linux-kernel - Re: [PATCH] Re: [bug] ata subsystem related crash with latest -git

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Date:	Thu, 18 Oct 2007 12:54:38 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Jeff Garzik <jeff@...zik.org>
Cc:	Jens Axboe <jens.axboe@...cle.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, Alan Cox <alan@...rguk.ukuu.org.uk>,
	Tejun Heo <htejun@...il.com>,
	Brian King <brking@...ux.vnet.ibm.com>
Subject: Re: [PATCH] Re: [bug] ata subsystem related crash with latest -git


* Jeff Garzik <jeff@...zik.org> wrote:

> >Tomo and I agreed to kill sg_last() a few days ago anyways, so this 
> >is perfectly fine with me.
> 
> Yep, the [attached] patch that kills ata_sg_is_last() is working here 
> on both machines that were previously croaking.
> 
> It would be nice to get pdc_adma, sata_sil24 and ipr it-works test 
> done, but IMO the patch is pretty straightforward and should be OK.

just a quick question: i have Jens's workarounds applied right now (see 
patch below). Am i now crash/corruption-safe, or do i need your patch 
too? And once your patch [and the other sg_*() patches] are upstream i 
dont need the workaround anymore, correct?

	Ingo

---
 block/ll_rw_blk.c         |    2 +-
 drivers/ata/libata-core.c |    2 +-
 drivers/scsi/scsi_lib.c   |    2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

Index: linux/block/ll_rw_blk.c
===================================================================
--- linux.orig/block/ll_rw_blk.c
+++ linux/block/ll_rw_blk.c
@@ -631,7 +631,7 @@ void blk_queue_max_phys_segments(struct 
 		printk("%s: set to minimum %d\n", __FUNCTION__, max_segments);
 	}
 
-	q->max_phys_segments = max_segments;
+	q->max_phys_segments = max_segments - 1;
 }
 
 EXPORT_SYMBOL(blk_queue_max_phys_segments);
Index: linux/drivers/ata/libata-core.c
===================================================================
--- linux.orig/drivers/ata/libata-core.c
+++ linux/drivers/ata/libata-core.c
@@ -4664,7 +4664,7 @@ static int ata_sg_setup(struct ata_queue
 {
 	struct ata_port *ap = qc->ap;
 	struct scatterlist *sg = qc->__sg;
-	struct scatterlist *lsg = sg_last(qc->__sg, qc->n_elem);
+	struct scatterlist *lsg = &qc->__sg[qc->n_elem - 1];
 	int n_elem, pre_n_elem, dir, trim_sg = 0;
 
 	VPRINTK("ENTER, ata%u\n", ap->print_id);
Index: linux/drivers/scsi/scsi_lib.c
===================================================================
--- linux.orig/drivers/scsi/scsi_lib.c
+++ linux/drivers/scsi/scsi_lib.c
@@ -39,7 +39,7 @@
  * (unless chaining is used). Should ideally fit inside a single page, to
  * avoid a higher order allocation.
  */
-#define SCSI_MAX_SG_SEGMENTS	128
+#define SCSI_MAX_SG_SEGMENTS	129
 
 struct scsi_host_sg_pool {
 	size_t		size;
-
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