* This file is released under the GPLv2.
*/
+#include <linux/sched.h>
#include <linux/fs.h>
#include <linux/namei.h>
#include <linux/idr.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 */
#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)
+{
+ return strlcpy(buf, kn->parent ? kn->name : "/", buflen);
+}
+
+static char * __must_check kernfs_path_locked(struct kernfs_node *kn, char *buf,
+ size_t buflen)
+{
+ char *p = buf + buflen;
+ int len;
+
+ *--p = '\0';
+
+ do {
+ len = strlen(kn->name);
+ if (p - buf < len + 1) {
+ buf[0] = '\0';
+ p = NULL;
+ break;
+ }
+ p -= len;
+ memcpy(p, kn->name, len);
+ *--p = '/';
+ kn = kn->parent;
+ } while (kn && kn->parent);
+
+ return p;
+}
+
+/**
+ * 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.
+ *
+ * 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 - build full path of a given node
+ * @kn: kernfs_node of interest
+ * @buf: buffer to copy @kn's name into
+ * @buflen: size of @buf
+ *
+ * Builds and returns the full path of @kn in @buf of @buflen bytes. The
+ * path is built from the end of @buf so the returned pointer usually
+ * doesn't match @buf. If @buf isn't long enough, @buf is nul terminated
+ * and %NULL is returned.
+ */
+char *kernfs_path(struct kernfs_node *kn, char *buf, size_t buflen)
+{
+ unsigned long flags;
+ char *p;
+
+ spin_lock_irqsave(&kernfs_rename_lock, flags);
+ p = kernfs_path_locked(kn, buf, buflen);
+ spin_unlock_irqrestore(&kernfs_rename_lock, flags);
+ return p;
+}
+EXPORT_SYMBOL_GPL(kernfs_path);
+
+/**
+ * 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;
+ char *p;
+
+ spin_lock_irqsave(&kernfs_rename_lock, flags);
+
+ p = kernfs_path_locked(kn, kernfs_pr_cont_buf,
+ sizeof(kernfs_pr_cont_buf));
+ if (p)
+ pr_cont("%s", p);
+ else
+ pr_cont("<name too long>");
+
+ 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
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)
+ if (hash < 2)
hash += 2;
if (hash >= INT_MAX)
hash = INT_MAX - 1;
* 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.
+ * 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 void kernfs_unlink_sibling(struct kernfs_node *kn)
+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;
}
/**
if (!atomic_inc_unless_negative(&kn->active))
return NULL;
- if (kn->flags & KERNFS_LOCKDEP)
+ if (kernfs_lockdep(kn))
rwsem_acquire_read(&kn->dep_map, 0, 1, _RET_IP_);
return kn;
}
*/
void kernfs_put_active(struct kernfs_node *kn)
{
+ struct kernfs_root *root = kernfs_root(kn);
int v;
if (unlikely(!kn))
return;
- if (kn->flags & KERNFS_LOCKDEP)
+ 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;
- /*
- * atomic_dec_return() is a mb(), we'll always see the updated
- * kn->u.completion.
- */
- complete(kn->u.completion);
+ wake_up_all(&root->deactivate_waitq);
}
/**
- * kernfs_deactivate - deactivate kernfs_node
- * @kn: kernfs_node to deactivate
+ * kernfs_drain - drain kernfs_node
+ * @kn: kernfs_node to drain
*
- * Deny new active references and drain existing ones.
+ * 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_deactivate(struct kernfs_node *kn)
+static void kernfs_drain(struct kernfs_node *kn)
+ __releases(&kernfs_mutex) __acquires(&kernfs_mutex)
{
- DECLARE_COMPLETION_ONSTACK(wait);
- int v;
+ struct kernfs_root *root = kernfs_root(kn);
- BUG_ON(!(kn->flags & KERNFS_REMOVED));
-
- if (!(kernfs_type(kn) & KERNFS_ACTIVE_REF))
- return;
+ lockdep_assert_held(&kernfs_mutex);
+ WARN_ON_ONCE(kernfs_active(kn));
- kn->u.completion = (void *)&wait;
+ mutex_unlock(&kernfs_mutex);
- if (kn->flags & KERNFS_LOCKDEP)
+ if (kernfs_lockdep(kn)) {
rwsem_acquire(&kn->dep_map, 0, 0, _RET_IP_);
- /* atomic_add_return() is a mb(), put_active() will always see
- * the updated kn->u.completion.
