v4.19.13 snapshot.
diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
new file mode 100644
index 0000000..814643f
--- /dev/null
+++ b/include/linux/kernfs.h
@@ -0,0 +1,557 @@
+/*
+ * kernfs.h - pseudo filesystem decoupled from vfs locking
+ *
+ * This file is released under the GPLv2.
+ */
+
+#ifndef __LINUX_KERNFS_H
+#define __LINUX_KERNFS_H
+
+#include <linux/kernel.h>
+#include <linux/err.h>
+#include <linux/list.h>
+#include <linux/mutex.h>
+#include <linux/idr.h>
+#include <linux/lockdep.h>
+#include <linux/rbtree.h>
+#include <linux/atomic.h>
+#include <linux/uidgid.h>
+#include <linux/wait.h>
+
+struct file;
+struct dentry;
+struct iattr;
+struct seq_file;
+struct vm_area_struct;
+struct super_block;
+struct file_system_type;
+
+struct kernfs_open_node;
+struct kernfs_iattrs;
+
+enum kernfs_node_type {
+ KERNFS_DIR = 0x0001,
+ KERNFS_FILE = 0x0002,
+ KERNFS_LINK = 0x0004,
+};
+
+#define KERNFS_TYPE_MASK 0x000f
+#define KERNFS_FLAG_MASK ~KERNFS_TYPE_MASK
+
+enum kernfs_node_flag {
+ KERNFS_ACTIVATED = 0x0010,
+ KERNFS_NS = 0x0020,
+ KERNFS_HAS_SEQ_SHOW = 0x0040,
+ KERNFS_HAS_MMAP = 0x0080,
+ KERNFS_LOCKDEP = 0x0100,
+ KERNFS_SUICIDAL = 0x0400,
+ KERNFS_SUICIDED = 0x0800,
+ KERNFS_EMPTY_DIR = 0x1000,
+ KERNFS_HAS_RELEASE = 0x2000,
+};
+
+/* @flags for kernfs_create_root() */
+enum kernfs_root_flag {
+ /*
+ * kernfs_nodes are created in the deactivated state and invisible.
+ * They require explicit kernfs_activate() to become visible. This
+ * can be used to make related nodes become visible atomically
+ * after all nodes are created successfully.
+ */
+ KERNFS_ROOT_CREATE_DEACTIVATED = 0x0001,
+
+ /*
+ * For regular flies, if the opener has CAP_DAC_OVERRIDE, open(2)
+ * succeeds regardless of the RW permissions. sysfs had an extra
+ * layer of enforcement where open(2) fails with -EACCES regardless
+ * of CAP_DAC_OVERRIDE if the permission doesn't have the
+ * respective read or write access at all (none of S_IRUGO or
+ * S_IWUGO) or the respective operation isn't implemented. The
+ * following flag enables that behavior.
+ */
+ KERNFS_ROOT_EXTRA_OPEN_PERM_CHECK = 0x0002,
+
+ /*
+ * The filesystem supports exportfs operation, so userspace can use
+ * fhandle to access nodes of the fs.
+ */
+ KERNFS_ROOT_SUPPORT_EXPORTOP = 0x0004,
+};
+
+/* type-specific structures for kernfs_node union members */
+struct kernfs_elem_dir {
+ unsigned long subdirs;
+ /* children rbtree starts here and goes through kn->rb */
+ struct rb_root children;
+
+ /*
+ * The kernfs hierarchy this directory belongs to. This fits
+ * better directly in kernfs_node but is here to save space.
+ */
+ struct kernfs_root *root;
+};
+
+struct kernfs_elem_symlink {
+ struct kernfs_node *target_kn;
+};
+
+struct kernfs_elem_attr {
+ const struct kernfs_ops *ops;
+ struct kernfs_open_node *open;
+ loff_t size;
+ struct kernfs_node *notify_next; /* for kernfs_notify() */
+};
+
+/* represent a kernfs node */
+union kernfs_node_id {
+ struct {
+ /*
+ * blktrace will export this struct as a simplified 'struct
+ * fid' (which is a big data struction), so userspace can use
+ * it to find kernfs node. The layout must match the first two
+ * fields of 'struct fid' exactly.
