blob: 1aeb57969bffe70b8deb44d95c417b2e0a591827 [file] [log] [blame]
/*
* 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);
#define rb_to_kn(X) rb_entry((X), struct kernfs_node, rb)
static bool kernfs_lockdep(struct kernfs_node *kn)
{
#ifdef CONFIG_DEBUG_LOCK_ALLOC
return kn->flags & KERNFS_LOCKDEP;
#else
return false;
#endif
}
/**
* 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();
unsigned int len = strlen(name);
while (len--)
hash = partial_name_hash(*name++, hash);
hash = (end_name_hash(hash) ^ hash_ptr((void *)ns, 31));
hash &= 0x7fffffffU;
/* Reserve hash numbers 0, 1 and INT_MAX for magic directory entries */
if (hash < 1)
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 hash - kn->hash;
if (ns != kn->ns)
return ns - kn->ns;
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;
if (kernfs_type(kn) == KERNFS_DIR)
kn->parent->dir.subdirs++;
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);
return 0;
}
/**
* kernfs_unlink_sibling - unlink kernfs_node from sibling rbtree
* @kn: kernfs_node of interest
*
* Unlink @kn from its sibling rbtree which starts from
* kn->parent->dir.children.
*
* 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 (kernfs_lockdep(kn))
rwsem_acquire_read(&kn->dep_map, 0, 1, _RET_IP_);
/*
* Try to obtain an active ref. If @kn is deactivated, we block
* till either it's reactivated or killed.
*/
do {
if (atomic_inc_unless_negative(&kn->active))
return kn;
wait_event(kernfs_root(kn)->deactivate_waitq,
atomic_read(&kn->active) >= 0 ||
RB_EMPTY_NODE(&kn->rb));
} while (!RB_EMPTY_NODE(&kn->rb));
if (kernfs_lockdep(kn))
rwsem_release(&kn->dep_map, 1, _RET_IP_);
return NULL;
}
/**
* 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 of @kn. Mutiple removers may invoke this function
* concurrently on @kn and all will return after draining is complete.
* Returns %true if drain is performed and kernfs_mutex was temporarily
* released. %false if @kn was already drained and no operation was
* necessary.
*
* The caller is responsible for ensuring @kn stays pinned while this
* function is in progress even if it gets removed by someone else.
*/
static bool 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(atomic_read(&kn->active) >= 0);
/*
* We want to go through the active ref lockdep annotation at least
* once for all node removals, but the lockdep annotation can't be
* nested inside kernfs_mutex and deactivation can't make forward
* progress if we keep dropping the mutex. Use JUST_ACTIVATED to
* force the slow path once for each deactivation if lockdep is
* enabled.
*/
if ((!kernfs_lockdep(kn) || !(kn->flags & KERNFS_JUST_DEACTIVATED)) &&
atomic_read(&kn->active) == KN_DEACTIVATED_BIAS)
return false;
kn->flags &= ~KERNFS_JUST_DEACTIVATED;
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_);
}
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_);
}
mutex_lock(&kernfs_mutex);
return true;
}
/**
* 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;
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);
if (!(kn->flags & KERNFS_STATIC_NAME))
kfree(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);
ida_simple_remove(&root->ino_ida, kn->ino);
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 */
ida_destroy(&root->ino_ida);
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 (!dentry->d_inode)
goto out_bad_unlocked;
kn = dentry->d_fsdata;
mutex_lock(&kernfs_mutex);
/* Force fresh lookup if removed */
if (kn->parent && RB_EMPTY_NODE(&kn->rb))
goto out_bad;
/* The kernfs node has been moved? */
if (dentry->d_parent->d_fsdata != 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);
out_valid:
return 1;
out_bad:
mutex_unlock(&kernfs_mutex);
out_bad_unlocked:
/*
* @dentry doesn't match the underlying kernfs node, drop the
* dentry and force lookup. If we have submounts we must allow the
* vfs caches to lie about the state of the filesystem to prevent
* leaks and other nasty things, so use check_submounts_and_drop()
* instead of d_drop().
