From: "Gao, Yunpeng" Subject: RE: Is it possible for the ext4/btrfs file system to pass some context related info to low level block driver? Date: Wed, 4 May 2011 18:31:19 +0800 Message-ID: References: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT Cc: "linux-btrfs@vger.kernel.org" , "linux-ext4@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" , "linux-mmc@vger.kernel.org" To: Kyungmin Park Return-path: Received: from mga09.intel.com ([134.134.136.24]:4515 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752636Ab1EDKeI convert rfc822-to-8bit (ORCPT ); Wed, 4 May 2011 06:34:08 -0400 In-Reply-To: Content-Language: en-US Sender: linux-ext4-owner@vger.kernel.org List-ID: Hi Park, Thanks a lot for the response. >It seems similar with TRIM. So how about to consider TRIM >implementation or extend it? Yes, file system set REQ_DISCARD flag to notify block device driver to execute TRIM. And I noticed there's already a flag REQ_META used for file system meta data. But seems only gfs2 file system uses the REQ_META flag, other file systems (including ext4 and btrfs) have not used this flag. Is the flag useless or any other reason? >I'm not familiar with NCQ implementation but it's also helpful to implement it. I don't know much about NCQ, too. Just have a impression that NCQ is only for SATA hard disk, can it also be used for block device, such as the mmc block device? Thanks. Regards, Yunpeng