On Sat, Nov 16, 2013 at 04:06:10AM -0800, Anatol Pomozov wrote: > Hi > > Follow-up for the issue. I stuck with this "invalid csum for free > space extent" error. Could anyone explain what does it mean? If this > is not data and just a free space, why do we care about its checksum? > And if we do really care then btrfs should have a way to fix this > error. I can "fix" a file checksum error by removing the file, but how > to "fix" free space extent checksum error? Probably drop the free space cache and rebuild it. > I decided to run --init-csum-tree to see if it fixes the issue with > free space csum. I expected that it will recalculate csum for data. > And found that it cleared csum tree completely and made my fs became > unusable. Any read returns csum error. The data is still on disk - I > can read it with filefrag+btrfs-map-logic+dd - it is just csum > information that got dropped. So I want to echo the request from Robin > http://www.spinics.net/lists/linux-btrfs/msg25271.html > Information about --init-csum-tree should be documented. What is the > use-case for this feature? In fact I expected that it will recalculate > the csum tree based on the data, not clear the tree. There's a patch in the pipeline that makes --init-csum-tree rebuild the csums as well. Hugo. -- === Hugo Mills: hugo@... carfax.org.uk | darksatanic.net | lug.org.uk === PGP key: 65E74AC0 from wwwkeys.eu.pgp.net or http://www.carfax.org.uk --- I write in C because using pointer arithmetic lets people --- know that you're virile. -- Matthew Garrett
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