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    SubjectRe: [patch] ext2/3: document conditions when reliable operation is possible
    Hi!

    > > > +* don't damage the old data on a failed write (ATOMIC-WRITES)
    > > > +
    > > > + (Thrash may get written into sectors during powerfail. And
    > > > + ext3 handles this surprisingly well at least in the
    > > > + catastrophic case of garbage getting written into the inode
    > > > + table, since the journal replay often will "repair" the
    > > > + garbage that was written into the filesystem metadata blocks.
    > >
    > > Isn't this by design? In other words, if the metadata doesn't survive
    > > non-atomic writes, wouldn't it be an ext3 bug?
    >
    > So I got confused when I quoted your note, which I had assumed was
    > exactly what Pavel had written in his documentation. In fact, what he
    > had written was this:
    >
    > +Don't damage the old data on a failed write (ATOMIC-WRITES)
    > +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    > +
    > +Either whole sector is correctly written or nothing is written during
    > +powerfail.
    > +
    > +....
    >
    > So he had explicitly stated that he only cared about the whole sector
    > being written (or not written) in the power fail case, and not any
    > other. I'd suggest changing ATOMIC-WRITES to
    > ATOMIC-WRITE-ON-POWERFAIL, since the one-line summary, "Don't damage
    > the old data on a failed write", is also singularly misleading.

    Ok, something like this?

    Don't damage the old data on a powerfail (ATOMIC-WRITES-ON-POWERFAIL)
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

    Either whole sector is correctly written or nothing is written during
    powerfail.


    Pavel

    --
    (english) http://www.livejournal.com/~pavelmachek
    (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html


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