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;
}
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_syscall_ops *scops = kernfs_root(kn)->syscall_ops;
int ret;
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;
}
static int kernfs_sop_show_options(struct seq_file *sf, struct dentry *dentry)
{
struct kernfs_root *root = kernfs_root(dentry->d_fsdata);
struct kernfs_syscall_ops *scops = root->syscall_ops;
if (scops && scops->show_options)
return scops->show_options(sf, root);
return 0;
}
/**
* 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_ts(&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;
}
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_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_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);
}
/*! 2017. 8.12 study -ing */
struct kernfs_node *kernfs_new_node(struct kernfs_node *parent,
const char *name, umode_t mode,
unsigned flags)
{
struct kernfs_node *kn;
kn = __kernfs_new_node(kernfs_root(parent), name, mode, flags);
if (kn) {
kernfs_get(parent);
kn->parent = parent;
}
return kn;
}
/**
* 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_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: /../..
*
* return value: length of the string. If greater than buflen,
* then contents of buf are undefined. On error, -1 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, nlen = 0;
char *p;
int i;
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 -1;
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 (kn = kn_to; kn != common; kn = kn->parent)
nlen += strlen(kn->name) + 1;
if (len + nlen >= buflen)
return len + nlen;
p = buf + len + nlen;
*p = '\0';
for (kn = kn_to; kn != common; kn = kn->parent) {
size_t tmp = strlen(kn->name);
p -= tmp;
memcpy(p, kn->name, tmp);
*(--p) = '/';
}
return len + nlen;
}
/**
* 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);
}
static int kernfs_iop_rmdir(struct inode *dir, struct dentry *dentry)
{
struct kernfs_node *kn = dentry->d_fsdata;
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_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;
}
/**
* 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);
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);
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);
}
}
/*! 2017. 3.18 study -ing */
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(!(kn->flags & KERNFS_REMOVED), "kernfs: free using entry: %s/%s\n",
parent ? parent->name : "", kn->name);
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)
/*! Do Nothing */
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);
}
}
