v4.19.13 snapshot.
diff --git a/fs/kernfs/Kconfig b/fs/kernfs/Kconfig
new file mode 100644
index 0000000..397b5f7
--- /dev/null
+++ b/fs/kernfs/Kconfig
@@ -0,0 +1,7 @@
+#
+# KERNFS should be selected by its users
+#
+
+config KERNFS
+ bool
+ default n
diff --git a/fs/kernfs/Makefile b/fs/kernfs/Makefile
new file mode 100644
index 0000000..674337c
--- /dev/null
+++ b/fs/kernfs/Makefile
@@ -0,0 +1,5 @@
+#
+# Makefile for the kernfs pseudo filesystem
+#
+
+obj-y := mount.o inode.o dir.o file.o symlink.o
diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
new file mode 100644
index 0000000..4ca0b5c
--- /dev/null
+++ b/fs/kernfs/dir.c
@@ -0,0 +1,1702 @@
+/*
+ * fs/kernfs/dir.c - kernfs directory implementation
+ *
+ * Copyright (c) 2001-3 Patrick Mochel
+ * Copyright (c) 2007 SUSE Linux Products GmbH
+ * Copyright (c) 2007, 2013 Tejun Heo <tj@kernel.org>
+ *
+ * This file is released under the GPLv2.
+ */
+
+#include <linux/sched.h>
+#include <linux/fs.h>
+#include <linux/namei.h>
+#include <linux/idr.h>
+#include <linux/slab.h>
+#include <linux/security.h>
+#include <linux/hash.h>
+
+#include "kernfs-internal.h"
+
+DEFINE_MUTEX(kernfs_mutex);
+static DEFINE_SPINLOCK(kernfs_rename_lock); /* kn->parent and ->name */
+static char kernfs_pr_cont_buf[PATH_MAX]; /* protected by rename_lock */
+static DEFINE_SPINLOCK(kernfs_idr_lock); /* root->ino_idr */
+
+#define rb_to_kn(X) rb_entry((X), struct kernfs_node, rb)
+
+static bool kernfs_active(struct kernfs_node *kn)
+{
+ lockdep_assert_held(&kernfs_mutex);
+ return atomic_read(&kn->active) >= 0;
+}
+
+static bool kernfs_lockdep(struct kernfs_node *kn)
+{
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+ return kn->flags & KERNFS_LOCKDEP;
+#else
+ return false;
+#endif
+}
+
+static int kernfs_name_locked(struct kernfs_node *kn, char *buf, size_t buflen)
+{
+ if (!kn)
+ return strlcpy(buf, "(null)", buflen);
+
+ return strlcpy(buf, kn->parent ? kn->name : "/", buflen);
+}
+
+/* kernfs_node_depth - compute depth from @from to @to */
+static size_t kernfs_depth(struct kernfs_node *from, struct kernfs_node *to)
+{
+ size_t depth = 0;
+
+ while (to->parent && to != from) {
+ depth++;
+ to = to->parent;
+ }
+ return depth;
+}
+
+static struct kernfs_node *kernfs_common_ancestor(struct kernfs_node *a,
+ struct kernfs_node *b)
+{
+ size_t da, db;
+ struct kernfs_root *ra = kernfs_root(a), *rb = kernfs_root(b);
+
+ if (ra != rb)
+ return NULL;
+
+ da = kernfs_depth(ra->kn, a);
+ db = kernfs_depth(rb->kn, b);
+
+ while (da > db) {
+ a = a->parent;
+ da--;
+ }
+ while (db > da) {
+ b = b->parent;
+ db--;
+ }
+
+ /* worst case b and a will be the same at root */
+ while (b != a) {
+ b = b->parent;
+ a = a->parent;
+ }
+
+ return a;
+}
+
+/**
+ * kernfs_path_from_node_locked - find a pseudo-absolute path to @kn_to,
+ * where kn_from is treated as root of the path.
+ * @kn_from: kernfs node which should be treated as root for the path
+ * @kn_to: kernfs node to which path is needed
+ * @buf: buffer to copy the path into
+ * @buflen: size of @buf
+ *
+ * We need to handle couple of scenarios here:
+ * [1] when @kn_from is an ancestor of @kn_to at some level
+ * kn_from: /n1/n2/n3
+ * kn_to: /n1/n2/n3/n4/n5
+ * result: /n4/n5
+ *
+ * [2] when @kn_from is on a different hierarchy and we need to find common
+ * ancestor between @kn_from and @kn_to.
+ * kn_from: /n1/n2/n3/n4
+ * kn_to: /n1/n2/n5
+ * result: /../../n5
+ * OR
+ * kn_from: /n1/n2/n3/n4/n5 [depth=5]
+ * kn_to: /n1/n2/n3 [depth=3]
+ * result: /../..
+ *
+ * [3] when @kn_to 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 int kernfs_path_from_node_locked(struct kernfs_node *kn_to,
+ struct kernfs_node *kn_from,
+ char *buf, size_t buflen)
+{
+ struct kernfs_node *kn, *common;
+ const char parent_str[] = "/..";
+ size_t depth_from, depth_to, len = 0;
+ int i, j;
+
+ if (!kn_to)
+ return strlcpy(buf, "(null)", buflen);
+
+ if (!kn_from)
+ kn_from = kernfs_root(kn_to)->kn;
+
+ if (kn_from == kn_to)
+ return strlcpy(buf, "/", buflen);
+
+ common = kernfs_common_ancestor(kn_from, kn_to);
+ if (WARN_ON(!common))
+ return -EINVAL;
+
+ depth_to = kernfs_depth(common, kn_to);
+ depth_from = kernfs_depth(common, kn_from);
+
+ if (buf)
+ buf[0] = '\0';
+
+ for (i = 0; i < depth_from; i++)
+ len += strlcpy(buf + len, parent_str,
+ len < buflen ? buflen - len : 0);
+
+ /* Calculate how many bytes we need for the rest */
+ for (i = depth_to - 1; i >= 0; i--) {
+ for (kn = kn_to, j = 0; j < i; j++)
+ kn = kn->parent;
+ len += strlcpy(buf + len, "/",
+ len < buflen ? buflen - len : 0);
+ len += strlcpy(buf + len, kn->name,
+ len < buflen ? buflen - len : 0);
+ }
+
+ return len;
+}
+
+/**
+ * kernfs_name - obtain the name of a given node
+ * @kn: kernfs_node of interest
+ * @buf: buffer to copy @kn's name into
+ * @buflen: size of @buf
+ *
+ * Copies the name of @kn into @buf of @buflen bytes. The behavior is
+ * similar to strlcpy(). It returns the length of @kn's name and if @buf
+ * isn't long enough, it's filled upto @buflen-1 and nul terminated.
+ *
+ * Fills buffer with "(null)" if @kn is NULL.
+ *
+ * This function can be called from any context.
+ */
+int kernfs_name(struct kernfs_node *kn, char *buf, size_t buflen)
+{
+ unsigned long flags;
+ int ret;
+
+ spin_lock_irqsave(&kernfs_rename_lock, flags);
+ ret = kernfs_name_locked(kn, buf, buflen);
+ spin_unlock_irqrestore(&kernfs_rename_lock, flags);
+ return ret;
+}
+
+/**
+ * kernfs_path_from_node - build path of node @to relative to @from.
+ * @from: parent kernfs_node relative to which we need to build the path
+ * @to: kernfs_node of interest
+ * @buf: buffer to copy @to's path into
+ * @buflen: size of @buf
+ *
+ * Builds @to's path relative to @from in @buf. @from and @to must
+ * be on the same kernfs-root. If @from is not parent of @to, then a relative
+ * path (which includes '..'s) as needed to reach from @from to @to is
+ * returned.
+ *
+ * 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.
+ */
+int kernfs_path_from_node(struct kernfs_node *to, struct kernfs_node *from,
+ char *buf, size_t buflen)
+{
+ unsigned long flags;
+ int ret;
+
+ spin_lock_irqsave(&kernfs_rename_lock, flags);
+ ret = kernfs_path_from_node_locked(to, from, buf, buflen);
+ spin_unlock_irqrestore(&kernfs_rename_lock, flags);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(kernfs_path_from_node);
+
+/**
+ * pr_cont_kernfs_name - pr_cont name of a kernfs_node
+ * @kn: kernfs_node of interest
+ *
+ * This function can be called from any context.
+ */
+void pr_cont_kernfs_name(struct kernfs_node *kn)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&kernfs_rename_lock, flags);
+
+ kernfs_name_locked(kn, kernfs_pr_cont_buf, sizeof(kernfs_pr_cont_buf));
+ pr_cont("%s", kernfs_pr_cont_buf);
+
+ spin_unlock_irqrestore(&kernfs_rename_lock, flags);
+}
+
+/**
+ * pr_cont_kernfs_path - pr_cont path of a kernfs_node
+ * @kn: kernfs_node of interest
+ *
+ * This function can be called from any context.
+ */
+void pr_cont_kernfs_path(struct kernfs_node *kn)
+{
+ unsigned long flags;
+ int sz;
+
+ spin_lock_irqsave(&kernfs_rename_lock, flags);
+
+ sz = kernfs_path_from_node_locked(kn, NULL, kernfs_pr_cont_buf,
+ sizeof(kernfs_pr_cont_buf));
+ if (sz < 0) {
+ pr_cont("(error)");
+ goto out;
+ }
+
+ if (sz >= sizeof(kernfs_pr_cont_buf)) {
+ pr_cont("(name too long)");
+ goto out;
+ }
+
+ pr_cont("%s", kernfs_pr_cont_buf);
+
+out:
+ spin_unlock_irqrestore(&kernfs_rename_lock, flags);
+}
+
+/**
+ * kernfs_get_parent - determine the parent node and pin it
+ * @kn: kernfs_node of interest
+ *
+ * Determines @kn's parent, pins and returns it. This function can be
+ * called from any context.
+ */
+struct kernfs_node *kernfs_get_parent(struct kernfs_node *kn)
+{
+ struct kernfs_node *parent;
+ unsigned long flags;
+
+ spin_lock_irqsave(&kernfs_rename_lock, flags);
+ parent = kn->parent;
+ kernfs_get(parent);
+ spin_unlock_irqrestore(&kernfs_rename_lock, flags);
+
+ return parent;
+}
+
+/**
+ * kernfs_name_hash
+ * @name: Null terminated string to hash
+ * @ns: Namespace tag to hash
+ *
+ * Returns 31 bit hash of ns + name (so it fits in an off_t )
+ */
+static unsigned int kernfs_name_hash(const char *name, const void *ns)
+{
+ unsigned long hash = init_name_hash(ns);
+ unsigned int len = strlen(name);
+ while (len--)
+ hash = partial_name_hash(*name++, hash);
+ hash = end_name_hash(hash);
+ hash &= 0x7fffffffU;
+ /* Reserve hash numbers 0, 1 and INT_MAX for magic directory entries */
+ if (hash < 2)
+ hash += 2;
+ if (hash >= INT_MAX)
+ hash = INT_MAX - 1;
+ return hash;
+}
+
+static int kernfs_name_compare(unsigned int hash, const char *name,
+ const void *ns, const struct kernfs_node *kn)
+{
+ if (hash < kn->hash)
+ return -1;
+ if (hash > kn->hash)
+ return 1;
+ if (ns < kn->ns)
+ return -1;
+ if (ns > kn->ns)
+ return 1;
+ return strcmp(name, kn->name);
+}
+
+static int kernfs_sd_compare(const struct kernfs_node *left,
+ const struct kernfs_node *right)
+{
+ return kernfs_name_compare(left->hash, left->name, left->ns, right);
+}
+
+/**
+ * kernfs_link_sibling - link kernfs_node into sibling rbtree
+ * @kn: kernfs_node of interest
+ *
+ * Link @kn into its sibling rbtree which starts from
+ * @kn->parent->dir.children.
+ *
+ * Locking:
+ * mutex_lock(kernfs_mutex)
+ *
+ * RETURNS:
+ * 0 on susccess -EEXIST on failure.
+ */
+static int kernfs_link_sibling(struct kernfs_node *kn)
+{
+ struct rb_node **node = &kn->parent->dir.children.rb_node;
+ struct rb_node *parent = NULL;
+
+ while (*node) {
+ struct kernfs_node *pos;
+ int result;
+
+ pos = rb_to_kn(*node);
+ parent = *node;
+ result = kernfs_sd_compare(kn, pos);
+ if (result < 0)
+ node = &pos->rb.rb_left;
+ else if (result > 0)
+ node = &pos->rb.rb_right;
+ else
+ return -EEXIST;
+ }
+
+ /* add new node and rebalance the tree */
+ rb_link_node(&kn->rb, parent, node);
+ rb_insert_color(&kn->rb, &kn->parent->dir.children);
+
+ /* successfully added, account subdir number */
+ if (kernfs_type(kn) == KERNFS_DIR)
+ kn->parent->dir.subdirs++;
+
+ return 0;
+}
+
+/**
+ * kernfs_unlink_sibling - unlink kernfs_node from sibling rbtree
+ * @kn: kernfs_node of interest
+ *
+ * Try to unlink @kn from its sibling rbtree which starts from
+ * kn->parent->dir.children. Returns %true if @kn was actually
+ * removed, %false if @kn wasn't on the rbtree.
+ *
+ * Locking:
+ * mutex_lock(kernfs_mutex)
+ */
+static bool kernfs_unlink_sibling(struct kernfs_node *kn)
+{
+ if (RB_EMPTY_NODE(&kn->rb))
+ return false;
+
+ if (kernfs_type(kn) == KERNFS_DIR)
+ kn->parent->dir.subdirs--;
+
+ rb_erase(&kn->rb, &kn->parent->dir.children);
+ RB_CLEAR_NODE(&kn->rb);
+ return true;
+}
+
+/**
+ * kernfs_get_active - get an active reference to kernfs_node
+ * @kn: kernfs_node to get an active reference to
+ *
+ * Get an active reference of @kn. This function is noop if @kn
+ * is NULL.
+ *
+ * RETURNS:
+ * Pointer to @kn on success, NULL on failure.
+ */
+struct kernfs_node *kernfs_get_active(struct kernfs_node *kn)
+{
+ if (unlikely(!kn))
+ return NULL;
+
+ if (!atomic_inc_unless_negative(&kn->active))
+ return NULL;
+
+ if (kernfs_lockdep(kn))
+ rwsem_acquire_read(&kn->dep_map, 0, 1, _RET_IP_);
+ return kn;
+}
+
+/**
+ * kernfs_put_active - put an active reference to kernfs_node
+ * @kn: kernfs_node to put an active reference to
+ *
+ * Put an active reference to @kn. This function is noop if @kn
+ * is NULL.
+ */
+void kernfs_put_active(struct kernfs_node *kn)
+{
+ struct kernfs_root *root = kernfs_root(kn);
+ int v;
+
+ if (unlikely(!kn))
+ return;
+
+ if (kernfs_lockdep(kn))
+ rwsem_release(&kn->dep_map, 1, _RET_IP_);
+ v = atomic_dec_return(&kn->active);
+ if (likely(v != KN_DEACTIVATED_BIAS))
+ return;
+
+ wake_up_all(&root->deactivate_waitq);
+}
+
+/**
+ * kernfs_drain - drain kernfs_node
+ * @kn: kernfs_node to drain
+ *
+ * Drain existing usages and nuke all existing mmaps of @kn. Mutiple
+ * removers may invoke this function concurrently on @kn and all will
+ * return after draining is complete.
