APPLIED: [PATCH][SRU][Disco] UBUNTU: SAUCE: shiftfs: enable overlayfs on shiftfs

[Khaled Elmously]

On 2019-08-01 20:08:29 , Christian Brauner wrote:
> From: Christian Brauner <christian.brauner at canonical.com>
> 
> BugLink: https://bugs.launchpad.net/bugs/1838677
> 
> This patch enables overlayfs to use shiftfs as an underlay.
> 
> Currently it is not possible to use overlayfs on top of shiftfs. This
> means Docker inside of LXD cannot make user of the overlay2 graph driver
> which is blocking users such as Travis from making use of it
> efficiently.
> 
> Co-Developed-by: Seth Forshee <seth.forshee at canonical.com>
> Signed-off-by: Seth Forshee <seth.forshee at canonical.com>
> Signed-off-by: Christian Brauner <christian.brauner at canonical.com>
> ---
>  fs/open.c            | 4 +++-
>  fs/overlayfs/file.c  | 1 +
>  fs/overlayfs/super.c | 5 +++--
>  fs/shiftfs.c         | 4 +++-
>  include/linux/fs.h   | 3 ++-
>  5 files changed, 12 insertions(+), 5 deletions(-)
> 
> diff --git a/fs/open.c b/fs/open.c
> index 14502dde6403..b8268a334dc9 100644
> --- a/fs/open.c
> +++ b/fs/open.c
> @@ -914,13 +914,15 @@ struct file *dentry_open(const struct path *path, int flags,
>  EXPORT_SYMBOL(dentry_open);
>  
>  struct file *open_with_fake_path(const struct path *path, int flags,
> -				struct inode *inode, const struct cred *cred)
> +				 struct inode *inode, struct dentry *dentry,
> +				 const struct cred *cred)
>  {
>  	struct file *f = alloc_empty_file_noaccount(flags, cred);
>  	if (!IS_ERR(f)) {
>  		int error;
>  
>  		f->f_path = *path;
> +		f->f_path.dentry = dentry;
>  		error = do_dentry_open(f, inode, NULL);
>  		if (error) {
>  			fput(f);
> diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
> index 6f6eb638a320..fe61b86c843b 100644
> --- a/fs/overlayfs/file.c
> +++ b/fs/overlayfs/file.c
> @@ -33,6 +33,7 @@ static struct file *ovl_open_realfile(const struct file *file,
>  
>  	old_cred = ovl_override_creds(inode->i_sb);
>  	realfile = open_with_fake_path(&file->f_path, flags, realinode,
> +				       ovl_dentry_real(file->f_path.dentry),
>  				       current_cred());
>  	revert_creds(old_cred);
>  
> diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
> index bb2a6f80ffd0..46def89a3664 100644
> --- a/fs/overlayfs/super.c
> +++ b/fs/overlayfs/super.c
> @@ -748,13 +748,14 @@ static int ovl_mount_dir(const char *name, struct path *path)
>  		ovl_unescape(tmp);
>  		err = ovl_mount_dir_noesc(tmp, path);
>  
> -		if (!err)
> -			if (ovl_dentry_remote(path->dentry)) {
> +		if (!err) {
> +			if ((path->dentry->d_sb->s_magic != SHIFTFS_MAGIC) && ovl_dentry_remote(path->dentry)) {
>  				pr_err("overlayfs: filesystem on '%s' not supported as upperdir\n",
>  				       tmp);
>  				path_put_init(path);
>  				err = -EINVAL;
>  			}
> +		}
>  		kfree(tmp);
>  	}
>  	return err;
> diff --git a/fs/shiftfs.c b/fs/shiftfs.c
> index 49f6714e9f95..400c3062365c 100644
> --- a/fs/shiftfs.c
> +++ b/fs/shiftfs.c
> @@ -1048,7 +1048,9 @@ static struct file *shiftfs_open_realfile(const struct file *file,
>  	oldcred = shiftfs_override_creds(inode->i_sb);
>  	/* XXX: open_with_fake_path() not gauranteed to stay around, if
>  	 * removed use dentry_open() */
> -	lowerf = open_with_fake_path(realpath, file->f_flags, loweri, info->creator_cred);
> +	lowerf = open_with_fake_path(realpath, file->f_flags, loweri,
> +				     realpath->dentry,
> +				     info->creator_cred);
>  	revert_creds(oldcred);
>  
>  	return lowerf;
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 5dd548c73f8d..4cb7a1124c5f 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -2524,7 +2524,8 @@ extern struct file *file_open_root(struct dentry *, struct vfsmount *,
>  				   const char *, int, umode_t);
>  extern struct file * dentry_open(const struct path *, int, const struct cred *);
>  extern struct file * open_with_fake_path(const struct path *, int,
> -					 struct inode*, const struct cred *);
> +					 struct inode*, struct dentry *dentry,
> +					 const struct cred *);
>  static inline struct file *file_clone_open(struct file *file)
>  {
>  	return dentry_open(&file->f_path, file->f_flags, file->f_cred);
> -- 
> 2.22.0
> 
> 
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