Re: O_DIRECT fails in some kernel and FS

[Andrew Morton]

Ricardo Galli wrote:
> 
> After some comments from Oliver Diedrich (editor of heise.de), which told me
> he couldn't make O_DIRECT work on 2.4.17, I tried with different versions and
> file systems:
> 
> This is the result:
> 
> 2.4.14 - Ext[23] - redhat7.2 glibs: OK (at least the bytes are written)
> 2.4.17 - ReiserFS - Debian Sid    : FAILS (0 bytes file, write returns -1)
> 2.4.17 - Ext2 - Debian Woody      : OK (bytes written)
> 2.4.17 - Ext3 - Debian Woody      : FAILS (0 bytes file, write returns -1)
> 
> Oliver Diedrich also told he could make work O_DIRECT with ext3 and 2.4.17.
> 
> Is this normal? Does it really work on 2.4.14? Or it doesn't but the kernel
> doesn't avoid caching?
> 

ext2 is the only filesystem which has O_DIRECT support.

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