+ */
+static void kernfs_drain(struct kernfs_node *kn)
+ __releases(&kernfs_mutex) __acquires(&kernfs_mutex)
+{
+ struct kernfs_root *root = kernfs_root(kn);
+
+ lockdep_assert_held(&kernfs_mutex);
+ WARN_ON_ONCE(kernfs_active(kn));
+
+ mutex_unlock(&kernfs_mutex);
+
+ if (kernfs_lockdep(kn)) {
+ rwsem_acquire(&kn->dep_map, 0, 0, _RET_IP_);
+ if (atomic_read(&kn->active) != KN_DEACTIVATED_BIAS)
+ lock_contended(&kn->dep_map, _RET_IP_);
+ }
+
+ /* but everyone should wait for draining */
+ wait_event(root->deactivate_waitq,
+ atomic_read(&kn->active) == KN_DEACTIVATED_BIAS);
+
+ if (kernfs_lockdep(kn)) {
+ lock_acquired(&kn->dep_map, _RET_IP_);
+ rwsem_release(&kn->dep_map, 1, _RET_IP_);
+ }
+
+ kernfs_drain_open_files(kn);
+
+ mutex_lock(&kernfs_mutex);
+}
+
+/**
+ * kernfs_get - get a reference count on a kernfs_node
+ * @kn: the target kernfs_node
+ */
+void kernfs_get(struct kernfs_node *kn)
+{
+ if (kn) {
+ WARN_ON(!atomic_read(&kn->count));
+ atomic_inc(&kn->count);
+ }
+}
+EXPORT_SYMBOL_GPL(kernfs_get);
+
+/**
+ * kernfs_put - put a reference count on a kernfs_node
+ * @kn: the target kernfs_node
+ *
+ * Put a reference count of @kn and destroy it if it reached zero.
+ */
+void kernfs_put(struct kernfs_node *kn)
+{
+ struct kernfs_node *parent;
+ struct kernfs_root *root;
+
+ /*
+ * kernfs_node is freed with ->count 0, kernfs_find_and_get_node_by_ino
+ * depends on this to filter reused stale node
+ */
+ if (!kn || !atomic_dec_and_test(&kn->count))
+ return;
+ root = kernfs_root(kn);
+ repeat:
+ /*
+ * Moving/renaming is always done while holding reference.
+ * kn->parent won't change beneath us.
+ */
+ parent = kn->parent;
+
+ WARN_ONCE(atomic_read(&kn->active) != KN_DEACTIVATED_BIAS,
+ "kernfs_put: %s/%s: released with incorrect active_ref %d\n",
+ parent ? parent->name : "", kn->name, atomic_read(&kn->active));
+
+ if (kernfs_type(kn) == KERNFS_LINK)
+ kernfs_put(kn->symlink.target_kn);
+
+ kfree_const(kn->name);
+
+ if (kn->iattr) {
+ if (kn->iattr->ia_secdata)
+ security_release_secctx(kn->iattr->ia_secdata,
+ kn->iattr->ia_secdata_len);
+ simple_xattrs_free(&kn->iattr->xattrs);
+ }
+ kfree(kn->iattr);
+ spin_lock(&kernfs_idr_lock);
+ idr_remove(&root->ino_idr, kn->id.ino);
+ spin_unlock(&kernfs_idr_lock);
+ kmem_cache_free(kernfs_node_cache, kn);
+
+ kn = parent;
+ if (kn) {
+ if (atomic_dec_and_test(&kn->count))
+ goto repeat;
+ } else {
+ /* just released the root kn, free @root too */
+ idr_destroy(&root->ino_idr);
+ kfree(root);
+ }
+}
+EXPORT_SYMBOL_GPL(kernfs_put);
+
+static int kernfs_dop_revalidate(struct dentry *dentry, unsigned int flags)
+{
+ struct kernfs_node *kn;
+
+ if (flags & LOOKUP_RCU)
+ return -ECHILD;
+
+ /* Always perform fresh lookup for negatives */
+ if (d_really_is_negative(dentry))
+ goto out_bad_unlocked;
+
+ kn = kernfs_dentry_node(dentry);
+ mutex_lock(&kernfs_mutex);
+
+ /* The kernfs node has been deactivated */
+ if (!kernfs_active(kn))
+ goto out_bad;
+
+ /* The kernfs node has been moved? */
+ if (kernfs_dentry_node(dentry->d_parent) != kn->parent)
+ goto out_bad;
+
+ /* The kernfs node has been renamed */
+ if (strcmp(dentry->d_name.name, kn->name) != 0)
+ goto out_bad;
+
+ /* The kernfs node has been moved to a different namespace */
+ if (kn->parent && kernfs_ns_enabled(kn->parent) &&
+ kernfs_info(dentry->d_sb)->ns != kn->ns)
+ goto out_bad;
+
+ mutex_unlock(&kernfs_mutex);
+ return 1;
+out_bad:
+ mutex_unlock(&kernfs_mutex);
+out_bad_unlocked:
+ return 0;
+}
+
+const struct dentry_operations kernfs_dops = {
+ .d_revalidate = kernfs_dop_revalidate,
+};
+
+/**
+ * kernfs_node_from_dentry - determine kernfs_node associated with a dentry
+ * @dentry: the dentry in question
+ *
+ * Return the kernfs_node associated with @dentry. If @dentry is not a
+ * kernfs one, %NULL is returned.
+ *
+ * While the returned kernfs_node will stay accessible as long as @dentry
+ * is accessible, the returned node can be in any state and the caller is
+ * fully responsible for determining what's accessible.
+ */
+struct kernfs_node *kernfs_node_from_dentry(struct dentry *dentry)
+{
+ if (dentry->d_sb->s_op == &kernfs_sops &&
+ !d_really_is_negative(dentry))
+ return kernfs_dentry_node(dentry);
+ return NULL;
+}
+
+static struct kernfs_node *__kernfs_new_node(struct kernfs_root *root,
+ const char *name, umode_t mode,
+ kuid_t uid, kgid_t gid,
+ unsigned flags)
+{
+ struct kernfs_node *kn;
+ u32 gen;
+ int cursor;
+ int ret;
+
+ name = kstrdup_const(name, GFP_KERNEL);
+ if (!name)
+ return NULL;
+
+ kn = kmem_cache_zalloc(kernfs_node_cache, GFP_KERNEL);
+ if (!kn)
+ goto err_out1;
+
+ idr_preload(GFP_KERNEL);
+ spin_lock(&kernfs_idr_lock);
+ cursor = idr_get_cursor(&root->ino_idr);
+ ret = idr_alloc_cyclic(&root->ino_idr, kn, 1, 0, GFP_ATOMIC);
+ if (ret >= 0 && ret < cursor)
+ root->next_generation++;
+ gen = root->next_generation;
+ spin_unlock(&kernfs_idr_lock);
+ idr_preload_end();
+ if (ret < 0)
+ goto err_out2;
+ kn->id.ino = ret;
+ kn->id.generation = gen;
+
+ /*
+ * set ino first. This barrier is paired with atomic_inc_not_zero in
+ * kernfs_find_and_get_node_by_ino
+ */
+ smp_mb__before_atomic();
+ atomic_set(&kn->count, 1);
+ atomic_set(&kn->active, KN_DEACTIVATED_BIAS);
+ RB_CLEAR_NODE(&kn->rb);
+
+ kn->name = name;
+ kn->mode = mode;
+ kn->flags = flags;
+
+ if (!uid_eq(uid, GLOBAL_ROOT_UID) || !gid_eq(gid, GLOBAL_ROOT_GID)) {
+ struct iattr iattr = {
+ .ia_valid = ATTR_UID | ATTR_GID,
+ .ia_uid = uid,
+ .ia_gid = gid,
+ };
+
+ ret = __kernfs_setattr(kn, &iattr);
+ if (ret < 0)
+ goto err_out3;
+ }
+
+ return kn;
+
+ err_out3:
+ idr_remove(&root->ino_idr, kn->id.ino);
+ err_out2:
+ kmem_cache_free(kernfs_node_cache, kn);
+ err_out1:
+ kfree_const(name);
+ return NULL;
+}
+
+struct kernfs_node *kernfs_new_node(struct kernfs_node *parent,
+ const char *name, umode_t mode,
+ kuid_t uid, kgid_t gid,
+ unsigned flags)
+{
+ struct kernfs_node *kn;
+
+ kn = __kernfs_new_node(kernfs_root(parent),
+ name, mode, uid, gid, flags);
+ if (kn) {
+ kernfs_get(parent);
+ kn->parent = parent;
+ }
+ return kn;
+}
+
+/*
+ * kernfs_find_and_get_node_by_ino - get kernfs_node from inode number
+ * @root: the kernfs root
+ * @ino: inode number
+ *
+ * RETURNS:
+ * NULL on failure. Return a kernfs node with reference counter incremented
+ */
+struct kernfs_node *kernfs_find_and_get_node_by_ino(struct kernfs_root *root,
+ unsigned int ino)
+{
+ struct kernfs_node *kn;
+
+ rcu_read_lock();
+ kn = idr_find(&root->ino_idr, ino);
+ if (!kn)
+ goto out;
+
+ /*
+ * Since kernfs_node is freed in RCU, it's possible an old node for ino
+ * is freed, but reused before RCU grace period. But a freed node (see
+ * kernfs_put) or an incompletedly initialized node (see
+ * __kernfs_new_node) should have 'count' 0. We can use this fact to
+ * filter out such node.
+ */
+ if (!atomic_inc_not_zero(&kn->count)) {
+ kn = NULL;
+ goto out;
+ }
+
+ /*
+ * The node could be a new node or a reused node. If it's a new node,
+ * we are ok. If it's reused because of RCU (because of
+ * SLAB_TYPESAFE_BY_RCU), the __kernfs_new_node always sets its 'ino'
+ * before 'count'. So if 'count' is uptodate, 'ino' should be uptodate,
+ * hence we can use 'ino' to filter stale node.
+ */
+ if (kn->id.ino != ino)
+ goto out;
+ rcu_read_unlock();
+
+ return kn;
+out:
+ rcu_read_unlock();
+ kernfs_put(kn);
+ return NULL;
+}
+
+/**
+ * kernfs_add_one - add kernfs_node to parent without warning
+ * @kn: kernfs_node to be added
+ *
+ * The caller must already have initialized @kn->parent. This
+ * function increments nlink of the parent's inode if @kn is a
+ * directory and link into the children list of the parent.
+ *
+ * RETURNS:
+ * 0 on success, -EEXIST if entry with the given name already
+ * exists.
+ */
+int kernfs_add_one(struct kernfs_node *kn)
+{
+ struct kernfs_node *parent = kn->parent;
+ struct kernfs_iattrs *ps_iattr;
+ bool has_ns;
+ int ret;
+
+ mutex_lock(&kernfs_mutex);
+
+ ret = -EINVAL;
+ has_ns = kernfs_ns_enabled(parent);
+ if (WARN(has_ns != (bool)kn->ns, KERN_WARNING "kernfs: ns %s in '%s' for '%s'\n",
+ has_ns ? "required" : "invalid", parent->name, kn->name))
+ goto out_unlock;
+
+ if (kernfs_type(parent) != KERNFS_DIR)
+ goto out_unlock;
+
+ ret = -ENOENT;
+ if (parent->flags & KERNFS_EMPTY_DIR)
+ goto out_unlock;
+
+ if ((parent->flags & KERNFS_ACTIVATED) && !kernfs_active(parent))
+ goto out_unlock;
+
+ kn->hash = kernfs_name_hash(kn->name, kn->ns);
+
+ ret = kernfs_link_sibling(kn);
+ if (ret)
+ goto out_unlock;
+
+ /* Update timestamps on the parent */
+ ps_iattr = parent->iattr;
+ if (ps_iattr) {
+ struct iattr *ps_iattrs = &ps_iattr->ia_iattr;
+ ktime_get_real_ts64(&ps_iattrs->ia_ctime);
+ ps_iattrs->ia_mtime = ps_iattrs->ia_ctime;
+ }
+
+ mutex_unlock(&kernfs_mutex);
+
+ /*
+ * Activate the new node unless CREATE_DEACTIVATED is requested.
+ * If not activated here, the kernfs user is responsible for
+ * activating the node with kernfs_activate(). A node which hasn't
+ * been activated is not visible to userland and its removal won't
+ * trigger deactivation.
+ */
+ if (!(kernfs_root(kn)->flags & KERNFS_ROOT_CREATE_DEACTIVATED))
+ kernfs_activate(kn);
+ return 0;
+
+out_unlock:
+ mutex_unlock(&kernfs_mutex);
+ return ret;
+}
+
+/**
+ * kernfs_find_ns - find kernfs_node with the given name
+ * @parent: kernfs_node to search under
+ * @name: name to look for
+ * @ns: the namespace tag to use
+ *
+ * Look for kernfs_node with name @name under @parent. Returns pointer to
+ * the found kernfs_node on success, %NULL on failure.
+ */
+static struct kernfs_node *kernfs_find_ns(struct kernfs_node *parent,
+ const unsigned char *name,
+ const void *ns)
+{
+ struct rb_node *node = parent->dir.children.rb_node;
+ bool has_ns = kernfs_ns_enabled(parent);
+ unsigned int hash;
+
+ lockdep_assert_held(&kernfs_mutex);
+
+ if (has_ns != (bool)ns) {
+ WARN(1, KERN_WARNING "kernfs: ns %s in '%s' for '%s'\n",
+ has_ns ? "required" : "invalid", parent->name, name);
+ return NULL;
+ }
+
+ hash = kernfs_name_hash(name, ns);
+ while (node) {
+ struct kernfs_node *kn;
+ int result;
+
+ kn = rb_to_kn(node);
+ result = kernfs_name_compare(hash, name, ns, kn);
+ if (result < 0)
+ node = node->rb_left;
+ else if (result > 0)
+ node = node->rb_right;
+ else
+ return kn;
+ }
+ return NULL;
+}
+
+static struct kernfs_node *kernfs_walk_ns(struct kernfs_node *parent,
+ const unsigned char *path,
+ const void *ns)
+{
+ size_t len;
+ char *p, *name;
+
+ lockdep_assert_held(&kernfs_mutex);
+
+ /* grab kernfs_rename_lock to piggy back on kernfs_pr_cont_buf */
+ spin_lock_irq(&kernfs_rename_lock);
+
+ len = strlcpy(kernfs_pr_cont_buf, path, sizeof(kernfs_pr_cont_buf));
+
+ if (len >= sizeof(kernfs_pr_cont_buf)) {
+ spin_unlock_irq(&kernfs_rename_lock);
+ return NULL;
+ }
+
+ p = kernfs_pr_cont_buf;
+
+ while ((name = strsep(&p, "/")) && parent) {
+ if (*name == '\0')
+ continue;
+ parent = kernfs_find_ns(parent, name, ns);
+ }
+
+ spin_unlock_irq(&kernfs_rename_lock);
+
+ return parent;
+}
+
+/**
+ * kernfs_find_and_get_ns - find and get kernfs_node with the given name
+ * @parent: kernfs_node to search under
+ * @name: name to look for
+ * @ns: the namespace tag to use
+ *
+ * Look for kernfs_node with name @name under @parent and get a reference
+ * if found. This function may sleep and returns pointer to the found
+ * kernfs_node on success, %NULL on failure.
+ */
+struct kernfs_node *kernfs_find_and_get_ns(struct kernfs_node *parent,
+ const char *name, const void *ns)
+{
+ struct kernfs_node *kn;
+
+ mutex_lock(&kernfs_mutex);
+ kn = kernfs_find_ns(parent, name, ns);
+ kernfs_get(kn);
+ mutex_unlock(&kernfs_mutex);
+
+ return kn;
+}
+EXPORT_SYMBOL_GPL(kernfs_find_and_get_ns);
+
+/**
+ * kernfs_walk_and_get_ns - find and get kernfs_node with the given path
+ * @parent: kernfs_node to search under
+ * @path: path to look for
+ * @ns: the namespace tag to use
+ *
+ * Look for kernfs_node with path @path under @parent and get a reference
+ * if found. This function may sleep and returns pointer to the found
+ * kernfs_node on success, %NULL on failure.
