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NAMEfs (vxfs) — format of VxFS file system volume SYNOPSIS#include <sys/param.h>
#include <sys/kern_sem.h>
#include <sys/fs/vx_hpux.h>
#include <sys/fs/vx_port.h>
#include <sys/fs/vx_inode.h>
#include <sys/fs/vx_fs.h> DESCRIPTIONThe
vxfs
super-block always begins at byte offset 8192
from the start of the file system.
The super-block location is fixed
so utilities know where to look for it. The super-block contains the following
fundamental sizes and offsets:
- fs_magic
The magic number for the file system
(VX_MAGIC).
This number identifies the file system as being a
vxfs
FSType. - fs_version
The version number of the file system layout
(VX_VERSION).
This is currently 2 for the
vxfs
Version 2 disk layout
and 3 for the Version 3 layout. - fs_ctime
The creation date of the file system.
The
time(2)
system call supplies the time. - fs_ectime
This field is a placeholder
in instances when the creation date for a file system
is expanded for more precision.
It currently is zero. - fs_logstart
The block address of the first Log Area block.
It currently is two. - fs_logend
The block address of the last Log Area block.
The Log Area size in blocks
may be specified as part of
mkfs(1M).
If not specified,
a default of 512 blocks is used.
A minimum size of 32 blocks is enforced.
For smaller file systems,
the default is reduced to avoid wasting space. - fs_bsize
The block size of the file system.
The current choices are 1024, 2048, 4096, and 8192 bytes. - fs_size
The number of blocks in the file system,
expressed as the number of blocks of size
fs_bsize.
The
fs_size
field is a signed 32 bit number.
The maximum number of blocks in a
vxfs
file system is limited to 31 bits. - fs_dsize
The number of data blocks in the file system.
A data block is a block which may be allocated
to a file in the file system. - fs_ninode
The number of inodes
in the file system allocation units.
For Version 2 or Version 3 layout file systems,
this field is 0. - fs_nau
The number of allocation units in the file system.
The number of allocation units may be specified as part of
mkfs(1M). - fs_defiextsize
The default size for indirect data extents,
expressed in blocks.
This field is currently set to 64 by default. - fs_oilbsize
The size of an old inode list block,
expressed in bytes.
For Version 2 and 3 layouts,
this is initialized to 0 and not used. - fs_immedlen
The size, in bytes,
of the immediate data area in each inode.
This value is 96 for the
vxfs
file system. - fs_ndaddr
The number of direct extents supported by the
VX_EXT4
mapping type
(see the section describing inode list).
This value is 10 for the
vxfs
file system.
The preceding fields define the size and makeup of the file system.
To reduce the calculations required in utilities,
a number of values are derived from the fundamental values
and placed in the super-block. The super-block contains the following derived offsets:
- fs_aufirst
The address, in blocks,
of the first allocation unit.
There can be a gap
between the end of the intent log
and the first allocation unit.
This gap could be used
to align the first allocation unit
on a desired boundary. - fs_emap
The offset in blocks
of the free extent map
(emap)
from the start of an allocation unit. - fs_imap
The offset in blocks
of the free inode map
(imap)
from the start of an allocation unit. - fs_iextop
The offset in blocks
of the extended inode operation map
from the start of an allocation unit.
For Version 2 and 3 layouts,
this is initialized to 0 and not used. - fs_istart
The offset in blocks
of the inode list
(ilist)
from the start of an allocation unit.
For Version 2 and 3 layouts,
this is initialized to 0 and not used. - fs_bstart
The offset in blocks
of the first data block
from the start of an allocation unit.
An allocation unit header may contain padding
to align the first data block. - fs_femap
The offset in blocks
of the first free extent map
(emap)
from the start of the file system. - fs_fimap
The offset in blocks
of the first free inode map
(imap)
from the start of the file system. - fs_fiextop
The offset in blocks
of the first extended inode operation map
from the start of the file system.
For Version 2 and 3 layouts,
this is initialized to 0 and not used. - fs_fistart
The offset in blocks
of the first ilist
from the start of the file system.
For Version 2 and 3 layouts,
this is initialized to 0 and not used. - fs_fbstart
The offset in blocks
of the first data block
from the start of the file system. - fs_nindir
The number of entries
in an indirect address extent.
An indirect address extent
is currently 8192 bytes in length,
making the current value for
fs_nindir
2048. - fs_aulen
The length of an allocation unit in blocks. - fs_auimlen
The length of a free inode map in blocks.
For Version 2 and 3 layouts,
this is initialized to 0 and not used. - fs_auemlen
The length of a free extent map in blocks. - fs_auilen
The length, in blocks,
of the inode list for this allocation unit.
