public inbox for linux-scsi@vger.kernel.org
 help / color / mirror / Atom feed
From: Christoph Hellwig <hch@infradead.org>
To: Webb Scales <webbnh@hp.com>
Cc: Hannes Reinecke <hare@suse.de>,
	James Bottomley <jbottomley@parallels.com>,
	Christoph Hellwig <hch@infradead.org>,
	linux-scsi@vger.kernel.org
Subject: Re: [PATCH] megaraid_sas: Enable shared tag map
Date: Wed, 1 Oct 2014 14:10:03 -0700	[thread overview]
Message-ID: <20141001211003.GA24820@infradead.org> (raw)
In-Reply-To: <542C4D33.2030401@hp.com>

On Wed, Oct 01, 2014 at 02:51:31PM -0400, Webb Scales wrote:
> Hannes,
> 
> In megasas_change_queue_type(), is it possible for sdev->queue_depth to be
> greater than 256?
> 
> Unless I'm misunderstanding the SCSI code, we can request a
> queue-depth/tag-map-size which is greater than 256, but, since the
> scsi_cmnd::tag field is an unsigned char, depths greater than 256 may
> overflow the field when high-numbered tags are used...do I have that right?

Yes, we really need to increase the size of the tag field.  SAM allows
a transport specific limit of up to 64 _bytes_ for it, although I don't
know implementation that large.  Given that the block layer can generate
up to 32-bit tags both for the old blk-tag.c code and the new
blk-mq-tag.c version it would be good to use a u32 there.  Can you send
me a patch?


  reply	other threads:[~2014-10-01 21:10 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-09-29 11:47 [PATCH] megaraid_sas: Enable shared tag map Hannes Reinecke
2014-09-29 16:52 ` Webb Scales
2014-09-29 17:08   ` James Bottomley
2014-09-30  7:43 ` Christoph Hellwig
2014-09-30  9:08   ` Hannes Reinecke
2014-10-01 18:51 ` Webb Scales
2014-10-01 21:10   ` Christoph Hellwig [this message]
2014-10-02  6:51     ` Hannes Reinecke
2014-10-02  9:19       ` Christoph Hellwig
2014-10-02  9:50         ` Hannes Reinecke
2014-10-02 11:36           ` Christoph Hellwig
2014-10-02 12:00             ` Hannes Reinecke
2014-10-02 14:32               ` Christoph Hellwig
2014-10-02 12:05       ` James Bottomley
2014-10-02 12:14         ` Hannes Reinecke
2014-10-02 13:06           ` James Bottomley

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20141001211003.GA24820@infradead.org \
    --to=hch@infradead.org \
    --cc=hare@suse.de \
    --cc=jbottomley@parallels.com \
    --cc=linux-scsi@vger.kernel.org \
    --cc=webbnh@hp.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox