[Ocfs2-devel] [PATCH] vfs: Set special lockdep map for dirs only if not set by fs

[Peter Zijlstra <peterz@infradead.org>]

On Tue, 2009-06-02 at 14:24 +0200, Jan Kara wrote:
> Some filesystems need to set lockdep map for i_mutex differently for
> different directories. For example OCFS2 has system directories (for
> orphan inode tracking and for gathering all system files like journal
> or quota files into a single place) which have different locking
> locking rules than standard directories. For a filesystem setting
> lockdep map is naturaly done when the inode is read but we have to
> modify unlock_new_inode() not to overwrite the lockdep map the filesystem
> has set.

Still looks good ;-)

Acked-by: peterz at infradead.org

> CC: mingo at redhat.com
> Signed-off-by: Jan Kara <jack@suse.cz>
> ---
>  fs/inode.c              |   17 +++++++++++------
>  include/linux/lockdep.h |   15 +++++++++++++++
>  2 files changed, 26 insertions(+), 6 deletions(-)
> 
> diff --git a/fs/inode.c b/fs/inode.c
> index 6ad14a1..44e1848 100644
> --- a/fs/inode.c
> +++ b/fs/inode.c
> @@ -654,12 +654,17 @@ void unlock_new_inode(struct inode *inode)
>  	if (inode->i_mode & S_IFDIR) {
>  		struct file_system_type *type = inode->i_sb->s_type;
>  
> -		/*
> -		 * ensure nobody is actually holding i_mutex
> -		 */
> -		mutex_destroy(&inode->i_mutex);
> -		mutex_init(&inode->i_mutex);
> -		lockdep_set_class(&inode->i_mutex, &type->i_mutex_dir_key);
> +		/* Set new key only if filesystem hasn't already changed it */
> +		if (!lockdep_match_class(&inode->i_mutex,
> +		    &type->i_mutex_key)) {
> +			/*
> +			 * ensure nobody is actually holding i_mutex
> +			 */
> +			mutex_destroy(&inode->i_mutex);
> +			mutex_init(&inode->i_mutex);
> +			lockdep_set_class(&inode->i_mutex,
> +					  &type->i_mutex_dir_key);
> +		}
>  	}
>  #endif
>  	/*
> diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
> index da5a5a1..b25d1b5 100644
> --- a/include/linux/lockdep.h
> +++ b/include/linux/lockdep.h
> @@ -258,6 +258,16 @@ extern void lockdep_init_map(struct lockdep_map *lock, const char *name,
>  #define lockdep_set_subclass(lock, sub)	\
>  		lockdep_init_map(&(lock)->dep_map, #lock, \
>  				 (lock)->dep_map.key, sub)
> +/*
> + * Compare locking classes
> + */
> +#define lockdep_match_class(lock, key) lockdep_match_key(&(lock)->dep_map, key)
> +
> +static inline int lockdep_match_key(struct lockdep_map *lock,
> +				    struct lock_class_key *key)
> +{
> +	return lock->key == key;
> +}
>  
>  /*
>   * Acquire a lock.
> @@ -326,6 +336,11 @@ static inline void lockdep_on(void)
>  #define lockdep_set_class_and_subclass(lock, key, sub) \
>  		do { (void)(key); } while (0)
>  #define lockdep_set_subclass(lock, sub)		do { } while (0)
> +/*
> + * We don't define lockdep_match_class() and lockdep_match_key() for !LOCKDEP
> + * case since the result is not well defined and the caller should rather
> + * #ifdef the call himself.
> + */
>  
>  # define INIT_LOCKDEP
>  # define lockdep_reset()		do { debug_locks = 1; } while (0)