For Version 2 and 3 layouts,
this is initialized to 0 and not used. - fs_aupad
The length, in blocks,
of the allocation unit alignment padding. - fs_aublocks
The number of data blocks in an allocation unit. - fs_maxtier
The log base 2 of
fs_aublocks. - fs_inopb
The number of inode entries per
fs_bsize
block in the inode list.
The
vxfs
inode is currently 256 bytes long. - fs_inopau
The number of inodes in an allocation unit. - fs_inopilb
The number of inode entries per
fs_oilbsize
block in the inode list.
For Version 2 and 3 layouts,
this field is obsolete. - fs_ndiripau
Expected number of directory inodes per allocation unit.
For Version 2 and 3 layouts,
this is initialized to 0 and not used. - fs_iaddrlen
The size, in blocks,
of an indirect address block.
An indirect address block is 8K bytes.
This field will be set to (8K /
fs_bsize). - fs_bshift
The log base 2 of
fs_bsize.
Used to convert a byte offset
into a block offset. - fs_inoshift
The log base 2 of
fs_inopb.
Used to convert an inode number
into a block offset in the inode list. - fs_bmask
A mask value such that
(byte_offset
&
fs_bmask)
rounds the offset
to the nearest smaller block boundary. - fs_boffmask
A mask value such that
(byte_offset
&
fs_boffmask)
yields the offset
from the start of the nearest smaller block boundary. - fs_inomask
A mask value such that
(inode_number
&
fs_inomask)
yields the offset
from the start of the containing inode list block
of the corresponding inode list entry.
For Version 2 and 3 layouts,
this field is obsolete. - fs_checksum
A simple checksum of the above fields.
A macro,
VX_FSCHECKSUM
is provided to verify or calculate the checksum.
The above fields are initialized
when the file system is created
and do not change unless the file system is resized.
These fields are replicated
in each allocation unit header. There are additional fields
which are considered to be dynamic:
- fs_free
The current number of free data blocks. - fs_ifree
The current number of free inodes.
For Version 2 and 3 layouts,
a separate free inode count is kept
for each fileset;
this is initialized to 0 and is not used. - fs_efree
An array of the current number of free extents
of each extent size in the file system. - fs_flags
The following flags are recognized:
- VX_FULLFSCK
Set when a file system
requires a full structural check
to recover from an error.
If this flag is set,
a full check will be performed
after the replay recovery is finished. - VX_NOLOG
Set when the file system
was mounted with the
VX_MS_NOLOG
option.
If this flag is set,
then no log replay recovery
will be performed. - VX_LOGBAD
Set when an I/O error has invalidated the log.
If this flag is set,
then no log replay recovery will be performed. - VX_LOGRESET
Set when the log ID runs over
VX_MAXLOGID
(2^30).
The log ID will be reset
at the next appropriate opportunity
(such as a mount or 60-second sync). - VX_RESIZE
Set when a file system resizing is in progress.
If an
fsck(1M)
sees this flag,
it will have to perform resize recovery.
Refer to
fsadm(1M)
for a description of file system expansion. - VX_UPGRADING
Set when a file system upgrade is in progress.
If an
fsck(1M)
sees this flag,
it will have to perform upgrade recovery.
- fs_mod
Set whenever a mounted file system is modified.
It is used to indicate
if the super-block needs to be written when a
sync
operation is performed. - fs_clean
Set to
VX_DIRTY
when a file system is mounted
for read/write access.
Set to
VX_CLEAN
upon
umount
or successful
fsck(1M).
The file system cannot be mounted
for read/write access
unless the
fs_clean
field is
VX_CLEAN. - fs_reserved
Reserved for future use. - fs_firstlogid
Initial log ID to use
when the file system is mounted. - fs_time
Last time the super-block
was written to disk,
indicated as the number of seconds
that have elapsed since 00:00 January 1, 1970. - fs_fname
File system name (6 characters). - fs_fpack
File system pack label (6 characters). - fs_logversion
The version number of the log format.
This field is set by the kernel on each mount
to ensure that an
fsck(1M)
running log replay
understands the log format written by the kernel. The log format may change with each release,
so all file systems should be clean
before upgrading to a new release.
The read-only area
that supports the
vxfs
Version 2 layout
has the following fields:
- fs_oltext
This is an array of two extent addresses.
These extent addresses
point to the two replicated copies
of the first object location table extent. - fs_oltsize
This is the size, in blocks,
of the object location table extents
pointed to by
fs_oltext. - fs_iauimlen
The length, in blocks,
of a free inode map
in an inode allocation unit. - fs_iausize
The size, in blocks,
of an inode allocation unit. - fs_dinosize
The size, in bytes,
of a disk inode.
This is currently 256 bytes. - fs_checksum2
This is a checksum of the fields
specific to the Version 2 layout.
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