diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c index c6f3b697064cb7a7fa3d084366a92362f06ded0f..987211296106998ba5632ab58949e8eeca62d516 100644 --- a/fs/sysfs/dir.c +++ b/fs/sysfs/dir.c @@ -62,6 +62,104 @@ void sysfs_unlink_sibling(struct sysfs_dirent *sd) } } +/** + * sysfs_get_dentry - get dentry for the given sysfs_dirent + * @sd: sysfs_dirent of interest + * + * Get dentry for @sd. Dentry is looked up if currently not + * present. This function climbs sysfs_dirent tree till it + * reaches a sysfs_dirent with valid dentry attached and descends + * down from there looking up dentry for each step. + * + * LOCKING: + * Kernel thread context (may sleep) + * + * RETURNS: + * Pointer to found dentry on success, ERR_PTR() value on error. + */ +struct dentry *sysfs_get_dentry(struct sysfs_dirent *sd) +{ + struct sysfs_dirent *cur; + struct dentry *parent_dentry, *dentry; + int i, depth; + + /* Find the first parent which has valid s_dentry and get the + * dentry. + */ + mutex_lock(&sysfs_mutex); + restart0: + spin_lock(&sysfs_assoc_lock); + restart1: + spin_lock(&dcache_lock); + + dentry = NULL; + depth = 0; + cur = sd; + while (!cur->s_dentry || !cur->s_dentry->d_inode) { + if (cur->s_flags & SYSFS_FLAG_REMOVED) { + dentry = ERR_PTR(-ENOENT); + depth = 0; + break; + } + cur = cur->s_parent; + depth++; + } + if (!IS_ERR(dentry)) + dentry = dget_locked(cur->s_dentry); + + spin_unlock(&dcache_lock); + spin_unlock(&sysfs_assoc_lock); + + /* from the found dentry, look up depth times */ + while (depth--) { + /* find and get depth'th ancestor */ + for (cur = sd, i = 0; cur && i < depth; i++) + cur = cur->s_parent; + + /* This can happen if tree structure was modified due + * to move/rename. Restart. + */ + if (i != depth) { + dput(dentry); + goto restart0; + } + + sysfs_get(cur); + + mutex_unlock(&sysfs_mutex); + + /* look it up */ + parent_dentry = dentry; + dentry = lookup_one_len_kern(cur->s_name, parent_dentry, + strlen(cur->s_name)); + dput(parent_dentry); + + if (IS_ERR(dentry)) { + sysfs_put(cur); + return dentry; + } + + mutex_lock(&sysfs_mutex); + spin_lock(&sysfs_assoc_lock); + + /* This, again, can happen if tree structure has + * changed and we looked up the wrong thing. Restart. + */ + if (cur->s_dentry != dentry) { + dput(dentry); + sysfs_put(cur); + goto restart1; + } + + spin_unlock(&sysfs_assoc_lock); + + sysfs_put(cur); + } + + mutex_unlock(&sysfs_mutex); + return dentry; +} + /** * sysfs_get_active - get an active reference to sysfs_dirent * @sd: sysfs_dirent to get an active reference to diff --git a/fs/sysfs/sysfs.h b/fs/sysfs/sysfs.h index 92fe1e51a29b10ca5e3d972725fb2e5dd1ba6495..72530dc666fd1628f90d5e9c91e8f5b95f9fa378 100644 --- a/fs/sysfs/sysfs.h +++ b/fs/sysfs/sysfs.h @@ -54,6 +54,7 @@ struct sysfs_addrm_cxt { extern struct vfsmount * sysfs_mount; extern struct kmem_cache *sysfs_dir_cachep; +extern struct dentry *sysfs_get_dentry(struct sysfs_dirent *sd); extern void sysfs_link_sibling(struct sysfs_dirent *sd); extern void sysfs_unlink_sibling(struct sysfs_dirent *sd); extern struct sysfs_dirent *sysfs_get_active(struct sysfs_dirent *sd);