mirror of
https://github.com/edk2-porting/linux-next.git
synced 2024-12-25 05:34:00 +08:00
0e4fb5e283
If the journal doesn't abort when it gets an IO error in file data blocks, the file data corruption will spread silently. Because most of applications and commands do buffered writes without fsync(), they don't notice the IO error. It's scary for mission critical systems. On the other hand, if the journal aborts whenever it gets an IO error in file data blocks, the system will easily become inoperable. So this patch introduces a filesystem option to determine whether it aborts the journal or just call printk() when it gets an IO error in file data. If you mount a ext3 fs with data_err=abort option, it aborts on file data write error. If you mount it with data_err=ignore, it doesn't abort, just call printk(). data_err=ignore is the default. Signed-off-by: Hidehiro Kawai <hidehiro.kawai.ez@hitachi.com> Cc: Jan Kara <jack@ucw.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
203 lines
6.8 KiB
Plaintext
203 lines
6.8 KiB
Plaintext
|
|
Ext3 Filesystem
|
|
===============
|
|
|
|
Ext3 was originally released in September 1999. Written by Stephen Tweedie
|
|
for the 2.2 branch, and ported to 2.4 kernels by Peter Braam, Andreas Dilger,
|
|
Andrew Morton, Alexander Viro, Ted Ts'o and Stephen Tweedie.
|
|
|
|
Ext3 is the ext2 filesystem enhanced with journalling capabilities.
|
|
|
|
Options
|
|
=======
|
|
|
|
When mounting an ext3 filesystem, the following option are accepted:
|
|
(*) == default
|
|
|
|
journal=update Update the ext3 file system's journal to the current
|
|
format.
|
|
|
|
journal=inum When a journal already exists, this option is ignored.
|
|
Otherwise, it specifies the number of the inode which
|
|
will represent the ext3 file system's journal file.
|
|
|
|
journal_dev=devnum When the external journal device's major/minor numbers
|
|
have changed, this option allows the user to specify
|
|
the new journal location. The journal device is
|
|
identified through its new major/minor numbers encoded
|
|
in devnum.
|
|
|
|
noload Don't load the journal on mounting.
|
|
|
|
data=journal All data are committed into the journal prior to being
|
|
written into the main file system.
|
|
|
|
data=ordered (*) All data are forced directly out to the main file
|
|
system prior to its metadata being committed to the
|
|
journal.
|
|
|
|
data=writeback Data ordering is not preserved, data may be written
|
|
into the main file system after its metadata has been
|
|
committed to the journal.
|
|
|
|
commit=nrsec (*) Ext3 can be told to sync all its data and metadata
|
|
every 'nrsec' seconds. The default value is 5 seconds.
|
|
This means that if you lose your power, you will lose
|
|
as much as the latest 5 seconds of work (your
|
|
filesystem will not be damaged though, thanks to the
|
|
journaling). This default value (or any low value)
|
|
will hurt performance, but it's good for data-safety.
|
|
Setting it to 0 will have the same effect as leaving
|
|
it at the default (5 seconds).
|
|
Setting it to very large values will improve
|
|
performance.
|
|
|
|
barrier=1 This enables/disables barriers. barrier=0 disables
|
|
it, barrier=1 enables it.
|
|
|
|
orlov (*) This enables the new Orlov block allocator. It is
|
|
enabled by default.
|
|
|
|
oldalloc This disables the Orlov block allocator and enables
|
|
the old block allocator. Orlov should have better
|
|
performance - we'd like to get some feedback if it's
|
|
the contrary for you.
|
|
|
|
user_xattr Enables Extended User Attributes. Additionally, you
|
|
need to have extended attribute support enabled in the
|
|
kernel configuration (CONFIG_EXT3_FS_XATTR). See the
|
|
attr(5) manual page and http://acl.bestbits.at/ to
|
|
learn more about extended attributes.
|
|
|
|
nouser_xattr Disables Extended User Attributes.
|
|
|
|
acl Enables POSIX Access Control Lists support.
|
|
Additionally, you need to have ACL support enabled in
|
|
the kernel configuration (CONFIG_EXT3_FS_POSIX_ACL).
|
|
See the acl(5) manual page and http://acl.bestbits.at/
|
|
for more information.
|
|
|
|
noacl This option disables POSIX Access Control List
|
|
support.
|
|
|
|
reservation
|
|
|
|
noreservation
|
|
|
|
bsddf (*) Make 'df' act like BSD.
|
|
minixdf Make 'df' act like Minix.
|
|
|
|
check=none Don't do extra checking of bitmaps on mount.
