static struct dentry *__lock_parent(struct dentry *dentry)
{
struct dentry *parent;
- rcu_read_lock();
- spin_unlock(&dentry->d_lock);
again:
parent = READ_ONCE(dentry->d_parent);
spin_lock(&parent->d_lock);
spin_unlock(&parent->d_lock);
goto again;
}
- rcu_read_unlock();
if (parent != dentry)
spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
else
return NULL;
if (likely(spin_trylock(&parent->d_lock)))
return parent;
- return __lock_parent(dentry);
+ rcu_read_lock();
+ spin_unlock(&dentry->d_lock);
+ parent = __lock_parent(dentry);
+ rcu_read_unlock();
+ return parent;
+}
+
+/*
+ * Lock a dentry for feeding it to __dentry_kill().
+ * Called under rcu_read_lock() and dentry->d_lock; the former
+ * guarantees that nothing we access will be freed under us.
+ * Note that dentry is *not* protected from concurrent dentry_kill(),
+ * d_delete(), etc.
+ *
+ * Return false if dentry is busy. Otherwise, return true and have
+ * that dentry's inode and parent both locked.
+ */
+
+static bool lock_for_kill(struct dentry *dentry)
+{
+ struct inode *inode = dentry->d_inode;
+ struct dentry *parent = dentry->d_parent;
+
+ if (unlikely(dentry->d_lockref.count))
+ return false;
+
+ if (inode && unlikely(!spin_trylock(&inode->i_lock)))
+ goto slow;
+ if (dentry == parent)
+ return true;
+ if (likely(spin_trylock(&parent->d_lock)))
+ return true;
+
+ if (inode)
+ spin_unlock(&inode->i_lock);
+slow:
+ spin_unlock(&dentry->d_lock);
+
+ for (;;) {
+ if (inode)
+ spin_lock(&inode->i_lock);
+ parent = __lock_parent(dentry);
+ if (likely(inode == dentry->d_inode))
+ break;
+ if (inode)
+ spin_unlock(&inode->i_lock);
+ inode = dentry->d_inode;
+ spin_unlock(&dentry->d_lock);
+ if (parent)
+ spin_unlock(&parent->d_lock);
+ }
+ if (likely(!dentry->d_lockref.count))
+ return true;
+ if (inode)
+ spin_unlock(&inode->i_lock);
+ if (parent)
+ spin_unlock(&parent->d_lock);
+ return false;
}
static inline bool retain_dentry(struct dentry *dentry)
static struct dentry *dentry_kill(struct dentry *dentry)
__releases(dentry->d_lock)
{
- struct inode *inode = dentry->d_inode;
- struct dentry *parent = NULL;
- if (inode && unlikely(!spin_trylock(&inode->i_lock)))
- goto slow_positive;
-
- if (!IS_ROOT(dentry)) {
- parent = dentry->d_parent;
- if (unlikely(!spin_trylock(&parent->d_lock))) {
- parent = __lock_parent(dentry);
- if (likely(inode || !dentry->d_inode))
- goto got_locks;
- /* negative that became positive */
- if (parent)
- spin_unlock(&parent->d_lock);
- inode = dentry->d_inode;
- goto slow_positive;
- }
- }
dentry->d_lockref.count--;
- __dentry_kill(dentry);
- return parent;
-
-slow_positive:
- spin_unlock(&dentry->d_lock);
- spin_lock(&inode->i_lock);
- spin_lock(&dentry->d_lock);
- parent = lock_parent(dentry);
-got_locks:
- dentry->d_lockref.count--;
- if (likely(dentry->d_lockref.count == 0)) {
+ rcu_read_lock();
+ if (likely(lock_for_kill(dentry))) {
+ struct dentry *parent = dentry->d_parent;
+ rcu_read_unlock();
__dentry_kill(dentry);
- return parent;
+ return parent != dentry ? parent : NULL;
}
- /* we are keeping it, after all */
- if (inode)
- spin_unlock(&inode->i_lock);
- if (parent)
- spin_unlock(&parent->d_lock);
+ rcu_read_unlock();
spin_unlock(&dentry->d_lock);
return NULL;
}
}
EXPORT_SYMBOL(d_prune_aliases);
-/*
- * Lock a dentry from shrink list.
- * Called under rcu_read_lock() and dentry->d_lock; the former
- * guarantees that nothing we access will be freed under us.
- * Note that dentry is *not* protected from concurrent dentry_kill(),
- * d_delete(), etc.
- *
- * Return false if dentry has been disrupted or grabbed, leaving
- * the caller to kick it off-list. Otherwise, return true and have
- * that dentry's inode and parent both locked.
- */
-static bool shrink_lock_dentry(struct dentry *dentry)
-{
- struct inode *inode;
- struct dentry *parent;
-
- if (dentry->d_lockref.count)
- return false;
-
- inode = dentry->d_inode;
- if (inode && unlikely(!spin_trylock(&inode->i_lock))) {
- spin_unlock(&dentry->d_lock);
- spin_lock(&inode->i_lock);
- spin_lock(&dentry->d_lock);
- if (unlikely(dentry->d_lockref.count))
- goto out;
- /* changed inode means that somebody had grabbed it */
- if (unlikely(inode != dentry->d_inode))
- goto out;
- }
-
- parent = dentry->d_parent;
- if (IS_ROOT(dentry) || likely(spin_trylock(&parent->d_lock)))
- return true;
-
- spin_unlock(&dentry->d_lock);
- spin_lock(&parent->d_lock);
- if (unlikely(parent != dentry->d_parent)) {
- spin_unlock(&parent->d_lock);
- spin_lock(&dentry->d_lock);
- goto out;
- }
- spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
- if (likely(!dentry->d_lockref.count))
- return true;
- spin_unlock(&parent->d_lock);
-out:
- if (inode)
- spin_unlock(&inode->i_lock);
- return false;
-}
-
static inline void shrink_kill(struct dentry *victim, struct list_head *list)
{
struct dentry *parent = victim->d_parent;
dentry = list_entry(list->prev, struct dentry, d_lru);
spin_lock(&dentry->d_lock);
rcu_read_lock();
- if (!shrink_lock_dentry(dentry)) {
+ if (!lock_for_kill(dentry)) {
bool can_free;
rcu_read_unlock();
d_shrink_del(dentry);
d_walk(parent, &data, select_collect2);
if (data.victim) {
spin_lock(&data.victim->d_lock);
- if (!shrink_lock_dentry(data.victim)) {
+ if (!lock_for_kill(data.victim)) {
spin_unlock(&data.victim->d_lock);
rcu_read_unlock();
} else {
projects / linux-2.6-block.git / blobdiff