Re: [PATCH] kernel BUG at scsi_merge.c:83

From: Douglas Gilbert (
Date: Wed Jan 02 2002 - 23:28:29 EST

Peter Osterlund <> wrote:

> Jens Axboe <> writes:
> > On Wed, Jan 02 2002, Peter Osterlund wrote:
> > > Hi!
> > >
> > > While doing some stress testing on the 2.5.2-pre5 kernel, I am hitting
> > > a kernel BUG at scsi_merge.c:83, followed by a kernel panic. The
> > > problem is that scsi_alloc_sgtable fails because the request contains
> > > too many physical segments. I think this patch is the correct fix:
> >
> > Correct, ll_rw_blk default is ok now. I missed this when killing
> > scsi_malloc/scsi_dma, thanks.
> It turns out this is still not enough to fix the problem for me,
> because ll_new_hw_segment is still allowing nr_phys_segments to become
> too large. Is the following patch the correct way to deal with this
> problem, or is that case supposed to be prevented by some other means?
> At least, this patch prevents the kernel panic during my stress test.

<snipped patches/>

I was able to get a repeatable oops at that line copying
files from /boot onto a "fake" scsi_debug disk with "pre5".
The first largish file it attempted to copy caused the
oops (which I sent to Jens).

Anyway, I just applied your 2 patches (to scsi.c and ll_rw_blk.c)
and the oops is no more.

Good work.

Doug Gilbert
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