From mboxrd@z Thu Jan 1 00:00:00 1970 From: James Bottomley Subject: Re: [BUG] 2.6.29-rc6-2450cf in scsi_lib.c (was: Large amount of scsi-sgpool)objects Date: Wed, 04 Mar 2009 18:13:49 -0600 Message-ID: <1236212029.32072.4.camel@localhost.localdomain> References: <49ACF8FE.2020904@panasas.com> <1236093718.3263.3.camel@localhost.localdomain> <1236097526.3263.17.camel@localhost.localdomain> <1236119195.24019.24.camel@localhost.localdomain> <1236207389.21486.19.camel@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1236207389.21486.19.camel@localhost.localdomain> Sender: linux-ide-owner@vger.kernel.org To: Thomas Gleixner Cc: Jan Engelhardt , Boaz Harrosh , linux-scsi@vger.kernel.org, Linux Kernel Mailing List , linux-ide List-Id: linux-scsi@vger.kernel.org On Wed, 2009-03-04 at 22:56 +0000, James Bottomley wrote: > On Wed, 2009-03-04 at 22:45 +0100, Thomas Gleixner wrote: > > On Wed, 4 Mar 2009, Thomas Gleixner wrote: > > > > Instrumented the code and the result of the failing request is > > below. Looks like the function which sets up the request gets > > nr_phys_segments wrong by one. > > > > If you need further trace data feel free to ask. > > OK, the mapping all checks out correctly ... there must be something > wrong with the way we count before mapping. > > If you're tracing everything, could you add these static prints to the > trace ... they'll trigger a lot, but capturing how they applied to the > failing request might tell us why the count is wrong. Debugging this on IRC, this is the point we reached: ftrace debugging patch: http://tglx.de/~tglx/dbg.patch We're tracing both blk_recalc_rq_segments() and blk_phys_contig_segment() The results are here: http://tglx.de/~tglx/t.txt.bz2 Although what they show is that we're missing the point where the counting goes wrong (blk_recalc_rq_segments only goes up to 5 max). James