Commit bca585d2 authored by Al Viro's avatar Al Viro
Browse files

new helper: d_find_alias_rcu() 



similar to d_find_alias(inode), except that
	* the caller must be holding rcu_read_lock()
	* inode must not be freed until matching rcu_read_unlock()
	* result is *NOT* pinned and can only be dereferenced until
the matching rcu_read_unlock().

Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent d36a1dd9

fs/dcache.c

+25 −0
Original line number Diff line number Diff line
@@ -1042,6 +1042,31 @@ struct dentry *d_find_alias(struct inode *inode) 
}

EXPORT_SYMBOL(d_find_alias);



/*

 *  Caller MUST be holding rcu_read_lock() and be guaranteed

 *  that inode won't get freed until rcu_read_unlock().

 */

struct dentry *d_find_alias_rcu(struct inode *inode)

{

	struct hlist_head *l = &inode->i_dentry;

	struct dentry *de = NULL;



	spin_lock(&inode->i_lock);

	// ->i_dentry and ->i_rcu are colocated, but the latter won't be

	// used without having I_FREEING set, which means no aliases left

	if (likely(!(inode->i_state & I_FREEING) && !hlist_empty(l))) {

		if (S_ISDIR(inode->i_mode)) {

			de = hlist_entry(l->first, struct dentry, d_u.d_alias);

		} else {

			hlist_for_each_entry(de, l, d_u.d_alias)

				if (!d_unhashed(de))

					break;

		}

	}

	spin_unlock(&inode->i_lock);

	return de;

}



/*

 *	Try to kill dentries associated with this inode.

 * WARNING: you must own a reference to inode.

include/linux/dcache.h

+2 −0
Original line number Diff line number Diff line
@@ -262,6 +262,8 @@ extern void d_tmpfile(struct dentry *, struct inode *); 
extern struct dentry *d_find_alias(struct inode *);

extern void d_prune_aliases(struct inode *);



extern struct dentry *d_find_alias_rcu(struct inode *);



/* test whether we have any submounts in a subdir tree */

extern int path_has_submounts(const struct path *);