+ */
+struct kernfs_node *kernfs_walk_and_get_ns(struct kernfs_node *parent,
+ const char *path, const void *ns)
+{
+ struct kernfs_node *kn;
+
+ mutex_lock(&kernfs_mutex);
+ kn = kernfs_walk_ns(parent, path, ns);
+ kernfs_get(kn);
+ mutex_unlock(&kernfs_mutex);
+
+ return kn;
+}
+
+/**
+ * kernfs_create_root - create a new kernfs hierarchy
+ * @scops: optional syscall operations for the hierarchy
+ * @flags: KERNFS_ROOT_* flags
+ * @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(struct kernfs_syscall_ops *scops,
+ unsigned int flags, void *priv)
+{
+ struct kernfs_root *root;
+ struct kernfs_node *kn;
+
+ root = kzalloc(sizeof(*root), GFP_KERNEL);
+ if (!root)
+ return ERR_PTR(-ENOMEM);
+
+ idr_init(&root->ino_idr);
+ INIT_LIST_HEAD(&root->supers);
+ root->next_generation = 1;
+
+ kn = __kernfs_new_node(root, "", S_IFDIR | S_IRUGO | S_IXUGO,
+ GLOBAL_ROOT_UID, GLOBAL_ROOT_GID,
+ KERNFS_DIR);
+ if (!kn) {
+ idr_destroy(&root->ino_idr);
+ kfree(root);
+ return ERR_PTR(-ENOMEM);
+ }
+
+ kn->priv = priv;
+ kn->dir.root = root;
+
+ root->syscall_ops = scops;
+ root->flags = flags;
+ root->kn = kn;
+ init_waitqueue_head(&root->deactivate_waitq);
+
+ if (!(root->flags & KERNFS_ROOT_CREATE_DEACTIVATED))
+ kernfs_activate(kn);
+
+ 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->kn); /* will also free @root */
+}
+
+/**
+ * kernfs_create_dir_ns - create a directory
+ * @parent: parent in which to create a new directory
+ * @name: name of the new directory
+ * @mode: mode of the new directory
+ * @uid: uid of the new directory
+ * @gid: gid of the new directory
+ * @priv: opaque data associated with the new directory
+ * @ns: optional namespace tag of the directory
+ *
+ * Returns the created node on success, ERR_PTR() value on failure.
+ */
+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 *kn;
+ int rc;
+
+ /* allocate */
+ kn = kernfs_new_node(parent, name, mode | S_IFDIR,
+ uid, gid, KERNFS_DIR);
+ if (!kn)
+ return ERR_PTR(-ENOMEM);
+
+ kn->dir.root = parent->dir.root;
+ kn->ns = ns;
+ kn->priv = priv;
+
+ /* link in */
+ rc = kernfs_add_one(kn);
+ if (!rc)
+ return kn;
+
+ kernfs_put(kn);
+ return ERR_PTR(rc);
+}
+
+/**
+ * kernfs_create_empty_dir - create an always empty directory
+ * @parent: parent in which to create a new directory
+ * @name: name of the new directory
+ *
+ * Returns the created node on success, ERR_PTR() value on failure.
+ */
+struct kernfs_node *kernfs_create_empty_dir(struct kernfs_node *parent,
+ const char *name)
+{
+ struct kernfs_node *kn;
+ int rc;
+
+ /* allocate */
+ kn = kernfs_new_node(parent, name, S_IRUGO|S_IXUGO|S_IFDIR,
+ GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, KERNFS_DIR);
+ if (!kn)
+ return ERR_PTR(-ENOMEM);
+
+ kn->flags |= KERNFS_EMPTY_DIR;
+ kn->dir.root = parent->dir.root;
+ kn->ns = NULL;
+ kn->priv = NULL;
+
+ /* link in */
+ rc = kernfs_add_one(kn);
+ if (!rc)
+ return kn;
+
+ kernfs_put(kn);
+ return ERR_PTR(rc);
+}
+
+static struct dentry *kernfs_iop_lookup(struct inode *dir,
+ struct dentry *dentry,
+ unsigned int flags)
+{
+ struct dentry *ret;
+ struct kernfs_node *parent = dir->i_private;
+ struct kernfs_node *kn;
+ struct inode *inode;
+ const void *ns = NULL;
+
+ mutex_lock(&kernfs_mutex);
+
+ if (kernfs_ns_enabled(parent))
+ ns = kernfs_info(dir->i_sb)->ns;
+
+ kn = kernfs_find_ns(parent, dentry->d_name.name, ns);
+
+ /* no such entry */
+ if (!kn || !kernfs_active(kn)) {
+ ret = NULL;
+ goto out_unlock;
+ }
+
+ /* attach dentry and inode */
+ inode = kernfs_get_inode(dir->i_sb, kn);
+ if (!inode) {
+ ret = ERR_PTR(-ENOMEM);
+ goto out_unlock;
+ }
+
+ /* instantiate and hash dentry */
+ ret = d_splice_alias(inode, dentry);
+ out_unlock:
+ mutex_unlock(&kernfs_mutex);
+ return ret;
+}
+
+static int kernfs_iop_mkdir(struct inode *dir, struct dentry *dentry,
+ umode_t mode)
+{
+ struct kernfs_node *parent = dir->i_private;
+ struct kernfs_syscall_ops *scops = kernfs_root(parent)->syscall_ops;
+ int ret;
+
+ if (!scops || !scops->mkdir)
+ return -EPERM;
+
+ if (!kernfs_get_active(parent))
+ return -ENODEV;
+
+ ret = scops->mkdir(parent, dentry->d_name.name, mode);
+
+ kernfs_put_active(parent);
+ return ret;
+}
+
+static int kernfs_iop_rmdir(struct inode *dir, struct dentry *dentry)
+{
+ struct kernfs_node *kn = kernfs_dentry_node(dentry);
+ struct kernfs_syscall_ops *scops = kernfs_root(kn)->syscall_ops;
+ int ret;
+
+ if (!scops || !scops->rmdir)
+ return -EPERM;
+
+ if (!kernfs_get_active(kn))
+ return -ENODEV;
+
+ ret = scops->rmdir(kn);
+
+ kernfs_put_active(kn);
+ return ret;
+}
+
+static int kernfs_iop_rename(struct inode *old_dir, struct dentry *old_dentry,
+ struct inode *new_dir, struct dentry *new_dentry,
+ unsigned int flags)
+{
+ struct kernfs_node *kn = kernfs_dentry_node(old_dentry);
+ struct kernfs_node *new_parent = new_dir->i_private;
+ struct kernfs_syscall_ops *scops = kernfs_root(kn)->syscall_ops;
+ int ret;
+
+ if (flags)
+ return -EINVAL;
+
+ if (!scops || !scops->rename)
+ return -EPERM;
+
+ if (!kernfs_get_active(kn))
+ return -ENODEV;
+
+ if (!kernfs_get_active(new_parent)) {
+ kernfs_put_active(kn);
+ return -ENODEV;
+ }
+
+ ret = scops->rename(kn, new_parent, new_dentry->d_name.name);
+
+ kernfs_put_active(new_parent);
+ kernfs_put_active(kn);
+ return ret;
+}
+
+const struct inode_operations kernfs_dir_iops = {
+ .lookup = kernfs_iop_lookup,
+ .permission = kernfs_iop_permission,
+ .setattr = kernfs_iop_setattr,
+ .getattr = kernfs_iop_getattr,
+ .listxattr = kernfs_iop_listxattr,
+
+ .mkdir = kernfs_iop_mkdir,
+ .rmdir = kernfs_iop_rmdir,
+ .rename = kernfs_iop_rename,
+};
+
+static struct kernfs_node *kernfs_leftmost_descendant(struct kernfs_node *pos)
+{
+ struct kernfs_node *last;
+
+ while (true) {
+ struct rb_node *rbn;
+
+ last = pos;
+
+ if (kernfs_type(pos) != KERNFS_DIR)
+ break;
+
+ rbn = rb_first(&pos->dir.children);
+ if (!rbn)
+ break;
+
+ pos = rb_to_kn(rbn);
+ }
+
+ return last;
+}
+
+/**
+ * kernfs_next_descendant_post - find the next descendant for post-order walk
+ * @pos: the current position (%NULL to initiate traversal)
+ * @root: kernfs_node whose descendants to walk
+ *
+ * Find the next descendant to visit for post-order traversal of @root's
+ * descendants. @root is included in the iteration and the last node to be
+ * visited.
+ */
+static struct kernfs_node *kernfs_next_descendant_post(struct kernfs_node *pos,
+ struct kernfs_node *root)
+{
+ struct rb_node *rbn;
+
+ lockdep_assert_held(&kernfs_mutex);
+
+ /* if first iteration, visit leftmost descendant which may be root */
+ if (!pos)
+ return kernfs_leftmost_descendant(root);
+
+ /* if we visited @root, we're done */
+ if (pos == root)
+ return NULL;
+
+ /* if there's an unvisited sibling, visit its leftmost descendant */
+ rbn = rb_next(&pos->rb);
+ if (rbn)
+ return kernfs_leftmost_descendant(rb_to_kn(rbn));
+
+ /* no sibling left, visit parent */
+ return pos->parent;
+}
+
+/**
+ * kernfs_activate - activate a node which started deactivated
+ * @kn: kernfs_node whose subtree is to be activated
+ *
+ * If the root has KERNFS_ROOT_CREATE_DEACTIVATED set, a newly created node
+ * needs to be explicitly activated. A node which hasn't been activated
+ * isn't visible to userland and deactivation is skipped during its
+ * removal. This is useful to construct atomic init sequences where
+ * creation of multiple nodes should either succeed or fail atomically.
+ *
+ * The caller is responsible for ensuring that this function is not called
+ * after kernfs_remove*() is invoked on @kn.
+ */
+void kernfs_activate(struct kernfs_node *kn)
+{
+ struct kernfs_node *pos;
+
+ mutex_lock(&kernfs_mutex);
+
+ pos = NULL;
+ while ((pos = kernfs_next_descendant_post(pos, kn))) {
+ if (!pos || (pos->flags & KERNFS_ACTIVATED))
+ continue;
+
+ WARN_ON_ONCE(pos->parent && RB_EMPTY_NODE(&pos->rb));
+ WARN_ON_ONCE(atomic_read(&pos->active) != KN_DEACTIVATED_BIAS);
+
+ atomic_sub(KN_DEACTIVATED_BIAS, &pos->active);
+ pos->flags |= KERNFS_ACTIVATED;
+ }
+
+ mutex_unlock(&kernfs_mutex);
+}
+
+static void __kernfs_remove(struct kernfs_node *kn)
+{
+ struct kernfs_node *pos;
+
+ lockdep_assert_held(&kernfs_mutex);
+
+ /*
+ * Short-circuit if non-root @kn has already finished removal.
+ * This is for kernfs_remove_self() which plays with active ref
+ * after removal.
+ */
+ if (!kn || (kn->parent && RB_EMPTY_NODE(&kn->rb)))
+ return;
+
+ pr_debug("kernfs %s: removing\n", kn->name);
+
+ /* prevent any new usage under @kn by deactivating all nodes */
+ pos = NULL;
+ while ((pos = kernfs_next_descendant_post(pos, kn)))
+ if (kernfs_active(pos))
+ atomic_add(KN_DEACTIVATED_BIAS, &pos->active);
+
+ /* deactivate and unlink the subtree node-by-node */
+ do {
+ pos = kernfs_leftmost_descendant(kn);
+
+ /*
+ * kernfs_drain() drops kernfs_mutex temporarily and @pos's
+ * base ref could have been put by someone else by the time
+ * the function returns. Make sure it doesn't go away
+ * underneath us.
+ */
+ kernfs_get(pos);
+
+ /*
+ * Drain iff @kn was activated. This avoids draining and
+ * its lockdep annotations for nodes which have never been
+ * activated and allows embedding kernfs_remove() in create
+ * error paths without worrying about draining.
+ */
+ if (kn->flags & KERNFS_ACTIVATED)
+ kernfs_drain(pos);
+ else
+ WARN_ON_ONCE(atomic_read(&kn->active) != KN_DEACTIVATED_BIAS);
+
+ /*
+ * kernfs_unlink_sibling() succeeds once per node. Use it
+ * to decide who's responsible for cleanups.
+ */
+ if (!pos->parent || kernfs_unlink_sibling(pos)) {
+ struct kernfs_iattrs *ps_iattr =
+ pos->parent ? pos->parent->iattr : NULL;
+
+ /* update timestamps on the parent */
+ if (ps_iattr) {
+ ktime_get_real_ts64(&ps_iattr->ia_iattr.ia_ctime);
+ ps_iattr->ia_iattr.ia_mtime =
+ ps_iattr->ia_iattr.ia_ctime;
+ }
+
+ kernfs_put(pos);
+ }
+
+ kernfs_put(pos);
+ } while (pos != kn);
+}
+
+/**
+ * kernfs_remove - remove a kernfs_node recursively
+ * @kn: the kernfs_node to remove
+ *
+ * Remove @kn along with all its subdirectories and files.
+ */
+void kernfs_remove(struct kernfs_node *kn)
+{
+ mutex_lock(&kernfs_mutex);
+ __kernfs_remove(kn);
+ mutex_unlock(&kernfs_mutex);
+}
+
+/**
+ * kernfs_break_active_protection - break out of active protection
+ * @kn: the self kernfs_node
+ *
+ * The caller must be running off of a kernfs operation which is invoked
+ * with an active reference - e.g. one of kernfs_ops. Each invocation of
+ * this function must also be matched with an invocation of
+ * kernfs_unbreak_active_protection().
+ *
+ * This function releases the active reference of @kn the caller is
+ * holding. Once this function is called, @kn may be removed at any point
+ * and the caller is solely responsible for ensuring that the objects it
+ * dereferences are accessible.
+ */
+void kernfs_break_active_protection(struct kernfs_node *kn)
+{
+ /*
+ * Take out ourself out of the active ref dependency chain. If
+ * we're called without an active ref, lockdep will complain.
+ */
+ kernfs_put_active(kn);
+}
+
+/**
+ * kernfs_unbreak_active_protection - undo kernfs_break_active_protection()
+ * @kn: the self kernfs_node
+ *
+ * If kernfs_break_active_protection() was called, this function must be
+ * invoked before finishing the kernfs operation. Note that while this
+ * function restores the active reference, it doesn't and can't actually
+ * restore the active protection - @kn may already or be in the process of
+ * being removed. Once kernfs_break_active_protection() is invoked, that
+ * protection is irreversibly gone for the kernfs operation instance.
+ *
+ * While this function may be called at any point after
+ * kernfs_break_active_protection() is invoked, its most useful location
+ * would be right before the enclosing kernfs operation returns.
+ */
+void kernfs_unbreak_active_protection(struct kernfs_node *kn)
+{
+ /*
+ * @kn->active could be in any state; however, the increment we do
+ * here will be undone as soon as the enclosing kernfs operation
+ * finishes and this temporary bump can't break anything. If @kn
+ * is alive, nothing changes. If @kn is being deactivated, the
+ * soon-to-follow put will either finish deactivation or restore
+ * deactivated state. If @kn is already removed, the temporary
+ * bump is guaranteed to be gone before @kn is released.
+ */
+ atomic_inc(&kn->active);
+ if (kernfs_lockdep(kn))
+ rwsem_acquire(&kn->dep_map, 0, 1, _RET_IP_);
+}
+
+/**
+ * kernfs_remove_self - remove a kernfs_node from its own method
+ * @kn: the self kernfs_node to remove
+ *
+ * The caller must be running off of a kernfs operation which is invoked
+ * with an active reference - e.g. one of kernfs_ops. This can be used to
+ * implement a file operation which deletes itself.
+ *
+ * For example, the "delete" file for a sysfs device directory can be
+ * implemented by invoking kernfs_remove_self() on the "delete" file
+ * itself. This function breaks the circular dependency of trying to
+ * deactivate self while holding an active ref itself. It isn't necessary
+ * to modify the usual removal path to use kernfs_remove_self(). The
+ * "delete" implementation can simply invoke kernfs_remove_self() on self
+ * before proceeding with the usual removal path. kernfs will ignore later
+ * kernfs_remove() on self.