- */
- v = atomic_add_return(KN_DEACTIVATED_BIAS, &kn->active);
-
- if (v != KN_DEACTIVATED_BIAS) {
- if (kn->flags & KERNFS_LOCKDEP)
+ if (atomic_read(&kn->active) != KN_DEACTIVATED_BIAS)
lock_contended(&kn->dep_map, _RET_IP_);
- wait_for_completion(&wait);
}
- if (kn->flags & KERNFS_LOCKDEP) {
+ /* 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_unmap_bin_file(kn);
+
+ mutex_lock(&kernfs_mutex);
}
/**
return;
root = kernfs_root(kn);
repeat:
- /* Moving/renaming is always done while holding reference.
+ /*
+ * 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);
+ 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);
kn = dentry->d_fsdata;
mutex_lock(&kernfs_mutex);
- /* The kernfs node has been deleted */
- if (kn->flags & KERNFS_REMOVED)
+ /* The kernfs node has been deactivated */
+ if (!kernfs_active(kn))
goto out_bad;
/* The kernfs node has been moved? */
.d_release = kernfs_dop_release,
};
+/**
+ * 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)
+ return dentry->d_fsdata;
+ return NULL;
+}
+
static struct kernfs_node *__kernfs_new_node(struct kernfs_root *root,
const char *name, umode_t mode,
unsigned flags)
kn->ino = ret;
atomic_set(&kn->count, 1);
- atomic_set(&kn->active, 0);
+ atomic_set(&kn->active, KN_DEACTIVATED_BIAS);
+ RB_CLEAR_NODE(&kn->rb);
kn->name = name;
kn->mode = mode;
- kn->flags = flags | KERNFS_REMOVED;
+ kn->flags = flags;
return kn;
return kn;
}
-/**
- * kernfs_addrm_start - prepare for kernfs_node add/remove
- * @acxt: pointer to kernfs_addrm_cxt to be used
- *
- * This function is called when the caller is about to add or remove
- * kernfs_node. This function acquires kernfs_mutex. @acxt is used
- * to keep and pass context to other addrm functions.
- *
- * LOCKING:
- * Kernel thread context (may sleep). kernfs_mutex is locked on
- * return.
- */
-void kernfs_addrm_start(struct kernfs_addrm_cxt *acxt)
- __acquires(kernfs_mutex)
-{
- memset(acxt, 0, sizeof(*acxt));
-
- mutex_lock(&kernfs_mutex);
-}
-
/**
* kernfs_add_one - add kernfs_node to parent without warning
- * @acxt: addrm context to use
* @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.
*
- * This function should be called between calls to
- * kernfs_addrm_start() and kernfs_addrm_finish() and should be passed
- * the same @acxt as passed to kernfs_addrm_start().
- *
- * LOCKING:
- * Determined by kernfs_addrm_start().
- *
* RETURNS:
* 0 on success, -EEXIST if entry with the given name already
* exists.
*/
-int kernfs_add_one(struct kernfs_addrm_cxt *acxt, struct kernfs_node *kn)
+int kernfs_add_one(struct kernfs_node *kn)
{
struct kernfs_node *parent = kn->parent;
- bool has_ns = kernfs_ns_enabled(parent);
struct kernfs_iattrs *ps_iattr;
+ bool has_ns;
int ret;
- if (has_ns != (bool)kn->ns) {
- WARN(1, KERN_WARNING "kernfs: ns %s in '%s' for '%s'\n",
- has_ns ? "required" : "invalid", parent->name, kn->name);
- return -EINVAL;
- }
+ 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)
- return -EINVAL;
+ goto out_unlock;
- if (parent->flags & KERNFS_REMOVED)
- return -ENOENT;
+ ret = -ENOENT;
+ 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)
- return ret;
+ goto out_unlock;
/* Update timestamps on the parent */
ps_iattr = parent->iattr;
ps_iattrs->ia_ctime = ps_iattrs->ia_mtime = CURRENT_TIME;
}
- /* Mark the entry added into directory tree */
- kn->flags &= ~KERNFS_REMOVED;
-
- return 0;
-}
-
-/**
- * kernfs_remove_one - remove kernfs_node from parent
- * @acxt: addrm context to use
- * @kn: kernfs_node to be removed
- *
- * Mark @kn removed and drop nlink of parent inode if @kn is a
- * directory. @kn is unlinked from the children list.