*/
if (check_submounts_and_drop(dentry) != 0)
goto out_valid;
return 0;
}
static void kernfs_dop_release(struct dentry *dentry)
{
kernfs_put(dentry->d_fsdata);
}
const struct dentry_operations kernfs_dops = {
.d_revalidate = kernfs_dop_revalidate,
.d_release = kernfs_dop_release,
};
struct kernfs_node *kernfs_new_node(struct kernfs_root *root, const char *name,
umode_t mode, unsigned flags)
{
char *dup_name = NULL;
struct kernfs_node *kn;
int ret;
if (!(flags & KERNFS_STATIC_NAME)) {
name = dup_name = kstrdup(name, GFP_KERNEL);
if (!name)
return NULL;
}
kn = kmem_cache_zalloc(kernfs_node_cache, GFP_KERNEL);
if (!kn)
goto err_out1;
ret = ida_simple_get(&root->ino_ida, 1, 0, GFP_KERNEL);
if (ret < 0)
goto err_out2;
kn->ino = ret;
atomic_set(&kn->count, 1);
atomic_set(&kn->active, KN_DEACTIVATED_BIAS);
kn->deact_depth = 1;
RB_CLEAR_NODE(&kn->rb);
kn->name = name;
kn->mode = mode;
kn->flags = flags;
return kn;
err_out2:
kmem_cache_free(kernfs_node_cache, kn);
err_out1:
kfree(dup_name);
return NULL;
}
/**
* kernfs_add_one - add kernfs_node to parent without warning
* @kn: kernfs_node to be added
* @parent: the parent kernfs_node to add @kn to
*
* Get @parent and set @kn->parent to it and increment nlink of the
* parent 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)
{
struct kernfs_iattrs *ps_iattr;
bool has_ns;
int ret;
if (!kernfs_get_active(parent))
return -ENOENT;
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;
kn->hash = kernfs_name_hash(kn->name, kn->ns);
kn->parent = parent;
kernfs_get(parent);
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;
ps_iattrs->ia_ctime = ps_iattrs->ia_mtime = CURRENT_TIME;
}
/* Mark the entry added into directory tree */
atomic_sub(KN_DEACTIVATED_BIAS, &kn->active);
kn->deact_depth--;
ret = 0;
out_unlock:
mutex_unlock(&kernfs_mutex);
kernfs_put_active(parent);
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;
}
/**
* 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_create_root - create a new kernfs hierarchy
* @kdops: optional directory syscall operations for the hierarchy
* @priv: opaque data associated with the new directory
*
* Returns the root of the new hierarchy on success, ERR_PTR() value on
* failure.
*/
struct kernfs_root *kernfs_create_root(struct kernfs_dir_ops *kdops, void *priv)
{
struct kernfs_root *root;
struct kernfs_node *kn;
root = kzalloc(sizeof(*root), GFP_KERNEL);
if (!root)
return ERR_PTR(-ENOMEM);
ida_init(&root->ino_ida);
kn = kernfs_new_node(root, "", S_IFDIR | S_IRUGO | S_IXUGO, KERNFS_DIR);
if (!kn) {
ida_destroy(&root->ino_ida);
kfree(root);
return ERR_PTR(-ENOMEM);
}
atomic_sub(KN_DEACTIVATED_BIAS, &kn->active);
kn->deact_depth--;
kn->priv = priv;
kn->dir.root = root;
root->dir_ops = kdops;
root->kn = kn;
init_waitqueue_head(&root->deactivate_waitq);
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
* @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,
void *priv, const void *ns)
{
struct kernfs_node *kn;
int rc;
/* allocate */
kn = kernfs_new_node(kernfs_root(parent), name, mode | S_IFDIR,
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, parent);
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 = dentry->d_parent->d_fsdata;
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) {
ret = NULL;
goto out_unlock;
}
kernfs_get(kn);
dentry->d_fsdata = kn;
/* 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_materialise_unique(dentry, inode);
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_dir_ops *kdops = kernfs_root(parent)->dir_ops;
if (!kdops || !kdops->mkdir)
return -EPERM;
return kdops->mkdir(parent, dentry->d_name.name, mode);
}
static int kernfs_iop_rmdir(struct inode *dir, struct dentry *dentry)
{
struct kernfs_node *kn = dentry->d_fsdata;
struct kernfs_dir_ops *kdops = kernfs_root(kn)->dir_ops;
if (!kdops || !kdops->rmdir)
return -EPERM;
return kdops->rmdir(kn);
}
