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Date: Thu, 28 Aug 2014 19:13:32 +0900
From: Changman Lee <cm224.lee@...sung.com>
To: Chao Yu <chao2.yu@...sung.com>
Cc: 'Jaegeuk Kim' <jaegeuk@...nel.org>, linux-kernel@...r.kernel.org,
linux-f2fs-devel@...ts.sourceforge.net
Subject: Re: [f2fs-dev] [PATCH] f2fs: reposition unlock_new_inode to prevent
accessing invalid inode
Hi,
On Thu, Aug 28, 2014 at 04:53:01PM +0800, Chao Yu wrote:
> Hi Changman,
>
> > -----Original Message-----
> > From: Changman Lee [mailto:cm224.lee@...sung.com]
> > Sent: Thursday, August 28, 2014 9:48 AM
> > To: Chao Yu
> > Cc: Jaegeuk Kim; linux-kernel@...r.kernel.org; linux-f2fs-devel@...ts.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 <chao2.yu@...sung.com>
> > > ---
> > > 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@...ts.sourceforge.net
> > > https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
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