+ */
+ u32 ino;
+ u32 generation;
+ };
+ u64 id;
+};
+
+/*
+ * kernfs_node - the building block of kernfs hierarchy. Each and every
+ * kernfs node is represented by single kernfs_node. Most fields are
+ * private to kernfs and shouldn't be accessed directly by kernfs users.
+ *
+ * As long as s_count reference is held, the kernfs_node itself is
+ * accessible. Dereferencing elem or any other outer entity requires
+ * active reference.
+ */
+struct kernfs_node {
+ atomic_t count;
+ atomic_t active;
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+ struct lockdep_map dep_map;
+#endif
+ /*
+ * Use kernfs_get_parent() and kernfs_name/path() instead of
+ * accessing the following two fields directly. If the node is
+ * never moved to a different parent, it is safe to access the
+ * parent directly.
+ */
+ struct kernfs_node *parent;
+ const char *name;
+
+ struct rb_node rb;
+
+ const void *ns; /* namespace tag */
+ unsigned int hash; /* ns + name hash */
+ union {
+ struct kernfs_elem_dir dir;
+ struct kernfs_elem_symlink symlink;
+ struct kernfs_elem_attr attr;
+ };
+
+ void *priv;
+
+ union kernfs_node_id id;
+ unsigned short flags;
+ umode_t mode;
+ struct kernfs_iattrs *iattr;
+};
+
+/*
+ * kernfs_syscall_ops may be specified on kernfs_create_root() to support
+ * syscalls. These optional callbacks are invoked on the matching syscalls
+ * and can perform any kernfs operations which don't necessarily have to be
+ * the exact operation requested. An active reference is held for each
+ * kernfs_node parameter.
+ */
+struct kernfs_syscall_ops {
+ int (*remount_fs)(struct kernfs_root *root, int *flags, char *data);
+ int (*show_options)(struct seq_file *sf, struct kernfs_root *root);
+
+ int (*mkdir)(struct kernfs_node *parent, const char *name,
+ umode_t mode);
+ int (*rmdir)(struct kernfs_node *kn);
+ int (*rename)(struct kernfs_node *kn, struct kernfs_node *new_parent,
+ const char *new_name);
+ int (*show_path)(struct seq_file *sf, struct kernfs_node *kn,
+ struct kernfs_root *root);
+};
+
+struct kernfs_root {
+ /* published fields */
+ struct kernfs_node *kn;
+ unsigned int flags; /* KERNFS_ROOT_* flags */
+
+ /* private fields, do not use outside kernfs proper */
+ struct idr ino_idr;
+ u32 next_generation;
+ struct kernfs_syscall_ops *syscall_ops;
+
+ /* list of kernfs_super_info of this root, protected by kernfs_mutex */
+ struct list_head supers;
+
+ wait_queue_head_t deactivate_waitq;
+};
+
+struct kernfs_open_file {
+ /* published fields */
+ struct kernfs_node *kn;
+ struct file *file;
+ struct seq_file *seq_file;
+ void *priv;
+
+ /* private fields, do not use outside kernfs proper */
+ struct mutex mutex;
+ struct mutex prealloc_mutex;
+ int event;
+ struct list_head list;
+ char *prealloc_buf;
+
+ size_t atomic_write_len;
+ bool mmapped:1;
+ bool released:1;
+ const struct vm_operations_struct *vm_ops;
+};
+
+struct kernfs_ops {
+ /*
+ * Optional open/release methods. Both are called with
+ * @of->seq_file populated.
+ */
+ int (*open)(struct kernfs_open_file *of);
+ void (*release)(struct kernfs_open_file *of);
+
+ /*
+ * Read is handled by either seq_file or raw_read().
+ *
+ * If seq_show() is present, seq_file path is active. Other seq
+ * operations are optional and if not implemented, the behavior is
+ * equivalent to single_open(). @sf->private points to the
+ * associated kernfs_open_file.
+ *
+ * read() is bounced through kernel buffer and a read larger than
+ * PAGE_SIZE results in partial operation of PAGE_SIZE.
+ */
+ int (*seq_show)(struct seq_file *sf, void *v);
+
+ void *(*seq_start)(struct seq_file *sf, loff_t *ppos);
+ void *(*seq_next)(struct seq_file *sf, void *v, loff_t *ppos);
+ void (*seq_stop)(struct seq_file *sf, void *v);
+
+ ssize_t (*read)(struct kernfs_open_file *of, char *buf, size_t bytes,
+ loff_t off);
+
+ /*
+ * write() is bounced through kernel buffer. If atomic_write_len
+ * is not set, a write larger than PAGE_SIZE results in partial
+ * operations of PAGE_SIZE chunks. If atomic_write_len is set,
+ * writes upto the specified size are executed atomically but
+ * larger ones are rejected with -E2BIG.
