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Date: Thu, 10 Jul 2014 23:31:14 +0200 From: Matteo Croce <technoboy85@...il.com> To: "Darrick J. Wong" <darrick.wong@...cle.com> Cc: Eric Whitney <enwlinux@...il.com>, "Theodore Ts'o" <tytso@....edu>, David Jander <david@...tonic.nl>, Dmitry Monakhov <dmonakhov@...nvz.org>, linux-ext4@...r.kernel.org Subject: Re: ext4: journal has aborted Will do, thanks! 2014-07-10 22:01 GMT+02:00 Darrick J. Wong <darrick.wong@...cle.com>: > On Thu, Jul 10, 2014 at 02:57:48PM -0400, Eric Whitney wrote: >> * Theodore Ts'o <tytso@....edu>: >> > On Mon, Jul 07, 2014 at 11:53:10AM -0400, Theodore Ts'o wrote: >> > > An update from today's ext4 concall. Eric Whitney can fairly reliably >> > > reproduce this on his Panda board with 3.15, and definitely not on >> > > 3.14. So at this point there seems to be at least some kind of 3.15 >> > > regression going on here, regardless of whether it's in the eMMC >> > > driver or the ext4 code. (It also means that the bug fix I found is >> > > irrelevant for the purposes of working this issue, since that's a much >> > > harder to hit, and that bug has been around long before 3.14.) >> > > >> > > The problem in terms of narrowing it down any further is that the >> > > Pandaboard is running into RCU bugs which makes it hard to test the >> > > early 3.15-rcX kernels..... >> > >> > In the hopes of making it easy to bisect, I've created a kernel branch >> > which starts with 3.14, and then adds on all of the ext4-related >> > commits since then. You can find it at: >> > >> > git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4.git test-mb_generate_buddy-failure >> > >> > https://git.kernel.org/cgit/linux/kernel/git/tytso/ext4.git/log/?h=test-mb_generate_buddy-failure >> > >> > Eric, can you see if you can repro the failure on your Panda Board? >> > If you can, try doing a bisection search on these series: >> > >> > git bisect start >> > git bisect good v3.14 >> > git bisect bad test-mb_generate_buddy-failure >> > >> > Hopefully if it is caused by one of the commits in this series, we'll >> > be able to pin point it this way. >> >> First, the good news (with luck): >> >> My testing currently suggests that the patch causing this regression was >> pulled into 3.15-rc3 - >> >> 007649375f6af242d5b1df2c15996949714303ba >> ext4: initialize multi-block allocator before checking block descriptors >> >> Bisection by selectively reverting ext4 commits in -rc3 identified this patch >> while running on the Pandaboard. I'm still using generic/068 as my reproducer. >> It occasionally yields a false negative, but it has passed 10 consecutive >> trials on my revert/bisect kernel derived from 3.15-rc3. Given the frequency >> of false negatives I've seen, I'm reasonably confident in that result. I'm >> going to run another series with just that patch reverted on 3.16-rc3. >> >> Looking at the patch, the call to ext4_mb_init() was hoisted above the code >> performing journal recovery in ext4_fill_super(). The regression occurs only >> after journal recovery on the root filesystem. > > Thanks for finding the culprit! :) > > Can you apply this patch, build with CONFIG_EXT4FS_DEBUG=y, and see if an > FS will mount without crashing? This was the cruddy patch I sent in (and later > killed) that fixed the crash on mount with EXT4FS_DEBUG in a somewhat silly > way. Maybe it's appropriate now. > http://www.spinics.net/lists/linux-ext4/msg43287.html > > --D > >> >> Secondly: >> >> Thanks for that git tree! However, I discovered that the same "RCU bug" I >> thought I was seeing on the Panda was also visible on the x86_64 KVM, and >> it was actually just RCU noticing stalls. These also occurred when using >> your git tree as well as on mainline 3.15-rc1 and 3.15-rc2 and during >> bisection attempts on 3.15-rc3 within the ext4 patches, and had the effect of >> masking the regression on the root filesystem. The test system would lock up >> completely - no console response - and made it impossible to force the reboot >> which was required to set up the failure. Hence the reversion approach, since >> RCU does not report stalls in 3.15-rc3 (final). >> >> Eric >> >> >> >> > >> > Thanks!! >> > >> > - Ted >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-ext4" in >> the body of a message to majordomo@...r.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html -- Matteo Croce OpenWrt Developer -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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