Re: [PATCH v5 14/14] VFS: introduce end_creating_keep()

On Thu, 2025-11-06 at 11:50 +1100, NeilBrown wrote:
> From: NeilBrown <[email protected]>
> 
> Occasionally the caller of end_creating() wants to keep using the dentry.
> Rather then requiring them to dget() the dentry (when not an error)
> before calling end_creating(), provide end_creating_keep() which does
> this.
> 
> cachefiles and overlayfs make use of this.
> 
> Reviewed-by: Amir Goldstein <[email protected]>
> Signed-off-by: NeilBrown <[email protected]>
> ---
>  fs/cachefiles/namei.c |  3 +--
>  fs/overlayfs/dir.c    |  8 ++------
>  fs/overlayfs/super.c  | 11 +++--------
>  include/linux/namei.h | 22 ++++++++++++++++++++++
>  4 files changed, 28 insertions(+), 16 deletions(-)
> 
> diff --git a/fs/cachefiles/namei.c b/fs/cachefiles/namei.c
> index 59327618ac42..ef22ac19545b 100644
> --- a/fs/cachefiles/namei.c
> +++ b/fs/cachefiles/namei.c
> @@ -155,8 +155,7 @@ struct dentry *cachefiles_get_directory(struct cachefiles_cache *cache,
>  
>  	/* Tell rmdir() it's not allowed to delete the subdir */
>  	inode_lock(d_inode(subdir));
> -	dget(subdir);
> -	end_creating(subdir);
> +	end_creating_keep(subdir);
>  
>  	if (!__cachefiles_mark_inode_in_use(NULL, d_inode(subdir))) {
>  		pr_notice("cachefiles: Inode already in use: %pd (B=%lx)\n",
> diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
> index a4a0dc261310..50717ff8cac7 100644
> --- a/fs/overlayfs/dir.c
> +++ b/fs/overlayfs/dir.c
> @@ -252,10 +252,7 @@ struct dentry *ovl_create_temp(struct ovl_fs *ofs, struct dentry *workdir,
>  	if (IS_ERR(ret))
>  		return ret;
>  	ret = ovl_create_real(ofs, workdir, ret, attr);
> -	if (!IS_ERR(ret))
> -		dget(ret);
> -	end_creating(ret);
> -	return ret;
> +	return end_creating_keep(ret);
>  }
>  
>  static int ovl_set_opaque_xerr(struct dentry *dentry, struct dentry *upper,
> @@ -365,8 +362,7 @@ static int ovl_create_upper(struct dentry *dentry, struct inode *inode,
>  	if (IS_ERR(newdentry))
>  		return PTR_ERR(newdentry);
>  
> -	dget(newdentry);
> -	end_creating(newdentry);
> +	end_creating_keep(newdentry);
>  
>  	if (ovl_type_merge(dentry->d_parent) && d_is_dir(newdentry) &&
>  	    !ovl_allow_offline_changes(ofs)) {
> diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
> index 3acda985c8a3..7b8fc1cab6eb 100644
> --- a/fs/overlayfs/super.c
> +++ b/fs/overlayfs/super.c
> @@ -319,8 +319,7 @@ static struct dentry *ovl_workdir_create(struct ovl_fs *ofs,
>  		};
>  
>  		if (work->d_inode) {
> -			dget(work);
> -			end_creating(work);
> +			end_creating_keep(work);
>  			if (persist)
>  				return work;
>  			err = -EEXIST;
> @@ -336,9 +335,7 @@ static struct dentry *ovl_workdir_create(struct ovl_fs *ofs,
>  		}
>  
>  		work = ovl_do_mkdir(ofs, dir, work, attr.ia_mode);
> -		if (!IS_ERR(work))
> -			dget(work);
> -		end_creating(work);
> +		end_creating_keep(work);
>  		err = PTR_ERR(work);
>  		if (IS_ERR(work))
>  			goto out_err;
> @@ -630,9 +627,7 @@ static struct dentry *ovl_lookup_or_create(struct ovl_fs *ofs,
>  		if (!child->d_inode)
>  			child = ovl_create_real(ofs, parent, child,
>  						OVL_CATTR(mode));
> -		if (!IS_ERR(child))
> -			dget(child);
> -		end_creating(child);
> +		end_creating_keep(child);
>  	}
>  	dput(parent);
>  
> diff --git a/include/linux/namei.h b/include/linux/namei.h
> index b4d95b79b5a8..58600cf234bc 100644
> --- a/include/linux/namei.h
> +++ b/include/linux/namei.h
> @@ -126,6 +126,28 @@ static inline void end_creating(struct dentry *child)
>  	end_dirop(child);
>  }
>  
> +/* end_creating_keep - finish action started with start_creating() and return result
> + * @child: dentry returned by start_creating() or vfs_mkdir()
> + *
> + * Unlock and return the child. This can be called after
> + * start_creating() whether that function succeeded or not,
> + * but it is not needed on failure.
> + *
> + * If vfs_mkdir() was called then the value returned from that function
> + * should be given for @child rather than the original dentry, as vfs_mkdir()
> + * may have provided a new dentry.
> + *
> + * Returns: @child, which may be a dentry or an error.
> + *
> + */
> +static inline struct dentry *end_creating_keep(struct dentry *child)
> +{
> +	if (!IS_ERR(child))
> +		dget(child);
> +	end_dirop(child);
> +	return child;
> +}
> +
>  /**
>   * end_removing - finish action started with start_removing
>   * @child:  dentry returned by start_removing()

Reviewed-by: Jeff Layton <[email protected]>