Re: [PATCH RFC v25 4/7] fs/lock: add helper locks_owner_has_blockers to check for blockers

[Jeff Layton <jlayton@kernel.org>]

On Mon, 2022-05-02 at 14:19 -0700, Dai Ngo wrote:
> Add helper locks_owner_has_blockers to check if there is any blockers
> for a given lockowner.
> 
> Reviewed-by: J. Bruce Fields <bfields@fieldses.org>
> Signed-off-by: Dai Ngo <dai.ngo@oracle.com>
> ---
>  fs/locks.c         | 28 ++++++++++++++++++++++++++++
>  include/linux/fs.h |  7 +++++++
>  2 files changed, 35 insertions(+)
> 
> diff --git a/fs/locks.c b/fs/locks.c
> index 8c6df10cd9ed..c369841ef7d1 100644
> --- a/fs/locks.c
> +++ b/fs/locks.c
> @@ -300,6 +300,34 @@ void locks_release_private(struct file_lock *fl)
>  }
>  EXPORT_SYMBOL_GPL(locks_release_private);
>  
> +/**
> + * locks_owner_has_blockers - Check for blocking lock requests
> + * @flctx: file lock context
> + * @owner: lock owner
> + *
> + * Return values:
> + *   %true: @owner has at least one blocker
> + *   %false: @owner has no blockers
> + */
> +bool locks_owner_has_blockers(struct file_lock_context *flctx,
> +		fl_owner_t owner)
> +{
> +	struct file_lock *fl;
> +
> +	spin_lock(&flctx->flc_lock);
> +	list_for_each_entry(fl, &flctx->flc_posix, fl_list) {
> +		if (fl->fl_owner != owner)
> +			continue;
> +		if (!list_empty(&fl->fl_blocked_requests)) {
> +			spin_unlock(&flctx->flc_lock);
> +			return true;
> +		}
> +	}
> +	spin_unlock(&flctx->flc_lock);
> +	return false;
> +}
> +EXPORT_SYMBOL_GPL(locks_owner_has_blockers);
> +
>  /* Free a lock which is not in use. */
>  void locks_free_lock(struct file_lock *fl)
>  {
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index bbde95387a23..b8ed7f974fb4 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -1174,6 +1174,8 @@ extern void lease_unregister_notifier(struct notifier_block *);
>  struct files_struct;
>  extern void show_fd_locks(struct seq_file *f,
>  			 struct file *filp, struct files_struct *files);
> +extern bool locks_owner_has_blockers(struct file_lock_context *flctx,
> +			fl_owner_t owner);
>  #else /* !CONFIG_FILE_LOCKING */
>  static inline int fcntl_getlk(struct file *file, unsigned int cmd,
>  			      struct flock __user *user)
> @@ -1309,6 +1311,11 @@ static inline int lease_modify(struct file_lock *fl, int arg,
>  struct files_struct;
>  static inline void show_fd_locks(struct seq_file *f,
>  			struct file *filp, struct files_struct *files) {}
> +static inline bool locks_owner_has_blockers(struct file_lock_context *flctx,
> +			fl_owner_t owner)
> +{
> +	return false;
> +}
>  #endif /* !CONFIG_FILE_LOCKING */
>  
>  static inline struct inode *file_inode(const struct file *f)

Reviewed-by: Jeff Layton <jlayton@kernel.org>