|
|
nocheck
|
|
|
|
debug Extra debugging information is sent to syslog.
|
|
|
|
errors=remount-ro(*) Remount the filesystem read-only on an error.
|
|
errors=continue Keep going on a filesystem error.
|
|
errors=panic Panic and halt the machine if an error occurs.
|
|
|
|
data_err=ignore(*) Just print an error message if an error occurs
|
|
in a file data buffer in ordered mode.
|
|
data_err=abort Abort the journal if an error occurs in a file
|
|
data buffer in ordered mode.
|
|
|
|
grpid Give objects the same group ID as their creator.
|
|
bsdgroups
|
|
|
|
nogrpid (*) New objects have the group ID of their creator.
|
|
sysvgroups
|
|
|
|
resgid=n The group ID which may use the reserved blocks.
|
|
|
|
resuid=n The user ID which may use the reserved blocks.
|
|
|
|
sb=n Use alternate superblock at this location.
|
|
|
|
quota
|
|
noquota
|
|
grpquota
|
|
usrquota
|
|
|
|
bh (*) ext3 associates buffer heads to data pages to
|
|
nobh (a) cache disk block mapping information
|
|
(b) link pages into transaction to provide
|
|
ordering guarantees.
|
|
"bh" option forces use of buffer heads.
|
|
"nobh" option tries to avoid associating buffer
|
|
heads (supported only for "writeback" mode).
|
|
|
|
|
|
Specification
|
|
=============
|
|
Ext3 shares all disk implementation with the ext2 filesystem, and adds
|
|
transactions capabilities to ext2. Journaling is done by the Journaling Block
|
|
Device layer.
|
|
|
|
Journaling Block Device layer
|
|
-----------------------------
|
|
The Journaling Block Device layer (JBD) isn't ext3 specific. It was designed
|
|
to add journaling capabilities to a block device. The ext3 filesystem code
|
|
will inform the JBD of modifications it is performing (called a transaction).
|
|
The journal supports the transactions start and stop, and in case of a crash,
|
|
the journal can replay the transactions to quickly put the partition back into
|
|
a consistent state.
|
|
|
|
Handles represent a single atomic update to a filesystem. JBD can handle an
|
|
external journal on a block device.
|
|
|
|
Data Mode
|
|
---------
|
|
There are 3 different data modes:
|
|
|
|
* writeback mode
|
|
In data=writeback mode, ext3 does not journal data at all. This mode provides
|
|
a similar level of journaling as that of XFS, JFS, and ReiserFS in its default
|
|
mode - metadata journaling. A crash+recovery can cause incorrect data to
|
|
appear in files which were written shortly before the crash. This mode will
|
|
typically provide the best ext3 performance.
|
|
|
|
* ordered mode
|
|
In data=ordered mode, ext3 only officially journals metadata, but it logically
|
|
groups metadata and data blocks into a single unit called a transaction. When
|
|
it's time to write the new metadata out to disk, the associated data blocks
|
|
are written first. In general, this mode performs slightly slower than
|
|
writeback but significantly faster than journal mode.
|
|
|
|
* journal mode
|
|
data=journal mode provides full data and metadata journaling. All new data is
|
|
written to the journal first, and then to its final location.
|
|
In the event of a crash, the journal can be replayed, bringing both data and
|
|
metadata into a consistent state. This mode is the slowest except when data
|
|
needs to be read from and written to disk at the same time where it
|
|
outperforms all other modes.
|
|
|
|
Compatibility
|
|
-------------
|
|
|
|
Ext2 partitions can be easily convert to ext3, with `tune2fs -j <dev>`.
|
|
Ext3 is fully compatible with Ext2. Ext3 partitions can easily be mounted as
|
|
Ext2.
|
|
|
|
|
|
External Tools
|
|
==============
|
|
See manual pages to learn more.
|
|
|
|
tune2fs: create a ext3 journal on a ext2 partition with the -j flag.
|
|
mke2fs: create a ext3 partition with the -j flag.
|
|
debugfs: ext2 and ext3 file system debugger.
|
|
ext2online: online (mounted) ext2 and ext3 filesystem resizer
|
|
|
|
|
|
References
|
|
==========
|
|
|
|
kernel source: <file:fs/ext3/>
|
|
<file:fs/jbd/>
|
|
|
|
programs: http://e2fsprogs.sourceforge.net/
|
|
http://ext2resize.sourceforge.net
|
|
|
|
useful links: http://www-106.ibm.com/developerworks/linux/library/l-fs7/
|
|
http://www-106.ibm.com/developerworks/linux/library/l-fs8/
|