From: Mike Hayward <hayward@loup.net>
To: dgilbert@interlog.com
Cc: bharrosh@panasas.com, James.Bottomley@suse.de,
linux-scsi@vger.kernel.org, mh-linux-kernel@loup.net
Subject: Re: [PATCH] sg: retrofit SG_FLAG_Q_AT_TAIL flag
Date: Mon, 22 Mar 2010 01:39:28 -0600 [thread overview]
Message-ID: <201003220739.o2M7dSdS002818@alien.loup.net> (raw)
In-Reply-To: <4BA65DC1.2020102@interlog.com> (message from Douglas Gilbert on Sun, 21 Mar 2010 13:56:17 -0400)
Hi Doug,
> Now I decided to check the SG_IO ioctl used directly
> against block devices and it calls:
> blk_execute_rq(q, bd_disk, rq, 0);
>
> The last argument is 'at_head' so it has been queuing
> at_tail for some time. How is that for compatibility??
>
> That almost suggests there should be a
> #define SG_FLAG_Q_AT_HEAD 0x20
>
> added to sg.h to cover all the bases.
I would have to agree that default should be queue at tail and option
should be to queue at head since that presents risk of starvation and
is generally not what is desired, just like normal SCSI queue at head
in the target.
I'll give your patch a spin on live hardware soon.
- Mike
next prev parent reply other threads:[~2010-03-22 8:49 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-03-20 19:15 [PATCH] sg: retrofit SG_FLAG_Q_AT_TAIL flag Douglas Gilbert
2010-03-21 11:36 ` Boaz Harrosh
2010-03-21 17:56 ` Douglas Gilbert
2010-03-22 7:39 ` Mike Hayward [this message]
2010-03-22 8:07 ` Boaz Harrosh
2010-03-22 8:32 ` FUJITA Tomonori
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