From: Boaz Harrosh <bharrosh@xxxxxxxxxxx> Subject: Re: [PATCH v2] add bidi support for block pc requests Date: Thu, 17 May 2007 17:00:21 +0300 > James Bottomley wrote: > > On Thu, 2007-05-17 at 11:49 +0300, Boaz Harrosh wrote: > >> These are regular fs (ext3) requests during bootup. The machine will not > >> boot. (Usually from the read ahead code) > >> Don't believe me look at the second patch Over Tomo's cleanup. > >> If I define SCSI_MAX_SG_SEGMENTS to 127 it will crash even when I > >> did in code: > >> blk_queue_max_phys_segments(q, SCSI_MAX_SG_SEGMENTS); > >> I suppose someone is looking at a different definition. Or there is > >> another call I need to do for this to work. > > > > It would really help us if you showed the actual code for what you did > > and where ... if this is wrong, we have bigger problems that quibbling > > about bidirectional slab sizes. The correct way to adjust this limit > > artificially to 127 is: > > > > diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c > > index 1f5a07b..4a27841 100644 > > --- a/drivers/scsi/scsi_lib.c > > +++ b/drivers/scsi/scsi_lib.c > > @@ -1576,7 +1576,7 @@ struct request_queue *__scsi_alloc_queue(struct Scsi_Host *shost, > > return NULL; > > > > blk_queue_max_hw_segments(q, shost->sg_tablesize); > > - blk_queue_max_phys_segments(q, SCSI_MAX_PHYS_SEGMENTS); > > + blk_queue_max_phys_segments(q, 127); > > blk_queue_max_sectors(q, shost->max_sectors); > > blk_queue_bounce_limit(q, scsi_calculate_bounce_limit(shost)); > > blk_queue_segment_boundary(q, shost->dma_boundary); > > > > (It doesn't alter the allocation pools or anything else, just limits the > > max phys segments of the queue). The way to check that this limit is > > being honoured is: > > > > diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c > > index 1f5a07b..ae42e4d 100644 > > --- a/drivers/scsi/scsi_lib.c > > +++ b/drivers/scsi/scsi_lib.c > > @@ -1000,6 +1000,7 @@ static int scsi_init_io(struct scsi_cmnd *cmd) > > * kmapping pages) > > */ > > cmd->use_sg = req->nr_phys_segments; > > + WARN_ON(req->nr_phys_segments > 127); > > > > /* > > * If sg table allocation fails, requeue request later. > > > > James > > > > > Yes Tomo found it at ata_scsi_slave_config(). Attached below the way I > fixed it. Now it works with 127. I think that we can just remove blk_queue_max_phys_segments since the ata drivers seem to set sg_tablesize to LIBATA_MAX_PRD. > (By the way Tomo, a printk like you did in scsi_init_io and > scsi_free_sgtable, 2 for every IO, or even 1 for every IO, will make > a SCSI booting PC like mine almost un-usable. Think of printk going > to log-file doing a printk...) Oops, I forgot to remove it since my SCSI booting pSeries box works with that. :) - 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
