layout description on disk.
.AP LfsFileLayoutParams *fileLayoutPtr in
Number of file descriptors to pack together per block.
.BE

.SH INTRODUCTION
.PP
The \fBDisk\fP package is used to read and write raw disks that
are formatted to contain Sprite file systems.  To use these routines correctly
it is important to understand disk \fIpartitions\fP,
file system \fIheader information\fP,
file system \fIblocks\fP, and file system block \fIfragments\fP.
.PP
Each physical disk is divided into as many as 8 partitions.
The letters 'a' through 'h' are used to distinguish these different
partitions in the names of the special device files that are
used to access them.  Thus ``/dev/rsd0a'' references the first (zero'th)
partition on disk \fBrsd0\fP.
.VS
The partitioning information is stored on the disk in the
``disk label''.
This label is in a machine-dependent format, and is referred to as
the ``native disk label''.
Native disk labels are kept in a machine-dependent
location on the disk.
This is usually in sector 0 or some other sector near
the start of the first partition.
The
\fBfsmake\fP program also
copies the label to a partition when it formats
it into a file system.
The routines \fBDisk_ReadSunLabel\fP and \fBDisk_ReadDecLabel\fP
can be used to read the native disk labels.
.PP
It is not always convenient to deal with native disk labels.
For this reason a generic label type and associated routines have been
provided.
The type \fBDisk_Label\fR is a standard format for disk labels.
The routine \fBDisk_ReadLabel\fR is used to read a native disk label
off the disk and convert it into a \fBDisk_Label\fR.
The routine \fBDisk_WriteLabel\fR will convert a \fBDisk_Label\fR
into a native disk label and write it on the disk.
Two more procedures are provided for manipulating disk labels.
\fBDisk_EraseLabel\fR will erase a native disk label from the disk,
and \fBDisk_NewLabel\fR is used to create a new label if the disk does not
have one already.
The contents of a \fBDisk_Label\fR are defined in <disk.h>.
.VE
.PP
\fBDisk_HasFilesystem\fR returns the type of file system on the
disk.  If the disk has a LFS file system, DISK_HAS_LFS is returned;
if the disk has an OFS file system, DISK_HAS_OFS is returned;
otherwise, DISK_HAS_NO_FS is returned.
.PP
The detailed structure of the old sprite file system is defined by a
Ofs_DomainHeader structure that is located on the disk according to the
\fBDisk_Label\fP.  This can be obtained with the
\fBDisk_ReadDomainHeader\fP procedure.  The Ofs_DomainHeader structure
is defined in <kernel/fsdm.h>, and is passed to the block and fragment
I/O routines so they can correctly locate blocks and fragments.
.PP
.VS
A secondary data structure called the summary information is kept on disk
following the domain header.
The summary information consists of a single sector and contains such
information as the number of free blocks and file descriptors.
The Ofs_SummaryInfo structure is defined in <kernel/fsdm.h>.
The location of the summary sector is stored in the \fBDisk_Label\fR.
The summary sector can be read and written using the
\fBDisk_ReadSummaryInfo\fR and \fBDisk_WriteSummaryInfo\fR procedures.
.PP
The detailed structure of a log structured file system is defined
by a LfsSuperBlock structure whose location on disk is determined
in <kernel/lfsSuperBlock.h>.  This structure can be read off of
a disk using \fBDisk_ReadLfsSuperBlock\fR, and written using
\fBDisk_WriteSuperBlock\fR.
.PP
\fBDisk_ReadLfsCheckpointHdr\fR returns the current LFS checkpoint
header, which is also a front for the current checkpoint area
whose bulk is hidden behind the \fBLfsCheckPointHdr\fR. If \fBareaPtr\fR
is non-NULL, the area number that the header is for gets returned
through the pointer.  (The area can be either zero or one, and only
makes a difference if the checkpoint header is going to be written
back out to disk.)
\fBDisk_CheckPointTrailer\fR accesses the tail of the checkpoint
area from a \fBLfsCheckPointHdr\fR returned from
\fBDisk_ReadLfsCheckPointHdr\fR. \fBDisk_WriteLfsCheckPointHdr\fR
will write to disk only the \fBLfsCheckPointHdr\fR structure of the
specified checkpoint area; \fBDisk_WriteLfsCheckPointArea\fR will
write to disk the entire checkpoint area headed by a \fBLfsCheckPointHdr\fR,
which is larger than just the structure itself (such as is returned
by \fBDisk_ReadLfsCheckPointHdr\fR).
\fBDisk_ForEachCheckPointRegions\fR takes a procedural argument
and iterates over the \fBLfsCheckPointRegions\fR in the checkpoint area
headed by a \fBLfsCheckPointHdr\fR, applying the procedural argument to
every region in the checkpoint area.  If the procedure returns a
non-zero value, then the iteration halts and that value is returned
from \fBDisk_ForEachCheckPointRegion\fR.