+ *
+ * kernfs_remove_self() can be called multiple times concurrently on the
+ * same kernfs_node. Only the first one actually performs removal and
+ * returns %true. All others will wait until the kernfs operation which
+ * won self-removal finishes and return %false. Note that the losers wait
+ * for the completion of not only the winning kernfs_remove_self() but also
+ * the whole kernfs_ops which won the arbitration. This can be used to
+ * guarantee, for example, all concurrent writes to a "delete" file to
+ * finish only after the whole operation is complete.
+ */
+bool kernfs_remove_self(struct kernfs_node *kn)
+{
+ bool ret;
+
+ mutex_lock(&kernfs_mutex);
+ kernfs_break_active_protection(kn);
+
+ /*
+ * SUICIDAL is used to arbitrate among competing invocations. Only
+ * the first one will actually perform removal. When the removal
+ * is complete, SUICIDED is set and the active ref is restored
+ * while holding kernfs_mutex. The ones which lost arbitration
+ * waits for SUICDED && drained which can happen only after the
+ * enclosing kernfs operation which executed the winning instance
+ * of kernfs_remove_self() finished.
+ */
+ if (!(kn->flags & KERNFS_SUICIDAL)) {
+ kn->flags |= KERNFS_SUICIDAL;
+ __kernfs_remove(kn);
+ kn->flags |= KERNFS_SUICIDED;
+ ret = true;
+ } else {
+ wait_queue_head_t *waitq = &kernfs_root(kn)->deactivate_waitq;
+ DEFINE_WAIT(wait);
+
+ while (true) {
+ prepare_to_wait(waitq, &wait, TASK_UNINTERRUPTIBLE);
+
+ if ((kn->flags & KERNFS_SUICIDED) &&
+ atomic_read(&kn->active) == KN_DEACTIVATED_BIAS)
+ break;
+
+ mutex_unlock(&kernfs_mutex);
+ schedule();
+ mutex_lock(&kernfs_mutex);
+ }
+ finish_wait(waitq, &wait);
+ WARN_ON_ONCE(!RB_EMPTY_NODE(&kn->rb));
+ ret = false;
+ }
+
+ /*
+ * This must be done while holding kernfs_mutex; otherwise, waiting
+ * for SUICIDED && deactivated could finish prematurely.
+ */
+ kernfs_unbreak_active_protection(kn);
+
+ mutex_unlock(&kernfs_mutex);
+ return ret;
+}
+
+/**
+ * kernfs_remove_by_name_ns - find a kernfs_node by name and remove it
+ * @parent: parent of the target
+ * @name: name of the kernfs_node to remove
+ * @ns: namespace tag of the kernfs_node to remove
+ *
+ * Look for the kernfs_node with @name and @ns under @parent and remove it.
+ * Returns 0 on success, -ENOENT if such entry doesn't exist.
+ */
+int kernfs_remove_by_name_ns(struct kernfs_node *parent, const char *name,
+ const void *ns)
+{
+ struct kernfs_node *kn;
+
+ if (!parent) {
+ WARN(1, KERN_WARNING "kernfs: can not remove '%s', no directory\n",
+ name);
+ return -ENOENT;
+ }
+
+ mutex_lock(&kernfs_mutex);
+
+ kn = kernfs_find_ns(parent, name, ns);
+ if (kn)
+ __kernfs_remove(kn);
+
+ mutex_unlock(&kernfs_mutex);
+
+ if (kn)
+ return 0;
+ else
+ return -ENOENT;
+}
+
+/**
+ * kernfs_rename_ns - move and rename a kernfs_node
+ * @kn: target node
+ * @new_parent: new parent to put @sd under
+ * @new_name: new name
+ * @new_ns: new namespace tag
+ */
+int kernfs_rename_ns(struct kernfs_node *kn, struct kernfs_node *new_parent,
+ const char *new_name, const void *new_ns)
+{
+ struct kernfs_node *old_parent;
+ const char *old_name = NULL;
+ int error;
+
+ /* can't move or rename root */
+ if (!kn->parent)
+ return -EINVAL;
+
+ mutex_lock(&kernfs_mutex);
+
+ error = -ENOENT;
+ if (!kernfs_active(kn) || !kernfs_active(new_parent) ||
+ (new_parent->flags & KERNFS_EMPTY_DIR))
+ goto out;
+
+ error = 0;
+ if ((kn->parent == new_parent) && (kn->ns == new_ns) &&
+ (strcmp(kn->name, new_name) == 0))
+ goto out; /* nothing to rename */
+
+ error = -EEXIST;
+ if (kernfs_find_ns(new_parent, new_name, new_ns))
+ goto out;
+
+ /* rename kernfs_node */
+ if (strcmp(kn->name, new_name) != 0) {
+ error = -ENOMEM;
+ new_name = kstrdup_const(new_name, GFP_KERNEL);
+ if (!new_name)
+ goto out;
+ } else {
+ new_name = NULL;
+ }
+
+ /*
+ * Move to the appropriate place in the appropriate directories rbtree.
+ */
+ kernfs_unlink_sibling(kn);
+ kernfs_get(new_parent);
+
+ /* rename_lock protects ->parent and ->name accessors */
+ spin_lock_irq(&kernfs_rename_lock);
+
+ old_parent = kn->parent;
+ kn->parent = new_parent;
+
+ kn->ns = new_ns;
+ if (new_name) {
+ old_name = kn->name;
+ kn->name = new_name;
+ }
+
+ spin_unlock_irq(&kernfs_rename_lock);
+
+ kn->hash = kernfs_name_hash(kn->name, kn->ns);
+ kernfs_link_sibling(kn);
+
+ kernfs_put(old_parent);
+ kfree_const(old_name);
+
+ error = 0;
+ out:
+ mutex_unlock(&kernfs_mutex);
+ return error;
+}
+
+/* Relationship between s_mode and the DT_xxx types */
+static inline unsigned char dt_type(struct kernfs_node *kn)
+{
+ return (kn->mode >> 12) & 15;
+}
+
+static int kernfs_dir_fop_release(struct inode *inode, struct file *filp)
+{
+ kernfs_put(filp->private_data);
+ return 0;
+}
+
+static struct kernfs_node *kernfs_dir_pos(const void *ns,
+ struct kernfs_node *parent, loff_t hash, struct kernfs_node *pos)
+{
+ if (pos) {
+ int valid = kernfs_active(pos) &&
+ pos->parent == parent && hash == pos->hash;
+ kernfs_put(pos);
+ if (!valid)
+ pos = NULL;
+ }
+ if (!pos && (hash > 1) && (hash < INT_MAX)) {
+ struct rb_node *node = parent->dir.children.rb_node;
+ while (node) {
+ pos = rb_to_kn(node);
+
+ if (hash < pos->hash)
+ node = node->rb_left;
+ else if (hash > pos->hash)
+ node = node->rb_right;
+ else
+ break;
+ }
+ }
+ /* Skip over entries which are dying/dead or in the wrong namespace */
+ while (pos && (!kernfs_active(pos) || pos->ns != ns)) {
+ struct rb_node *node = rb_next(&pos->rb);
+ if (!node)
+ pos = NULL;
+ else
+ pos = rb_to_kn(node);
+ }
+ return pos;
+}
+
+static struct kernfs_node *kernfs_dir_next_pos(const void *ns,
+ struct kernfs_node *parent, ino_t ino, struct kernfs_node *pos)
+{
+ pos = kernfs_dir_pos(ns, parent, ino, pos);
+ if (pos) {
+ do {
+ struct rb_node *node = rb_next(&pos->rb);
+ if (!node)
+ pos = NULL;
+ else
+ pos = rb_to_kn(node);
+ } while (pos && (!kernfs_active(pos) || pos->ns != ns));
+ }
+ return pos;
+}
+
+static int kernfs_fop_readdir(struct file *file, struct dir_context *ctx)
+{
+ struct dentry *dentry = file->f_path.dentry;
+ struct kernfs_node *parent = kernfs_dentry_node(dentry);
+ struct kernfs_node *pos = file->private_data;
+ const void *ns = NULL;
+
+ if (!dir_emit_dots(file, ctx))
+ return 0;
+ mutex_lock(&kernfs_mutex);
+
+ if (kernfs_ns_enabled(parent))
+ ns = kernfs_info(dentry->d_sb)->ns;
+
+ for (pos = kernfs_dir_pos(ns, parent, ctx->pos, pos);
+ pos;
+ pos = kernfs_dir_next_pos(ns, parent, ctx->pos, pos)) {
+ const char *name = pos->name;
+ unsigned int type = dt_type(pos);
+ int len = strlen(name);
+ ino_t ino = pos->id.ino;
+
+ ctx->pos = pos->hash;
+ file->private_data = pos;
+ kernfs_get(pos);
+
+ mutex_unlock(&kernfs_mutex);
+ if (!dir_emit(ctx, name, len, ino, type))
+ return 0;
+ mutex_lock(&kernfs_mutex);
+ }
+ mutex_unlock(&kernfs_mutex);
+ file->private_data = NULL;
+ ctx->pos = INT_MAX;
+ return 0;
+}
+
+const struct file_operations kernfs_dir_fops = {
+ .read = generic_read_dir,
+ .iterate_shared = kernfs_fop_readdir,
+ .release = kernfs_dir_fop_release,
+ .llseek = generic_file_llseek,
+};
diff --git a/fs/kernfs/file.c b/fs/kernfs/file.c
new file mode 100644
index 0000000..dbf5bc2
--- /dev/null
+++ b/fs/kernfs/file.c
@@ -0,0 +1,1027 @@
+/*
+ * fs/kernfs/file.c - kernfs file implementation
+ *
+ * Copyright (c) 2001-3 Patrick Mochel
+ * Copyright (c) 2007 SUSE Linux Products GmbH
+ * Copyright (c) 2007, 2013 Tejun Heo <tj@kernel.org>
+ *
+ * This file is released under the GPLv2.
+ */
+
+#include <linux/fs.h>
+#include <linux/seq_file.h>
+#include <linux/slab.h>
+#include <linux/poll.h>
+#include <linux/pagemap.h>
+#include <linux/sched/mm.h>
+#include <linux/fsnotify.h>
+
+#include "kernfs-internal.h"
+
+/*
+ * 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.
+ *
+ * kernfs_node->attr.open points to kernfs_open_node. attr.open is
+ * protected by kernfs_open_node_lock.
+ *
+ * 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_open_file_mutex.
+ */
+static DEFINE_SPINLOCK(kernfs_open_node_lock);
+static DEFINE_MUTEX(kernfs_open_file_mutex);
+
+struct kernfs_open_node {
+ atomic_t refcnt;
+ atomic_t event;
+ wait_queue_head_t poll;
+ struct list_head files; /* goes through kernfs_open_file.list */
+};
+
+/*
+ * kernfs_notify() may be called from any context and bounces notifications
+ * through a work item. To minimize space overhead in kernfs_node, the
+ * pending queue is implemented as a singly linked list of kernfs_nodes.
+ * The list is terminated with the self pointer so that whether a
+ * kernfs_node is on the list or not can be determined by testing the next
+ * pointer for NULL.
+ */
+#define KERNFS_NOTIFY_EOL ((void *)&kernfs_notify_list)
+
+static DEFINE_SPINLOCK(kernfs_notify_lock);
+static struct kernfs_node *kernfs_notify_list = KERNFS_NOTIFY_EOL;
+
+static struct kernfs_open_file *kernfs_of(struct file *file)
+{
+ return ((struct seq_file *)file->private_data)->private;
+}
+
+/*
+ * Determine the kernfs_ops for the given kernfs_node. This function must
+ * be called while holding an active reference.
+ */
+static const struct kernfs_ops *kernfs_ops(struct kernfs_node *kn)
+{
+ if (kn->flags & KERNFS_LOCKDEP)
+ lockdep_assert_held(kn);
+ return kn->attr.ops;
+}
+
+/*
+ * As kernfs_seq_stop() is also called after kernfs_seq_start() or
+ * kernfs_seq_next() failure, it needs to distinguish whether it's stopping
+ * a seq_file iteration which is fully initialized with an active reference
+ * or an aborted kernfs_seq_start() due to get_active failure. The
+ * position pointer is the only context for each seq_file iteration and
+ * thus the stop condition should be encoded in it. As the return value is
+ * directly visible to userland, ERR_PTR(-ENODEV) is the only acceptable
+ * choice to indicate get_active failure.
+ *
+ * Unfortunately, this is complicated due to the optional custom seq_file
+ * operations which may return ERR_PTR(-ENODEV) too. kernfs_seq_stop()
+ * can't distinguish whether ERR_PTR(-ENODEV) is from get_active failure or
+ * custom seq_file operations and thus can't decide whether put_active
+ * should be performed or not only on ERR_PTR(-ENODEV).
+ *
+ * This is worked around by factoring out the custom seq_stop() and
+ * put_active part into kernfs_seq_stop_active(), skipping it from
+ * kernfs_seq_stop() if ERR_PTR(-ENODEV) while invoking it directly after
+ * custom seq_file operations fail with ERR_PTR(-ENODEV) - this ensures
+ * that kernfs_seq_stop_active() is skipped only after get_active failure.
+ */
+static void kernfs_seq_stop_active(struct seq_file *sf, void *v)
+{
+ struct kernfs_open_file *of = sf->private;
+ const struct kernfs_ops *ops = kernfs_ops(of->kn);
+
+ if (ops->seq_stop)
+ ops->seq_stop(sf, v);
+ kernfs_put_active(of->kn);
+}
+
+static void *kernfs_seq_start(struct seq_file *sf, loff_t *ppos)
+{
+ struct kernfs_open_file *of = sf->private;
+ const struct kernfs_ops *ops;
+
+ /*
+ * @of->mutex nests outside active ref and is primarily to ensure that
+ * the ops aren't called concurrently for the same open file.
+ */
+ mutex_lock(&of->mutex);
+ if (!kernfs_get_active(of->kn))
+ return ERR_PTR(-ENODEV);
+
+ ops = kernfs_ops(of->kn);
+ if (ops->seq_start) {
+ void *next = ops->seq_start(sf, ppos);
+ /* see the comment above kernfs_seq_stop_active() */
+ if (next == ERR_PTR(-ENODEV))
+ kernfs_seq_stop_active(sf, next);
+ return next;
+ } else {
+ /*
+ * The same behavior and code as single_open(). Returns
+ * !NULL if pos is at the beginning; otherwise, NULL.
+ */
+ return NULL + !*ppos;
+ }
+}
+
+static void *kernfs_seq_next(struct seq_file *sf, void *v, loff_t *ppos)
+{
+ struct kernfs_open_file *of = sf->private;
+ const struct kernfs_ops *ops = kernfs_ops(of->kn);
+
+ if (ops->seq_next) {
+ void *next = ops->seq_next(sf, v, ppos);
+ /* see the comment above kernfs_seq_stop_active() */
+ if (next == ERR_PTR(-ENODEV))
+ kernfs_seq_stop_active(sf, next);
+ return next;
+ } else {
+ /*
+ * The same behavior and code as single_open(), always
+ * terminate after the initial read.
+ */
+ ++*ppos;
+ return NULL;
+ }
+}
+
+static void kernfs_seq_stop(struct seq_file *sf, void *v)
+{
+ struct kernfs_open_file *of = sf->private;
+
+ if (v != ERR_PTR(-ENODEV))
+ kernfs_seq_stop_active(sf, v);
+ mutex_unlock(&of->mutex);
+}
+
+static int kernfs_seq_show(struct seq_file *sf, void *v)
+{
+ struct kernfs_open_file *of = sf->private;
+
+ of->event = atomic_read(&of->kn->attr.open->event);
+
+ return of->kn->attr.ops->seq_show(sf, v);
+}
+
+static const struct seq_operations kernfs_seq_ops = {
+ .start = kernfs_seq_start,
+ .next = kernfs_seq_next,
+ .stop = kernfs_seq_stop,
+ .show = kernfs_seq_show,
+};
+
+/*
+ * As reading a bin file can have side-effects, the exact offset and bytes
+ * specified in read(2) call should be passed to the read callback making
+ * it difficult to use seq_file. Implement simplistic custom buffering for
+ * bin files.
