From: Theodore Ts'o Subject: Re: Apparent serious progressive ext4 data corruption bug in 3.6.3 (and other stable branches?) Date: Fri, 26 Oct 2012 16:56:18 -0400 Message-ID: <20121026205618.GC8614@thunk.org> References: <87objupjlr.fsf@spindle.srvr.nix> <20121023013343.GB6370@fieldses.org> <87mwzdnuww.fsf@spindle.srvr.nix> <20121023143019.GA3040@fieldses.org> <874nllxi7e.fsf_-_@spindle.srvr.nix> <87pq48nbyz.fsf_-_@spindle.srvr.nix> <508AF3FA.4020506@redhat.com> <87wqydx957.fsf@spindle.srvr.nix> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Eric Sandeen , linux-ext4-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, "J. Bruce Fields" , Bryan Schumaker , Peng Tao , Trond.Myklebust-HgOvQuBEEgTQT0dZR+AlfA@public.gmane.org, gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org, linux-nfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Nix Return-path: Content-Disposition: inline In-Reply-To: <87wqydx957.fsf-AdTWujXS48Mg67Zj9sPl2A@public.gmane.org> Sender: linux-nfs-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-ext4.vger.kernel.org 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 -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html