summaryrefslogtreecommitdiffstats
path: root/include/linux/kernfs.h
diff options
context:
space:
mode:
Diffstat (limited to 'include/linux/kernfs.h')
-rw-r--r--include/linux/kernfs.h632
1 files changed, 632 insertions, 0 deletions
diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
new file mode 100644
index 000000000..2a36f3218
--- /dev/null
+++ b/include/linux/kernfs.h
@@ -0,0 +1,632 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * kernfs.h - pseudo filesystem decoupled from vfs locking
+ */
+
+#ifndef __LINUX_KERNFS_H
+#define __LINUX_KERNFS_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/bug.h>
+#include <linux/types.h>
+#include <linux/uidgid.h>
+#include <linux/wait.h>
+#include <linux/rwsem.h>
+#include <linux/cache.h>
+
+struct file;
+struct dentry;
+struct iattr;
+struct seq_file;
+struct vm_area_struct;
+struct vm_operations_struct;
+struct super_block;
+struct file_system_type;
+struct poll_table_struct;
+struct fs_context;
+
+struct kernfs_fs_context;
+struct kernfs_open_node;
+struct kernfs_iattrs;
+
+/*
+ * NR_KERNFS_LOCK_BITS determines size (NR_KERNFS_LOCKS) of hash
+ * table of locks.
+ * Having a small hash table would impact scalability, since
+ * more and more kernfs_node objects will end up using same lock
+ * and having a very large hash table would waste memory.
+ *
+ * At the moment size of hash table of locks is being set based on
+ * the number of CPUs as follows:
+ *
+ * NR_CPU NR_KERNFS_LOCK_BITS NR_KERNFS_LOCKS
+ * 1 1 2
+ * 2-3 2 4
+ * 4-7 4 16
+ * 8-15 6 64
+ * 16-31 8 256
+ * 32 and more 10 1024
+ *
+ * The above relation between NR_CPU and number of locks is based
+ * on some internal experimentation which involved booting qemu
+ * with different values of smp, performing some sysfs operations
+ * on all CPUs and observing how increase in number of locks impacts
+ * completion time of these sysfs operations on each CPU.
+ */
+#ifdef CONFIG_SMP
+#define NR_KERNFS_LOCK_BITS (2 * (ilog2(NR_CPUS < 32 ? NR_CPUS : 32)))
+#else
+#define NR_KERNFS_LOCK_BITS 1
+#endif
+
+#define NR_KERNFS_LOCKS (1 << NR_KERNFS_LOCK_BITS)
+
+/*
+ * There's one kernfs_open_file for each open file and one kernfs_open_node
+ * for each kernfs_node with one or more open files.
+ *
+ * filp->private_data points to seq_file whose ->private points to
+ * kernfs_open_file.
+ *
+ * kernfs_open_files are chained at kernfs_open_node->files, which is
+ * protected by kernfs_global_locks.open_file_mutex[i].
+ *
+ * To reduce possible contention in sysfs access, arising due to single
+ * locks, use an array of locks (e.g. open_file_mutex) and use kernfs_node
+ * object address as hash keys to get the index of these locks.
+ *
+ * Hashed mutexes are safe to use here because operations using these don't
+ * rely on global exclusion.
+ *
+ * In future we intend to replace other global locks with hashed ones as well.
+ * kernfs_global_locks acts as a holder for all such hash tables.
+ */
+struct kernfs_global_locks {
+ struct mutex open_file_mutex[NR_KERNFS_LOCKS];
+};
+
+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
+#define KERNFS_MAX_USER_XATTRS 128
+#define KERNFS_USER_XATTR_SIZE_LIMIT (128 << 10)
+
+enum kernfs_node_flag {
+ KERNFS_ACTIVATED = 0x0010,
+ KERNFS_NS = 0x0020,
+ KERNFS_HAS_SEQ_SHOW = 0x0040,
+ KERNFS_HAS_MMAP = 0x0080,
+ KERNFS_LOCKDEP = 0x0100,
+ KERNFS_HIDDEN = 0x0200,
+ KERNFS_SUICIDAL = 0x0400,
+ KERNFS_SUICIDED = 0x0800,
+ KERNFS_EMPTY_DIR = 0x1000,
+ KERNFS_HAS_RELEASE = 0x2000,
+ KERNFS_REMOVING = 0x4000,
+};
+
+/* @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 files, 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,
+
+ /*
+ * Support user xattrs to be written to nodes rooted at this root.
+ */
+ KERNFS_ROOT_SUPPORT_USER_XATTR = 0x0008,
+};
+
+/* 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;
+ /*
+ * Monotonic revision counter, used to identify if a directory
+ * node has changed during negative dentry revalidation.
