1 files changed, 245 insertions, 35 deletions

diff --git a/fs/dcache.c b/fs/dcache.c
index 19b751806789..ad4a542e9bab 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -111,6 +111,17 @@ static inline struct hlist_bl_head *d_hash(const struct dentry *parent,
 	return dentry_hashtable + hash_32(hash, d_hash_shift);
 }
 
+#define IN_LOOKUP_SHIFT 10
+static struct hlist_bl_head in_lookup_hashtable[1 << IN_LOOKUP_SHIFT];
+
+static inline struct hlist_bl_head *in_lookup_hash(const struct dentry *parent,
+					unsigned int hash)
+{
+	hash += (unsigned long) parent / L1_CACHE_BYTES;
+	return in_lookup_hashtable + hash_32(hash, IN_LOOKUP_SHIFT);
+}
+
+
 /* Statistics gathering. */
 struct dentry_stat_t dentry_stat = {
 	.age_limit = 45,
@@ -761,6 +772,8 @@ repeat:
 	/* Slow case: now with the dentry lock held */
 	rcu_read_unlock();
 
+	WARN_ON(d_in_lookup(dentry));
+
 	/* Unreachable? Get rid of it */
 	if (unlikely(d_unhashed(dentry)))
 		goto kill_it;
@@ -1558,7 +1571,11 @@ struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name)
 	 * be overwriting an internal NUL character
 	 */
 	dentry->d_iname[DNAME_INLINE_LEN-1] = 0;
-	if (name->len > DNAME_INLINE_LEN-1) {
+	if (unlikely(!name)) {
+		static const struct qstr anon = QSTR_INIT("/", 1);
+		name = &anon;
+		dname = dentry->d_iname;
+	} else if (name->len > DNAME_INLINE_LEN-1) {
 		size_t size = offsetof(struct external_name, name[1]);
 		struct external_name *p = kmalloc(size + name->len,
 						  GFP_KERNEL_ACCOUNT);
@@ -1745,6 +1762,7 @@ type_determined:
 static void __d_instantiate(struct dentry *dentry, struct inode *inode)
 {
 	unsigned add_flags = d_flags_for_inode(inode);
+	WARN_ON(d_in_lookup(dentry));
 
 	spin_lock(&dentry->d_lock);
 	hlist_add_head(&dentry->d_u.d_alias, &inode->i_dentry);
@@ -1774,11 +1792,11 @@ void d_instantiate(struct dentry *entry, struct inode * inode)
 {
 	BUG_ON(!hlist_unhashed(&entry->d_u.d_alias));
 	if (inode) {
+		security_d_instantiate(entry, inode);
 		spin_lock(&inode->i_lock);
 		__d_instantiate(entry, inode);
 		spin_unlock(&inode->i_lock);
 	}
-	security_d_instantiate(entry, inode);
 }
 EXPORT_SYMBOL(d_instantiate);
 
@@ -1795,6 +1813,7 @@ int d_instantiate_no_diralias(struct dentry *entry, struct inode *inode)
 {
 	BUG_ON(!hlist_unhashed(&entry->d_u.d_alias));
 
+	security_d_instantiate(entry, inode);
 	spin_lock(&inode->i_lock);
 	if (S_ISDIR(inode->i_mode) && !hlist_empty(&inode->i_dentry)) {
 		spin_unlock(&inode->i_lock);
@@ -1803,7 +1822,6 @@ int d_instantiate_no_diralias(struct dentry *entry, struct inode *inode)
 	}
 	__d_instantiate(entry, inode);
 	spin_unlock(&inode->i_lock);
-	security_d_instantiate(entry, inode);
 
 	return 0;
 }
@@ -1814,9 +1832,7 @@ struct dentry *d_make_root(struct inode *root_inode)
 	struct dentry *res = NULL;
 
 	if (root_inode) {
-		static const struct qstr name = QSTR_INIT("/", 1);
-
-		res = __d_alloc(root_inode->i_sb, &name);
+		res = __d_alloc(root_inode->i_sb, NULL);
 		if (res)
 			d_instantiate(res, root_inode);
 		else
@@ -1857,7 +1873,6 @@ EXPORT_SYMBOL(d_find_any_alias);
 
 static struct dentry *__d_obtain_alias(struct inode *inode, int disconnected)
 {
-	static const struct qstr anonstring = QSTR_INIT("/", 1);
 	struct dentry *tmp;
 	struct dentry *res;
 	unsigned add_flags;
@@ -1871,12 +1886,13 @@ static struct dentry *__d_obtain_alias(struct inode *inode, int disconnected)
 	if (res)
 		goto out_iput;
 
