On 02/16/2012 03:03 PM, Mike Snitzer wrote: > On Thu, Feb 16 2012 at 3:02pm -0500, > Mike Snitzer <snitzer@xxxxxxxxxx> wrote: > >> FYI, I'll bounce a message detailing the iSCSI scatter-gather NULL >> pointer I _always_ hit with dm-io issuing async WRITE_SAME. > > I developed a patch for dm-io so that the new dm-thinp target can > leverage your new WRITE SAME functionality for, hopefully, more > efficient zeroing of the disk (see: dm-io-WRITE_SAME.patch at the end of > the following patchset). > > Here is the patchset I'm using ontop of Linux 3.2: > http://people.redhat.com/msnitzer/patches/upstream/dm-io-WRITE_SAME/series.html > > All works great on FC (tested against NetApp 3040 LUN)... I'm using the > thinp-test-suite to test dm-thinp's use of dm_kcopyd_zero(). > > But testing with iSCSI, I get a NULL pointer _every_ time in the iSCSI > scatter-gather code, see: > http://people.redhat.com/msnitzer/patches/upstream/dm-io-WRITE_SAME/async-WRITE_SAME-makes-iscsi-sg-die.txt > -- in the middle of that file you'll see my 'crash' analysis of the > issue -- but that is just the NULL pointer.. no idea what the smoking > gun is that caused the iscsi_segment to become NULL. > > Anyway, taking a step back... WRITE SAME is all about transfering a > single logical block, backed by a single empty_zero_page in this test > case, so I'm wondering if for some reason iSCSI's sg code is getting > confused and thinking that more pages need to be transferred than were > in the original bio's payload (but iSCSI is way beneath the bio -> SCSI > command translation... grr) Yeah, probably a request/scsi_cmnd/sg sector/length/offset value is off or iscsi is making a bad assumption. Do: echo 1 > /sys/module/libiscsi/parameters/debug_libiscsi_session echo 1 > /sys/module/libiscsi/parameters/debug_libiscsi_session echo 1 > /sys/module/libiscsi_tcp/parameters/debug_libiscsi_tcp echo 1 > /sys/module/libiscsi_tcp/parameters/iscsi_tcp then rerun your test. -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
