From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751392AbdBOBSk (ORCPT ); Tue, 14 Feb 2017 20:18:40 -0500 Received: from szxga01-in.huawei.com ([58.251.152.64]:11400 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750930AbdBOBSi (ORCPT ); Tue, 14 Feb 2017 20:18:38 -0500 Subject: Re: [f2fs-dev] [PATCH] f2fs: fix multiple f2fs_add_link() calls having same name To: Jaegeuk Kim , , , References: <20170214180345.2074-1-jaegeuk@kernel.org> CC: From: Chao Yu Message-ID: <4fb2c86e-a50c-512f-2fa7-964540101138@huawei.com> Date: Wed, 15 Feb 2017 09:18:27 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.0 MIME-Version: 1.0 In-Reply-To: <20170214180345.2074-1-jaegeuk@kernel.org> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.134.22.195] X-CFilter-Loop: Reflected X-Mirapoint-Virus-RAPID-Raw: score=unknown(0), refid=str=0001.0A020204.58A3AC67.0007,ss=1,re=0.000,recu=0.000,reip=0.000,cl=1,cld=1,fgs=0, ip=0.0.0.0, so=2013-06-18 04:22:30, dmn=2013-03-21 17:37:32 X-Mirapoint-Loop-Id: 37aa3881d978cb81ec313f9ccff72cf2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2017/2/15 2:03, Jaegeuk Kim wrote: > VFS uses f2fs_lookup() to decide f2fs_add_link() call during file creation. > But, if there is a race condition, f2fs_add_link() can be called multiple > times, resulting in multiple dentries with a same name. This patches fixes > it by adding __f2fs_find_entry() in f2fs_add_link() path. As during ->lookup, i_mutex will be held all the time, so there is no race condition in between different file creators? Thanks, > > Cc: > Signed-off-by: Jaegeuk Kim > --- > fs/f2fs/dir.c | 14 ++++++++++++-- > 1 file changed, 12 insertions(+), 2 deletions(-) > > diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c > index 827c5daef4fc..bc7c48839bec 100644 > --- a/fs/f2fs/dir.c > +++ b/fs/f2fs/dir.c > @@ -643,14 +643,24 @@ int __f2fs_add_link(struct inode *dir, const struct qstr *name, > struct inode *inode, nid_t ino, umode_t mode) > { > struct fscrypt_name fname; > + struct page *page; > + struct f2fs_dir_entry *de; > int err; > > err = fscrypt_setup_filename(dir, name, 0, &fname); > if (err) > return err; > > - err = __f2fs_do_add_link(dir, &fname, inode, ino, mode); > - > + de = __f2fs_find_entry(dir, &fname, &page); > + if (de) { > + f2fs_dentry_kunmap(dir, page); > + f2fs_put_page(page, 0); > + err = -EEXIST; > + } else if (!IS_ERR(page)) { > + err = __f2fs_do_add_link(dir, &fname, inode, ino, mode); > + } else { > + err = PTR_ERR(page); > + } > fscrypt_free_filename(&fname); > return err; > } >