- *
- * This function should be called between calls to
- * kernfs_addrm_start() and kernfs_addrm_finish() and should be
- * passed the same @acxt as passed to kernfs_addrm_start().
- *
- * LOCKING:
- * Determined by kernfs_addrm_start().
- */
-static void kernfs_remove_one(struct kernfs_addrm_cxt *acxt,
- struct kernfs_node *kn)
-{
- struct kernfs_iattrs *ps_iattr;
+ mutex_unlock(&kernfs_mutex);
/*
- * Removal can be called multiple times on the same node. Only the
- * first invocation is effective and puts the base ref.
+ * 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 (kn->flags & KERNFS_REMOVED)
- return;
-
- if (kn->parent) {
- kernfs_unlink_sibling(kn);
-
- /* Update timestamps on the parent */
- ps_iattr = kn->parent->iattr;
- if (ps_iattr) {
- ps_iattr->ia_iattr.ia_ctime = CURRENT_TIME;
- ps_iattr->ia_iattr.ia_mtime = CURRENT_TIME;
- }
- }
-
- kn->flags |= KERNFS_REMOVED;
- kn->u.removed_list = acxt->removed;
- acxt->removed = kn;
-}
+ if (!(kernfs_root(kn)->flags & KERNFS_ROOT_CREATE_DEACTIVATED))
+ kernfs_activate(kn);
+ return 0;
-/**
- * kernfs_addrm_finish - finish up kernfs_node add/remove
- * @acxt: addrm context to finish up
- *
- * Finish up kernfs_node add/remove. Resources acquired by
- * kernfs_addrm_start() are released and removed kernfs_nodes are
- * cleaned up.
- *
- * LOCKING:
- * kernfs_mutex is released.
- */
-void kernfs_addrm_finish(struct kernfs_addrm_cxt *acxt)
- __releases(kernfs_mutex)
-{
- /* release resources acquired by kernfs_addrm_start() */
+out_unlock:
mutex_unlock(&kernfs_mutex);
-
- /* kill removed kernfs_nodes */
- while (acxt->removed) {
- struct kernfs_node *kn = acxt->removed;
-
- acxt->removed = kn->u.removed_list;
-
- kernfs_deactivate(kn);
- kernfs_unmap_bin_file(kn);
- kernfs_put(kn);
- }
+ return ret;
}
/**
/**
* kernfs_create_root - create a new kernfs hierarchy
- * @kdops: optional directory syscall operations for the 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_dir_ops *kdops, void *priv)
+struct kernfs_root *kernfs_create_root(struct kernfs_syscall_ops *scops,
+ unsigned int flags, void *priv)
{
struct kernfs_root *root;
struct kernfs_node *kn;
return ERR_PTR(-ENOMEM);
}
- kn->flags &= ~KERNFS_REMOVED;
kn->priv = priv;
kn->dir.root = root;
- root->dir_ops = kdops;
+ 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;
}
const char *name, umode_t mode,
void *priv, const void *ns)
{
- struct kernfs_addrm_cxt acxt;
struct kernfs_node *kn;
int rc;
kn->priv = priv;
/* link in */
- kernfs_addrm_start(&acxt);
- rc = kernfs_add_one(&acxt, kn);
- kernfs_addrm_finish(&acxt);
-
+ rc = kernfs_add_one(kn);
if (!rc)
return kn;
kn = kernfs_find_ns(parent, dentry->d_name.name, ns);
/* no such entry */
- if (!kn) {
+ if (!kn || !kernfs_active(kn)) {
ret = NULL;
goto out_unlock;
}
umode_t mode)
{
struct kernfs_node *parent = dir->i_private;
- struct kernfs_dir_ops *kdops = kernfs_root(parent)->dir_ops;
+ struct kernfs_syscall_ops *scops = kernfs_root(parent)->syscall_ops;
+ int ret;
- if (!kdops || !kdops->mkdir)
+ if (!scops || !scops->mkdir)
return -EPERM;
- return kdops->mkdir(parent, dentry->d_name.name, mode);
+ 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 = dentry->d_fsdata;
- struct kernfs_dir_ops *kdops = kernfs_root(kn)->dir_ops;
+ struct kernfs_syscall_ops *scops = kernfs_root(kn)->syscall_ops;
+ int ret;
- if (!kdops || !kdops->rmdir)
