From htejun@gmail.com Wed Jun 13 11:45:34 2007 From: Tejun Heo Cc: Tejun Heo , Greg Kroah-Hartman Subject: [PATCH 11/31] sysfs: add sysfs_dirent->s_parent Date: Thu, 14 Jun 2007 03:45:14 +0900 Message-Id: <1181760314471-git-send-email-htejun@gmail.com> To: greg@kroah.com, rjw@sisk.pl, akpm@linux-foundation.org, htejun@gmail.com From: Tejun Heo Add sysfs_dirent->s_parent. With this patch, each sd points to and holds a reference to its parent. This allows walking sysfs tree without referencing sd->s_dentry which can go away anytime if the user doesn't control when it's deleted. sd->s_parent is initialized and parent is referenced in sysfs_attach_dirent(). Reference to parent is released when the sd is released, so as long as reference to a sd is held, s_parent can be followed. dentry walk in sysfs_readdir() is convereted to s_parent walk. This will be used to reimplement symlink such that it uses only sysfs_dirent tree. Signed-off-by: Tejun Heo Signed-off-by: Greg Kroah-Hartman --- fs/sysfs/dir.c | 30 +++++++++++++++++++++++------- fs/sysfs/mount.c | 1 + fs/sysfs/sysfs.h | 1 + 3 files changed, 25 insertions(+), 7 deletions(-) --- a/fs/sysfs/dir.c +++ b/fs/sysfs/dir.c @@ -47,6 +47,11 @@ static void sysfs_free_ino(ino_t ino) void release_sysfs_dirent(struct sysfs_dirent * sd) { + struct sysfs_dirent *parent_sd; + + repeat: + parent_sd = sd->s_parent; + if (sd->s_type & SYSFS_KOBJ_LINK) { struct sysfs_symlink * sl = sd->s_element; kfree(sl->link_name); @@ -56,6 +61,10 @@ void release_sysfs_dirent(struct sysfs_d kfree(sd->s_iattr); sysfs_free_ino(sd->s_ino); kmem_cache_free(sysfs_dir_cachep, sd); + + sd = parent_sd; + if (sd && atomic_dec_and_test(&sd->s_count)) + goto repeat; } static void sysfs_d_iput(struct dentry * dentry, struct inode * inode) @@ -119,8 +128,10 @@ void sysfs_attach_dirent(struct sysfs_di dentry->d_op = &sysfs_dentry_ops; } - if (parent_sd) + if (parent_sd) { + sd->s_parent = sysfs_get(parent_sd); list_add(&sd->s_sibling, &parent_sd->s_children); + } } /* @@ -571,7 +582,10 @@ static int sysfs_readdir(struct file * f i++; /* fallthrough */ case 1: - ino = parent_ino(dentry); + if (parent_sd->s_parent) + ino = parent_sd->s_parent->s_ino; + else + ino = parent_sd->s_ino; if (filldir(dirent, "..", 2, i, ino, DT_DIR) < 0) break; filp->f_pos++; @@ -688,13 +702,13 @@ int sysfs_make_shadowed_dir(struct kobje struct dentry *sysfs_create_shadow_dir(struct kobject *kobj) { + struct dentry *dir = kobj->dentry; + struct inode *inode = dir->d_inode; + struct dentry *parent = dir->d_parent; + struct sysfs_dirent *parent_sd = parent->d_fsdata; + struct dentry *shadow; struct sysfs_dirent *sd; - struct dentry *parent, *dir, *shadow; - struct inode *inode; - dir = kobj->dentry; - inode = dir->d_inode; - parent = dir->d_parent; shadow = ERR_PTR(-EINVAL); if (!sysfs_is_shadowed_inode(inode)) goto out; @@ -706,6 +720,8 @@ struct dentry *sysfs_create_shadow_dir(s sd = sysfs_new_dirent(kobj, inode->i_mode, SYSFS_DIR); if (!sd) goto nomem; + /* point to parent_sd but don't attach to it */ + sd->s_parent = sysfs_get(parent_sd); sysfs_attach_dirent(sd, NULL, shadow); d_instantiate(shadow, igrab(inode)); --- a/fs/sysfs/mount.c +++ b/fs/sysfs/mount.c @@ -28,6 +28,7 @@ static const struct super_operations sys }; static struct sysfs_dirent sysfs_root = { + .s_count = ATOMIC_INIT(1), .s_sibling = LIST_HEAD_INIT(sysfs_root.s_sibling), .s_children = LIST_HEAD_INIT(sysfs_root.s_children), .s_element = NULL, --- a/fs/sysfs/sysfs.h +++ b/fs/sysfs/sysfs.h @@ -1,5 +1,6 @@ struct sysfs_dirent { atomic_t s_count; + struct sysfs_dirent * s_parent; struct list_head s_sibling; struct list_head s_children; void * s_element;