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Re: Still seeing hangs in xlog_grant_log_space

To: Dave Chinner <david@xxxxxxxxxxxxx>
Subject: Re: Still seeing hangs in xlog_grant_log_space
From: Chris J Arges <chris.j.arges@xxxxxxxxxxxxx>
Date: Tue, 12 Jun 2012 08:28:38 -0500
Cc: xfs@xxxxxxxxxxx
In-reply-to: <20120611235337.GE22848@dastard>
References: <CADLDEKsP4DsXf_G07ub+a-ODbrJbsiprRJUX1fJdaQ41TB7+Xg@xxxxxxxxxxxxxx> <CAH4wwdGWHSZoveLJMxu5pjr22NEEeW7oG8TS+snoM8RY=ZeRmg@xxxxxxxxxxxxxx> <CADLDEKsGtsw-rrSOE7gY4T81u+p41b34ixv0B7Dh07afJ73n2w@xxxxxxxxxxxxxx> <CAH4wwdFu7DEkHFZ5Bf7_PtLPsG0hUyUDoov03q=82R6t+QkERg@xxxxxxxxxxxxxx> <20120605235447.GF22848@dastard> <4FCF5DB9.2000808@xxxxxxxxxx> <4FCF9655.3070300@xxxxxxx> <33996217.post@xxxxxxxxxxxxxxx> <20120611235337.GE22848@dastard>
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On 06/11/2012 06:53 PM, Dave Chinner wrote:
> On Mon, Jun 11, 2012 at 01:42:31PM -0700, Chris J Arges wrote:
>> Mark Tinguely-3 wrote:
>>> The perl script to recreate this problem is very similar to xfstest 273.
>>> I use that because it avoids all the filesystem mount/unmount that
>>> happen between the test 273 loops. You can build the log size that you
>>> want to test, create the directories and let it run until it hangs.
>> I tested xfstest 273, and it looks like it exhibits a different issue than
>> the OP in this thread.
>> For example, if I run this test in a while [1] loop, I get the following
>> backtrace:
>> [16413.073946] XFS (sda5): Invalid block length (0xfffff48b) for buffer
> That looks bad. How big is the log on this filesystem?
The test and scratch partitions were created with the following commands:
mkfs.xfs -b size=1024 -l size=576b /dev/sda5
mkfs.xfs -b size=1024 -l size=576b /dev/sda6

>> [16413.073963] BUG: unable to handle kernel NULL pointer dereference at
>> 0000000000000130
>> [16413.074274] IP: [<ffffffffa02bb870>] uuid_is_nil+0x10/0x50 [xfs]
> I can't really see how this function can get a null pointer
> dereference. It checks the pointer passed in for being null before
> doing anything, and otherwise it just increments and dereferences
> the char pointer 16 times. I can't see how that results in a NULL
> being dereferenced - I might just be blind though.
Yea, this is odd. What I'm really trying to accomplish is seeing if this
xfstest 273 produces a similar hang to Juerg's original bug. If you've
already run this test and it produced a hang can you post the backtrace
or let me know if it is similar?


> Cheers,
> Dave.

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