Messages in this thread | | | Date | Fri, 26 Oct 2012 16:56:18 -0400 | From | Theodore Ts'o <> | Subject | Re: Apparent serious progressive ext4 data corruption bug in 3.6.3 (and other stable branches?) |
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On Fri, Oct 26, 2012 at 09:37:08PM +0100, Nix wrote: > > I can reproduce this on a small filesystem and stick the image somewhere > if that would be of any use to anyone. (If I'm very lucky, merely making > this offer will make the problem go away. :} )
I'm not sure the image is going to be that useful. What we really need to do is to get a reliable reproduction of what _you_ are seeing.
It's clear from Eric's experiments that journal_checksum is dangerous. In fact, I will likely put it under an #ifdef EXT4_EXPERIMENTAL to try to discourage people from using it in the future. There are things I've been planning on doing to make it be safer, but there's a very good *reason* that both journal_checksum and journal_async_commit are not on by default.
That's why one of the things I asked you to do when you had time was to see if you could reproduce the problem you are seeing w/o nobarrier,journal_checksum,journal_async_commit.
The other experiment that would be really useful if you could do is to try to apply these two patches which I sent earlier this week:
[PATCH 1/2] ext4: revert "jbd2: don't write superblock when if its empty [PATCH 2/2] ext4: fix I/O error when unmounting an ro file system
... and see if they make a difference.
If they don't make a difference, I don't want to apply patches just for placebo/PR reasons. And for Eric at least, he can reproduce the journal checksum error followed by fairly significant corruption reported by e2fsck with journal_checksum, and the presence or absense of these patches make no difference for him. So I really don't want to push these patches to Linus until I get confirmation that they make a difference to *somebody*.
Regards,
- Ted
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