linux-kernel - RE: [PATCH v3 04/10] fs/ntfs3: Add file operations and implementation

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Message-ID: <d82dae3c12d94db7a2a212a8b8b79e8b@paragon-software.com>
Date:   Fri, 4 Sep 2020 12:41:24 +0000
From:   Konstantin Komarov <almaz.alexandrovich@...agon-software.com>
To:     Al Viro <viro@...iv.linux.org.uk>
CC:     "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "pali@...nel.org" <pali@...nel.org>,
        "dsterba@...e.cz" <dsterba@...e.cz>,
        "aaptel@...e.com" <aaptel@...e.com>,
        "willy@...radead.org" <willy@...radead.org>,
        "rdunlap@...radead.org" <rdunlap@...radead.org>,
        "joe@...ches.com" <joe@...ches.com>,
        "mark@...mstone.com" <mark@...mstone.com>
Subject: RE: [PATCH v3 04/10] fs/ntfs3: Add file operations and implementation

From: Al Viro <viro@....linux.org.uk>
Sent: Friday, August 28, 2020 6:46 PM
> On Fri, Aug 28, 2020 at 07:39:32AM -0700, Konstantin Komarov wrote:
> 
> > +static struct dentry *__ntfs_lookup(struct inode *dir, struct dentry *dentry,
> > +				    struct ntfs_fnd *fnd)
> > +{
> > +	struct dentry *d;
> > +	struct inode *inode;
> > +
> > +	inode = dir_search(dir, &dentry->d_name, fnd);
> > +
> > +	if (!inode) {
> > +		d_add(dentry, NULL);
> > +		d = NULL;
> > +		goto out;
> > +	}
> > +
> > +	if (IS_ERR(inode)) {
> > +		d = ERR_CAST(inode);
> > +		goto out;
> > +	}
> > +
> > +	d = d_splice_alias(inode, dentry);
> > +	if (IS_ERR(d)) {
> > +		iput(inode);
> > +		goto out;
> > +	}
> > +
> > +out:
> > +	return d;
> > +}
> 
> This is bollocks.  First and foremost, d_splice_alias() *does* iput() on
> failure, so you've got double-put there.  What's more
> 	* d_splice_alias(ERR_PTR(err), dentry) return err
> 	* d_splice_alias(NULL, dentry) is equivalent to d_add(dentry, NULL) and returns NULL
> 
> IOW, all that boilerplate could be replaced with one line:
> 
> 	return d_splice_alias(dir_search(dir, &dentry->d_name, fnd), dentry);

Hi Al! Agreed. Will be fixed in v4.
Thanks.