+ */
+static ssize_t kernfs_file_direct_read(struct kernfs_open_file *of,
+ char __user *user_buf, size_t count,
+ loff_t *ppos)
+{
+ ssize_t len = min_t(size_t, count, PAGE_SIZE);
+ const struct kernfs_ops *ops;
+ char *buf;
+
+ buf = of->prealloc_buf;
+ if (buf)
+ mutex_lock(&of->prealloc_mutex);
+ else
+ buf = kmalloc(len, GFP_KERNEL);
+ if (!buf)
+ return -ENOMEM;
+
+ /*
+ * @of->mutex nests outside active ref and is used both to ensure that
+ * the ops aren't called concurrently for the same open file.
+ */
+ mutex_lock(&of->mutex);
+ if (!kernfs_get_active(of->kn)) {
+ len = -ENODEV;
+ mutex_unlock(&of->mutex);
+ goto out_free;
+ }
+
+ of->event = atomic_read(&of->kn->attr.open->event);
+ ops = kernfs_ops(of->kn);
+ if (ops->read)
+ len = ops->read(of, buf, len, *ppos);
+ else
+ len = -EINVAL;
+
+ kernfs_put_active(of->kn);
+ mutex_unlock(&of->mutex);
+
+ if (len < 0)
+ goto out_free;
+
+ if (copy_to_user(user_buf, buf, len)) {
+ len = -EFAULT;
+ goto out_free;
+ }
+
+ *ppos += len;
+
+ out_free:
+ if (buf == of->prealloc_buf)
+ mutex_unlock(&of->prealloc_mutex);
+ else
+ kfree(buf);
+ return len;
+}
+
+/**
+ * kernfs_fop_read - kernfs vfs read callback
+ * @file: file pointer
+ * @user_buf: data to write
+ * @count: number of bytes
+ * @ppos: starting offset
+ */
+static ssize_t kernfs_fop_read(struct file *file, char __user *user_buf,
+ size_t count, loff_t *ppos)
+{
+ struct kernfs_open_file *of = kernfs_of(file);
+
+ if (of->kn->flags & KERNFS_HAS_SEQ_SHOW)
+ return seq_read(file, user_buf, count, ppos);
+ else
+ return kernfs_file_direct_read(of, user_buf, count, ppos);
+}
+
+/**
+ * kernfs_fop_write - kernfs vfs write callback
+ * @file: file pointer
+ * @user_buf: data to write
+ * @count: number of bytes
+ * @ppos: starting offset
+ *
+ * Copy data in from userland and pass it to the matching kernfs write
+ * operation.
+ *
+ * There is no easy way for us to know if userspace is only doing a partial
+ * write, so we don't support them. We expect the entire buffer to come on
+ * the first write. Hint: if you're writing a value, first read the file,
+ * modify only the the value you're changing, then write entire buffer
+ * back.
+ */
+static ssize_t kernfs_fop_write(struct file *file, const char __user *user_buf,
+ size_t count, loff_t *ppos)
+{
+ struct kernfs_open_file *of = kernfs_of(file);
+ const struct kernfs_ops *ops;
+ ssize_t len;
+ char *buf;
+
+ if (of->atomic_write_len) {
+ len = count;
+ if (len > of->atomic_write_len)
+ return -E2BIG;
+ } else {
+ len = min_t(size_t, count, PAGE_SIZE);
+ }
+
+ buf = of->prealloc_buf;
+ if (buf)
+ mutex_lock(&of->prealloc_mutex);
+ else
+ buf = kmalloc(len + 1, GFP_KERNEL);
+ if (!buf)
+ return -ENOMEM;
+
+ if (copy_from_user(buf, user_buf, len)) {
+ len = -EFAULT;
+ goto out_free;
+ }
+ buf[len] = '\0'; /* guarantee string termination */
+
+ /*
+ * @of->mutex nests outside active ref and is used both to ensure that
+ * the ops aren't called concurrently for the same open file.
+ */
+ mutex_lock(&of->mutex);
+ if (!kernfs_get_active(of->kn)) {
+ mutex_unlock(&of->mutex);
+ len = -ENODEV;
+ goto out_free;
+ }
+
+ ops = kernfs_ops(of->kn);
+ if (ops->write)
+ len = ops->write(of, buf, len, *ppos);
+ else
+ len = -EINVAL;
+
+ kernfs_put_active(of->kn);
+ mutex_unlock(&of->mutex);
+
+ if (len > 0)
+ *ppos += len;
+
+out_free:
+ if (buf == of->prealloc_buf)
+ mutex_unlock(&of->prealloc_mutex);
+ else
+ kfree(buf);
+ return len;
+}
+
+static void kernfs_vma_open(struct vm_area_struct *vma)
+{
+ struct file *file = vma->vm_file;
+ struct kernfs_open_file *of = kernfs_of(file);
+
+ if (!of->vm_ops)
+ return;
+
+ if (!kernfs_get_active(of->kn))
+ return;
+
+ if (of->vm_ops->open)
+ of->vm_ops->open(vma);
+
+ kernfs_put_active(of->kn);
+}
+
+static vm_fault_t kernfs_vma_fault(struct vm_fault *vmf)
+{
+ struct file *file = vmf->vma->vm_file;
+ struct kernfs_open_file *of = kernfs_of(file);
+ vm_fault_t ret;
+
+ if (!of->vm_ops)
+ return VM_FAULT_SIGBUS;
+
+ if (!kernfs_get_active(of->kn))
+ return VM_FAULT_SIGBUS;
+
+ ret = VM_FAULT_SIGBUS;
+ if (of->vm_ops->fault)
+ ret = of->vm_ops->fault(vmf);
+
+ kernfs_put_active(of->kn);
+ return ret;
+}
+
+static vm_fault_t kernfs_vma_page_mkwrite(struct vm_fault *vmf)
+{
+ struct file *file = vmf->vma->vm_file;
+ struct kernfs_open_file *of = kernfs_of(file);
+ vm_fault_t ret;
+
+ if (!of->vm_ops)
+ return VM_FAULT_SIGBUS;
+
+ if (!kernfs_get_active(of->kn))
+ return VM_FAULT_SIGBUS;
+
+ ret = 0;
+ if (of->vm_ops->page_mkwrite)
+ ret = of->vm_ops->page_mkwrite(vmf);
+ else
+ file_update_time(file);
+
+ kernfs_put_active(of->kn);
+ return ret;
+}
+
+static int kernfs_vma_access(struct vm_area_struct *vma, unsigned long addr,
+ void *buf, int len, int write)
+{
+ struct file *file = vma->vm_file;
+ struct kernfs_open_file *of = kernfs_of(file);
+ int ret;
+
+ if (!of->vm_ops)
+ return -EINVAL;
+
+ if (!kernfs_get_active(of->kn))
+ return -EINVAL;
+
+ ret = -EINVAL;
+ if (of->vm_ops->access)
+ ret = of->vm_ops->access(vma, addr, buf, len, write);
+
+ kernfs_put_active(of->kn);
+ return ret;
+}
+
+#ifdef CONFIG_NUMA
+static int kernfs_vma_set_policy(struct vm_area_struct *vma,
+ struct mempolicy *new)
+{
+ struct file *file = vma->vm_file;
+ struct kernfs_open_file *of = kernfs_of(file);
+ int ret;
+
+ if (!of->vm_ops)
+ return 0;
+
+ if (!kernfs_get_active(of->kn))
+ return -EINVAL;
+
+ ret = 0;
+ if (of->vm_ops->set_policy)
+ ret = of->vm_ops->set_policy(vma, new);
+
+ kernfs_put_active(of->kn);
+ return ret;
+}
+
+static struct mempolicy *kernfs_vma_get_policy(struct vm_area_struct *vma,
+ unsigned long addr)
+{
+ struct file *file = vma->vm_file;
+ struct kernfs_open_file *of = kernfs_of(file);
+ struct mempolicy *pol;
+
+ if (!of->vm_ops)
+ return vma->vm_policy;
+
+ if (!kernfs_get_active(of->kn))
+ return vma->vm_policy;
+
+ pol = vma->vm_policy;
+ if (of->vm_ops->get_policy)
+ pol = of->vm_ops->get_policy(vma, addr);
+
+ kernfs_put_active(of->kn);
+ return pol;
+}
+
+#endif
+
+static const struct vm_operations_struct kernfs_vm_ops = {
+ .open = kernfs_vma_open,
+ .fault = kernfs_vma_fault,
+ .page_mkwrite = kernfs_vma_page_mkwrite,
+ .access = kernfs_vma_access,
+#ifdef CONFIG_NUMA
+ .set_policy = kernfs_vma_set_policy,
+ .get_policy = kernfs_vma_get_policy,
+#endif
+};
+
+static int kernfs_fop_mmap(struct file *file, struct vm_area_struct *vma)
+{
+ struct kernfs_open_file *of = kernfs_of(file);
+ const struct kernfs_ops *ops;
+ int rc;
+
+ /*
+ * mmap path and of->mutex are prone to triggering spurious lockdep
+ * warnings and we don't want to add spurious locking dependency
+ * between the two. Check whether mmap is actually implemented
+ * without grabbing @of->mutex by testing HAS_MMAP flag. See the
+ * comment in kernfs_file_open() for more details.
+ */
+ if (!(of->kn->flags & KERNFS_HAS_MMAP))
+ return -ENODEV;
+
+ mutex_lock(&of->mutex);
+
+ rc = -ENODEV;
+ if (!kernfs_get_active(of->kn))
+ goto out_unlock;
+
+ ops = kernfs_ops(of->kn);
+ rc = ops->mmap(of, vma);
+ if (rc)
+ goto out_put;
+
+ /*
+ * PowerPC's pci_mmap of legacy_mem uses shmem_zero_setup()
+ * to satisfy versions of X which crash if the mmap fails: that
+ * substitutes a new vm_file, and we don't then want bin_vm_ops.
+ */
+ if (vma->vm_file != file)
+ goto out_put;
+
+ rc = -EINVAL;
+ if (of->mmapped && of->vm_ops != vma->vm_ops)
+ goto out_put;
+
+ /*
+ * It is not possible to successfully wrap close.
+ * So error if someone is trying to use close.
+ */
+ rc = -EINVAL;
+ if (vma->vm_ops && vma->vm_ops->close)
+ goto out_put;
+
+ rc = 0;
+ of->mmapped = true;
+ of->vm_ops = vma->vm_ops;
+ vma->vm_ops = &kernfs_vm_ops;
+out_put:
+ kernfs_put_active(of->kn);
+out_unlock:
+ mutex_unlock(&of->mutex);
+
+ return rc;
+}
+
+/**
+ * kernfs_get_open_node - get or create kernfs_open_node
+ * @kn: target kernfs_node
+ * @of: kernfs_open_file for this instance of open
+ *
+ * If @kn->attr.open exists, increment its reference count; otherwise,
+ * create one. @of is chained to the files list.
+ *
+ * LOCKING:
+ * Kernel thread context (may sleep).
+ *
+ * RETURNS:
+ * 0 on success, -errno on failure.
+ */
+static int kernfs_get_open_node(struct kernfs_node *kn,
+ struct kernfs_open_file *of)
+{
+ struct kernfs_open_node *on, *new_on = NULL;
+
+ retry:
+ mutex_lock(&kernfs_open_file_mutex);
+ spin_lock_irq(&kernfs_open_node_lock);
+
+ if (!kn->attr.open && new_on) {
+ kn->attr.open = new_on;
+ new_on = NULL;
+ }
+
+ on = kn->attr.open;
+ if (on) {
+ atomic_inc(&on->refcnt);
+ list_add_tail(&of->list, &on->files);
+ }
+
+ spin_unlock_irq(&kernfs_open_node_lock);
+ mutex_unlock(&kernfs_open_file_mutex);
+
+ if (on) {
+ kfree(new_on);
+ return 0;
+ }
+
+ /* not there, initialize a new one and retry */
+ new_on = kmalloc(sizeof(*new_on), GFP_KERNEL);
+ if (!new_on)
+ return -ENOMEM;
+
+ atomic_set(&new_on->refcnt, 0);
+ atomic_set(&new_on->event, 1);
+ init_waitqueue_head(&new_on->poll);
+ INIT_LIST_HEAD(&new_on->files);
+ goto retry;
+}
+
+/**
+ * kernfs_put_open_node - put kernfs_open_node
+ * @kn: target kernfs_nodet
+ * @of: associated kernfs_open_file
+ *
+ * Put @kn->attr.open and unlink @of from the files list. If
+ * reference count reaches zero, disassociate and free it.
+ *
+ * LOCKING:
+ * None.
+ */
+static void kernfs_put_open_node(struct kernfs_node *kn,
+ struct kernfs_open_file *of)
+{
+ struct kernfs_open_node *on = kn->attr.open;
+ unsigned long flags;
+
+ mutex_lock(&kernfs_open_file_mutex);
+ spin_lock_irqsave(&kernfs_open_node_lock, flags);
+
+ if (of)
+ list_del(&of->list);
+
+ if (atomic_dec_and_test(&on->refcnt))
+ kn->attr.open = NULL;
+ else
+ on = NULL;
+
+ spin_unlock_irqrestore(&kernfs_open_node_lock, flags);
+ mutex_unlock(&kernfs_open_file_mutex);
+
+ kfree(on);
+}
+
+static int kernfs_fop_open(struct inode *inode, struct file *file)
+{
+ struct kernfs_node *kn = inode->i_private;
+ struct kernfs_root *root = kernfs_root(kn);
+ const struct kernfs_ops *ops;
+ struct kernfs_open_file *of;
+ bool has_read, has_write, has_mmap;
+ int error = -EACCES;
+
+ if (!kernfs_get_active(kn))
+ return -ENODEV;
+
+ ops = kernfs_ops(kn);
+
+ has_read = ops->seq_show || ops->read || ops->mmap;
+ has_write = ops->write || ops->mmap;
+ has_mmap = ops->mmap;
+
+ /* see the flag definition for details */
+ if (root->flags & KERNFS_ROOT_EXTRA_OPEN_PERM_CHECK) {
+ if ((file->f_mode & FMODE_WRITE) &&
+ (!(inode->i_mode & S_IWUGO) || !has_write))
+ goto err_out;
+
+ if ((file->f_mode & FMODE_READ) &&
+ (!(inode->i_mode & S_IRUGO) || !has_read))
+ goto err_out;
+ }
+
+ /* allocate a kernfs_open_file for the file */
+ error = -ENOMEM;
+ of = kzalloc(sizeof(struct kernfs_open_file), GFP_KERNEL);
+ if (!of)
+ goto err_out;
+
+ /*
+ * The following is done to give a different lockdep key to
+ * @of->mutex for files which implement mmap. This is a rather
+ * crude way to avoid false positive lockdep warning around
+ * mm->mmap_sem - mmap nests @of->mutex under mm->mmap_sem and
+ * reading /sys/block/sda/trace/act_mask grabs sr_mutex, under
+ * which mm->mmap_sem nests, while holding @of->mutex. As each
+ * open file has a separate mutex, it's okay as long as those don't
+ * happen on the same file. At this point, we can't easily give
+ * each file a separate locking class. Let's differentiate on
+ * whether the file has mmap or not for now.
+ *
+ * Both paths of the branch look the same. They're supposed to
+ * look that way and give @of->mutex different static lockdep keys.
+ */
+ if (has_mmap)
+ mutex_init(&of->mutex);
+ else
+ mutex_init(&of->mutex);
+
+ of->kn = kn;
+ of->file = file;
+
+ /*
+ * Write path needs to atomic_write_len outside active reference.
+ * Cache it in open_file. See kernfs_fop_write() for details.
+ */
+ of->atomic_write_len = ops->atomic_write_len;
+
+ error = -EINVAL;
+ /*
+ * ->seq_show is incompatible with ->prealloc,
+ * as seq_read does its own allocation.