.SH "SECTOR I/O"
.PP
\fBDisk_SectorRead\fP and \fBDisk_SectorWrite\fP read and write sectors
from the disk without regard to the underlying block structure.  Their
\fIindex\fP argument specifies the first sector (starting from zero)
to transfer, relative to the start of the partition.  The sector
offsets given in the \fBDisk_Label\fP structure are useful with
this routine.
.SH "BLOCK I/O"
.PP
The file system is arranged in block-sized chunks on the disk.
\fBFS_BLOCK_SIZE\fP defines how many bytes this is (currently 4 Kbytes).
Due to disk geometry considerations consecutive blocks may or may not
be contiguous on disk.  \fBDisk_BlockRead\fP and \fBDisk_BlockWrite\fP
use geometry and block layout information in the Ofs_DomainHeader to
correctly locate disk blocks.  The \fIindex\fP argument to these routines
is a block index, counting from the beginning of the partition
(see the warning below!).
.PP
\fBDisk_BadBlockRead\fP is used to re-read a bad file system block and
determine which sectors are bad.  It returns a bitmask with bits
set to indicate which of the sectors were successfully read.
Bit \fIi\fP in the mask corresponds
to sector \fIi\fP in the block.  \fBDISK_SECTORS_PER_BLOCK\fP defines
how many sector there are in each file system block.
.SH "FRAGMENT I/O"
.PP
Each file system block is sub-divided into fragments to optimize allocation
of small files.  Currently the fragment size is 1 Kbyte, so there are
4 fragments to each block.
\fBDisk_FragRead\fP and \fBDisk_FragWrite\fP
are used to read and write fragments.
The \fIindex\fP argument to these routines
is a fragment index, counting from the beginning of the partition
(see the warning below!).  The \fIcount\fP argument to these routines
should not be greater than the number of fragments per file system block.
.SH "BLOCK AND FRAGMENT INDEXES"
\fBWARNING:\fP there are several caveats about block numbers and
fragment numbers as used by the Sprite file system.
A partition is divided into areas for bitmaps, file descriptors,
and data blocks.  These divisions are specified in the Ofs_DomainHeader
structure in terms of block offsets and number of blocks.
However, \fIblock numbers are not kept in disk maps, only fragment numbers\fP.
When traversing the direct and indirect blocks that define where
a file's blocks are, fragment indexes must be converted to block
indexes before using either \fBDisk_BlockRead\fP or \fBDisk_BlockWrite\fP.
Also, \fIdirect block pointers in the maps are fragment indexes
relative to the start of the data block area of the file system\fP.
Thus to convert from a direct block pointer to a physical fragment index:
.DS
fragIndex = blockPointer + (headerPtr->dataOffset * FS_FRAGMENTS_PER_BLOCK);
blockIndex = fragIndex / FS_FRAGMENTS_PER_BLOCK;
.DE
.PP
The last main caveat is that \fIindirect block pointers are
physical fragment indexes\fP.  They do not need to be offset in the
same way as direct block pointers.  This applies to any block pointer
that points to an indirect block, never to a block pointer that points
to a data block.
.SH "PRINTING UTILITIES"
.PP
The last set of procedures in this package are used to print
out contents of the file system.  \fBDisk_PrintDomainHeader\fP
prints out the domain header information.
\fBDisk_PrintSummaryInfo\fP prints out the summary disk sector.
This sector is used to keep the prefix under which the disk is
exported, the current number of blocks allocated and free,
and whether or not the disk was safely sync'ed at last reboot.
\fBDisk_PrintFileDescBitmap\fP and \fPDisk_PrintDataBlockBitmap\fP
print out the file descriptor and data block bitmaps in hex.
A zero bit represents a free descriptor or block.
\fBDisk_PrintDirEntry\fP prints out a directory entry.
\fBDisk_PrintLfsSuperBlock\fP prints out the contents of a
LFS Super Block structure.
\fBDisk_PrintLfsSuperBlockHdr\fP prints out the
static parameters describing the LFS layout on disk.
\fBDisk_PrintLfsCheckPointHdr\fP prints out the
structure describing and heading a LFS checkpoint area.
\fBDisk_PrintLfsCheckPointTrailer\fP prints out the
structure capping a LFS checkpoinit area.
\fBDisk_PrintLfsStableMemParams\fP prints out the
configuration parameters for LFS stable memory data structures.
\fBDisk_PrintLfsDescMapParams\fP prints out the
LFS descriptor map layout on disk.
\fBDisk_PrintLfsSegUsageParams\fP prints out the
LFS segment usage array layout description on disk.
\fBDisk_PrintLfsFileLayoutParams\fP prints out the
number of file descriptors packed together per block.
.SH SEE ALSO
fscheck, fsmake, labeldisk, installboot
.SH KEYWORDS
disk, block, sector, fragment