[PATCH resend 0/1] USB: uas: Fix slave queue_depth not being set

[PATCH resend 0/1] USB: uas: Fix slave queue_depth not being set

[Hans de Goede]

Hi Greg,

There was some discussion about this patch during its initial posting,
but the concensus seems to be that this patch, which is in essence a
partial revert of the patch causing the problem, is the best way to fix
this.

So I'm resending this to make sure it does not fall through the cracks,
given that this fixes a (performance) regression.

Regards,

Hans
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[PATCH resend] USB: uas: Fix slave queue_depth not being set

[Hans de Goede]

Commit 198de51dbc34 ("USB: uas: Limit qdepth at the scsi-host level")
removed the scsi_change_queue_depth() call from uas_slave_configure()
assuming that the slave would inherit the host's queue_depth, which
that commit sets to the same value.

This is incorrect, without the scsi_change_queue_depth() call the slave's
queue_depth defaults to 1, introducing a performance regression.

This commit restores the call, fixing the performance regression.

Cc: stable@vger.kernel.org
Fixes: 198de51dbc34 ("USB: uas: Limit qdepth at the scsi-host level")
Reported-by: Tom Yan <tom.ty89@gmail.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
 drivers/usb/storage/uas.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/usb/storage/uas.c b/drivers/usb/storage/uas.c
index 16bc679..ecc7d4b 100644
--- a/drivers/usb/storage/uas.c
+++ b/drivers/usb/storage/uas.c
@@ -835,6 +835,7 @@ static int uas_slave_configure(struct scsi_device *sdev)
 	if (devinfo->flags & US_FL_BROKEN_FUA)
 		sdev->broken_fua = 1;
 
+	scsi_change_queue_depth(sdev, devinfo->qdepth - 2);
 	return 0;
 }
 
-- 
2.7.4

Re: [PATCH resend] USB: uas: Fix slave queue_depth not being set

[Oliver Neukum]

On Tue, 2016-05-31 at 09:18 +0200, Hans de Goede wrote:
> Commit 198de51dbc34 ("USB: uas: Limit qdepth at the scsi-host level")
> removed the scsi_change_queue_depth() call from uas_slave_configure()
> assuming that the slave would inherit the host's queue_depth, which
> that commit sets to the same value.
> 
> This is incorrect, without the scsi_change_queue_depth() call the slave's
> queue_depth defaults to 1, introducing a performance regression.

Hans, may I ask what become of this patch? I don't see it in the queue.

	Regards
		Oliver

Re: [PATCH resend] USB: uas: Fix slave queue_depth not being set

[Hans de Goede]

Hi,

On 13-06-16 14:05, Oliver Neukum wrote:
> On Tue, 2016-05-31 at 09:18 +0200, Hans de Goede wrote:
>> Commit 198de51dbc34 ("USB: uas: Limit qdepth at the scsi-host level")
>> removed the scsi_change_queue_depth() call from uas_slave_configure()
>> assuming that the slave would inherit the host's queue_depth, which
>> that commit sets to the same value.
>>
>> This is incorrect, without the scsi_change_queue_depth() call the slave's
>> queue_depth defaults to 1, introducing a performance regression.
>
> Hans, may I ask what become of this patch? I don't see it in the queue.

It is here:

https://git.kernel.org/cgit/linux/kernel/git/gregkh/usb.git/commit/?h=usb-linus&id=593224ea77b1ca842f45cf76f4deeef44dfbacd1

Which is part of:

https://git.kernel.org/cgit/linux/kernel/git/gregkh/usb.git/log/?h=usb-linus

Regards,

Hans
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