Re: [Bug #39732] JBD: Spotted dirty metadata buffer (dev = dm-2, blocknr = 2512725). There's a risk of filesystem corruption in case of system crash.

[Jan Kara <jack@suse.cz>]

  Hi,

On Tue 13-12-11 05:11:44, Witold Baryluk wrote:
> On 08-28 21:01, Rafael J. Wysocki wrote:
> > This message has been generated automatically as a part of a report
> > of regressions introduced between 2.6.39 and 3.0.
> > 
> > The following bug entry is on the current list of known regressions
> > introduced between 2.6.39 and 3.0.  Please verify if it still should
> > be listed and let the tracking team know (either way).
> > 
> > 
> > Bug-Entry	: http://bugzilla.kernel.org/show_bug.cgi?id=39732
> > Subject		: JBD: Spotted dirty metadata buffer (dev = dm-2, blocknr = 2512725). There's a risk of filesystem corruption in case of system crash.
> > Submitter	: Witold Baryluk <baryluk@smp.if.uj.edu.pl>
> > Date		: 2011-07-22 04:22 (38 days old)
> 
> This bug still exists in 3.1.0 and 3.2.0-rc5
> 
> I spoted it again few days ago, because I moved from me laptop with 2GB
> to temporary desktop with 256MB of RAM, and not it
> triggers like a mad.
> 
> So my initial suspicious that it only shows up on big memory
> presure was correct.
> 
> 
> It is just like this 
> # dmesg | grep dirty
> [122647.953872] JBD: Spotted dirty metadata buffer (dev = dm-3, blocknr = 1019852). There's a risk of filesystem corruption in case of system crash.
> [122647.954598] JBD: Spotted dirty metadata buffer (dev = dm-3, blocknr = 1043195). There's a risk of filesystem corruption in case of system crash.
> [122647.955213] JBD: Spotted dirty metadata buffer (dev = dm-3, blocknr = 1043197). There's a risk of filesystem corruption in case of system crash.
> [122689.978864] JBD: Spotted dirty metadata buffer (dev = dm-3, blocknr = 498559). There's a risk of filesystem corruption in case of system crash.
> [122705.485461] JBD: Spotted dirty metadata buffer (dev = dm-3, blocknr = 68282). There's a risk of filesystem corruption in case of system crash.
> [122705.486046] JBD: Spotted dirty metadata buffer (dev = dm-3, blocknr = 68284). There's a risk of filesystem corruption in case of system crash.
> [122705.496916] JBD: Spotted dirty metadata buffer (dev = dm-3, blocknr = 68365). There's a risk of filesystem corruption in case of system crash.
> [122705.612423] JBD: Spotted dirty metadata buffer (dev = dm-3, blocknr = 69218). There's a risk of filesystem corruption in case of system crash.
> [122706.531297] JBD: Spotted dirty metadata buffer (dev = dm-3, blocknr = 833896). There's a risk of filesystem corruption in case of system crash.
> [122720.863807] JBD: Spotted dirty metadata buffer (dev = dm-3, blocknr = 914979). There's a risk of filesystem corruption in case of system crash.
> [122721.046789] JBD: Spotted dirty metadata buffer (dev = dm-3, blocknr = 890090). There's a risk of filesystem corruption in case of system crash.
> [122721.088280] JBD: Spotted dirty metadata buffer (dev = dm-3, blocknr = 916474). There's a risk of filesystem corruption in case of system crash.
> [122721.176979] JBD: Spotted dirty metadata buffer (dev = dm-3, blocknr = 928182). There's a risk of filesystem corruption in case of system crash.
> [122721.177593] JBD: Spotted dirty metadata buffer (dev = dm-3, blocknr = 927783). There's a risk of filesystem corruption in case of system crash.
> [122721.371654] JBD: Spotted dirty metadata buffer (dev = dm-3, blocknr = 920655). There's a risk of filesystem corruption in case of system crash.
> [122721.543676] JBD: Spotted dirty metadata buffer (dev = dm-3, blocknr = 967035). There's a risk of filesystem corruption in case of system crash.
> [122728.396687] JBD: Spotted dirty metadata buffer (dev = dm-3, blocknr = 1043474). There's a risk of filesystem corruption in case of system crash.
> [122736.283876] JBD: Spotted dirty metadata buffer (dev = dm-3, blocknr = 713478). There's a risk of filesystem corruption in case of system crash.
> [122743.576350] JBD: Spotted dirty metadata buffer (dev = dm-3, blocknr = 745551). There's a risk of filesystem corruption in case of system crash.
> [122743.889259] JBD: Spotted dirty metadata buffer (dev = dm-3, blocknr = 828117). There's a risk of filesystem corruption in case of system crash.
> [122752.077022] JBD: Spotted dirty metadata buffer (dev = dm-3, blocknr = 905082). There's a risk of filesystem corruption in case of system crash.
> [122752.125005] JBD: Spotted dirty metadata buffer (dev = dm-3, blocknr = 905294). There's a risk of filesystem corruption in case of system crash.
> [122752.784390] JBD: Spotted dirty metadata buffer (dev = dm-3, blocknr = 1030306). There's a risk of filesystem corruption in case of system crash.
> [122752.785053] JBD: Spotted dirty metadata buffer (dev = dm-3, blocknr = 1031593). There's a risk of filesystem corruption in case of system crash.
> #
> 
> dm-4 is ext4 partition mounted at /var
> dm-4 is on LVM on luksCrypt on ATA drive.
> 
> I'm using currently stock Debian testing kernel:
> $ uname -a
> Linux sredniczarny 3.1.0-1-686-pae #1 SMP Tue Nov 29 19:01:56 UTC 2011 i686 GNU/Linux
> $ cat /proc/version
> Linux version 3.1.0-1-686-pae (Debian 3.1.4-1) (waldi@debian.org) (gcc version 4.6.2 (Debian 4.6.2-4) ) #1 SMP Tue Nov 29 19:01:56 UTC 2011
> $
> 
> 32-bit intel compatible cpu
  Thanks for report. Actually I was able to reproduce these messages with
data=journal mode as well when running bash_shared_mapping test. The
culprit of the problem is that block_mkwrite() as used in
ext4_page_mkwrite() marks buffers dirty and JBD2 notices this before
we clear dirty bits later in ext4_page_mkwrite() (since JBD2 doesn't use
page lock for protection when inspecting buffers). So for data=journal mode
we'll probably have to reimplement what block_page_mkwrite() does in a
slightly different manner tweaked for the needs of data=journal mode.

								Honza
-- 
Jan Kara <jack@suse.cz>
SUSE Labs, CR