Re: [PATCH 09/12] locks: helper functions for delegation breaking

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On Wed,  3 Jul 2013 16:12:33 -0400
"J. Bruce Fields" <bfields@xxxxxxxxxx> wrote:

> From: "J. Bruce Fields" <bfields@xxxxxxxxxx>
> 
> We'll need the same logic for rename and link.
> 
> Signed-off-by: J. Bruce Fields <bfields@xxxxxxxxxx>
> ---
>  fs/namei.c         |   13 +++----------
>  include/linux/fs.h |   33 +++++++++++++++++++++++++++++++--
>  2 files changed, 34 insertions(+), 12 deletions(-)
> 
> diff --git a/fs/namei.c b/fs/namei.c
> index cba3db1..a9d4031 100644
> --- a/fs/namei.c
> +++ b/fs/namei.c
> @@ -3401,14 +3401,9 @@ int vfs_unlink(struct inode *dir, struct dentry *dentry, struct inode **delegate
>  	else {
>  		error = security_inode_unlink(dir, dentry);
>  		if (!error) {
> -			error = break_deleg(target, O_WRONLY|O_NONBLOCK);
> -			if (error) {
> -				if (error == -EWOULDBLOCK && delegated_inode) {
> -					*delegated_inode = target;
> -					ihold(target);
> -				}
> +			error = try_break_deleg(target, delegated_inode);
> +			if (error)
>  				goto out;
> -			}
>  			error = dir->i_op->unlink(dir, dentry);
>  			if (!error)
>  				dont_mount(dentry);
> @@ -3478,9 +3473,7 @@ exit2:
>  		iput(inode);	/* truncate the inode here */
>  	inode = NULL;
>  	if (delegated_inode) {
> -		error = break_deleg(delegated_inode, O_WRONLY);
> -		iput(delegated_inode);
> -		delegated_inode = NULL;
> +		error = break_deleg_wait(&delegated_inode);
>  		if (!error)
>  			goto retry_deleg;
>  	}
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index f951588..c37e463 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -1894,6 +1894,9 @@ extern bool our_mnt(struct vfsmount *mnt);
>  
>  extern int current_umask(void);
>  
> +extern void ihold(struct inode * inode);
> +extern void iput(struct inode *);
> +
>  /* /sys/fs */
>  extern struct kobject *fs_kobj;
>  
> @@ -1962,6 +1965,28 @@ static inline int break_deleg(struct inode *inode, unsigned int mode)
>  	return 0;
>  }
>  
> +static inline int try_break_deleg(struct inode *inode, struct inode **delegated_inode)
> +{
> +	int ret;
> +
> +	ret = break_deleg(inode, O_WRONLY|O_NONBLOCK);
> +	if (ret == -EWOULDBLOCK && delegated_inode) {
> +		*delegated_inode = inode;
> +		ihold(inode);
> +	}
> +	return ret;
> +}
> +

Actually, now that I look...

Suppose a vfs_unlink caller passes in a NULL delegated_inode pointer.
He'll get back a -EWOULDBLOCK here if there's a delegation on it.
Presumably he'll just treat that as a hard error and the delegation
would never get broken. Is that expected?

> +static inline int break_deleg_wait(struct inode **delegated_inode)
> +{
> +	int ret;
> +
> +	ret = break_deleg(*delegated_inode, O_WRONLY);
> +	iput(*delegated_inode);
> +	*delegated_inode = NULL;
> +	return ret;
> +}
> +
>  #else /* !CONFIG_FILE_LOCKING */
>  static inline int locks_mandatory_locked(struct inode *inode)
>  {
> @@ -2005,6 +2030,12 @@ static inline int break_deleg(struct inode *inode, unsigned int mode)
>  {
>  	return 0;
>  }
> +
> +static inline int try_break_deleg(struct inode *inode, struct delegated_inode **inode)
> +{
> +	return 0;
> +}
> +
>  #endif /* CONFIG_FILE_LOCKING */
>  
>  /* fs/open.c */
> @@ -2335,8 +2366,6 @@ extern loff_t vfs_llseek(struct file *file, loff_t offset, int whence);
>  extern int inode_init_always(struct super_block *, struct inode *);
>  extern void inode_init_once(struct inode *);
>  extern void address_space_init_once(struct address_space *mapping);
> -extern void ihold(struct inode * inode);
> -extern void iput(struct inode *);
>  extern struct inode * igrab(struct inode *);
>  extern ino_t iunique(struct super_block *, ino_t);
>  extern int inode_needs_sync(struct inode *inode);


-- 
Jeff Layton <jlayton@xxxxxxxxxxxxxxx>
--
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