Re: precise characterization of ext3 atomicity

[Hans Reiser]

Andrew Morton wrote:

> Hans Reiser <reiser@xxxxxxxxxxx> wrote:
>  
>
> > Is it correct to say of ext3 that it guarantees and only guarantees 
> > atomicity of writes that do not cross page boundaries?
> >    
>
> Yes.
>
>  
>
> >    By contrast, ext3 only guarantees the atomicity of a single write 
> > that does not span a page boundary, and it guarantees that its internal 
> > metadata will not be corrupted even if your applications data is 
> > corrupted after the crash.
> >    
>
> Not sure that I understand this.  In data=writeback mode, metadata
> integrity is preserved but data writes may be lost.  In data=journal and
> data=ordered modes the data and the metadata which refers to it are always
> in sync on-disk.
>
>
>
>  
Perhaps the following is correct?

   By contrast, ext3 in data=journal and data=ordered modes only guarantees the atomicity of a single write 
that does not span a page boundary, and it guarantees that its internal 
metadata will not be corrupted even if your application's data is 
corrupted after the crash (due to the application spreading what should be committed atomically across more than one block).





--
Hans


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