linux-kernel - Re: [PATCH v2 0/9] fix max discard sectors limit

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Date:	Mon, 22 Apr 2013 14:23:24 -0700
From:	Kent Overstreet <koverstreet@...gle.com>
To:	Namjae Jeon <linkinjeon@...il.com>
Cc:	dwmw2@...radead.org, axboe@...nel.dk, shli@...nel.org,
	Paul.Clements@...eleye.com, npiggin@...nel.dk, neilb@...e.de,
	cjb@...top.org, adrian.hunter@...el.com,
	James.Bottomley@...senPartnership.com, JBottomley@...allels.com,
	linux-scsi@...r.kernel.org, linux-mtd@...ts.infradead.org,
	nbd-general@...ts.sourceforge.net, linux-raid@...r.kernel.org,
	linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org,
	jcmvbkbc@...il.com, Namjae Jeon <namjae.jeon@...sung.com>
Subject: Re: [PATCH v2 0/9] fix max discard sectors limit

On Sat, Apr 20, 2013 at 01:40:02AM +0900, Namjae Jeon wrote:
> From: Namjae Jeon <namjae.jeon@...sung.com>
> 
> linux-v3.8-rc1 and later support for plug for blkdev_issue_discard with
> commit 0cfbcafcae8b7364b5fa96c2b26ccde7a3a296a9 
> (block: add plug for blkdev_issue_discard )
> 
> For example,
> 1) DISCARD rq-1 with size size 4GB
> 2) DISCARD rq-2 with size size 1GB
> 
> If these 2 discard requests get merged, final request size will be 5GB.
> 
> In this case, request's __data_len field may overflow as it can store
> max 4GB(unsigned int).

Complete NACK - like James said, this fix is nonsensical. This should be
fixed by just checking for overflow before merging requests, not with
weird hacks in the drivers.
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