Messages in this thread | | | Date | Mon, 24 Aug 2009 09:50:35 -0400 | From | Theodore Tso <> | Subject | Re: [patch] ext2/3: document conditions when reliable operation is possible |
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On Mon, Aug 24, 2009 at 11:19:01AM +0000, Florian Weimer wrote: > > +* 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.
- Ted
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