+ */
+ size_t atomic_write_len;
+ /*
+ * "prealloc" causes a buffer to be allocated at open for
+ * all read/write requests. As ->seq_show uses seq_read()
+ * which does its own allocation, it is incompatible with
+ * ->prealloc. Provide ->read and ->write with ->prealloc.
+ */
+ bool prealloc;
+ ssize_t (*write)(struct kernfs_open_file *of, char *buf, size_t bytes,
+ loff_t off);
+
+ int (*mmap)(struct kernfs_open_file *of, struct vm_area_struct *vma);
+
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+ struct lock_class_key lockdep_key;
+#endif
+};
+
+#ifdef CONFIG_KERNFS
+
+static inline enum kernfs_node_type kernfs_type(struct kernfs_node *kn)
+{
+ return kn->flags & KERNFS_TYPE_MASK;
+}
+
+/**
+ * kernfs_enable_ns - enable namespace under a directory
+ * @kn: directory of interest, should be empty
+ *
+ * This is to be called right after @kn is created to enable namespace
+ * under it. All children of @kn must have non-NULL namespace tags and
+ * only the ones which match the super_block's tag will be visible.
+ */
+static inline void kernfs_enable_ns(struct kernfs_node *kn)
+{
+ WARN_ON_ONCE(kernfs_type(kn) != KERNFS_DIR);
+ WARN_ON_ONCE(!RB_EMPTY_ROOT(&kn->dir.children));
+ kn->flags |= KERNFS_NS;
+}
+
+/**
+ * kernfs_ns_enabled - test whether namespace is enabled
+ * @kn: the node to test
+ *
+ * Test whether namespace filtering is enabled for the children of @ns.
+ */
+static inline bool kernfs_ns_enabled(struct kernfs_node *kn)
+{
+ return kn->flags & KERNFS_NS;
+}
+
+int kernfs_name(struct kernfs_node *kn, char *buf, size_t buflen);
+int kernfs_path_from_node(struct kernfs_node *root_kn, struct kernfs_node *kn,
+ char *buf, size_t buflen);
+void pr_cont_kernfs_name(struct kernfs_node *kn);
+void pr_cont_kernfs_path(struct kernfs_node *kn);
+struct kernfs_node *kernfs_get_parent(struct kernfs_node *kn);
+struct kernfs_node *kernfs_find_and_get_ns(struct kernfs_node *parent,
+ const char *name, const void *ns);
+struct kernfs_node *kernfs_walk_and_get_ns(struct kernfs_node *parent,
+ const char *path, const void *ns);
+void kernfs_get(struct kernfs_node *kn);
+void kernfs_put(struct kernfs_node *kn);
+
+struct kernfs_node *kernfs_node_from_dentry(struct dentry *dentry);
+struct kernfs_root *kernfs_root_from_sb(struct super_block *sb);
+struct inode *kernfs_get_inode(struct super_block *sb, struct kernfs_node *kn);
+
+struct dentry *kernfs_node_dentry(struct kernfs_node *kn,
+ struct super_block *sb);
+struct kernfs_root *kernfs_create_root(struct kernfs_syscall_ops *scops,
+ unsigned int flags, void *priv);
+void kernfs_destroy_root(struct kernfs_root *root);
+
+struct kernfs_node *kernfs_create_dir_ns(struct kernfs_node *parent,
+ const char *name, umode_t mode,
+ kuid_t uid, kgid_t gid,
+ void *priv, const void *ns);
+struct kernfs_node *kernfs_create_empty_dir(struct kernfs_node *parent,
+ const char *name);
+struct kernfs_node *__kernfs_create_file(struct kernfs_node *parent,
+ const char *name, umode_t mode,
+ kuid_t uid, kgid_t gid,
+ loff_t size,
+ const struct kernfs_ops *ops,
+ void *priv, const void *ns,
+ struct lock_class_key *key);
+struct kernfs_node *kernfs_create_link(struct kernfs_node *parent,
+ const char *name,
+ struct kernfs_node *target);
+void kernfs_activate(struct kernfs_node *kn);
+void kernfs_remove(struct kernfs_node *kn);
+void kernfs_break_active_protection(struct kernfs_node *kn);
+void kernfs_unbreak_active_protection(struct kernfs_node *kn);
