Re: [PATCH v3 04/10] fs/ntfs3: Add file operations and implementation

Al Viro
2020-08-28T15:55:44Z

On Fri, Aug 28, 2020 at 07:39:32AM -0700, Konstantin Komarov wrote:

> +static int ntfs_atomic_open(struct inode *dir, struct dentry *dentry,
> + struct file *file, u32 flags, umode_t mode)
> +{
> + int err;
> + bool excl = !!(flags & O_EXCL);
> + struct inode *inode;
> + struct ntfs_fnd *fnd = NULL;
> + struct ntfs_inode *ni = ntfs_i(dir);
> +
> + ni_lock(ni);
> +
> + if (d_in_lookup(dentry)) {
> + struct dentry *d;
> +
> + fnd = fnd_get(&ntfs_i(dir)->dir);
> + if (!fnd) {
> + err = -ENOMEM;
> + goto out;
> + }
> +
> + d = __ntfs_lookup(dir, dentry, fnd);
> + if (IS_ERR(d)) {
> + err = PTR_ERR(d);
> + d = NULL;
> + goto out1;
> + }
> +
> + if (d)
> + dentry = d;
> +
> + if (d_really_is_positive(dentry)) {
> + if (file->f_mode & FMODE_OPENED) {

How do we get FMODE_OPENED here?

> + dput(d);
> + err = 0;
> + } else
> + err = finish_no_open(file, d);
> + goto out1;
> + }
> + WARN_ON(d);
> + }
> +
> + if (!(flags & O_CREAT)) {
> + err = -ENOENT;
> + goto out1;
> + }

Just return finish_no_open() in that case. And let the caller handle
that.

> + err = ntfs_create_inode(dir, dentry, file, mode, 0, NULL, 0, excl, fnd,
> + &inode);
> +
> +out1:
> + fnd_put(fnd);
> +out:
> + ni_unlock(ni);
> +
> + return err;
> +}

BTW, what's the point of that ni_lock() here? d_in_lookup() is stable
regardless of that and any attempts to create something in the parent
are serialized by ->i_rwsem. If you want it around the actual file
creation, why not take it just there, and replace the open-coded
ntfs_lookup() with the call of the real thing? As in
if (d_in_lookup(dentry)) {
d = ntfs_lookup(....);
if (IS_ERR(d))
return d;
if (d)
dentry = d;
}
if (!(flags & O_CREAT) || d_really_is_positive(dentry))
return finish_no_open(file, d);
/* deal with creation of file */
ni_lock(...);
....