linux-kernel - RE: [PATCH] ntfs: avoid incorrectly release for root inode in fill

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Date:	Fri, 25 Jul 2014 16:54:05 +0800
From:	Chao Yu <chao2.yu@...sung.com>
To:	'Anton Altaparmakov' <anton@...era.com>
Cc:	linux-ntfs-dev@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
	'Anton Altaparmakov' <aia21@...mes.cam.ac.uk>
Subject: RE: [PATCH] ntfs: avoid incorrectly release for root inode in
 fill_super

Hi,

> -----Original Message-----
> From: Anton Altaparmakov [mailto:aia21@...mes.cam.ac.uk] On Behalf Of Anton Altaparmakov
> Sent: Friday, July 25, 2014 3:47 PM
> To: Chao Yu
> Cc: linux-ntfs-dev@...ts.sourceforge.net; linux-kernel@...r.kernel.org
> Subject: Re: [PATCH] ntfs: avoid incorrectly release for root inode in fill_super
> 
> Hi,
> 
> NAK
> 
> This patch is incorrect.  Perhaps you failed to see the ihold() above the d_make_root() call?
> That means we hold two references on the inode - one from the load_system_files()::ntfs_iget()
> and one from the ihold() before d_make_root().
> 
> Thus in the error code path d_make_root() does iput() which releases one reference and then
> we do iput() in the error handling path of ntfs_fill_super() which releases the second reference.

Yes, you're right. It's my mistaken to missing the code ihold(), sorry about that.
Thank you for correcting me, and please ignore this patch.

> 
> Best regards,
> 
> 	Anton
> 
> On 25 Jul 2014, at 03:25, Chao Yu <chao2.yu@...sung.com> wrote:
> 
> > In d_make_root, when we fail to allocate dentry for root inode, we will iput
> > root inode in this function.
> > So we do not need to release this inode again at d_make_root's caller.
> >
> > Signed-off-by: Chao Yu <chao2.yu@...sung.com>
> > ---
> > fs/ntfs/super.c | 6 +++++-
> > 1 file changed, 5 insertions(+), 1 deletion(-)
> >
> > diff --git a/fs/ntfs/super.c b/fs/ntfs/super.c
> > index 6c3296e..99c5cc6 100644
> > --- a/fs/ntfs/super.c
> > +++ b/fs/ntfs/super.c
> > @@ -2975,7 +2975,11 @@ static int ntfs_fill_super(struct super_block *sb, void *opt, const
> int silent)
> > 			vol->secure_ino = NULL;
> > 		}
> > 	}
> > -	iput(vol->root_ino);
> > +
> > +	/*
> > +	 * Just set NULL value here because we have already iput root_ino
> > +	 * in d_make_root.
> > +	 */
> > 	vol->root_ino = NULL;
> > 	iput(vol->lcnbmp_ino);
> > 	vol->lcnbmp_ino = NULL;
> 
> --
> Anton Altaparmakov <aia21 at cam.ac.uk> (replace at with @)
> University of Cambridge Information Services, Roger Needham Building
> 7 JJ Thomson Avenue, Cambridge, CB3 0RB, UK

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