ext3有3个日记选项：journal,ordered和writeback.根据维基百科entry,这些范围从最小风险到最危险的崩溃恢复.出于某种原因,Android的Linux版本仅支持后两个选项,默认为回写. (我正在经营Froyo)
有没有办法添加对日记模式的支持？我想在/ data分区上执行此操作,这是ext3,也是大多数文件写入的地方.我的设备没有电池,所以当有人断电时,我需要确保它是防撞的.
如果有人感兴趣,Linux选项在kernel / fs / ext3 / Kconfig中定义.具体选项是EXT3_DEFAULTS_TO_ORDERED.
最佳答案
解决方案是将以下内容添加到kernel / fs / ext3 / Kconfig,并使用EXT3_DEFAULTS_TO_JOURNAL重建内核.
choice
prompt "EXT3 default journal mode"
default EXT3_DEFAULTS_TO_ORDERED
help
The journal mode options for ext3 have different tradeoffs
between when data is guaranteed to be on disk and
performance. The use of "data=writeback" can cause
unwritten data to appear in files after an system crash or
power failure,which can be a security issue. However,"data=ordered" mode can also result in major performance
problems,including seconds-long delays before an fsync()
call returns. "data=journal" is the safest option but possibly
the the great perfromance burden. For details,see:
http://ext4.wiki.kernel.org/index.PHP/Ext3_data_mode_tradeoffs
If you have been historically happy with ext3's performance,data=ordered mode will be a safe choice.
config EXT3_DEFAULTS_TO_JOURNAL
bool "Default to 'data=journal' in ext3"
depends on EXT3_FS
help
Both data and Metadata are journaled. Should be safe
against crashes,power failure,etc.
config EXT3_DEFAULTS_TO_ORDERED
bool "Default to 'data=ordered' in ext3"
depends on EXT3_FS
help
Only Metadata are journaled. Data is written first and then
Metadata is update. Mostly safe against crashes,power
failures,etc.,except if the anomally occurred while a file
is being overwritten. Most of the time files are appended and
not over written.
config EXT3_DEFAULTS_TO_WRITEBACK
bool "Default to 'data=writeback' in ext3"
depends on EXT3_FS
help
Ext2 with a fast ckfs. Not always safe against crashes,but has the best preformance
endchoice
