From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christoph Hellwig <hch@infradead.org>
Subject: Re: [PATCH 1/4] block: Allow drivers to implement BLKDISCARD and add
 BLKSECDISCARD
Date: Thu, 10 Jun 2010 04:19:50 -0400
Message-ID: <20100610081950.GA15888@infradead.org>
References: <4C081AEC.7010302@nokia.com>
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To: Adrian Hunter <adrian.hunter@nokia.com>
Cc: Jens Axboe <axboe@kernel.dk>, Andrew Morton <akpm@linux-foundation.org>, "linux-mmc@vger.kernel.org" <linux-mmc@vger.kernel.org>, LKML <linux-kernel@vger.kernel.org>, Christoph Hellwig <hch@infradead.org>

On Fri, Jun 04, 2010 at 12:13:16AM +0300, Adrian Hunter wrote:
> SD/MMC cards provide an erase operation that is too inefficient to
> allow file systems to use it, however it is still useful for
> userspace tools because it is still 10 - 100 times faster than
> writing zeroes.  Allow the MMC block driver to provide its own
> BLKDISCARD implementation for this purpose.

That's no good reason.  Almost all current SSD TRIM implementations
have the same issue, that's why filesustems require the -o discard
option to enabled it.  In addition I've not actually seen any numbers
from you on a current kernel.