From mboxrd@z Thu Jan 1 00:00:00 1970 From: Al Viro Subject: Re: [PATCH] fs: namespace: Simplify function commit_tree() Date: Tue, 13 Jan 2015 05:28:01 +0000 Message-ID: <20150113052801.GH22149@ZenIV.linux.org.uk> References: <1421125686-23765-1-git-send-email-jiang.liu@linux.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org To: Jiang Liu Return-path: Content-Disposition: inline In-Reply-To: <1421125686-23765-1-git-send-email-jiang.liu@linux.intel.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On Tue, Jan 13, 2015 at 01:08:06PM +0800, Jiang Liu wrote: > Simplify function commit_tree() in fs/namespace.c, it also improves code > readability. Huh? > static void commit_tree(struct mount *mnt, struct mount *shadows) > { > struct mount *parent = mnt->mnt_parent; > - struct mount *m; > - LIST_HEAD(head); > struct mnt_namespace *n = parent->mnt_ns; > > BUG_ON(parent == mnt); > - > - list_add_tail(&head, &mnt->mnt_list); > - list_for_each_entry(m, &head, mnt_list) > - m->mnt_ns = n; > - > - list_splice(&head, n->list.prev); > - > + mnt->mnt_ns = n; > + list_add_tail(&mnt->mnt_list, &n->list); And who will set ->mnt_ns on other mounts reachable via ->mnt_list from mnt? Not to mention putting them on n->list... What you seem to have missed is that list_add_tail(&head, &mnt->mnt_list) is not the same thing as list_add_tail(&mnt->mnt_list, &head). We are not ripping mnt->mnt_list from whatever list it was on and insert it into a previously empty one in head. We take an unanchored cyclic list (all elements being some_mnt->mnt_list) and anchor it at head, then go through all elements of the original list and move them all at once into the end of n->list.