static int kernfs_iop_rename(struct inode *old_dir, struct dentry *old_dentry,
struct inode *new_dir, struct dentry *new_dentry)
{
struct kernfs_node *kn = old_dentry->d_fsdata;
struct kernfs_node *new_parent = new_dir->i_private;
struct kernfs_dir_ops *kdops = kernfs_root(kn)->dir_ops;
if (!kdops || !kdops->rename)
return -EPERM;
return kdops->rename(kn, new_parent, new_dentry->d_name.name);
}
const struct inode_operations kernfs_dir_iops = {
.lookup = kernfs_iop_lookup,
.permission = kernfs_iop_permission,
.setattr = kernfs_iop_setattr,
.getattr = kernfs_iop_getattr,
.setxattr = kernfs_iop_setxattr,
.removexattr = kernfs_iop_removexattr,
.getxattr = kernfs_iop_getxattr,
.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;
}
static void __kernfs_deactivate(struct kernfs_node *kn)
{
struct kernfs_node *pos;
lockdep_assert_held(&kernfs_mutex);
/* prevent any new usage under @kn by deactivating all nodes */
pos = NULL;
while ((pos = kernfs_next_descendant_post(pos, kn))) {
if (!pos->deact_depth++) {
WARN_ON_ONCE(atomic_read(&pos->active) < 0);
atomic_add(KN_DEACTIVATED_BIAS, &pos->active);
pos->flags |= KERNFS_JUST_DEACTIVATED;
}
}
/*
* Drain the subtree. If kernfs_drain() blocked to drain, which is
* indicated by %true return, it temporarily released kernfs_mutex
* and the rbtree might have been modified inbetween breaking our
* future walk. Restart the walk after each %true return.
*/
pos = NULL;
while ((pos = kernfs_next_descendant_post(pos, kn))) {
bool drained;
kernfs_get(pos);
drained = kernfs_drain(pos);
kernfs_put(pos);
if (drained)
pos = NULL;
}
}
static void __kernfs_reactivate(struct kernfs_node *kn)
{
struct kernfs_node *pos;
lockdep_assert_held(&kernfs_mutex);
pos = NULL;
while ((pos = kernfs_next_descendant_post(pos, kn))) {
if (!--pos->deact_depth) {
WARN_ON_ONCE(atomic_read(&pos->active) >= 0);
atomic_sub(KN_DEACTIVATED_BIAS, &pos->active);
}
WARN_ON_ONCE(pos->deact_depth < 0);
}
/* some nodes reactivated, kick get_active waiters */
wake_up_all(&kernfs_root(kn)->deactivate_waitq);
}
static void __kernfs_deactivate_self(struct kernfs_node *kn)
{
/*
* Take out ourself out of the active ref dependency chain and
* deactivate. If we're called without an active ref, lockdep will
* complain.
*/
kernfs_put_active(kn);
__kernfs_deactivate(kn);
}
static void __kernfs_reactivate_self(struct kernfs_node *kn)
{
__kernfs_reactivate(kn);
/*
* Restore active ref dropped by deactivate_self() so that it's
* balanced on return. put_active() will soon be called on @kn, so
* this can't break anything regardless of @kn's state.
*/
atomic_inc(&kn->active);
if (kernfs_lockdep(kn))
rwsem_acquire(&kn->dep_map, 0, 1, _RET_IP_);
}
/**
* kernfs_deactivate - deactivate subtree of a node
* @kn: kernfs_node to deactivate subtree of
*
* Deactivate the subtree of @kn. On return, there's no active operation
* going on under @kn and creation or renaming of a node under @kn is
* blocked until @kn is reactivated or removed. This function can be
* called multiple times and nests properly. Each invocation should be
* paired with kernfs_reactivate().
*
* For a kernfs user which uses simple locking, the subsystem lock would
* nest inside active reference. This becomes problematic if the user
* tries to remove nodes while holding the subystem lock as it would create
* a reverse locking dependency from the subsystem lock to active ref.
* This function can be used to break such reverse dependency. The user
* can call this function outside the subsystem lock and then proceed to
* invoke kernfs_remove() while holding the subsystem lock without
* introducing such reverse dependency.
*/
void kernfs_deactivate(struct kernfs_node *kn)
{
mutex_lock(&kernfs_mutex);
__kernfs_deactivate(kn);
mutex_unlock(&kernfs_mutex);
}
/**
* kernfs_reactivate - reactivate subtree of a node
* @kn: kernfs_node to reactivate subtree of
*
* Undo kernfs_deactivate().