-	tmp = __d_alloc(inode->i_sb, &anonstring);
+	tmp = __d_alloc(inode->i_sb, NULL);
 	if (!tmp) {
 		res = ERR_PTR(-ENOMEM);
 		goto out_iput;
 	}
 
+	security_d_instantiate(tmp, inode);
 	spin_lock(&inode->i_lock);
 	res = __d_find_any_alias(inode);
 	if (res) {
@@ -1899,13 +1915,10 @@ static struct dentry *__d_obtain_alias(struct inode *inode, int disconnected)
 	hlist_bl_unlock(&tmp->d_sb->s_anon);
 	spin_unlock(&tmp->d_lock);
 	spin_unlock(&inode->i_lock);
-	security_d_instantiate(tmp, inode);
 
 	return tmp;
 
  out_iput:
-	if (res && !IS_ERR(res))
-		security_d_instantiate(res, inode);
 	iput(inode);
 	return res;
 }
@@ -1974,28 +1987,36 @@ EXPORT_SYMBOL(d_obtain_root);
 struct dentry *d_add_ci(struct dentry *dentry, struct inode *inode,
 			struct qstr *name)
 {
-	struct dentry *found;
-	struct dentry *new;
+	struct dentry *found, *res;
 
 	/*
 	 * First check if a dentry matching the name already exists,
 	 * if not go ahead and create it now.
 	 */
 	found = d_hash_and_lookup(dentry->d_parent, name);
-	if (!found) {
-		new = d_alloc(dentry->d_parent, name);
-		if (!new) {
-			found = ERR_PTR(-ENOMEM);
-		} else {
-			found = d_splice_alias(inode, new);
-			if (found) {
-				dput(new);
-				return found;
-			}
-			return new;
+	if (found) {
+		iput(inode);
+		return found;
+	}
+	if (d_in_lookup(dentry)) {
+		found = d_alloc_parallel(dentry->d_parent, name,
+					dentry->d_wait);
+		if (IS_ERR(found) || !d_in_lookup(found)) {
+			iput(inode);
+			return found;
 		}
+	} else {
+		found = d_alloc(dentry->d_parent, name);
+		if (!found) {
+			iput(inode);
+			return ERR_PTR(-ENOMEM);
+		} 
+	}
+	res = d_splice_alias(inode, found);
+	if (res) {
+		dput(found);
+		return res;
 	}
-	iput(inode);
 	return found;
 }
 EXPORT_SYMBOL(d_add_ci);
@@ -2362,17 +2383,194 @@ void d_rehash(struct dentry * entry)
 }
 EXPORT_SYMBOL(d_rehash);
 
