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Re: XFS hung on kernel

To: Ilia Mirkin <imirkin@xxxxxxxxxxxx>
Subject: Re: XFS hung on kernel
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Sat, 7 Aug 2010 20:08:21 +1000
Cc: xfs@xxxxxxxxxxx
In-reply-to: <AANLkTinhwA1greZdCnoDvd9ieYinhjv0M07sNkbVdy3_@xxxxxxxxxxxxxx>
References: <AANLkTilX3l8TbUztLStj_u9OqOZnBrsNQxmeV4DuBmYJ@xxxxxxxxxxxxxx> <20100718012033.GA18888@dastard> <AANLkTikEv75KRyRTs4awmG894NSKMnBkJNJPYsypMdWf@xxxxxxxxxxxxxx> <20100718235036.GC32635@dastard> <AANLkTi=EzePfBRdEFQo2BRtKy=464Ci6zPG=UyYJiwNp@xxxxxxxxxxxxxx> <20100805062541.GC26402@dastard> <AANLkTinhwA1greZdCnoDvd9ieYinhjv0M07sNkbVdy3_@xxxxxxxxxxxxxx>
User-agent: Mutt/1.5.20 (2009-06-14)
On Thu, Aug 05, 2010 at 02:42:38AM -0400, Ilia Mirkin wrote:
> On Thu, Aug 5, 2010 at 2:25 AM, Dave Chinner <david@xxxxxxxxxxxxx> wrote:
> > a couple of things to see if the hang can be caused faster? Maybe
> > trying these different initial conditions:
> Together or independently?

independently first - then if that does't work, maybe together?

> >        - allocate the file with worst case fragmentation by
> >          writing it backwards in synchronous 4k blocks before
> >          running the test
> I created the file with
> dd if=/dev/zero of=... bs=1M count=...
> How would I "write backwards"? Like truncate and then seek to the end,
> write, seek back, write, etc? Is there a utility that might do it
> already?

For a 1GB file:

$ for i in `seq 256000 1 0`; do
> dd if=/dev/zero of=testfile bs=4k count=1 seek=$i conv=notrunc,sync
> done


Dave Chinner

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