+ * ->read must be used instead.
+ */
+ if (ops->prealloc && ops->seq_show)
+ goto err_free;
+ if (ops->prealloc) {
+ int len = of->atomic_write_len ?: PAGE_SIZE;
+ of->prealloc_buf = kmalloc(len + 1, GFP_KERNEL);
+ error = -ENOMEM;
+ if (!of->prealloc_buf)
+ goto err_free;
+ mutex_init(&of->prealloc_mutex);
+ }
+
+ /*
+ * Always instantiate seq_file even if read access doesn't use
+ * seq_file or is not requested. This unifies private data access
+ * and readable regular files are the vast majority anyway.
+ */
+ if (ops->seq_show)
+ error = seq_open(file, &kernfs_seq_ops);
+ else
+ error = seq_open(file, NULL);
+ if (error)
+ goto err_free;
+
+ of->seq_file = file->private_data;
+ of->seq_file->private = of;
+
+ /* seq_file clears PWRITE unconditionally, restore it if WRITE */
+ if (file->f_mode & FMODE_WRITE)
+ file->f_mode |= FMODE_PWRITE;
+
+ /* make sure we have open node struct */
+ error = kernfs_get_open_node(kn, of);
+ if (error)
+ goto err_seq_release;
+
+ if (ops->open) {
+ /* nobody has access to @of yet, skip @of->mutex */
+ error = ops->open(of);
+ if (error)
+ goto err_put_node;
+ }
+
+ /* open succeeded, put active references */
+ kernfs_put_active(kn);
+ return 0;
+
+err_put_node:
+ kernfs_put_open_node(kn, of);
+err_seq_release:
+ seq_release(inode, file);
+err_free:
+ kfree(of->prealloc_buf);
+ kfree(of);
+err_out:
+ kernfs_put_active(kn);
+ return error;
+}
+
+/* used from release/drain to ensure that ->release() is called exactly once */
+static void kernfs_release_file(struct kernfs_node *kn,
+ struct kernfs_open_file *of)
+{
+ /*
+ * @of is guaranteed to have no other file operations in flight and
+ * we just want to synchronize release and drain paths.
+ * @kernfs_open_file_mutex is enough. @of->mutex can't be used
+ * here because drain path may be called from places which can
+ * cause circular dependency.
+ */
+ lockdep_assert_held(&kernfs_open_file_mutex);
+
+ if (!of->released) {
+ /*
+ * A file is never detached without being released and we
+ * need to be able to release files which are deactivated
+ * and being drained. Don't use kernfs_ops().
+ */
+ kn->attr.ops->release(of);
+ of->released = true;
+ }
+}
+
+static int kernfs_fop_release(struct inode *inode, struct file *filp)
+{
+ struct kernfs_node *kn = inode->i_private;
+ struct kernfs_open_file *of = kernfs_of(filp);
+
+ if (kn->flags & KERNFS_HAS_RELEASE) {
+ mutex_lock(&kernfs_open_file_mutex);
+ kernfs_release_file(kn, of);
+ mutex_unlock(&kernfs_open_file_mutex);
+ }
+
+ kernfs_put_open_node(kn, of);
+ seq_release(inode, filp);
+ kfree(of->prealloc_buf);
+ kfree(of);
+
+ return 0;
+}
+
+void kernfs_drain_open_files(struct kernfs_node *kn)
+{
+ struct kernfs_open_node *on;
+ struct kernfs_open_file *of;
+
+ if (!(kn->flags & (KERNFS_HAS_MMAP | KERNFS_HAS_RELEASE)))
+ return;
+
+ spin_lock_irq(&kernfs_open_node_lock);
+ on = kn->attr.open;
+ if (on)
+ atomic_inc(&on->refcnt);
+ spin_unlock_irq(&kernfs_open_node_lock);
+ if (!on)
+ return;
+
+ mutex_lock(&kernfs_open_file_mutex);
+
+ list_for_each_entry(of, &on->files, list) {
+ struct inode *inode = file_inode(of->file);
+
+ if (kn->flags & KERNFS_HAS_MMAP)
+ unmap_mapping_range(inode->i_mapping, 0, 0, 1);
+
+ if (kn->flags & KERNFS_HAS_RELEASE)
+ kernfs_release_file(kn, of);
+ }
+
+ mutex_unlock(&kernfs_open_file_mutex);
+
+ kernfs_put_open_node(kn, NULL);
+}
+
+/*
+ * Kernfs attribute files are pollable. The idea is that you read
+ * the content and then you use 'poll' or 'select' to wait for
+ * the content to change. When the content changes (assuming the
+ * manager for the kobject supports notification), poll will
+ * return EPOLLERR|EPOLLPRI, and select will return the fd whether
+ * it is waiting for read, write, or exceptions.
+ * Once poll/select indicates that the value has changed, you
+ * need to close and re-open the file, or seek to 0 and read again.
+ * Reminder: this only works for attributes which actively support
+ * it, and it is not possible to test an attribute from userspace
+ * to see if it supports poll (Neither 'poll' nor 'select' return
+ * an appropriate error code). When in doubt, set a suitable timeout value.
+ */
+static __poll_t kernfs_fop_poll(struct file *filp, poll_table *wait)
+{
+ struct kernfs_open_file *of = kernfs_of(filp);
+ struct kernfs_node *kn = kernfs_dentry_node(filp->f_path.dentry);
+ struct kernfs_open_node *on = kn->attr.open;
+
+ if (!kernfs_get_active(kn))
+ goto trigger;
+
+ poll_wait(filp, &on->poll, wait);
+
+ kernfs_put_active(kn);
+
+ if (of->event != atomic_read(&on->event))
+ goto trigger;
+
+ return DEFAULT_POLLMASK;
+
+ trigger:
+ return DEFAULT_POLLMASK|EPOLLERR|EPOLLPRI;
+}
+
+static void kernfs_notify_workfn(struct work_struct *work)
+{
+ struct kernfs_node *kn;
+ struct kernfs_open_node *on;
+ struct kernfs_super_info *info;
+repeat:
+ /* pop one off the notify_list */
+ spin_lock_irq(&kernfs_notify_lock);
+ kn = kernfs_notify_list;
+ if (kn == KERNFS_NOTIFY_EOL) {
+ spin_unlock_irq(&kernfs_notify_lock);
+ return;
+ }
+ kernfs_notify_list = kn->attr.notify_next;
+ kn->attr.notify_next = NULL;
+ spin_unlock_irq(&kernfs_notify_lock);
+
+ /* kick poll */
+ spin_lock_irq(&kernfs_open_node_lock);
+
+ on = kn->attr.open;
+ if (on) {
+ atomic_inc(&on->event);
+ wake_up_interruptible(&on->poll);
+ }
+
+ spin_unlock_irq(&kernfs_open_node_lock);
+
+ /* kick fsnotify */
+ mutex_lock(&kernfs_mutex);
+
+ list_for_each_entry(info, &kernfs_root(kn)->supers, node) {
+ struct kernfs_node *parent;
+ struct inode *inode;
+
+ /*
+ * We want fsnotify_modify() on @kn but as the
+ * modifications aren't originating from userland don't
+ * have the matching @file available. Look up the inodes
+ * and generate the events manually.
+ */
+ inode = ilookup(info->sb, kn->id.ino);
+ if (!inode)
+ continue;
+
+ parent = kernfs_get_parent(kn);
+ if (parent) {
+ struct inode *p_inode;
+
+ p_inode = ilookup(info->sb, parent->id.ino);
+ if (p_inode) {
+ fsnotify(p_inode, FS_MODIFY | FS_EVENT_ON_CHILD,
+ inode, FSNOTIFY_EVENT_INODE, kn->name, 0);
+ iput(p_inode);
+ }
+
+ kernfs_put(parent);
+ }
+
+ fsnotify(inode, FS_MODIFY, inode, FSNOTIFY_EVENT_INODE,
+ kn->name, 0);
+ iput(inode);
+ }
+
+ mutex_unlock(&kernfs_mutex);
+ kernfs_put(kn);
+ goto repeat;
+}
+
+/**
+ * kernfs_notify - notify a kernfs file
+ * @kn: file to notify
+ *
+ * Notify @kn such that poll(2) on @kn wakes up. Maybe be called from any
+ * context.
+ */
+void kernfs_notify(struct kernfs_node *kn)
+{
+ static DECLARE_WORK(kernfs_notify_work, kernfs_notify_workfn);
+ unsigned long flags;
+
+ if (WARN_ON(kernfs_type(kn) != KERNFS_FILE))
+ return;
+
+ spin_lock_irqsave(&kernfs_notify_lock, flags);
+ if (!kn->attr.notify_next) {
+ kernfs_get(kn);
+ kn->attr.notify_next = kernfs_notify_list;
+ kernfs_notify_list = kn;
+ schedule_work(&kernfs_notify_work);
+ }
+ spin_unlock_irqrestore(&kernfs_notify_lock, flags);
+}
+EXPORT_SYMBOL_GPL(kernfs_notify);
+
+const struct file_operations kernfs_file_fops = {
+ .read = kernfs_fop_read,
+ .write = kernfs_fop_write,
+ .llseek = generic_file_llseek,
+ .mmap = kernfs_fop_mmap,
+ .open = kernfs_fop_open,
+ .release = kernfs_fop_release,
+ .poll = kernfs_fop_poll,
+ .fsync = noop_fsync,
+};
+
+/**
+ * __kernfs_create_file - kernfs internal function to create a file
+ * @parent: directory to create the file in
+ * @name: name of the file
+ * @mode: mode of the file
+ * @uid: uid of the file
+ * @gid: gid of the file
+ * @size: size of the file
+ * @ops: kernfs operations for the file
+ * @priv: private data for the file
+ * @ns: optional namespace tag of the file
+ * @key: lockdep key for the file's active_ref, %NULL to disable lockdep
+ *
+ * Returns the created node on success, ERR_PTR() value on error.
+ */
+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 *kn;
+ unsigned flags;
+ int rc;
+
+ flags = KERNFS_FILE;
+
+ kn = kernfs_new_node(parent, name, (mode & S_IALLUGO) | S_IFREG,
+ uid, gid, flags);
+ if (!kn)
+ return ERR_PTR(-ENOMEM);
+
+ kn->attr.ops = ops;
+ kn->attr.size = size;
+ kn->ns = ns;
+ kn->priv = priv;
+
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+ if (key) {
+ lockdep_init_map(&kn->dep_map, "kn->count", key, 0);
+ kn->flags |= KERNFS_LOCKDEP;
+ }
+#endif
+
+ /*
+ * kn->attr.ops is accesible only while holding active ref. We
+ * need to know whether some ops are implemented outside active
+ * ref. Cache their existence in flags.
+ */
+ if (ops->seq_show)
+ kn->flags |= KERNFS_HAS_SEQ_SHOW;
+ if (ops->mmap)
+ kn->flags |= KERNFS_HAS_MMAP;
+ if (ops->release)
+ kn->flags |= KERNFS_HAS_RELEASE;
+
+ rc = kernfs_add_one(kn);
+ if (rc) {
+ kernfs_put(kn);
+ return ERR_PTR(rc);
+ }
+ return kn;
+}
diff --git a/fs/kernfs/inode.c b/fs/kernfs/inode.c
new file mode 100644
index 0000000..80cebcd
--- /dev/null
+++ b/fs/kernfs/inode.c
@@ -0,0 +1,386 @@
+/*
+ * fs/kernfs/inode.c - kernfs inode implementation
+ *
+ * Copyright (c) 2001-3 Patrick Mochel
+ * Copyright (c) 2007 SUSE Linux Products GmbH
+ * Copyright (c) 2007, 2013 Tejun Heo <tj@kernel.org>
+ *
+ * This file is released under the GPLv2.
+ */
+
+#include <linux/pagemap.h>
+#include <linux/backing-dev.h>
+#include <linux/capability.h>
+#include <linux/errno.h>
+#include <linux/slab.h>
+#include <linux/xattr.h>
+#include <linux/security.h>
+
+#include "kernfs-internal.h"
+
+static const struct address_space_operations kernfs_aops = {
+ .readpage = simple_readpage,
+ .write_begin = simple_write_begin,
+ .write_end = simple_write_end,
+};
+
+static const struct inode_operations kernfs_iops = {
+ .permission = kernfs_iop_permission,
+ .setattr = kernfs_iop_setattr,
+ .getattr = kernfs_iop_getattr,
+ .listxattr = kernfs_iop_listxattr,
+};
+
+static struct kernfs_iattrs *kernfs_iattrs(struct kernfs_node *kn)
+{
+ static DEFINE_MUTEX(iattr_mutex);
+ struct kernfs_iattrs *ret;
+ struct iattr *iattrs;
+
+ mutex_lock(&iattr_mutex);
+
+ if (kn->iattr)
+ goto out_unlock;
+
+ kn->iattr = kzalloc(sizeof(struct kernfs_iattrs), GFP_KERNEL);
+ if (!kn->iattr)
+ goto out_unlock;
+ iattrs = &kn->iattr->ia_iattr;
+
+ /* assign default attributes */
+ iattrs->ia_mode = kn->mode;
+ iattrs->ia_uid = GLOBAL_ROOT_UID;
+ iattrs->ia_gid = GLOBAL_ROOT_GID;
+
+ ktime_get_real_ts64(&iattrs->ia_atime);
+ iattrs->ia_mtime = iattrs->ia_atime;
+ iattrs->ia_ctime = iattrs->ia_atime;
+
+ simple_xattrs_init(&kn->iattr->xattrs);
+out_unlock:
+ ret = kn->iattr;
+ mutex_unlock(&iattr_mutex);
+ return ret;
+}
+
+int __kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr)
+{
+ struct kernfs_iattrs *attrs;
+ struct iattr *iattrs;
+ unsigned int ia_valid = iattr->ia_valid;
+
+ attrs = kernfs_iattrs(kn);
+ if (!attrs)
+ return -ENOMEM;
+
+ iattrs = &attrs->ia_iattr;
+
+ if (ia_valid & ATTR_UID)
+ iattrs->ia_uid = iattr->ia_uid;
+ if (ia_valid & ATTR_GID)
+ iattrs->ia_gid = iattr->ia_gid;
+ if (ia_valid & ATTR_ATIME)
+ iattrs->ia_atime = iattr->ia_atime;
+ if (ia_valid & ATTR_MTIME)
+ iattrs->ia_mtime = iattr->ia_mtime;
+ if (ia_valid & ATTR_CTIME)
+ iattrs->ia_ctime = iattr->ia_ctime;
+ if (ia_valid & ATTR_MODE) {
+ umode_t mode = iattr->ia_mode;
+ iattrs->ia_mode = kn->mode = mode;
+ }
+ return 0;
+}
+
+/**
+ * kernfs_setattr - set iattr on a node
+ * @kn: target node
+ * @iattr: iattr to set
+ *
+ * Returns 0 on success, -errno on failure.
