[ltp] Make disk-protect work on 2.6.24 (was: enabling protect file for hdaps on t61)

[Elias Oltmanns]

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[cc'ing hdaps-devel]

Vincent C Jones <v.jones@networkingunlimited.com> wrote:
> On Mon, 2008-02-11 at 07:58 +0100, Elias Oltmanns wrote:
>> Vincent C Jones <v.jones@networkingunlimited.com> wrote:
>> >
>> > SATA drive here as well (7675 X61, AHCI mode, SuSE 10.3, 2.6.24 with
>> > SuSE, acpi, protect, & tp_smapi patches applied) and I have no problem
>> > invoking a freeze. What is your magic incantation to avoid the problem?
>> > I really would like to get HDAPS back...
>> 
>> The difference isn't so much SATA vs PATA but SMP system vs uniprocessor
>> / non-SMP system. Probably Rolf is running an SMP kernel on a dual core
>> machine whereas your system is lacking SMP support.
>
> Huh? SMP -> problem or SMP is OK? SMP kernel with dual core CPU = freeze

Quite right, my analysis was flawed since we seem to have a busy loop
rather than an infinite recursion. Since some of you don't have the
freeze problem, I suppose some kernel config options influence the
scheduler in such a way that I/O either gets a chance or not.

Anyway, there is a temporary solution to this problem. If you apply the
little patch attached to this email, the usual disk-protect patch will
work on 2.6.24. This change is supposed to fix a generic problem in
libata and may eventually be merged upstream, but Tejun Heo (libata
developer) said that some testing was required first.

This change is absolutely safe for everyone using a non-NCQ capable
system. In particular, ata_piix doesn't support NCQ. If you are using
ahci and /sys/class/scsi_disk/.../device/queue_depth reports a value
greater than 1, i.e. NCQ is enabled, then the patch shouldn't cause any
harm either but it may or may not affect I/O performance.

Enjoy,

Elias


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Content-Type: text/x-patch
Content-Disposition: attachment; filename=adjust-blocked-counters.patch

---

 drivers/ata/libata-scsi.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
index 14daf48..bab372b 100644
--- a/drivers/ata/libata-scsi.c
+++ b/drivers/ata/libata-scsi.c
@@ -823,7 +823,7 @@ static void ata_scsi_sdev_config(struct 
 	 * prevent SCSI midlayer from automatically deferring
 	 * requests.
 	 */
-	sdev->max_device_blocked = 1;
+	sdev->max_device_blocked = 2;
 }
 
 static void ata_scsi_dev_config(struct scsi_device *sdev,
@@ -3120,7 +3120,7 @@ int ata_scsi_add_hosts(struct ata_host *
 		 * Set host_blocked to 1 to prevent SCSI midlayer from
 		 * automatically deferring requests.
 		 */
-		shost->max_host_blocked = 1;
+		shost->max_host_blocked = 2;
 
 		rc = scsi_add_host(ap->scsi_host, ap->host->dev);
 		if (rc)

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