+ */
+ unsigned long rev;
+};
+
+struct kernfs_elem_symlink {
+ struct kernfs_node *target_kn;
+};
+
+struct kernfs_elem_attr {
+ const struct kernfs_ops *ops;
+ struct kernfs_open_node __rcu *open;
+ loff_t size;
+ struct kernfs_node *notify_next; /* for kernfs_notify() */
+};
+
+/*
+ * 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 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;
+
+ /*
+ * 64bit unique ID. On 64bit ino setups, id is the ino. On 32bit,
+ * the low 32bits are ino and upper generation.
+ */
+ u64 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 (*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_node *kernfs_root_to_node(struct kernfs_root *root);
+
+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);
+
+ __poll_t (*poll)(struct kernfs_open_file *of,
+ struct poll_table_struct *pt);
+
+ int (*mmap)(struct kernfs_open_file *of, struct vm_area_struct *vma);
+};
+
+/*
+ * The kernfs superblock creation/mount parameter context.
+ */
+struct kernfs_fs_context {
+ struct kernfs_root *root; /* Root of the hierarchy being mounted */
+ void *ns_tag; /* Namespace tag of the mount (or NULL) */
+ unsigned long magic; /* File system specific magic number */
+
+ /* The following are set/used by kernfs_mount() */
+ bool new_sb_created; /* Set to T if we allocated a new sb */
+};
+
+#ifdef CONFIG_KERNFS
+
+static inline enum kernfs_node_type kernfs_type(struct kernfs_node *kn)
+{
+ return kn->flags & KERNFS_TYPE_MASK;
+}
+
+static inline ino_t kernfs_id_ino(u64 id)
+{
+ /* id is ino if ino_t is 64bit; otherwise, low 32bits */
+ if (sizeof(ino_t) >= sizeof(u64))
+ return id;
+ else
+ return (u32)id;
+}
+
+static inline u32 kernfs_id_gen(u64 id)
+{
+ /* gen is fixed at 1 if ino_t is 64bit; otherwise, high 32bits */
+ if (sizeof(ino_t) >= sizeof(u64))
+ return 1;
+ else
+ return id >> 32;
+}
+
+static inline ino_t kernfs_ino(struct kernfs_node *kn)
+{
+ return kernfs_id_ino(kn->id);
+}
+
+static inline ino_t kernfs_gen(struct kernfs_node *kn)
+{
+ return kernfs_id_gen(kn->id);
+}
+
+/**
+ * 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_show(struct kernfs_node *kn, bool show);
+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);
+__poll_t kernfs_generic_poll(struct kernfs_open_file *of,
+ struct poll_table_struct *pt);
+void kernfs_notify(struct kernfs_node *kn);
+
+int kernfs_xattr_get(struct kernfs_node *kn, const char *name,
+ void *value, size_t size);
+int kernfs_xattr_set(struct kernfs_node *kn, const char *name,
+ const void *value, size_t size, int flags);
+
+const void *kernfs_super_ns(struct super_block *sb);
+int kernfs_get_tree(struct fs_context *fc);
+void kernfs_free_fs_context(struct fs_context *fc);
+void kernfs_kill_sb(struct super_block *sb);
+
+void kernfs_init(void);
+
+struct kernfs_node *kernfs_find_and_get_node_by_id(struct kernfs_root *root,
+ u64 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 __poll_t kernfs_generic_poll(struct kernfs_open_file *of,
+ struct poll_table_struct *pt)
+{ return -ENOSYS; }
+
+static inline void kernfs_notify(struct kernfs_node *kn) { }
+
+static inline int kernfs_xattr_get(struct kernfs_node *kn, const char *name,
+ void *value, size_t size)
+{ return -ENOSYS; }
+
+static inline int kernfs_xattr_set(struct kernfs_node *kn, const char *name,
+ const void *value, size_t size, int flags)
+{ return -ENOSYS; }
+
+static inline const void *kernfs_super_ns(struct super_block *sb)
+{ return NULL; }
+
+static inline int kernfs_get_tree(struct fs_context *fc)
+{ return -ENOSYS; }
+
+static inline void kernfs_free_fs_context(struct fs_context *fc) { }
+
+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
+ *
+ * If @kn is NULL result will be "(null)".
+ *
+ * Returns the length of the full path. If the full length is equal to or
+ * greater than @buflen, @buf contains the truncated path with the trailing
+ * '\0'. On error, -errno 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 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);
+}
+
+#endif /* __LINUX_KERNFS_H */
generated by cgit v1.2.3 (git 2.39.1) at 2024-05-25 20:44:51 +0000