+ */
+int kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr)
+{
+ int ret;
+
+ mutex_lock(&kernfs_mutex);
+ ret = __kernfs_setattr(kn, iattr);
+ mutex_unlock(&kernfs_mutex);
+ return ret;
+}
+
+int kernfs_iop_setattr(struct dentry *dentry, struct iattr *iattr)
+{
+ struct inode *inode = d_inode(dentry);
+ struct kernfs_node *kn = inode->i_private;
+ int error;
+
+ if (!kn)
+ return -EINVAL;
+
+ mutex_lock(&kernfs_mutex);
+ error = setattr_prepare(dentry, iattr);
+ if (error)
+ goto out;
+
+ error = __kernfs_setattr(kn, iattr);
+ if (error)
+ goto out;
+
+ /* this ignores size changes */
+ setattr_copy(inode, iattr);
+
+out:
+ mutex_unlock(&kernfs_mutex);
+ return error;
+}
+
+static int kernfs_node_setsecdata(struct kernfs_iattrs *attrs, void **secdata,
+ u32 *secdata_len)
+{
+ void *old_secdata;
+ size_t old_secdata_len;
+
+ old_secdata = attrs->ia_secdata;
+ old_secdata_len = attrs->ia_secdata_len;
+
+ attrs->ia_secdata = *secdata;
+ attrs->ia_secdata_len = *secdata_len;
+
+ *secdata = old_secdata;
+ *secdata_len = old_secdata_len;
+ return 0;
+}
+
+ssize_t kernfs_iop_listxattr(struct dentry *dentry, char *buf, size_t size)
+{
+ struct kernfs_node *kn = kernfs_dentry_node(dentry);
+ struct kernfs_iattrs *attrs;
+
+ attrs = kernfs_iattrs(kn);
+ if (!attrs)
+ return -ENOMEM;
+
+ return simple_xattr_list(d_inode(dentry), &attrs->xattrs, buf, size);
+}
+
+static inline void set_default_inode_attr(struct inode *inode, umode_t mode)
+{
+ inode->i_mode = mode;
+ inode->i_atime = inode->i_mtime =
+ inode->i_ctime = current_time(inode);
+}
+
+static inline void set_inode_attr(struct inode *inode, struct iattr *iattr)
+{
+ struct super_block *sb = inode->i_sb;
+ inode->i_uid = iattr->ia_uid;
+ inode->i_gid = iattr->ia_gid;
+ inode->i_atime = timespec64_trunc(iattr->ia_atime, sb->s_time_gran);
+ inode->i_mtime = timespec64_trunc(iattr->ia_mtime, sb->s_time_gran);
+ inode->i_ctime = timespec64_trunc(iattr->ia_ctime, sb->s_time_gran);
+}
+
+static void kernfs_refresh_inode(struct kernfs_node *kn, struct inode *inode)
+{
+ struct kernfs_iattrs *attrs = kn->iattr;
+
+ inode->i_mode = kn->mode;
+ if (attrs) {
+ /*
+ * kernfs_node has non-default attributes get them from
+ * persistent copy in kernfs_node.
+ */
+ set_inode_attr(inode, &attrs->ia_iattr);
+ security_inode_notifysecctx(inode, attrs->ia_secdata,
+ attrs->ia_secdata_len);
+ }
+
+ if (kernfs_type(kn) == KERNFS_DIR)
+ set_nlink(inode, kn->dir.subdirs + 2);
+}
+
+int kernfs_iop_getattr(const struct path *path, struct kstat *stat,
+ u32 request_mask, unsigned int query_flags)
+{
+ struct inode *inode = d_inode(path->dentry);
+ struct kernfs_node *kn = inode->i_private;
+
+ mutex_lock(&kernfs_mutex);
+ kernfs_refresh_inode(kn, inode);
+ mutex_unlock(&kernfs_mutex);
+
+ generic_fillattr(inode, stat);
+ return 0;
+}
+
+static void kernfs_init_inode(struct kernfs_node *kn, struct inode *inode)
+{
+ kernfs_get(kn);
+ inode->i_private = kn;
+ inode->i_mapping->a_ops = &kernfs_aops;
+ inode->i_op = &kernfs_iops;
+ inode->i_generation = kn->id.generation;
+
+ set_default_inode_attr(inode, kn->mode);
+ kernfs_refresh_inode(kn, inode);
+
+ /* initialize inode according to type */
+ switch (kernfs_type(kn)) {
+ case KERNFS_DIR:
+ inode->i_op = &kernfs_dir_iops;
+ inode->i_fop = &kernfs_dir_fops;
+ if (kn->flags & KERNFS_EMPTY_DIR)
+ make_empty_dir_inode(inode);
+ break;
+ case KERNFS_FILE:
+ inode->i_size = kn->attr.size;
+ inode->i_fop = &kernfs_file_fops;
+ break;
+ case KERNFS_LINK:
+ inode->i_op = &kernfs_symlink_iops;
+ break;
+ default:
+ BUG();
+ }
+
+ unlock_new_inode(inode);
+}
+
+/**
+ * kernfs_get_inode - get inode for kernfs_node
+ * @sb: super block
+ * @kn: kernfs_node to allocate inode for
+ *
+ * Get inode for @kn. If such inode doesn't exist, a new inode is
+ * allocated and basics are initialized. New inode is returned
+ * locked.
+ *
+ * LOCKING:
+ * Kernel thread context (may sleep).
+ *
+ * RETURNS:
+ * Pointer to allocated inode on success, NULL on failure.
+ */
+struct inode *kernfs_get_inode(struct super_block *sb, struct kernfs_node *kn)
+{
+ struct inode *inode;
+
+ inode = iget_locked(sb, kn->id.ino);
+ if (inode && (inode->i_state & I_NEW))
+ kernfs_init_inode(kn, inode);
+
+ return inode;
+}
+
+/*
+ * The kernfs_node serves as both an inode and a directory entry for
+ * kernfs. To prevent the kernfs inode numbers from being freed
+ * prematurely we take a reference to kernfs_node from the kernfs inode. A
+ * super_operations.evict_inode() implementation is needed to drop that
+ * reference upon inode destruction.
+ */
+void kernfs_evict_inode(struct inode *inode)
+{
+ struct kernfs_node *kn = inode->i_private;
+
+ truncate_inode_pages_final(&inode->i_data);
+ clear_inode(inode);
+ kernfs_put(kn);
+}
+
+int kernfs_iop_permission(struct inode *inode, int mask)
+{
+ struct kernfs_node *kn;
+
+ if (mask & MAY_NOT_BLOCK)
+ return -ECHILD;
+
+ kn = inode->i_private;
+
+ mutex_lock(&kernfs_mutex);
+ kernfs_refresh_inode(kn, inode);
+ mutex_unlock(&kernfs_mutex);
+
+ return generic_permission(inode, mask);
+}
+
+static int kernfs_xattr_get(const struct xattr_handler *handler,
+ struct dentry *unused, struct inode *inode,
+ const char *suffix, void *value, size_t size)
+{
+ const char *name = xattr_full_name(handler, suffix);
+ struct kernfs_node *kn = inode->i_private;
+ struct kernfs_iattrs *attrs;
+
+ attrs = kernfs_iattrs(kn);
+ if (!attrs)
+ return -ENOMEM;
+
+ return simple_xattr_get(&attrs->xattrs, name, value, size);
+}
+
+static int kernfs_xattr_set(const struct xattr_handler *handler,
+ struct dentry *unused, struct inode *inode,
+ const char *suffix, const void *value,
+ size_t size, int flags)
+{
+ const char *name = xattr_full_name(handler, suffix);
+ struct kernfs_node *kn = inode->i_private;
+ struct kernfs_iattrs *attrs;
+
+ attrs = kernfs_iattrs(kn);
+ if (!attrs)
+ return -ENOMEM;
+
+ return simple_xattr_set(&attrs->xattrs, name, value, size, flags);
+}
+
+static const struct xattr_handler kernfs_trusted_xattr_handler = {
+ .prefix = XATTR_TRUSTED_PREFIX,
+ .get = kernfs_xattr_get,
+ .set = kernfs_xattr_set,
+};
+
+static int kernfs_security_xattr_set(const struct xattr_handler *handler,
+ struct dentry *unused, struct inode *inode,
+ const char *suffix, const void *value,
+ size_t size, int flags)
+{
+ struct kernfs_node *kn = inode->i_private;
+ struct kernfs_iattrs *attrs;
+ void *secdata;
+ u32 secdata_len = 0;
+ int error;
+
+ attrs = kernfs_iattrs(kn);
+ if (!attrs)
+ return -ENOMEM;
+
+ error = security_inode_setsecurity(inode, suffix, value, size, flags);
+ if (error)
+ return error;
+ error = security_inode_getsecctx(inode, &secdata, &secdata_len);
+ if (error)
+ return error;
+
+ mutex_lock(&kernfs_mutex);
+ error = kernfs_node_setsecdata(attrs, &secdata, &secdata_len);
+ mutex_unlock(&kernfs_mutex);
+
+ if (secdata)
+ security_release_secctx(secdata, secdata_len);
+ return error;
+}
+
+static const struct xattr_handler kernfs_security_xattr_handler = {
+ .prefix = XATTR_SECURITY_PREFIX,
+ .get = kernfs_xattr_get,
+ .set = kernfs_security_xattr_set,
+};
+
+const struct xattr_handler *kernfs_xattr_handlers[] = {
+ &kernfs_trusted_xattr_handler,
+ &kernfs_security_xattr_handler,
+ NULL
+};
diff --git a/fs/kernfs/kernfs-internal.h b/fs/kernfs/kernfs-internal.h
new file mode 100644
index 0000000..3d83b11
--- /dev/null
+++ b/fs/kernfs/kernfs-internal.h
@@ -0,0 +1,125 @@
+/*
+ * fs/kernfs/kernfs-internal.h - kernfs internal header file
+ *
+ * Copyright (c) 2001-3 Patrick Mochel
+ * Copyright (c) 2007 SUSE Linux Products GmbH
+ * Copyright (c) 2007, 2013 Tejun Heo <teheo@suse.de>
+ *
+ * This file is released under the GPLv2.
+ */
+
+#ifndef __KERNFS_INTERNAL_H
+#define __KERNFS_INTERNAL_H
+
+#include <linux/lockdep.h>
+#include <linux/fs.h>
+#include <linux/mutex.h>
+#include <linux/xattr.h>
+
+#include <linux/kernfs.h>
+
+struct kernfs_iattrs {
+ struct iattr ia_iattr;
+ void *ia_secdata;
+ u32 ia_secdata_len;
+
+ struct simple_xattrs xattrs;
+};
+
+/* +1 to avoid triggering overflow warning when negating it */
+#define KN_DEACTIVATED_BIAS (INT_MIN + 1)
+
+/* KERNFS_TYPE_MASK and types are defined in include/linux/kernfs.h */
+
+/**
+ * kernfs_root - find out the kernfs_root a kernfs_node belongs to
+ * @kn: kernfs_node of interest
+ *
+ * Return the kernfs_root @kn belongs to.
+ */
+static inline struct kernfs_root *kernfs_root(struct kernfs_node *kn)
+{
+ /* if parent exists, it's always a dir; otherwise, @sd is a dir */
+ if (kn->parent)
+ kn = kn->parent;
+ return kn->dir.root;
+}
+
+/*
+ * mount.c
+ */
+struct kernfs_super_info {
+ struct super_block *sb;
+
+ /*
+ * The root associated with this super_block. Each super_block is
+ * identified by the root and ns it's associated with.
+ */
+ struct kernfs_root *root;
+
+ /*
+ * Each sb is associated with one namespace tag, currently the
+ * network namespace of the task which mounted this kernfs
+ * instance. If multiple tags become necessary, make the following
+ * an array and compare kernfs_node tag against every entry.
+ */
+ const void *ns;
+
+ /* anchored at kernfs_root->supers, protected by kernfs_mutex */
+ struct list_head node;
+};
+#define kernfs_info(SB) ((struct kernfs_super_info *)(SB->s_fs_info))
+
+static inline struct kernfs_node *kernfs_dentry_node(struct dentry *dentry)
+{
+ if (d_really_is_negative(dentry))
+ return NULL;
+ return d_inode(dentry)->i_private;
+}
+
+extern const struct super_operations kernfs_sops;
+extern struct kmem_cache *kernfs_node_cache;
+
+/*
+ * inode.c
+ */
+extern const struct xattr_handler *kernfs_xattr_handlers[];
+void kernfs_evict_inode(struct inode *inode);
+int kernfs_iop_permission(struct inode *inode, int mask);
+int kernfs_iop_setattr(struct dentry *dentry, struct iattr *iattr);
+int kernfs_iop_getattr(const struct path *path, struct kstat *stat,
+ u32 request_mask, unsigned int query_flags);
+ssize_t kernfs_iop_listxattr(struct dentry *dentry, char *buf, size_t size);
+int __kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr);
+
+/*
+ * dir.c
+ */
+extern struct mutex kernfs_mutex;
+extern const struct dentry_operations kernfs_dops;
+extern const struct file_operations kernfs_dir_fops;
+extern const struct inode_operations kernfs_dir_iops;
+
+struct kernfs_node *kernfs_get_active(struct kernfs_node *kn);
+void kernfs_put_active(struct kernfs_node *kn);
+int kernfs_add_one(struct kernfs_node *kn);
+struct kernfs_node *kernfs_new_node(struct kernfs_node *parent,
+ const char *name, umode_t mode,
+ kuid_t uid, kgid_t gid,
+ unsigned flags);
+struct kernfs_node *kernfs_find_and_get_node_by_ino(struct kernfs_root *root,
+ unsigned int ino);
+
+/*
+ * file.c
+ */
+extern const struct file_operations kernfs_file_fops;
+
+void kernfs_drain_open_files(struct kernfs_node *kn);
+
+/*
+ * symlink.c
+ */
+extern const struct inode_operations kernfs_symlink_iops;
+
+#endif /* __KERNFS_INTERNAL_H */
diff --git a/fs/kernfs/mount.c b/fs/kernfs/mount.c
new file mode 100644
index 0000000..ff2716f
--- /dev/null
+++ b/fs/kernfs/mount.c
@@ -0,0 +1,417 @@
+/*
+ * fs/kernfs/mount.c - kernfs mount implementation
+ *
+ * Copyright (c) 2001-3 Patrick Mochel
+ * Copyright (c) 2007 SUSE Linux Products GmbH
+ * Copyright (c) 2007, 2013 Tejun Heo <tj@kernel.org>
+ *
+ * This file is released under the GPLv2.
+ */
+
+#include <linux/fs.h>
+#include <linux/mount.h>
+#include <linux/init.h>
+#include <linux/magic.h>
+#include <linux/slab.h>
+#include <linux/pagemap.h>
+#include <linux/namei.h>
+#include <linux/seq_file.h>
+#include <linux/exportfs.h>
+
+#include "kernfs-internal.h"
+
+struct kmem_cache *kernfs_node_cache;
+
+static int kernfs_sop_remount_fs(struct super_block *sb, int *flags, char *data)
+{
+ struct kernfs_root *root = kernfs_info(sb)->root;
+ struct kernfs_syscall_ops *scops = root->syscall_ops;
+
+ if (scops && scops->remount_fs)
+ return scops->remount_fs(root, flags, data);
+ return 0;
+}
+
+static int kernfs_sop_show_options(struct seq_file *sf, struct dentry *dentry)
+{
+ struct kernfs_root *root = kernfs_root(kernfs_dentry_node(dentry));
+ struct kernfs_syscall_ops *scops = root->syscall_ops;
+
+ if (scops && scops->show_options)
+ return scops->show_options(sf, root);
+ return 0;
+}
+
+static int kernfs_sop_show_path(struct seq_file *sf, struct dentry *dentry)
+{
+ struct kernfs_node *node = kernfs_dentry_node(dentry);
+ struct kernfs_root *root = kernfs_root(node);
+ struct kernfs_syscall_ops *scops = root->syscall_ops;
+
+ if (scops && scops->show_path)
+ return scops->show_path(sf, node, root);
+
+ seq_dentry(sf, dentry, " \t\n\\");
+ return 0;
+}
+
+const struct super_operations kernfs_sops = {
+ .statfs = simple_statfs,
+ .drop_inode = generic_delete_inode,
+ .evict_inode = kernfs_evict_inode,
+
+ .remount_fs = kernfs_sop_remount_fs,
+ .show_options = kernfs_sop_show_options,
+ .show_path = kernfs_sop_show_path,
+};
+
+/*
+ * Similar to kernfs_fh_get_inode, this one gets kernfs node from inode
+ * number and generation
+ */
+struct kernfs_node *kernfs_get_node_by_id(struct kernfs_root *root,
+ const union kernfs_node_id *id)
+{
+ struct kernfs_node *kn;
+
+ kn = kernfs_find_and_get_node_by_ino(root, id->ino);
+ if (!kn)
+ return NULL;
+ if (kn->id.generation != id->generation) {
+ kernfs_put(kn);
+ return NULL;
+ }
+ return kn;
+}
+
+static struct inode *kernfs_fh_get_inode(struct super_block *sb,
+ u64 ino, u32 generation)
+{
+ struct kernfs_super_info *info = kernfs_info(sb);
+ struct inode *inode;
+ struct kernfs_node *kn;
+
+ if (ino == 0)
+ return ERR_PTR(-ESTALE);
+
+ kn = kernfs_find_and_get_node_by_ino(info->root, ino);
+ if (!kn)
+ return ERR_PTR(-ESTALE);
+ inode = kernfs_get_inode(sb, kn);
+ kernfs_put(kn);
+ if (!inode)
+ return ERR_PTR(-ESTALE);
+
+ if (generation && inode->i_generation != generation) {
+ /* we didn't find the right inode.. */
+ iput(inode);
+ return ERR_PTR(-ESTALE);
+ }
+ return inode;
+}
+
+static struct dentry *kernfs_fh_to_dentry(struct super_block *sb, struct fid *fid,
+ int fh_len, int fh_type)
+{
+ return generic_fh_to_dentry(sb, fid, fh_len, fh_type,
+ kernfs_fh_get_inode);
+}
+
+static struct dentry *kernfs_fh_to_parent(struct super_block *sb, struct fid *fid,
+ int fh_len, int fh_type)
+{
+ return generic_fh_to_parent(sb, fid, fh_len, fh_type,
+ kernfs_fh_get_inode);
+}
+
+static struct dentry *kernfs_get_parent_dentry(struct dentry *child)
+{
+ struct kernfs_node *kn = kernfs_dentry_node(child);
+
+ return d_obtain_alias(kernfs_get_inode(child->d_sb, kn->parent));
+}
+
+static const struct export_operations kernfs_export_ops = {
+ .fh_to_dentry = kernfs_fh_to_dentry,
+ .fh_to_parent = kernfs_fh_to_parent,
+ .get_parent = kernfs_get_parent_dentry,
+};
+
+/**
+ * kernfs_root_from_sb - determine kernfs_root associated with a super_block
+ * @sb: the super_block in question
+ *
+ * Return the kernfs_root associated with @sb. If @sb is not a kernfs one,
+ * %NULL is returned.
