From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2993542AbbEOXda (ORCPT ); Fri, 15 May 2015 19:33:30 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:43137 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2992650AbbEOXLH (ORCPT ); Fri, 15 May 2015 19:11:07 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Al Viro , Ben Hutchings , hujianyang Subject: [PATCH 3.14 36/51] deal with deadlock in d_walk() Date: Fri, 15 May 2015 16:10:38 -0700 Message-Id: <20150515230951.765831860@linuxfoundation.org> X-Mailer: git-send-email 2.4.0 In-Reply-To: <20150515230950.640453239@linuxfoundation.org> References: <20150515230950.640453239@linuxfoundation.org> User-Agent: quilt/0.64 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Al Viro commit ca5358ef75fc69fee5322a38a340f5739d997c10 upstream. ... by not hitting rename_retry for reasons other than rename having happened. In other words, do _not_ restart when finding that between unlocking the child and locking the parent the former got into __dentry_kill(). Skip the killed siblings instead... Signed-off-by: Al Viro Cc: Ben Hutchings [hujianyang: Backported to 3.14 refer to the work of Ben Hutchings in 3.2: - Adjust context to make __dentry_kill() apply to d_kill()] Signed-off-by: hujianyang Signed-off-by: Greg Kroah-Hartman --- fs/dcache.c | 31 ++++++++++++++++--------------- 1 file changed, 16 insertions(+), 15 deletions(-) --- a/fs/dcache.c +++ b/fs/dcache.c @@ -435,7 +435,7 @@ static struct dentry *d_kill(struct dent __releases(parent->d_lock) __releases(dentry->d_inode->i_lock) { - list_del(&dentry->d_child); + __list_del_entry(&dentry->d_child); /* * Inform d_walk() that we are no longer attached to the * dentry tree @@ -1123,33 +1123,31 @@ resume: /* * All done at this level ... ascend and resume the search. */ + rcu_read_lock(); +ascend: if (this_parent != parent) { struct dentry *child = this_parent; this_parent = child->d_parent; - rcu_read_lock(); spin_unlock(&child->d_lock); spin_lock(&this_parent->d_lock); - /* - * might go back up the wrong parent if we have had a rename - * or deletion - */ - if (this_parent != child->d_parent || - (child->d_flags & DCACHE_DENTRY_KILLED) || - need_seqretry(&rename_lock, seq)) { - spin_unlock(&this_parent->d_lock); - rcu_read_unlock(); + /* might go back up the wrong parent if we have had a rename. */ + if (need_seqretry(&rename_lock, seq)) goto rename_retry; + next = child->d_child.next; + while (unlikely(child->d_flags & DCACHE_DENTRY_KILLED)) { + if (next == &this_parent->d_subdirs) + goto ascend; + child = list_entry(next, struct dentry, d_child); + next = next->next; } rcu_read_unlock(); - next = child->d_child.next; goto resume; } - if (need_seqretry(&rename_lock, seq)) { - spin_unlock(&this_parent->d_lock); + if (need_seqretry(&rename_lock, seq)) goto rename_retry; - } + rcu_read_unlock(); if (finish) finish(data); @@ -1159,6 +1157,9 @@ out_unlock: return; rename_retry: + spin_unlock(&this_parent->d_lock); + rcu_read_unlock(); + BUG_ON(seq & 1); if (!retry) return; seq = 1;