From ba7443bc656e5236c316b2acacc8b551f872910f Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Thu, 28 Nov 2013 14:54:40 -0500 Subject: sysfs, kernfs: implement kernfs_create/destroy_root() There currently is single kernfs hierarchy in the whole system which is used for sysfs. kernfs needs to support multiple hierarchies to allow other users. This patch introduces struct kernfs_root which serves as the root of each kernfs hierarchy and implements kernfs_create/destroy_root(). * Each kernfs_root is associated with a root sd (sysfs_dentry). The root is freed when the root sd is released and kernfs_destory_root() simply invokes kernfs_remove() on the root sd. sysfs_remove_one() is updated to handle release of the root sd. Note that ps_iattr update in sysfs_remove_one() is trivially updated for readability. * Root sd's are now dynamically allocated using sysfs_new_dirent(). Update sysfs_alloc_ino() so that it gives out ino from 1 so that the root sd still gets ino 1. * While kernfs currently only points to the root sd, it'll soon grow fields which are specific to each hierarchy. As determining a given sd's root will be necessary, sd->s_dir.root is added. This backlink fits better as a separate field in sd; however, sd->s_dir is inside union with space to spare, so use it to save space and provide kernfs_root() accessor to determine the root sd. * As hierarchies may be destroyed now, each mount needs to hold onto the hierarchy it's attached to. Update sysfs_fill_super() and sysfs_kill_sb() so that they get and put the kernfs_root respectively. * sysfs_root is replaced with kernfs_root which is dynamically created by invoking kernfs_create_root() from sysfs_init(). This patch doesn't introduce any visible behavior changes. v2: kernfs_create_root() forgot to set @sd->priv. Fixed. Signed-off-by: Tejun Heo Signed-off-by: Greg Kroah-Hartman --- fs/kernfs/kernfs-internal.h | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) (limited to 'fs/kernfs/kernfs-internal.h') diff --git a/fs/kernfs/kernfs-internal.h b/fs/kernfs/kernfs-internal.h index 62ae35f997f7..7dfe06278350 100644 --- a/fs/kernfs/kernfs-internal.h +++ b/fs/kernfs/kernfs-internal.h @@ -25,6 +25,12 @@ struct sysfs_elem_dir { unsigned long subdirs; /* children rbtree starts here and goes through sd->s_rb */ struct rb_root children; + + /* + * The kernfs hierarchy this directory belongs to. This fits + * better directly in sysfs_dirent but is here to save space. + */ + struct kernfs_root *root; }; struct sysfs_elem_symlink { @@ -104,6 +110,20 @@ static inline unsigned int sysfs_type(struct sysfs_dirent *sd) return sd->s_flags & SYSFS_TYPE_MASK; } +/** + * kernfs_root - find out the kernfs_root a sysfs_dirent belongs to + * @sd: sysfs_dirent of interest + * + * Return the kernfs_root @sd belongs to. + */ +static inline struct kernfs_root *kernfs_root(struct sysfs_dirent *sd) +{ + /* if parent exists, it's always a dir; otherwise, @sd is a dir */ + if (sd->s_parent) + sd = sd->s_parent; + return sd->s_dir.root; +} + /* * Context structure to be used while adding/removing nodes. */ -- cgit v1.2.3