ACK/cmnt: [PATCH][SRU][Disco] UBUNTU: SAUCE: shiftfs: enable overlayfs on shiftfs

[Christian Brauner]

On August 12, 2019 4:02:33 PM GMT+02:00, Kleber Souza <kleber.souza at canonical.com> wrote:
>On 8/1/19 8:08 PM, 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>
>
>Hi Christian,
>
>The LP bug states:
>
>> Target kernels: All LTS kernels that do support shiftfs, if possible.
>
>Will this patch be submitted for Bionic and Xenial as well?

Sorry, was on vacation.
It should go into all kernels that have shiftfs support. :)
Seth probably knows better whether we have this in Bionic and Xenial. I reckon we do.
Seth, do I need to submit this separate patches?

Christian

>
>
>Acked-by: Kleber Sacilotto de Souza <kleber.souza at canonical.com>
>
>Thanks,
>Kleber
>
>> ---
>>  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);
>>