Re: [Jfs-discussion] Strange behavior after a crash
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From: Dave K. <sh...@au...> - 2005-01-08 02:47:36
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On Fri, 2005-01-07 at 17:03 -0600, John Goerzen wrote: > > Actually, jfs does the equivalent of data=writeback. In the 2.4 kernel, > > it does the equivalent of data=ordered, but I changed the behavior do > > avoid a deadlock in 2.6 which I never found the correct fix for. > > You might consider this one vote for the data=ordered behavior. This is > probably why I haven't noticed this problem from ext3 filesystems. Noted. For what it's worth, I haven't personally noticed this kind of corruption, and haven't had reports of it, so I have assumed that in practice it is a kind of rare problem. Maybe you crashed at an unlucky point, or it may be more common than I'm aware of. > > The data=ordered behavior would prevent random data from showing up in a > > file, but it would not prevent the blocks of NULLs that you reported (if > > these are really file holes as I suspect). These would be caused when a > > file written non-sequentially was committed before it was completely > > written to. > > I believe -- but can't prove at the moment -- that these files would > have been written to sequentially. That may be true, and the nulls you saw in the files could have just been the same kind of random data, that happened to be null, due to some past use of the disk blocks. > In any case, if the file was written to non-sequentially, couldn't you > resort to the old data in the file instead of the NULLs? > > And if you mean a sparse file -- where the program seeks past the end, > then writes -- the NULLs do seem to be the proper behavior there. Yes, I did mean sparse files. > > I'll have to look again at implementing the data=ordered behavior. > > That would be great, thanks! > > I wonder -- does anyone know what the other journaling filesystems (XFS, > Reiser3/4, etc.) are doing? > > FWIW, the original reason I switched to JFS was because Reiser was doing > this same thing, just much worse :-) > > -- John -- David Kleikamp IBM Linux Technology Center |