Re: [PATCH 01/13] vfs: add i_op->open()

["J. Bruce Fields" <bfields@fieldses.org>]

On Wed, Aug 15, 2012 at 05:48:08PM +0200, Miklos Szeredi wrote:
> From: Miklos Szeredi <mszeredi@suse.cz>
> 
> Add a new inode operation i_op->open().  This is for stacked

Shouldn't that "->open()" be "->dentry_open()" ?

--b.

> filesystems that want to return a struct file from a different
> filesystem.
> 
> Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
> ---
>  Documentation/filesystems/Locking |    2 ++
>  Documentation/filesystems/vfs.txt |    7 +++++++
>  fs/namei.c                        |    9 ++++++---
>  fs/open.c                         |   23 +++++++++++++++++++++--
>  include/linux/fs.h                |    2 ++
>  5 files changed, 38 insertions(+), 5 deletions(-)
> 
> diff --git a/Documentation/filesystems/Locking b/Documentation/filesystems/Locking
> index 0f103e3..d222b6a 100644
> --- a/Documentation/filesystems/Locking
> +++ b/Documentation/filesystems/Locking
> @@ -64,6 +64,7 @@ prototypes:
>  	int (*atomic_open)(struct inode *, struct dentry *,
>  				struct file *, unsigned open_flag,
>  				umode_t create_mode, int *opened);
> +	int (*dentry_open)(struct dentry *, struct file *, const struct cred *);
>  
>  locking rules:
>  	all may block
> @@ -92,6 +93,7 @@ removexattr:	yes
>  fiemap:		no
>  update_time:	no
>  atomic_open:	yes
> +open:		no
>  
>  	Additionally, ->rmdir(), ->unlink() and ->rename() have ->i_mutex on
>  victim.
> diff --git a/Documentation/filesystems/vfs.txt b/Documentation/filesystems/vfs.txt
> index 065aa2d..f53d93c 100644
> --- a/Documentation/filesystems/vfs.txt
> +++ b/Documentation/filesystems/vfs.txt
> @@ -367,6 +367,7 @@ struct inode_operations {
>  	int (*atomic_open)(struct inode *, struct dentry *,
>  				struct file *, unsigned open_flag,
>  				umode_t create_mode, int *opened);
> +	int (*dentry_open)(struct dentry *, struct file *, const struct cred *);
>  };
>  
>  Again, all methods are called without any locks being held, unless
> @@ -696,6 +697,12 @@ struct address_space_operations {
>    	but instead uses bmap to find out where the blocks in the file
>    	are and uses those addresses directly.
>  
> +  dentry_open: this is an alternative to f_op->open(), the difference is that
> +	this method may open a file not necessarily originating from the same
> +	filesystem as the one i_op->open() was called on.  It may be
> +	useful for stacking filesystems which want to allow native I/O directly
> +	on underlying files.
> +
>  
>    invalidatepage: If a page has PagePrivate set, then invalidatepage
>          will be called when part or all of the page is to be removed
> diff --git a/fs/namei.c b/fs/namei.c
> index 1b46439..ac2526d 100644
> --- a/fs/namei.c
> +++ b/fs/namei.c
> @@ -2816,9 +2816,12 @@ finish_open_created:
>  	error = may_open(&nd->path, acc_mode, open_flag);
>  	if (error)
>  		goto out;
> -	file->f_path.mnt = nd->path.mnt;
> -	error = finish_open(file, nd->path.dentry, NULL, opened);
> -	if (error) {
> +
> +	BUG_ON(*opened & FILE_OPENED); /* once it's opened, it's opened */
> +	error = vfs_open(&nd->path, file, current_cred());
> +	if (!error) {
> +		*opened |= FILE_OPENED;
> +	} else {
>  		if (error == -EOPENSTALE)
>  			goto stale_open;
>  		goto out;
> diff --git a/fs/open.c b/fs/open.c
> index f3d96e7..c5a8cac 100644
> --- a/fs/open.c
> +++ b/fs/open.c
> @@ -787,8 +787,7 @@ struct file *dentry_open(const struct path *path, int flags,
>  		return ERR_PTR(error);
>  
>  	f->f_flags = flags;
> -	f->f_path = *path;
> -	error = do_dentry_open(f, NULL, cred);
> +	error = vfs_open(path, f, cred);
>  	if (!error) {
>  		error = open_check_o_direct(f);
>  		if (error) {
> @@ -803,6 +802,26 @@ struct file *dentry_open(const struct path *path, int flags,
>  }
>  EXPORT_SYMBOL(dentry_open);
>  
> +/**
> + * vfs_open - open the file at the given path
> + * @path: path to open
> + * @filp: newly allocated file with f_flag initialized
> + * @cred: credentials to use
> + */
> +int vfs_open(const struct path *path, struct file *filp,
> +	     const struct cred *cred)
> +{
> +	struct inode *inode = path->dentry->d_inode;
> +
> +	if (inode->i_op->dentry_open)
> +		return inode->i_op->dentry_open(path->dentry, filp, cred);
> +	else {
> +		filp->f_path = *path;
> +		return do_dentry_open(filp, NULL, cred);
> +	}
> +}
> +EXPORT_SYMBOL(vfs_open);
> +
>  static void __put_unused_fd(struct files_struct *files, unsigned int fd)
>  {
>  	struct fdtable *fdt = files_fdtable(files);
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 38dba16..abc7a53 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -1836,6 +1836,7 @@ struct inode_operations {
>  	int (*atomic_open)(struct inode *, struct dentry *,
>  			   struct file *, unsigned open_flag,
>  			   umode_t create_mode, int *opened);
> +	int (*dentry_open)(struct dentry *, struct file *, const struct cred *);
>  } ____cacheline_aligned;
>  
>  struct seq_file;
> @@ -2201,6 +2202,7 @@ extern long do_sys_open(int dfd, const char __user *filename, int flags,
>  extern struct file *filp_open(const char *, int, umode_t);
>  extern struct file *file_open_root(struct dentry *, struct vfsmount *,
>  				   const char *, int);
> +extern int vfs_open(const struct path *, struct file *, const struct cred *);
>  extern struct file * dentry_open(const struct path *, int, const struct cred *);
>  extern int filp_close(struct file *, fl_owner_t id);
>  extern char * getname(const char __user *);
> -- 
> 1.7.7
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/