On Sun 12-05-13 13:01:11, Dmitry Monakhov wrote: > On Sat, 11 May 2013 19:05:59 -0400, Theodore Ts'o <tytso@xxxxxxx> wrote: > > On Sat, May 11, 2013 at 03:00:53PM +0400, Dmitry Monakhov wrote: > > > I've bisected ext4 related issue. It is appeared that it is pure ext4 > > > specific. Regression caused by following commit > > > commit 4eec708d263f0ee10861d69251708a225b64cac7 > > > Author: Jan Kara <jack@xxxxxxx> > > > Date: Thu Apr 11 23:56:53 2013 -0400 > > > ext4: use io_end for multiple bios > > > > Hmm... the next question is why did I see this in my testing. Did you > > find this on ia64, or x86? > No simple x86_64. > > Also what about the slab corruption which > > you saw when running XFS; was that unrelated? > My theory about mysterious corruption in mm layer which broke everything > was wrong. We have to absolutely independent regressions in different > filesystems: > * Slub corruption on XFS > - testcase: xfstests/generic/007 > - bad commit: 666d64 > - LINK: https://lkml.org/lkml/2013/5/11/154 > > * Slub corruption on EXT4 > - testcase: xfstests/generic/299 > - bad commit: 4eec70 > - link: https://lkml.org/lkml/2013/5/11/37 > - fix: https://lkml.org/lkml/2013/5/11/142 > > In fact '4eec70' are vexing because I have reviewed and tested this patch > before it was marked as Review-by, but missed the bug. This is because > xfstests was executed manually logs was full of warnings but tainted flag > was not checked at the end. To prevent this thing in future I'll always > use my local autotest(http://autotest.github.io/) farm next time. OK, so I finally nailed this down. DIO code has that peculiarity that it doesn't call ->end_io callback when no IO was actually submitted. As a bonus the generic code does a cleanup of generic stuff that is otherwise left to ->end_io callback. Since I need to do io_end cleanup in ->end_io callback I have to compensate for that in ext4_ext_direct_IO(). Sadly I've got the condition wrong and also forgot that generic code already decremented i_dio_count in the error failure case so cleanup sometimes happened twice. I'll add fixed version of the patch back in my series (since the patch got reverted upstream). Honza -- Jan Kara <jack@xxxxxxx> SUSE Labs, CR -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