+static inline unsigned start_dir_add(struct inode *dir)
+{
+
+	for (;;) {
+		unsigned n = dir->i_dir_seq;
+		if (!(n & 1) && cmpxchg(&dir->i_dir_seq, n, n + 1) == n)
+			return n;
+		cpu_relax();
+	}
+}
+
+static inline void end_dir_add(struct inode *dir, unsigned n)
+{
+	smp_store_release(&dir->i_dir_seq, n + 2);
+}
+
+static void d_wait_lookup(struct dentry *dentry)
+{
+	if (d_in_lookup(dentry)) {
+		DECLARE_WAITQUEUE(wait, current);
+		add_wait_queue(dentry->d_wait, &wait);
+		do {
+			set_current_state(TASK_UNINTERRUPTIBLE);
+			spin_unlock(&dentry->d_lock);
+			schedule();
+			spin_lock(&dentry->d_lock);
+		} while (d_in_lookup(dentry));
+	}
+}
+
+struct dentry *d_alloc_parallel(struct dentry *parent,
+				const struct qstr *name,
+				wait_queue_head_t *wq)
+{
+	unsigned int len = name->len;
+	unsigned int hash = name->hash;
+	const unsigned char *str = name->name;
+	struct hlist_bl_head *b = in_lookup_hash(parent, hash);
+	struct hlist_bl_node *node;
+	struct dentry *new = d_alloc(parent, name);
+	struct dentry *dentry;
+	unsigned seq, r_seq, d_seq;
+
+	if (unlikely(!new))
+		return ERR_PTR(-ENOMEM);
+
+retry:
+	rcu_read_lock();
+	seq = smp_load_acquire(&parent->d_inode->i_dir_seq) & ~1;
+	r_seq = read_seqbegin(&rename_lock);
+	dentry = __d_lookup_rcu(parent, name, &d_seq);
+	if (unlikely(dentry)) {
+		if (!lockref_get_not_dead(&dentry->d_lockref)) {
+			rcu_read_unlock();
+			goto retry;
+		}
+		if (read_seqcount_retry(&dentry->d_seq, d_seq)) {
+			rcu_read_unlock();
+			dput(dentry);
+			goto retry;
+		}
+		rcu_read_unlock();
+		dput(new);
+		return dentry;
+	}
+	if (unlikely(read_seqretry(&rename_lock, r_seq))) {
+		rcu_read_unlock();
+		goto retry;
+	}
+	hlist_bl_lock(b);
+	if (unlikely(parent->d_inode->i_dir_seq != seq)) {
+		hlist_bl_unlock(b);
+		rcu_read_unlock();
+		goto retry;
+	}
+	rcu_read_unlock();
+	/*
+	 * No changes for the parent since the beginning of d_lookup().
+	 * Since all removals from the chain happen with hlist_bl_lock(),
+	 * any potential in-lookup matches are going to stay here until
+	 * we unlock the chain.  All fields are stable in everything
+	 * we encounter.
+	 */
+	hlist_bl_for_each_entry(dentry, node, b, d_u.d_in_lookup_hash) {
+		if (dentry->d_name.hash != hash)
+			continue;
+		if (dentry->d_parent != parent)
+			continue;
+		if (d_unhashed(dentry))
+			continue;
+		if (parent->d_flags & DCACHE_OP_COMPARE) {
+			int tlen = dentry->d_name.len;
+			const char *tname = dentry->d_name.name;
+			if (parent->d_op->d_compare(parent, dentry, tlen, tname, name))
+				continue;
+		} else {
+			if (dentry->d_name.len != len)
+				continue;
+			if (dentry_cmp(dentry, str, len))
+				continue;
+		}
+		dget(dentry);
+		hlist_bl_unlock(b);
+		/* somebody is doing lookup for it right now; wait for it */
+		spin_lock(&dentry->d_lock);
+		d_wait_lookup(dentry);
+		/*
+		 * it's not in-lookup anymore; in principle we should repeat
+		 * everything from dcache lookup, but it's likely to be what
+		 * d_lookup() would've found anyway.  If it is, just return it;
+		 * otherwise we really have to repeat the whole thing.
+		 */
+		if (unlikely(dentry->d_name.hash != hash))
+			goto mismatch;
+		if (unlikely(dentry->d_parent != parent))
+			goto mismatch;
+		if (unlikely(d_unhashed(dentry)))
+			goto mismatch;
+		if (parent->d_flags & DCACHE_OP_COMPARE) {
+			int tlen = dentry->d_name.len;
+			const char *tname = dentry->d_name.name;
+			if (parent->d_op->d_compare(parent, dentry, tlen, tname, name))
+				goto mismatch;
+		} else {
+			if (unlikely(dentry->d_name.len != len))
+				goto mismatch;
+			if (unlikely(dentry_cmp(dentry, str, len)))
+				goto mismatch;
+		}
+		/* OK, it *is* a hashed match; return it */
+		spin_unlock(&dentry->d_lock);
+		dput(new);
+		return dentry;
+	}
+	/* we can't take ->d_lock here; it's OK, though. */
+	new->d_flags |= DCACHE_PAR_LOOKUP;
+	new->d_wait = wq;
+	hlist_bl_add_head_rcu(&new->d_u.d_in_lookup_hash, b);
+	hlist_bl_unlock(b);
+	return new;
+mismatch:
+	spin_unlock(&dentry->d_lock);
+	dput(dentry);
+	goto retry;
+}
+EXPORT_SYMBOL(d_alloc_parallel);
+
+void __d_lookup_done(struct dentry *dentry)
+{
+	struct hlist_bl_head *b = in_lookup_hash(dentry->d_parent,
+						 dentry->d_name.hash);
+	hlist_bl_lock(b);
+	dentry->d_flags &= ~DCACHE_PAR_LOOKUP;
+	__hlist_bl_del(&dentry->d_u.d_in_lookup_hash);
+	wake_up_all(dentry->d_wait);
+	dentry->d_wait = NULL;
+	hlist_bl_unlock(b);
+	INIT_HLIST_NODE(&dentry->d_u.d_alias);
+	INIT_LIST_HEAD(&dentry->d_lru);
+}
+EXPORT_SYMBOL(__d_lookup_done);
 