+bool kernfs_remove_self(struct kernfs_node *kn);
+int kernfs_remove_by_name_ns(struct kernfs_node *parent, const char *name,
+ const void *ns);
+int kernfs_rename_ns(struct kernfs_node *kn, struct kernfs_node *new_parent,
+ const char *new_name, const void *new_ns);
+int kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr);
+void kernfs_notify(struct kernfs_node *kn);
+
+const void *kernfs_super_ns(struct super_block *sb);
+struct dentry *kernfs_mount_ns(struct file_system_type *fs_type, int flags,
+ struct kernfs_root *root, unsigned long magic,
+ bool *new_sb_created, const void *ns);
+void kernfs_kill_sb(struct super_block *sb);
+struct super_block *kernfs_pin_sb(struct kernfs_root *root, const void *ns);
+
+void kernfs_init(void);
+
+struct kernfs_node *kernfs_get_node_by_id(struct kernfs_root *root,
+ const union kernfs_node_id *id);
+#else /* CONFIG_KERNFS */
+
+static inline enum kernfs_node_type kernfs_type(struct kernfs_node *kn)
+{ return 0; } /* whatever */
+
+static inline void kernfs_enable_ns(struct kernfs_node *kn) { }
+
+static inline bool kernfs_ns_enabled(struct kernfs_node *kn)
+{ return false; }
+
+static inline int kernfs_name(struct kernfs_node *kn, char *buf, size_t buflen)
+{ return -ENOSYS; }
+
+static inline int kernfs_path_from_node(struct kernfs_node *root_kn,
+ struct kernfs_node *kn,
+ char *buf, size_t buflen)
+{ return -ENOSYS; }
+
+static inline void pr_cont_kernfs_name(struct kernfs_node *kn) { }
+static inline void pr_cont_kernfs_path(struct kernfs_node *kn) { }
+
+static inline struct kernfs_node *kernfs_get_parent(struct kernfs_node *kn)
+{ return NULL; }
+
+static inline struct kernfs_node *
+kernfs_find_and_get_ns(struct kernfs_node *parent, const char *name,
+ const void *ns)
+{ return NULL; }
+static inline struct kernfs_node *
+kernfs_walk_and_get_ns(struct kernfs_node *parent, const char *path,
+ const void *ns)
+{ return NULL; }
+
+static inline void kernfs_get(struct kernfs_node *kn) { }
+static inline void kernfs_put(struct kernfs_node *kn) { }
+
+static inline struct kernfs_node *kernfs_node_from_dentry(struct dentry *dentry)
+{ return NULL; }
+
+static inline struct kernfs_root *kernfs_root_from_sb(struct super_block *sb)
+{ return NULL; }
+
+static inline struct inode *
+kernfs_get_inode(struct super_block *sb, struct kernfs_node *kn)
+{ return NULL; }
+
+static inline struct kernfs_root *
+kernfs_create_root(struct kernfs_syscall_ops *scops, unsigned int flags,
+ void *priv)
+{ return ERR_PTR(-ENOSYS); }
+
+static inline void kernfs_destroy_root(struct kernfs_root *root) { }
+
+static inline struct kernfs_node *
+kernfs_create_dir_ns(struct kernfs_node *parent, const char *name,
+ umode_t mode, kuid_t uid, kgid_t gid,
+ void *priv, const void *ns)
+{ return ERR_PTR(-ENOSYS); }
+
+static inline struct kernfs_node *
+__kernfs_create_file(struct kernfs_node *parent, const char *name,
+ umode_t mode, kuid_t uid, kgid_t gid,
+ loff_t size, const struct kernfs_ops *ops,
+ void *priv, const void *ns, struct lock_class_key *key)
+{ return ERR_PTR(-ENOSYS); }
+
+static inline struct kernfs_node *
+kernfs_create_link(struct kernfs_node *parent, const char *name,
+ struct kernfs_node *target)
+{ return ERR_PTR(-ENOSYS); }
+
+static inline void kernfs_activate(struct kernfs_node *kn) { }
+
+static inline void kernfs_remove(struct kernfs_node *kn) { }
+
+static inline bool kernfs_remove_self(struct kernfs_node *kn)
