linux-kernel - Re: [RFC 1/3] x86/vdso: create vdso file, use it for mapping

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Date:   Tue, 30 Aug 2016 16:33:12 +0200
From:   Oleg Nesterov <oleg@...hat.com>
To:     Dmitry Safonov <dsafonov@...tuozzo.com>
Cc:     linux-kernel@...r.kernel.org, mingo@...hat.com,
        luto@...capital.net, tglx@...utronix.de, hpa@...or.com,
        x86@...nel.org, 0x7f454c46@...il.com, rostedt@...dmis.org,
        viro@...iv.linux.org.uk
Subject: Re: [RFC 1/3] x86/vdso: create vdso file, use it for mapping

On 08/25, Dmitry Safonov wrote:
>
> +static __init struct file *init_vdso_file(const struct vdso_image *vdso_image,
> +					const char *name)
> +{
> +	struct super_block *sb;
> +	struct qstr name_str;
> +	struct inode *inode;
> +	struct path path;
> +	struct file *res;
> +
> +	if (IS_ERR(vdso_mnt))
> +		return ERR_CAST(vdso_mnt);
> +	sb = vdso_mnt->mnt_sb;
> +
> +	name_str.hash = 0;
> +	name_str.len = strlen(name);
> +	name_str.name = name;
> +
> +	res = ERR_PTR(-ENOMEM);
> +	path.mnt = mntget(vdso_mnt);
> +	path.dentry = d_alloc_pseudo(sb, &name_str);
> +	if (!path.dentry)
> +		goto put_path;
> +	d_set_d_op(path.dentry, &vdso_dops);
> +
> +	res = ERR_PTR(-ENOSPC);
> +	inode = ramfs_get_inode(sb, NULL, S_IFREG | S_IRUGO | S_IXUGO, 0);
> +	if (!inode)
> +		goto put_path;
> +
> +	inode->i_flags |= S_PRIVATE;
> +	d_instantiate(path.dentry, inode);
> +	inode->i_size = vdso_image->size;
> +
> +	res = ERR_PTR(add_vdso_pages_to_page_cache(vdso_image, inode));
> +	if (IS_ERR(res))
> +		goto put_path;
> +
> +	res = alloc_file(&path, FMODE_READ, &ramfs_file_operations);
> +	if (!IS_ERR(res))
> +		return res;
> +
> +put_path:
> +	path_put(&path);
> +	return res;
> +}

Not sure... I think alloc_anon_inode() makes more sense.

Perhaps you can look at fs/aio.c and extract some bits of code into
the new helpers which could be used by both aio_fs and vdso_fs?

Oleg.