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 <tj@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Родитель
061447a496
Коммит
ba7443bc65
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@ -211,7 +211,7 @@ static int sysfs_alloc_ino(unsigned int *pino)
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retry:
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spin_lock(&sysfs_ino_lock);
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rc = ida_get_new_above(&sysfs_ino_ida, 2, &ino);
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rc = ida_get_new_above(&sysfs_ino_ida, 1, &ino);
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spin_unlock(&sysfs_ino_lock);
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if (rc == -EAGAIN) {
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@ -253,9 +253,11 @@ EXPORT_SYMBOL_GPL(kernfs_get);
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void kernfs_put(struct sysfs_dirent *sd)
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{
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struct sysfs_dirent *parent_sd;
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struct kernfs_root *root;
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if (!sd || !atomic_dec_and_test(&sd->s_count))
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return;
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root = kernfs_root(sd);
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repeat:
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/* Moving/renaming is always done while holding reference.
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* sd->s_parent won't change beneath us.
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@ -278,8 +280,13 @@ void kernfs_put(struct sysfs_dirent *sd)
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kmem_cache_free(sysfs_dir_cachep, sd);
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sd = parent_sd;
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if (sd && atomic_dec_and_test(&sd->s_count))
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goto repeat;
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if (sd) {
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if (atomic_dec_and_test(&sd->s_count))
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goto repeat;
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} else {
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/* just released the root sd, free @root too */
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kfree(root);
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}
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}
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EXPORT_SYMBOL_GPL(kernfs_put);
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@ -493,13 +500,15 @@ static void sysfs_remove_one(struct sysfs_addrm_cxt *acxt,
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if (sd->s_flags & SYSFS_FLAG_REMOVED)
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return;
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sysfs_unlink_sibling(sd);
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if (sd->s_parent) {
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sysfs_unlink_sibling(sd);
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/* Update timestamps on the parent */
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ps_iattr = sd->s_parent->s_iattr;
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if (ps_iattr) {
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struct iattr *ps_iattrs = &ps_iattr->ia_iattr;
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ps_iattrs->ia_ctime = ps_iattrs->ia_mtime = CURRENT_TIME;
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/* Update timestamps on the parent */
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ps_iattr = sd->s_parent->s_iattr;
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if (ps_iattr) {
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ps_iattr->ia_iattr.ia_ctime = CURRENT_TIME;
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ps_iattr->ia_iattr.ia_mtime = CURRENT_TIME;
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}
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}
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sd->s_flags |= SYSFS_FLAG_REMOVED;
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@ -603,6 +612,49 @@ struct sysfs_dirent *kernfs_find_and_get_ns(struct sysfs_dirent *parent,
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}
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EXPORT_SYMBOL_GPL(kernfs_find_and_get_ns);
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/**
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* kernfs_create_root - create a new kernfs hierarchy
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* @priv: opaque data associated with the new directory
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*
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* Returns the root of the new hierarchy on success, ERR_PTR() value on
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* failure.
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*/
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struct kernfs_root *kernfs_create_root(void *priv)
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{
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struct kernfs_root *root;
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struct sysfs_dirent *sd;
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root = kzalloc(sizeof(*root), GFP_KERNEL);
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if (!root)
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return ERR_PTR(-ENOMEM);
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sd = sysfs_new_dirent("", S_IFDIR | S_IRUGO | S_IXUGO, SYSFS_DIR);
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if (!sd) {
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kfree(root);
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return ERR_PTR(-ENOMEM);
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}
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sd->s_flags &= ~SYSFS_FLAG_REMOVED;
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sd->priv = priv;
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sd->s_dir.root = root;
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root->sd = sd;
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return root;
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}
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/**
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* kernfs_destroy_root - destroy a kernfs hierarchy
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* @root: root of the hierarchy to destroy
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*
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* Destroy the hierarchy anchored at @root by removing all existing
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* directories and destroying @root.
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*/
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void kernfs_destroy_root(struct kernfs_root *root)
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{
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kernfs_remove(root->sd); /* will also free @root */
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}
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/**
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* kernfs_create_dir_ns - create a directory
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* @parent: parent in which to create a new directory
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@ -626,6 +678,7 @@ struct sysfs_dirent *kernfs_create_dir_ns(struct sysfs_dirent *parent,
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if (!sd)
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return ERR_PTR(-ENOMEM);
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sd->s_dir.root = parent->s_dir.root;
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sd->s_ns = ns;
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sd->priv = priv;
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@ -25,6 +25,12 @@ struct sysfs_elem_dir {
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unsigned long subdirs;
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/* children rbtree starts here and goes through sd->s_rb */
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struct rb_root children;
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/*
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* The kernfs hierarchy this directory belongs to. This fits
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* better directly in sysfs_dirent but is here to save space.
