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/dir.c | 71 +++++++++++++++++++++++++++++++++++++++------ fs/kernfs/kernfs-internal.h | 20 +++++++++++++ 2 files changed, 82 insertions(+), 9 deletions(-) (limited to 'fs/kernfs') diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c index a4ca4de3cb21..246740a741ef 100644 --- a/fs/kernfs/dir.c +++ b/fs/kernfs/dir.c @@ -211,7 +211,7 @@ static int sysfs_alloc_ino(unsigned int *pino) retry: spin_lock(&sysfs_ino_lock); - rc = ida_get_new_above(&sysfs_ino_ida, 2, &ino); + rc = ida_get_new_above(&sysfs_ino_ida, 1, &ino); spin_unlock(&sysfs_ino_lock); if (rc == -EAGAIN) { @@ -253,9 +253,11 @@ EXPORT_SYMBOL_GPL(kernfs_get); void kernfs_put(struct sysfs_dirent *sd) { struct sysfs_dirent *parent_sd; + struct kernfs_root *root; if (!sd || !atomic_dec_and_test(&sd->s_count)) return; + root = kernfs_root(sd); repeat: /* Moving/renaming is always done while holding reference. * sd->s_parent won't change beneath us. @@ -278,8 +280,13 @@ void kernfs_put(struct sysfs_dirent *sd) kmem_cache_free(sysfs_dir_cachep, sd); sd = parent_sd; - if (sd && atomic_dec_and_test(&sd->s_count)) - goto repeat; + if (sd) { + if (atomic_dec_and_test(&sd->s_count)) + goto repeat; + } else { + /* just released the root sd, free @root too */ + kfree(root); + } } EXPORT_SYMBOL_GPL(kernfs_put); @@ -493,13 +500,15 @@ static void sysfs_remove_one(struct sysfs_addrm_cxt *acxt, if (sd->s_flags & SYSFS_FLAG_REMOVED) return; - sysfs_unlink_sibling(sd); + if (sd->s_parent) { + sysfs_unlink_sibling(sd); - /* Update timestamps on the parent */ - ps_iattr = sd->s_parent->s_iattr; - if (ps_iattr) { - struct iattr *ps_iattrs = &ps_iattr->ia_iattr; - ps_iattrs->ia_ctime = ps_iattrs->ia_mtime = CURRENT_TIME; + /* Update timestamps on the parent */ + ps_iattr = sd->s_parent->s_iattr; + if (ps_iattr) { + ps_iattr->ia_iattr.ia_ctime = CURRENT_TIME; + ps_iattr->ia_iattr.ia_mtime = CURRENT_TIME; + } } sd->s_flags |= SYSFS_FLAG_REMOVED; @@ -603,6 +612,49 @@ struct sysfs_dirent *kernfs_find_and_get_ns(struct sysfs_dirent *parent, } EXPORT_SYMBOL_GPL(kernfs_find_and_get_ns); +/** + * kernfs_create_root - create a new kernfs hierarchy + * @priv: opaque data associated with the new directory + * + * Returns the root of the new hierarchy on success, ERR_PTR() value on + * failure. + */ +struct kernfs_root *kernfs_create_root(void *priv) +{ + struct kernfs_root *root; + struct sysfs_dirent *sd; + + root = kzalloc(sizeof(*root), GFP_KERNEL); + if (!root) + return ERR_PTR(-ENOMEM); + + sd = sysfs_new_dirent("", S_IFDIR | S_IRUGO | S_IXUGO, SYSFS_DIR); + if (!sd) { + kfree(root); + return ERR_PTR(-ENOMEM); + } + + sd->s_flags &= ~SYSFS_FLAG_REMOVED; + sd->priv = priv; + sd->s_dir.root = root; + + root->sd = sd; + + return root; +} + +/** + * kernfs_destroy_root - destroy a kernfs hierarchy + * @root: root of the hierarchy to destroy + * + * Destroy the hierarchy anchored at @root by removing all existing + * directories and destroying @root. + */ +void kernfs_destroy_root(struct kernfs_root *root) +{ + kernfs_remove(root->sd); /* will also free @root */ +} + /** * kernfs_create_dir_ns - create a directory * @parent: parent in which to create a new directory @@ -626,6 +678,7 @@ struct sysfs_dirent *kernfs_create_dir_ns(struct sysfs_dirent *parent, if (!sd) return ERR_PTR(-ENOMEM); + sd->s_dir.root = parent->s_dir.root; sd->s_ns = ns; sd->priv = priv; 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