*/
void kernfs_reactivate(struct kernfs_node *kn)
{
mutex_lock(&kernfs_mutex);
__kernfs_reactivate(kn);
mutex_unlock(&kernfs_mutex);
}
/**
* kernfs_deactivate_self - deactivate subtree of a node from its own method
* @kn: the self kernfs_node to deactivate subtree of
*
* The caller must be running off of a kernfs operation which is invoked
* with an active reference - e.g. one of kernfs_ops. Once this function
* is called, @kn may be removed by someone else while the enclosing method
* is in progress. Other than that, this function is equivalent to
* kernfs_deactivate() and should be paired with kernfs_reactivate_self().
*/
void kernfs_deactivate_self(struct kernfs_node *kn)
{
mutex_lock(&kernfs_mutex);
__kernfs_deactivate_self(kn);
mutex_unlock(&kernfs_mutex);
}
/**
* kernfs_reactivate_self - reactivate subtree of a node from its own method
* @kn: the self kernfs_node to reactivate subtree of
*
* Undo kernfs_deactivate_self().
*/
void kernfs_reactivate_self(struct kernfs_node *kn)
{
mutex_lock(&kernfs_mutex);
__kernfs_reactivate_self(kn);
mutex_unlock(&kernfs_mutex);
}
static void __kernfs_remove(struct kernfs_node *kn)
{
struct kernfs_root *root = kernfs_root(kn);
struct kernfs_node *pos;
lockdep_assert_held(&kernfs_mutex);
if (!kn)
return;
pr_debug("kernfs %s: removing\n", kn->name);
__kernfs_deactivate(kn);
/* unlink the subtree node-by-node */
do {
pos = kernfs_leftmost_descendant(kn);
/*
* We're gonna release kernfs_mutex to unmap bin files,
* Make sure @pos doesn't go away inbetween.
*/
kernfs_get(pos);
/*
* This must be come before unlinking; otherwise, when
* there are multiple removers, some may finish before
* unmapping is complete.
*/
if (pos->flags & KERNFS_HAS_MMAP) {
mutex_unlock(&kernfs_mutex);
kernfs_unmap_file(pos);
mutex_lock(&kernfs_mutex);
}
/*
* 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) {
ps_iattr->ia_iattr.ia_ctime = CURRENT_TIME;
ps_iattr->ia_iattr.ia_mtime = CURRENT_TIME;
}
kernfs_put(pos);
}
kernfs_put(pos);
} while (pos != kn);
/* some nodes killed, kick get_active waiters */
wake_up_all(&root->deactivate_waitq);
}
/**
* 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_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)
{
int error;
error = -ENOENT;
if (!kernfs_get_active(new_parent))
goto out;
if (!kernfs_get_active(kn))
goto out_put_new_parent;
mutex_lock(&kernfs_mutex);
error = 0;
if ((kn->parent == new_parent) && (kn->ns == new_ns) &&
(strcmp(kn->name, new_name) == 0))
goto out_unlock; /* nothing to rename */
error = -EEXIST;
if (kernfs_find_ns(new_parent, new_name, new_ns))
goto out_unlock;
/* rename kernfs_node */
if (strcmp(kn->name, new_name) != 0) {
error = -ENOMEM;
new_name = kstrdup(new_name, GFP_KERNEL);
if (!new_name)
goto out_unlock;
if (kn->flags & KERNFS_STATIC_NAME)
kn->flags &= ~KERNFS_STATIC_NAME;
else
kfree(kn->name);
kn->name = new_name;
}
/*
* Move to the appropriate place in the appropriate directories rbtree.
*/
kernfs_unlink_sibling(kn);
kernfs_get(new_parent);
kernfs_put(kn->parent);
kn->ns = new_ns;
kn->hash = kernfs_name_hash(kn->name, kn->ns);
kn->parent = new_parent;
kernfs_link_sibling(kn);
error = 0;
out_unlock:
mutex_unlock(&kernfs_mutex);
kernfs_put_active(kn);
out_put_new_parent:
kernfs_put_active(new_parent);
out:
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 = 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 in the wrong namespace */
while (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 && 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 = dentry->d_fsdata;
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->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;
}
static loff_t kernfs_dir_fop_llseek(struct file *file, loff_t offset,
int whence)
{
struct inode *inode = file_inode(file);
loff_t ret;
mutex_lock(&inode->i_mutex);
ret = generic_file_llseek(file, offset, whence);
mutex_unlock(&inode->i_mutex);
return ret;
}
const struct file_operations kernfs_dir_fops = {
.read = generic_read_dir,
.iterate = kernfs_fop_readdir,
.release = kernfs_dir_fop_release,
.llseek = kernfs_dir_fop_llseek,
};