 /* inode->i_lock held if inode is non-NULL */
 
 static inline void __d_add(struct dentry *dentry, struct inode *inode)
 {
+	struct inode *dir = NULL;
+	unsigned n;
+	spin_lock(&dentry->d_lock);
+	if (unlikely(d_in_lookup(dentry))) {
+		dir = dentry->d_parent->d_inode;
+		n = start_dir_add(dir);
+		__d_lookup_done(dentry);
+	}
 	if (inode) {
-		__d_instantiate(dentry, inode);
+		unsigned add_flags = d_flags_for_inode(inode);
+		hlist_add_head(&dentry->d_u.d_alias, &inode->i_dentry);
+		raw_write_seqcount_begin(&dentry->d_seq);
+		__d_set_inode_and_type(dentry, inode, add_flags);
+		raw_write_seqcount_end(&dentry->d_seq);
+		__fsnotify_d_instantiate(dentry);
+	}
+	_d_rehash(dentry);
+	if (dir)
+		end_dir_add(dir, n);
+	spin_unlock(&dentry->d_lock);
+	if (inode)
 		spin_unlock(&inode->i_lock);
-	}
-	security_d_instantiate(dentry, inode);
-	d_rehash(dentry);
 }
 
 /**
@@ -2386,8 +2584,10 @@ static inline void __d_add(struct dentry *dentry, struct inode *inode)
 
 void d_add(struct dentry *entry, struct inode *inode)
 {
-	if (inode)
+	if (inode) {
+		security_d_instantiate(entry, inode);
 		spin_lock(&inode->i_lock);
+	}
 	__d_add(entry, inode);
 }
 EXPORT_SYMBOL(d_add);
@@ -2597,6 +2797,8 @@ static void dentry_unlock_for_move(struct dentry *dentry, struct dentry *target)
 static void __d_move(struct dentry *dentry, struct dentry *target,
 		     bool exchange)
 {
+	struct inode *dir = NULL;
+	unsigned n;
 	if (!dentry->d_inode)
 		printk(KERN_WARNING "VFS: moving negative dcache entry\n");
 
@@ -2604,6 +2806,11 @@ static void __d_move(struct dentry *dentry, struct dentry *target,
 	BUG_ON(d_ancestor(target, dentry));
 
 	dentry_lock_for_move(dentry, target);
+	if (unlikely(d_in_lookup(target))) {
+		dir = target->d_parent->d_inode;
+		n = start_dir_add(dir);
+		__d_lookup_done(target);
+	}
 
 	write_seqcount_begin(&dentry->d_seq);
 	write_seqcount_begin_nested(&target->d_seq, DENTRY_D_LOCK_NESTED);
@@ -2653,6 +2860,8 @@ static void __d_move(struct dentry *dentry, struct dentry *target,
 	write_seqcount_end(&target->d_seq);
 	write_seqcount_end(&dentry->d_seq);
 
+	if (dir)
+		end_dir_add(dir, n);
 	dentry_unlock_for_move(dentry, target);
 }
 
@@ -2723,7 +2932,8 @@ struct dentry *d_ancestor(struct dentry *p1, struct dentry *p2)
 static int __d_unalias(struct inode *inode,
 		struct dentry *dentry, struct dentry *alias)
 {
-	struct mutex *m1 = NULL, *m2 = NULL;
+	struct mutex *m1 = NULL;
+	struct rw_semaphore *m2 = NULL;
 	int ret = -ESTALE;
 
 	/* If alias and dentry share a parent, then no extra locks required */
@@ -2734,15 +2944,15 @@ static int __d_unalias(struct inode *inode,
 	if (!mutex_trylock(&dentry->d_sb->s_vfs_rename_mutex))
 		goto out_err;
 	m1 = &dentry->d_sb->s_vfs_rename_mutex;
-	if (!inode_trylock(alias->d_parent->d_inode))
+	if (!inode_trylock_shared(alias->d_parent->d_inode))
 		goto out_err;
-	m2 = &alias->d_parent->d_inode->i_mutex;
+	m2 = &alias->d_parent->d_inode->i_rwsem;
 out_unalias:
 	__d_move(alias, dentry, false);
 	ret = 0;
 out_err:
 	if (m2)
-		mutex_unlock(m2);
+		up_read(m2);
 	if (m1)
 		mutex_unlock(m1);
 	return ret;
@@ -2781,6 +2991,7 @@ struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry)
 	if (!inode)
 		goto out;
 
+	security_d_instantiate(dentry, inode);
 	spin_lock(&inode->i_lock);
 	if (S_ISDIR(inode->i_mode)) {
 		struct dentry *new = __d_find_any_alias(inode);
@@ -2808,7 +3019,6 @@ struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry)
 			} else {
 				__d_move(new, dentry, false);
 				write_sequnlock(&rename_lock);
-				security_d_instantiate(new, inode);
 			}
 			iput(inode);
 			return new;