+{ return false; }
+
+static inline int kernfs_remove_by_name_ns(struct kernfs_node *kn,
+ const char *name, const void *ns)
+{ return -ENOSYS; }
+
+static inline int kernfs_rename_ns(struct kernfs_node *kn,
+ struct kernfs_node *new_parent,
+ const char *new_name, const void *new_ns)
+{ return -ENOSYS; }
+
+static inline int kernfs_setattr(struct kernfs_node *kn,
+ const struct iattr *iattr)
+{ return -ENOSYS; }
+
+static inline void kernfs_notify(struct kernfs_node *kn) { }
+
+static inline const void *kernfs_super_ns(struct super_block *sb)
+{ return NULL; }
+
+static inline struct dentry *
+kernfs_mount_ns(struct file_system_type *fs_type, int flags,
+ struct kernfs_root *root, unsigned long magic,
+ bool *new_sb_created, const void *ns)
+{ return ERR_PTR(-ENOSYS); }
+
+static inline void kernfs_kill_sb(struct super_block *sb) { }
+
+static inline void kernfs_init(void) { }
+
+#endif /* CONFIG_KERNFS */
+
+/**
+ * kernfs_path - build full path of a given node
+ * @kn: kernfs_node of interest
+ * @buf: buffer to copy @kn's name into
+ * @buflen: size of @buf
+ *
+ * Builds and returns the full path of @kn in @buf of @buflen bytes. The
+ * path is built from the end of @buf so the returned pointer usually
+ * doesn't match @buf. If @buf isn't long enough, @buf is nul terminated
+ * and %NULL is returned.
+ */
+static inline int kernfs_path(struct kernfs_node *kn, char *buf, size_t buflen)
+{
+ return kernfs_path_from_node(kn, NULL, buf, buflen);
+}
+
+static inline struct kernfs_node *
+kernfs_find_and_get(struct kernfs_node *kn, const char *name)
+{
+ return kernfs_find_and_get_ns(kn, name, NULL);
+}
+
+static inline struct kernfs_node *
+kernfs_walk_and_get(struct kernfs_node *kn, const char *path)
+{
+ return kernfs_walk_and_get_ns(kn, path, NULL);
+}
+
+static inline struct kernfs_node *
+kernfs_create_dir(struct kernfs_node *parent, const char *name, umode_t mode,
+ void *priv)
+{
+ return kernfs_create_dir_ns(parent, name, mode,
+ GLOBAL_ROOT_UID, GLOBAL_ROOT_GID,
+ priv, NULL);
+}
+
+static inline struct kernfs_node *
+kernfs_create_file_ns(struct kernfs_node *parent, const char *name,
+ umode_t mode, kuid_t uid, kgid_t gid,
+ loff_t size, const struct kernfs_ops *ops,
+ void *priv, const void *ns)
+{
+ struct lock_class_key *key = NULL;
+
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+ key = (struct lock_class_key *)&ops->lockdep_key;
+#endif
+ return __kernfs_create_file(parent, name, mode, uid, gid,
+ size, ops, priv, ns, key);
+}
+
+static inline struct kernfs_node *
+kernfs_create_file(struct kernfs_node *parent, const char *name, umode_t mode,
+ loff_t size, const struct kernfs_ops *ops, void *priv)
+{
+ return kernfs_create_file_ns(parent, name, mode,
+ GLOBAL_ROOT_UID, GLOBAL_ROOT_GID,
+ size, ops, priv, NULL);
+}
+
+static inline int kernfs_remove_by_name(struct kernfs_node *parent,
+ const char *name)
+{
+ return kernfs_remove_by_name_ns(parent, name, NULL);
+}
+
+static inline int kernfs_rename(struct kernfs_node *kn,
+ struct kernfs_node *new_parent,
+ const char *new_name)
+{
+ return kernfs_rename_ns(kn, new_parent, new_name, NULL);
+}
+
+static inline struct dentry *
+kernfs_mount(struct file_system_type *fs_type, int flags,
+ struct kernfs_root *root, unsigned long magic,
+ bool *new_sb_created)
+{
+ return kernfs_mount_ns(fs_type, flags, root,
+ magic, new_sb_created, NULL);
+}
+
+#endif /* __LINUX_KERNFS_H */