From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from cn.fujitsu.com ([59.151.112.132]:21180 "EHLO heian.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1750701AbaJ0EIb convert rfc822-to-8bit (ORCPT ); Mon, 27 Oct 2014 00:08:31 -0400 Message-ID: <544DC5A7.7020302@cn.fujitsu.com> Date: Mon, 27 Oct 2014 12:10:15 +0800 From: Qu Wenruo MIME-Version: 1.0 To: , Subject: Re: [PATCH] btrfs: Add show_path function for btrfs_super_ops. References: <1405933349-6215-1-git-send-email-quwenruo@cn.fujitsu.com> <20140724130928.GY1553@twin.jikos.cz> <53D1A78E.8020802@cn.fujitsu.com> <53D9BCF3.80001@cn.fujitsu.com> In-Reply-To: <53D9BCF3.80001@cn.fujitsu.com> Content-Type: text/plain; charset="utf-8"; format=flowed Sender: linux-btrfs-owner@vger.kernel.org List-ID: Ping？ Any new comments? It has been a long time and the patch still not merged.... Thanks, Qu -------- Original Message -------- Subject: Re: [PATCH] btrfs: Add show_path function for btrfs_super_ops. From: Qu Wenruo To: , Date: 2014年07月31日 11:50 > Hi David, > > No mean to disturb you, but it has been serveral days since last comment. > > If you have any comment about the new patch, since due to my lack of > explain the patch seems not > reviewed, I am very glad to hear. > > If any other ideas occur to you, like the pro and cons about old mount > trick vs show_path() implement, > it would be also quite nice. > > Thanks, > Qu > > > -------- Original Message -------- > Subject: Re: [PATCH] btrfs: Add show_path function for btrfs_super_ops. > From: Qu Wenruo > To: dsterba@suse.cz, linux-btrfs@vger.kernel.org > Date: 2014年07月25日 08:40 >> Thanks for the comment. >> >> -------- Original Message -------- >> Subject: Re: [PATCH] btrfs: Add show_path function for btrfs_super_ops. >> From: David Sterba >> To: Qu Wenruo >> Date: 2014年07月24日 21:09 >>> On Mon, Jul 21, 2014 at 05:02:29PM +0800, Qu Wenruo wrote: >>>> show_path() function in struct super_operations is used to output >>>> subtree mount info for mountinfo. >>>> Without the implement of show_path() function, user can not found >>>> where >>>> each subvolume is mounted if using 'subvolid=' mount option. >>>> (When mounted with 'subvol=' mount option, vfs is aware of subtree >>>> mount >>>> and can to the path resolve by vfs itself) >>> Your previous patches unify both to call mount_subtree, then the >>> default >>> vfs implementation of show_path will do the right thing, ie >>> seq_dentry(...), and the path will be resolved for free. >>> >>> Means this patch is not needed, so I'll skip commenting it. >> >> I'm sorry that I forgot to mention this patch is going to replace the >> previous patch(use mount_subtree method). >> >> Since vfs provide the show_path() function to do the fs specific >> subtree showing things, >> I would like to use it other than previous mount_subtree() trick. >> >> Also. as mentioned by Chandan Rajendra, previous subtree patch can't >> handle subvolume behind normal directory. >> This show_path() patch is somewhat v2 version of previous patch. >>> >>>> With this patch, end users will be able to use findmnt(8) or other >>>> programs reading mountinfo to find which btrfs subvolume is mounted. >>>> >>>> Though we use fs_info->subvol_sem to protect show_path() from >>>> subvolume >>>> destroying/creating, if user renames/moves the parent non-subvolume >>>> dir of a subvolume, it is still possible that concurrency may >>>> happen and >>>> cause btrfs_search_slot() fails to find the desired key. >>>> In that case, we just return -EBUSY and info user to try again since >>>> extra locking like locking the whole subvolume tree is too >>>> expensive for >>>> such usage. >>> And the subvolume renames will be handled as well. > > -- > To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html