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*/
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struct kernfs_root *root;
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};
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struct sysfs_elem_symlink {
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@ -104,6 +110,20 @@ static inline unsigned int sysfs_type(struct sysfs_dirent *sd)
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return sd->s_flags & SYSFS_TYPE_MASK;
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}
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/**
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* kernfs_root - find out the kernfs_root a sysfs_dirent belongs to
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* @sd: sysfs_dirent of interest
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*
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* Return the kernfs_root @sd belongs to.
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*/
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static inline struct kernfs_root *kernfs_root(struct sysfs_dirent *sd)
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{
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/* if parent exists, it's always a dir; otherwise, @sd is a dir */
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if (sd->s_parent)
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sd = sd->s_parent;
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return sd->s_dir.root;
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}
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/*
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* Context structure to be used while adding/removing nodes.
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*/
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@ -32,15 +32,8 @@ static const struct super_operations sysfs_ops = {
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.evict_inode = sysfs_evict_inode,
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};
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static struct sysfs_dirent sysfs_root = {
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.s_name = "",
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.s_count = ATOMIC_INIT(1),
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.s_flags = SYSFS_DIR,
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.s_mode = S_IFDIR | S_IRUGO | S_IXUGO,
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.s_ino = 1,
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};
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struct sysfs_dirent *sysfs_root_sd = &sysfs_root;
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static struct kernfs_root *sysfs_root;
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struct sysfs_dirent *sysfs_root_sd;
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static int sysfs_fill_super(struct super_block *sb)
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{
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@ -68,6 +61,7 @@ static int sysfs_fill_super(struct super_block *sb)
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pr_debug("%s: could not get root dentry!\n", __func__);
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return -ENOMEM;
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}
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kernfs_get(sysfs_root_sd);
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root->d_fsdata = sysfs_root_sd;
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sb->s_root = root;
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sb->s_d_op = &sysfs_dentry_ops;
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@ -138,11 +132,15 @@ static struct dentry *sysfs_mount(struct file_system_type *fs_type,
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static void sysfs_kill_sb(struct super_block *sb)
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{
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struct sysfs_super_info *info = sysfs_info(sb);
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/* Remove the superblock from fs_supers/s_instances
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struct sysfs_dirent *root_sd = sb->s_root->d_fsdata;
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/*
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* Remove the superblock from fs_supers/s_instances
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* so we can't find it, before freeing sysfs_super_info.
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*/
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kill_anon_super(sb);
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free_sysfs_super_info(info);
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kernfs_put(root_sd);
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}
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static struct file_system_type sysfs_fs_type = {
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@ -166,12 +164,21 @@ int __init sysfs_init(void)
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if (err)
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goto out_err;
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sysfs_root = kernfs_create_root(NULL);
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if (IS_ERR(sysfs_root)) {
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err = PTR_ERR(sysfs_root);
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goto out_err;
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}
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sysfs_root_sd = sysfs_root->sd;
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err = register_filesystem(&sysfs_fs_type);
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if (err)
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goto out_err;
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goto out_destroy_root;
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return 0;
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out_destroy_root:
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kernfs_destroy_root(sysfs_root);
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out_err:
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kmem_cache_destroy(sysfs_dir_cachep);
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sysfs_dir_cachep = NULL;
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@ -20,6 +20,11 @@ struct vm_area_struct;
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struct sysfs_dirent;
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struct kernfs_root {
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/* published fields */
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struct sysfs_dirent *sd;
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};
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struct sysfs_open_file {
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/* published fields */
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struct sysfs_dirent *sd;
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@ -76,6 +81,9 @@ struct sysfs_dirent *kernfs_find_and_get_ns(struct sysfs_dirent *parent,
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void kernfs_get(struct sysfs_dirent *sd);
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void kernfs_put(struct sysfs_dirent *sd);
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struct kernfs_root *kernfs_create_root(void *priv);
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void kernfs_destroy_root(struct kernfs_root *root);
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struct sysfs_dirent *kernfs_create_dir_ns(struct sysfs_dirent *parent,
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const char *name, void *priv,
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const void *ns);
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static inline void kernfs_get(struct sysfs_dirent *sd) { }
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static inline void kernfs_put(struct sysfs_dirent *sd) { }
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static inline struct kernfs_root *kernfs_create_root(void *priv)
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{ return ERR_PTR(-ENOSYS); }
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static inline void kernfs_destroy_root(struct kernfs_root *root) { }
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static inline struct sysfs_dirent *
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kernfs_create_dir_ns(struct sysfs_dirent *parent, const char *name, void *priv,
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const void *ns)
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