From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tao Ma Subject: Re: [PATCH] ext3: fix trim length underflow with small trim length. Date: Wed, 19 Jan 2011 21:50:41 +0800 Message-ID: <4D36EC31.30708@tao.ma> References: <1295430550-8978-1-git-send-email-tm@tao.ma> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: linux-ext4@vger.kernel.org, Jan Kara To: Lukas Czerner Return-path: Received: from oproxy3-pub.bluehost.com ([69.89.21.8]:37664 "HELO oproxy3-pub.bluehost.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1754506Ab1ASNuw (ORCPT ); Wed, 19 Jan 2011 08:50:52 -0500 In-Reply-To: Sender: linux-ext4-owner@vger.kernel.org List-ID: On 01/19/2011 06:42 PM, Lukas Czerner wrote: > On Wed, 19 Jan 2011, Tao Ma wrote: > >> From: Tao Ma >> >> We adjust 'len' with s_first_data_block - start in case of start is less >> than s_first_data_block, but it could underflow in case blocksize=1K, while >> fstrim_range.len=512 and fstrim_range.start = 0. In this case len happens >> to be underflow and in the end, although we are safe that last_group check >> will limit the trim to the whole volume, I am afraid that isn't what the user >> really want. >> >> So this patch fix it. It also adds a new variable s_first_data_block so that >> the 4 le32_to_cpu can be replaced with 1. > Well, I just realized that what are we doing is not exactly what will > user expect. User does not really care where the first data block is. > What the user will expect is, to trim let's say first one gigabyte > of his filesystem, not gigabyte - first data block. It is hard to tell, anyway, it is just 1kb(in case bs=1k and first_data_block != 0), so I guess either is ok. ;) > So what I suggest is to always add first_data_block to > fstrim_range.start and do all the necessary checks for overflow. If no > one has any objections I'll put it to the patch. I am fine with it. And it should make the code more clear and easy to read I guess. Regards, Tao