+ if (!scops || !scops->rmdir)
return -EPERM;
- return kdops->rmdir(kn);
+ 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 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;
+ struct kernfs_syscall_ops *scops = kernfs_root(kn)->syscall_ops;
+ int ret;
- if (!kdops || !kdops->rename)
+ if (!scops || !scops->rename)
return -EPERM;
- return kdops->rename(kn, new_parent, new_dentry->d_name.name);
+ 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 = {
return pos->parent;
}
-static void __kernfs_remove(struct kernfs_addrm_cxt *acxt,
- struct kernfs_node *kn)
+/**
+ * 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, *next;
+ struct kernfs_node *pos;
- if (!kn)
+ 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);
- next = NULL;
+ /* 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 = next;
- next = kernfs_next_descendant_post(pos, kn);
- if (pos)
- kernfs_remove_one(acxt, pos);
- } while (next);
+ 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) {
+ 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);
}
/**
*/
void kernfs_remove(struct kernfs_node *kn)
{
- struct kernfs_addrm_cxt acxt;
+ mutex_lock(&kernfs_mutex);
+ __kernfs_remove(kn);
+ mutex_unlock(&kernfs_mutex);
+}
- kernfs_addrm_start(&acxt);
- __kernfs_remove(&acxt, kn);
- kernfs_addrm_finish(&acxt);
+/**
+ * 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;
}
/**
int kernfs_remove_by_name_ns(struct kernfs_node *parent, const char *name,
const void *ns)
{
- struct kernfs_addrm_cxt acxt;
struct kernfs_node *kn;
if (!parent) {
return -ENOENT;
}
- kernfs_addrm_start(&acxt);
+ mutex_lock(&kernfs_mutex);
kn = kernfs_find_ns(parent, name, ns);
if (kn)
- __kernfs_remove(&acxt, kn);
+ __kernfs_remove(kn);
- kernfs_addrm_finish(&acxt);
+ mutex_unlock(&kernfs_mutex);
if (kn)
return 0;
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 ((kn->flags | new_parent->flags) & KERNFS_REMOVED)
+ if (!kernfs_active(kn) || !kernfs_active(new_parent))
goto out;
error = 0;
new_name = kstrdup(new_name, GFP_KERNEL);
if (!new_name)
goto out;
-
- if (kn->flags & KERNFS_STATIC_NAME)
- kn->flags &= ~KERNFS_STATIC_NAME;
- else
- kfree(kn->name);
-
- kn->name = new_name;
+ } else {
+ new_name = NULL;
}
/*
*/
kernfs_unlink_sibling(kn);
kernfs_get(new_parent);
- kernfs_put(kn->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) {
+ if (!(kn->flags & KERNFS_STATIC_NAME))
+ old_name = kn->name;
+ kn->flags &= ~KERNFS_STATIC_NAME;
+ kn->name = new_name;
+ }
+
+ spin_unlock_irq(&kernfs_rename_lock);
+
kn->hash = kernfs_name_hash(kn->name, kn->ns);
- kn->parent = new_parent;
kernfs_link_sibling(kn);
+ kernfs_put(old_parent);
+ kfree(old_name);
+
error = 0;
out:
mutex_unlock(&kernfs_mutex);
struct kernfs_node *parent, loff_t hash, struct kernfs_node *pos)
{
if (pos) {
- int valid = !(pos->flags & KERNFS_REMOVED) &&
+ int valid = kernfs_active(pos) &&
pos->parent == parent && hash == pos->hash;
kernfs_put(pos);
if (!valid)
break;
}
}
- /* Skip over entries in the wrong namespace */
- while (pos && pos->ns != ns) {
+ /* 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;
struct kernfs_node *parent, ino_t ino, struct kernfs_node *pos)
{
pos = kernfs_dir_pos(ns, parent, ino, pos);
- if (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);
+ } while (pos && (!kernfs_active(pos) || pos->ns != ns));
+ }
return pos;
}
projects / cascardo / linux.git / blobdiff