+ */
+struct kernfs_root *kernfs_root_from_sb(struct super_block *sb)
+{
+ if (sb->s_op == &kernfs_sops)
+ return kernfs_info(sb)->root;
+ return NULL;
+}
+
+/*
+ * find the next ancestor in the path down to @child, where @parent was the
+ * ancestor whose descendant we want to find.
+ *
+ * Say the path is /a/b/c/d. @child is d, @parent is NULL. We return the root
+ * node. If @parent is b, then we return the node for c.
+ * Passing in d as @parent is not ok.
+ */
+static struct kernfs_node *find_next_ancestor(struct kernfs_node *child,
+ struct kernfs_node *parent)
+{
+ if (child == parent) {
+ pr_crit_once("BUG in find_next_ancestor: called with parent == child");
+ return NULL;
+ }
+
+ while (child->parent != parent) {
+ if (!child->parent)
+ return NULL;
+ child = child->parent;
+ }
+
+ return child;
+}
+
+/**
+ * kernfs_node_dentry - get a dentry for the given kernfs_node
+ * @kn: kernfs_node for which a dentry is needed
+ * @sb: the kernfs super_block
+ */
+struct dentry *kernfs_node_dentry(struct kernfs_node *kn,
+ struct super_block *sb)
+{
+ struct dentry *dentry;
+ struct kernfs_node *knparent = NULL;
+
+ BUG_ON(sb->s_op != &kernfs_sops);
+
+ dentry = dget(sb->s_root);
+
+ /* Check if this is the root kernfs_node */
+ if (!kn->parent)
+ return dentry;
+
+ knparent = find_next_ancestor(kn, NULL);
+ if (WARN_ON(!knparent))
+ return ERR_PTR(-EINVAL);
+
+ do {
+ struct dentry *dtmp;
+ struct kernfs_node *kntmp;
+
+ if (kn == knparent)
+ return dentry;
+ kntmp = find_next_ancestor(kn, knparent);
+ if (WARN_ON(!kntmp))
+ return ERR_PTR(-EINVAL);
+ dtmp = lookup_one_len_unlocked(kntmp->name, dentry,
+ strlen(kntmp->name));
+ dput(dentry);
+ if (IS_ERR(dtmp))
+ return dtmp;
+ knparent = kntmp;
+ dentry = dtmp;
+ } while (true);
+}
+
+static int kernfs_fill_super(struct super_block *sb, unsigned long magic)
+{
+ struct kernfs_super_info *info = kernfs_info(sb);
+ struct inode *inode;
+ struct dentry *root;
+
+ info->sb = sb;
+ /* Userspace would break if executables or devices appear on sysfs */
+ sb->s_iflags |= SB_I_NOEXEC | SB_I_NODEV;
+ sb->s_blocksize = PAGE_SIZE;
+ sb->s_blocksize_bits = PAGE_SHIFT;
+ sb->s_magic = magic;
+ sb->s_op = &kernfs_sops;
+ sb->s_xattr = kernfs_xattr_handlers;
+ if (info->root->flags & KERNFS_ROOT_SUPPORT_EXPORTOP)
+ sb->s_export_op = &kernfs_export_ops;
+ sb->s_time_gran = 1;
+
+ /* get root inode, initialize and unlock it */
+ mutex_lock(&kernfs_mutex);
+ inode = kernfs_get_inode(sb, info->root->kn);
+ mutex_unlock(&kernfs_mutex);
+ if (!inode) {
+ pr_debug("kernfs: could not get root inode\n");
+ return -ENOMEM;
+ }
+
+ /* instantiate and link root dentry */
+ root = d_make_root(inode);
+ if (!root) {
+ pr_debug("%s: could not get root dentry!\n", __func__);
+ return -ENOMEM;
+ }
+ sb->s_root = root;
+ sb->s_d_op = &kernfs_dops;
+ return 0;
+}
+
+static int kernfs_test_super(struct super_block *sb, void *data)
+{
+ struct kernfs_super_info *sb_info = kernfs_info(sb);
+ struct kernfs_super_info *info = data;
+
+ return sb_info->root == info->root && sb_info->ns == info->ns;
+}
+
+static int kernfs_set_super(struct super_block *sb, void *data)
+{
+ int error;
+ error = set_anon_super(sb, data);
+ if (!error)
+ sb->s_fs_info = data;
+ return error;
+}
+
+/**
+ * kernfs_super_ns - determine the namespace tag of a kernfs super_block
+ * @sb: super_block of interest
+ *
+ * Return the namespace tag associated with kernfs super_block @sb.
+ */
+const void *kernfs_super_ns(struct super_block *sb)
+{
+ struct kernfs_super_info *info = kernfs_info(sb);
+
+ return info->ns;
+}
+
+/**
+ * kernfs_mount_ns - kernfs mount helper
+ * @fs_type: file_system_type of the fs being mounted
+ * @flags: mount flags specified for the mount
+ * @root: kernfs_root of the hierarchy being mounted
+ * @magic: file system specific magic number
+ * @new_sb_created: tell the caller if we allocated a new superblock
+ * @ns: optional namespace tag of the mount
+ *
+ * This is to be called from each kernfs user's file_system_type->mount()
+ * implementation, which should pass through the specified @fs_type and
+ * @flags, and specify the hierarchy and namespace tag to mount via @root
+ * and @ns, respectively.
+ *
+ * The return value can be passed to the vfs layer verbatim.
+ */
+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)
+{
+ struct super_block *sb;
+ struct kernfs_super_info *info;
+ int error;
+
+ info = kzalloc(sizeof(*info), GFP_KERNEL);
+ if (!info)
+ return ERR_PTR(-ENOMEM);
+
+ info->root = root;
+ info->ns = ns;
+ INIT_LIST_HEAD(&info->node);
+
+ sb = sget_userns(fs_type, kernfs_test_super, kernfs_set_super, flags,
+ &init_user_ns, info);
+ if (IS_ERR(sb) || sb->s_fs_info != info)
+ kfree(info);
+ if (IS_ERR(sb))
+ return ERR_CAST(sb);
+
+ if (new_sb_created)
+ *new_sb_created = !sb->s_root;
+
+ if (!sb->s_root) {
+ struct kernfs_super_info *info = kernfs_info(sb);
+
+ error = kernfs_fill_super(sb, magic);
+ if (error) {
+ deactivate_locked_super(sb);
+ return ERR_PTR(error);
+ }
+ sb->s_flags |= SB_ACTIVE;
+
+ mutex_lock(&kernfs_mutex);
+ list_add(&info->node, &root->supers);
+ mutex_unlock(&kernfs_mutex);
+ }
+
+ return dget(sb->s_root);
+}
+
+/**
+ * kernfs_kill_sb - kill_sb for kernfs
+ * @sb: super_block being killed
+ *
+ * This can be used directly for file_system_type->kill_sb(). If a kernfs
+ * user needs extra cleanup, it can implement its own kill_sb() and call
+ * this function at the end.
+ */
+void kernfs_kill_sb(struct super_block *sb)
+{
+ struct kernfs_super_info *info = kernfs_info(sb);
+
+ mutex_lock(&kernfs_mutex);
+ list_del(&info->node);
+ mutex_unlock(&kernfs_mutex);
+
+ /*
+ * Remove the superblock from fs_supers/s_instances
+ * so we can't find it, before freeing kernfs_super_info.
+ */
+ kill_anon_super(sb);
+ kfree(info);
+}
+
+/**
+ * kernfs_pin_sb: try to pin the superblock associated with a kernfs_root
+ * @kernfs_root: the kernfs_root in question
+ * @ns: the namespace tag
+ *
+ * Pin the superblock so the superblock won't be destroyed in subsequent
+ * operations. This can be used to block ->kill_sb() which may be useful
+ * for kernfs users which dynamically manage superblocks.
+ *
+ * Returns NULL if there's no superblock associated to this kernfs_root, or
+ * -EINVAL if the superblock is being freed.
+ */
+struct super_block *kernfs_pin_sb(struct kernfs_root *root, const void *ns)
+{
+ struct kernfs_super_info *info;
+ struct super_block *sb = NULL;
+
+ mutex_lock(&kernfs_mutex);
+ list_for_each_entry(info, &root->supers, node) {
+ if (info->ns == ns) {
+ sb = info->sb;
+ if (!atomic_inc_not_zero(&info->sb->s_active))
+ sb = ERR_PTR(-EINVAL);
+ break;
+ }
+ }
+ mutex_unlock(&kernfs_mutex);
+ return sb;
+}
+
+void __init kernfs_init(void)
+{
+
+ /*
+ * the slab is freed in RCU context, so kernfs_find_and_get_node_by_ino
+ * can access the slab lock free. This could introduce stale nodes,
+ * please see how kernfs_find_and_get_node_by_ino filters out stale
+ * nodes.
+ */
+ kernfs_node_cache = kmem_cache_create("kernfs_node_cache",
+ sizeof(struct kernfs_node),
+ 0,
+ SLAB_PANIC | SLAB_TYPESAFE_BY_RCU,
+ NULL);
+}
diff --git a/fs/kernfs/symlink.c b/fs/kernfs/symlink.c
new file mode 100644
index 0000000..305b220
--- /dev/null
+++ b/fs/kernfs/symlink.c
@@ -0,0 +1,151 @@
+/*
+ * fs/kernfs/symlink.c - kernfs symlink implementation
+ *
+ * Copyright (c) 2001-3 Patrick Mochel
+ * Copyright (c) 2007 SUSE Linux Products GmbH
+ * Copyright (c) 2007, 2013 Tejun Heo <tj@kernel.org>
+ *
+ * This file is released under the GPLv2.
+ */
+
+#include <linux/fs.h>
+#include <linux/gfp.h>
+#include <linux/namei.h>
+
+#include "kernfs-internal.h"
+
+/**
+ * kernfs_create_link - create a symlink
+ * @parent: directory to create the symlink in
+ * @name: name of the symlink
+ * @target: target node for the symlink to point to
+ *
+ * Returns the created node on success, ERR_PTR() value on error.
+ * Ownership of the link matches ownership of the target.
+ */
+struct kernfs_node *kernfs_create_link(struct kernfs_node *parent,
+ const char *name,
+ struct kernfs_node *target)
+{
+ struct kernfs_node *kn;
+ int error;
+ kuid_t uid = GLOBAL_ROOT_UID;
+ kgid_t gid = GLOBAL_ROOT_GID;
+
+ if (target->iattr) {
+ uid = target->iattr->ia_iattr.ia_uid;
+ gid = target->iattr->ia_iattr.ia_gid;
+ }
+
+ kn = kernfs_new_node(parent, name, S_IFLNK|S_IRWXUGO, uid, gid,
+ KERNFS_LINK);
+ if (!kn)
+ return ERR_PTR(-ENOMEM);
+
+ if (kernfs_ns_enabled(parent))
+ kn->ns = target->ns;
+ kn->symlink.target_kn = target;
+ kernfs_get(target); /* ref owned by symlink */
+
+ error = kernfs_add_one(kn);
+ if (!error)
+ return kn;
+
+ kernfs_put(kn);
+ return ERR_PTR(error);
+}
+
+static int kernfs_get_target_path(struct kernfs_node *parent,
+ struct kernfs_node *target, char *path)
+{
+ struct kernfs_node *base, *kn;
+ char *s = path;
+ int len = 0;
+
+ /* go up to the root, stop at the base */
+ base = parent;
+ while (base->parent) {
+ kn = target->parent;
+ while (kn->parent && base != kn)
+ kn = kn->parent;
+
+ if (base == kn)
+ break;
+
+ strcpy(s, "../");
+ s += 3;
+ base = base->parent;
+ }
+
+ /* determine end of target string for reverse fillup */
+ kn = target;
+ while (kn->parent && kn != base) {
+ len += strlen(kn->name) + 1;
+ kn = kn->parent;
+ }
+
+ /* check limits */
+ if (len < 2)
+ return -EINVAL;
+ len--;
+ if ((s - path) + len > PATH_MAX)
+ return -ENAMETOOLONG;
+
+ /* reverse fillup of target string from target to base */
+ kn = target;
+ while (kn->parent && kn != base) {
+ int slen = strlen(kn->name);
+
+ len -= slen;
+ memcpy(s + len, kn->name, slen);
+ if (len)
+ s[--len] = '/';
+
+ kn = kn->parent;
+ }
+
+ return 0;
+}
+
+static int kernfs_getlink(struct inode *inode, char *path)
+{
+ struct kernfs_node *kn = inode->i_private;
+ struct kernfs_node *parent = kn->parent;
+ struct kernfs_node *target = kn->symlink.target_kn;
+ int error;
+
+ mutex_lock(&kernfs_mutex);
+ error = kernfs_get_target_path(parent, target, path);
+ mutex_unlock(&kernfs_mutex);
+
+ return error;
+}
+
+static const char *kernfs_iop_get_link(struct dentry *dentry,
+ struct inode *inode,
+ struct delayed_call *done)
+{
+ char *body;
+ int error;
+
+ if (!dentry)
+ return ERR_PTR(-ECHILD);
+ body = kzalloc(PAGE_SIZE, GFP_KERNEL);
+ if (!body)
+ return ERR_PTR(-ENOMEM);
+ error = kernfs_getlink(inode, body);
+ if (unlikely(error < 0)) {
+ kfree(body);
+ return ERR_PTR(error);
+ }
+ set_delayed_call(done, kfree_link, body);
+ return body;
+}
+
+const struct inode_operations kernfs_symlink_iops = {
+ .listxattr = kernfs_iop_listxattr,
+ .get_link = kernfs_iop_get_link,
+ .setattr = kernfs_iop_setattr,
+ .getattr = kernfs_iop_getattr,
+ .permission = kernfs_iop_permission,
+};