Re: Changes to Linux/SCSI target mode infrastructure for v2.6.28

[Nicholas A. Bellinger]

On Tue, 2008-12-02 at 00:30 -0800, Nicholas A. Bellinger wrote:
> On Mon, 2008-12-01 at 22:40 -0800, Mike Anderson wrote:
> > Nicholas A. Bellinger <nab@xxxxxxxxxxxxxxx> wrote:
> > > On Tue, 2008-12-02 at 13:18 +0900, Tejun Heo wrote:
> > > > 
> > > > >>> The other one is a BUG_ON in blk/blk-timeout.c:177 in blk_add_timeout()
> > > > >>> that happens after a few hundred MB of READ_10 traffic, which also
> > > > >>> appears to pass through elv_dequeue_request() at some point:
> > > > >>>
> > > > >>> http://linux-iscsi.org/builds/user/nab/2.6.28-rc6-oops-2.png
> > > > >>> http://linux-iscsi.org/builds/user/nab/2.6.28-rc6-oops-4.png
> > > >
> > > > Hmmm... this means blk_add_timer() is being called after the request
> > > > is already completed.
> > 
> > or is it possible since elv_dequeue_request BUG_ON check of queuelist did
> > not trigger a request is on the queuelist with a timeout_list not empty.
> > 
> > It would be interesting for a debug run to change the
> > "BUG_ON(!list_empty(&req->timeout_list))" in blk_add_timer to print out
> > the cmd_flags plus req->atomic_flags and also add a
> > "BUG_ON(!list_empty(&rq->timeout_list))" to elv_insert to ensure a request
> > is never added to the queuelist with a timeout_list not empty.
> > 
> 
> Ok, so blk_dump_rq_flags() is now being called in
> block/blk-timeout.c:blk_add_timer() for the case
> BUG_ON(list_empty(&req->timeout_list)) case:
> 
> http://linux-iscsi.org/builds/user/nab/2.6.28-rc6-oops-6.png
> 
> Hmm, the outputted "sector " range is definately is bogus, as the only
> READ_10 that have been sent are at LBA offset 0 for 8 * 512 byte sectors
> for the partition table during Open/iSCSI LUN scanning.
> 

Also, the following code from block/blk-core.c:blk_dump_rq_flags():

        if (blk_pc_request(rq)) {
                printk(KERN_INFO "  cdb: ");
                for (bit = 0; bit < BLK_MAX_CDB; bit++)
                        printk("%02x ", rq->cmd[bit]);
                printk("\n");
        }

is not printing out the copied CDB in struct request->cmd[], which makes
me think the struct request->cmd_flags (that blk_pc_request() is
checking) are also bogus when blk_add_timer() is being called..

--nab

> --nab
> 
> 
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