From mboxrd@z Thu Jan 1 00:00:00 1970 From: Changman Lee Subject: Re: [PATCH] f2fs: reposition unlock_new_inode to prevent accessing invalid inode Date: Thu, 28 Aug 2014 19:13:32 +0900 Message-ID: <20140828101332.GB6808@lcm> References: <009101cfc119$8e7a5a00$ab6f0e00$@samsung.com> <20140828014736.GA6808@lcm> <003801cfc29d$a370dad0$ea529070$@samsung.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from sog-mx-4.v43.ch3.sourceforge.com ([172.29.43.194] helo=mx.sourceforge.net) by sfs-ml-2.v29.ch3.sourceforge.com with esmtp (Exim 4.76) (envelope-from ) id 1XMwjg-0000mh-Ln for linux-f2fs-devel@lists.sourceforge.net; Thu, 28 Aug 2014 10:15:20 +0000 Received: from mailout4.samsung.com ([203.254.224.34]) by sog-mx-4.v43.ch3.sourceforge.com with esmtps (TLSv1:RC4-MD5:128) (Exim 4.76) id 1XMwja-0001Mx-Fs for linux-f2fs-devel@lists.sourceforge.net; Thu, 28 Aug 2014 10:15:20 +0000 Received: from epcpsbgr5.samsung.com (u145.gpu120.samsung.co.kr [203.254.230.145]) by mailout4.samsung.com (Oracle Communications Messaging Server 7u4-24.01 (7.0.4.24.0) 64bit (built Nov 17 2011)) with ESMTP id <0NB000FJEHSSSSC0@mailout4.samsung.com> for linux-f2fs-devel@lists.sourceforge.net; Thu, 28 Aug 2014 19:14:52 +0900 (KST) Content-disposition: inline In-reply-to: <003801cfc29d$a370dad0$ea529070$@samsung.com> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linux-f2fs-devel-bounces@lists.sourceforge.net To: Chao Yu Cc: 'Jaegeuk Kim' , linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net Hi, On Thu, Aug 28, 2014 at 04:53:01PM +0800, Chao Yu wrote: > Hi Changman, > > > -----Original Message----- > > From: Changman Lee [mailto:cm224.lee@samsung.com] > > Sent: Thursday, August 28, 2014 9:48 AM > > To: Chao Yu > > Cc: Jaegeuk Kim; linux-kernel@vger.kernel.org; linux-f2fs-devel@lists.sourceforge.net > > Subject: Re: [f2fs-dev] [PATCH] f2fs: reposition unlock_new_inode to prevent accessing invalid > > inode > > > > Hi Chao, > > > > I agree it's correct unlock_new_inode should be located after make_bad_inode. > > > > About this scenario, > > I think we should check some condition if this could be occured; > > I think this condition is the almost impossible but which can happen theoretically. > > > A inode allocated newly could be victim by gc thread. > > Then, f2fs_iget called by Thread A have to fail because we handled it as > > bad_inode in Thread B. However, f2fs_iget could still get inode. > > How about check it using is_bad_inode() in f2fs_iget. > > Yes, agreed. How about return -EIO when this inode we iget_locked is bad? Hmm.. It might be better to check return value of f2fs_iget like other f/s. - a/fs/f2fs/gc.c +++ b/fs/f2fs/gc.c @@ -595,6 +595,8 @@ next_step: inode = f2fs_iget(sb, dni.ino); if (IS_ERR(inode)) continue; + else if (is_bad_inode(inode)) + continue; Thanks, Changman > > Thanks, > Yu > > > > > Thanks, > > > > On Tue, Aug 26, 2014 at 06:35:29PM +0800, Chao Yu wrote: > > > As the race condition on the inode cache, following scenario can appear: > > > [Thread a] [Thread b] > > > ->f2fs_mkdir > > > ->f2fs_add_link > > > ->__f2fs_add_link > > > ->init_inode_metadata failed here > > > ->gc_thread_func > > > ->f2fs_gc > > > ->do_garbage_collect > > > ->gc_data_segment > > > ->f2fs_iget > > > ->iget_locked > > > ->wait_on_inode > > > ->unlock_new_inode > > > ->move_data_page > > > ->make_bad_inode > > > ->iput > > > > > > When we fail in create/symlink/mkdir/mknod/tmpfile, the new allocated inode > > > should be set as bad to avoid being accessed by other thread. But in above > > > scenario, it allows f2fs to access the invalid inode before this inode was set > > > as bad. > > > This patch fix the potential problem, and this issue was found by code review. > > > > > > Signed-off-by: Chao Yu > > > --- > > > fs/f2fs/namei.c | 10 +++++----- > > > 1 file changed, 5 insertions(+), 5 deletions(-) > > > > > > diff --git a/fs/f2fs/namei.c b/fs/f2fs/namei.c > > > index 6b53ce9..845f1be 100644 > > > --- a/fs/f2fs/namei.c > > > +++ b/fs/f2fs/namei.c > > > @@ -134,8 +134,8 @@ static int f2fs_create(struct inode *dir, struct dentry *dentry, umode_t > > mode, > > > return 0; > > > out: > > > clear_nlink(inode); > > > - unlock_new_inode(inode); > > > make_bad_inode(inode); > > > + unlock_new_inode(inode); > > > iput(inode); > > > alloc_nid_failed(sbi, ino); > > > return err; > > > @@ -267,8 +267,8 @@ static int f2fs_symlink(struct inode *dir, struct dentry *dentry, > > > return err; > > > out: > > > clear_nlink(inode); > > > - unlock_new_inode(inode); > > > make_bad_inode(inode); > > > + unlock_new_inode(inode); > > > iput(inode); > > > alloc_nid_failed(sbi, inode->i_ino); > > > return err; > > > @@ -308,8 +308,8 @@ static int f2fs_mkdir(struct inode *dir, struct dentry *dentry, umode_t > > mode) > > > out_fail: > > > clear_inode_flag(F2FS_I(inode), FI_INC_LINK); > > > clear_nlink(inode); > > > - unlock_new_inode(inode); > > > make_bad_inode(inode); > > > + unlock_new_inode(inode); > > > iput(inode); > > > alloc_nid_failed(sbi, inode->i_ino); > > > return err; > > > @@ -354,8 +354,8 @@ static int f2fs_mknod(struct inode *dir, struct dentry *dentry, > > > return 0; > > > out: > > > clear_nlink(inode); > > > - unlock_new_inode(inode); > > > make_bad_inode(inode); > > > + unlock_new_inode(inode); > > > iput(inode); > > > alloc_nid_failed(sbi, inode->i_ino); > > > return err; > > > @@ -688,8 +688,8 @@ release_out: > > > out: > > > f2fs_unlock_op(sbi); > > > clear_nlink(inode); > > > - unlock_new_inode(inode); > > > make_bad_inode(inode); > > > + unlock_new_inode(inode); > > > iput(inode); > > > alloc_nid_failed(sbi, inode->i_ino); > > > return err; > > > -- > > > 2.0.0.421.g786a89d > > > > > > > > > > > > ------------------------------------------------------------------------------ > > > Slashdot TV. > > > Video for Nerds. Stuff that matters. > > > http://tv.slashdot.org/ > > > _______________________________________________ > > > Linux-f2fs-devel mailing list > > > Linux-f2fs-devel@lists.sourceforge.net > > > https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel ------------------------------------------------------------------------------ Slashdot TV. Video for Nerds. Stuff that matters. http://tv.slashdot.org/