From mboxrd@z Thu Jan  1 00:00:00 1970
From: mlin@kernel.org (Ming Lin)
Date: Thu, 17 Mar 2016 10:27:23 -0700
Subject: [PATCH RFC] nvme: rewrite discard support
In-Reply-To: <20160317153335.GB6217@localhost.lm.intel.com>
References: <1458170132-16031-1-git-send-email-mlin@kernel.org>
 <20160317153335.GB6217@localhost.lm.intel.com>
Message-ID: <1458235643.11458.2.camel@ssi>

On Thu, 2016-03-17@15:33 +0000, Keith Busch wrote:
> On Wed, Mar 16, 2016@04:15:32PM -0700, Ming Lin wrote:
> > From: Ming Lin <ming.l at ssi.samsung.com>
> > 
> > This rewrites nvme_setup_discard() similar as sd_setup_discard_cmnd().
> > And moves it to common code so fabrics driver can also use it.
> 
> Initial thoughts on this, I see the appeal to having a generic NVMe
> discard setup, but I liked the existing implementation not needing a
> special case for discard check on every IO in the completion handler.
> 
> Allocating a page for just 16 bytes of data seems a bit wasteful even
> if it is short-lived. When it was allocating 256b from the DMA pool,
> the smaller amount of additional data seemed worth it for not creating
> a conditional completion.

How about moving the prp_small_pool to the core(and rename it to
nvme_small_pool)?

Then DISCARD can also use this pool. So we don't need a special case
check in the completion handler.