16 files changed, 700 insertions, 37 deletions

diff --git a/fs/btrfs/Makefile b/fs/btrfs/Makefile
index f341a98031d2..6d1d0b93b1aa 100644
--- a/fs/btrfs/Makefile
+++ b/fs/btrfs/Makefile
@@ -16,4 +16,4 @@ btrfs-$(CONFIG_BTRFS_FS_CHECK_INTEGRITY) += check-integrity.o
 
 btrfs-$(CONFIG_BTRFS_FS_RUN_SANITY_TESTS) += tests/free-space-tests.o \
 	tests/extent-buffer-tests.o tests/btrfs-tests.o \
-	tests/extent-io-tests.o tests/inode-tests.o
+	tests/extent-io-tests.o tests/inode-tests.o tests/qgroup-tests.o
diff --git a/fs/btrfs/backref.c b/fs/btrfs/backref.c
index 10db21fa0926..f09aa18ab710 100644
--- a/fs/btrfs/backref.c
+++ b/fs/btrfs/backref.c
@@ -900,7 +900,11 @@ again:
 		goto out;
 	BUG_ON(ret == 0);
 
+#ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
+	if (trans && likely(trans->type != __TRANS_DUMMY)) {
+#else
 	if (trans) {
+#endif
 		/*
 		 * look if there are updates for this ref queued and lock the
 		 * head
diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index bbbe4f1c5086..d99d9651dd58 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -1506,6 +1506,10 @@ static inline int should_cow_block(struct btrfs_trans_handle *trans,
 				   struct btrfs_root *root,
 				   struct extent_buffer *buf)
 {
+#ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
+	if (unlikely(test_bit(BTRFS_ROOT_DUMMY_ROOT, &root->state)))
+		return 0;
+#endif
 	/* ensure we can see the force_cow */
 	smp_rmb();
 
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 06cc384933cc..4896d7a947eb 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1798,6 +1798,10 @@ struct btrfs_root {
 
 	u64 highest_objectid;
 
+#ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
+	u64 alloc_bytenr;
+#endif
+
 	u64 defrag_trans_start;
 	struct btrfs_key defrag_progress;
 	struct btrfs_key defrag_max;
@@ -4111,6 +4115,8 @@ static inline int btrfs_defrag_cancelled(struct btrfs_fs_info *fs_info)
 /* Sanity test specific functions */
 #ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
 void btrfs_test_destroy_inode(struct inode *inode);
+int btrfs_verify_qgroup_counts(struct btrfs_fs_info *fs_info, u64 qgroupid,
+			       u64 rfer, u64 excl);
 #endif
 
 #endif
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 77f92a32e230..0c0fa78ef452 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1110,6 +1110,11 @@ struct extent_buffer *btrfs_find_tree_block(struct btrfs_root *root,
 struct extent_buffer *btrfs_find_create_tree_block(struct btrfs_root *root,
 						 u64 bytenr, u32 blocksize)
 {
+#ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
+	if (unlikely(test_bit(BTRFS_ROOT_DUMMY_ROOT, &root->state)))
+		return alloc_test_extent_buffer(root->fs_info, bytenr,
+						blocksize);
+#endif
 	return alloc_extent_buffer(root->fs_info, bytenr, blocksize);
 }
 
@@ -1288,6 +1293,7 @@ struct btrfs_root *btrfs_alloc_dummy_root(void)
 		return ERR_PTR(-ENOMEM);
 	__setup_root(4096, 4096, 4096, 4096, root, NULL, 1);
 	set_bit(BTRFS_ROOT_DUMMY_ROOT, &root->state);
+	root->alloc_bytenr = 0;
 
 	return root;
 }
@@ -2089,7 +2095,7 @@ static void free_root_pointers(struct btrfs_fs_info *info, int chunk_root)
 		free_root_extent_buffers(info->chunk_root);
 }
 
-static void del_fs_roots(struct btrfs_fs_info *fs_info)
+void btrfs_free_fs_roots(struct btrfs_fs_info *fs_info)
 {
 	int ret;
 	struct btrfs_root *gang[8];
@@ -2969,7 +2975,7 @@ fail_qgroup:
 fail_trans_kthread:
 	kthread_stop(fs_info->transaction_kthread);
 	btrfs_cleanup_transaction(fs_info->tree_root);
-	del_fs_roots(fs_info);
+	btrfs_free_fs_roots(fs_info);
 fail_cleaner:
 	kthread_stop(fs_info->cleaner_kthread);
 
@@ -3504,8 +3510,10 @@ void btrfs_drop_and_free_fs_root(struct btrfs_fs_info *fs_info,
 	if (test_bit(BTRFS_FS_STATE_ERROR, &fs_info->fs_state))
 		btrfs_free_log(NULL, root);
 
-	__btrfs_remove_free_space_cache(root->free_ino_pinned);
-	__btrfs_remove_free_space_cache(root->free_ino_ctl);
+	if (root->free_ino_pinned)
+		__btrfs_remove_free_space_cache(root->free_ino_pinned);
+	if (root->free_ino_ctl)
+		__btrfs_remove_free_space_cache(root->free_ino_ctl);
 	free_fs_root(root);
 }
 
@@ -3655,7 +3663,7 @@ int close_ctree(struct btrfs_root *root)
 
 	btrfs_sysfs_remove_one(fs_info);
 
-	del_fs_roots(fs_info);
+	btrfs_free_fs_roots(fs_info);
 
 	btrfs_put_block_group_cache(fs_info);
 
diff --git a/fs/btrfs/disk-io.h b/fs/btrfs/disk-io.h
index 53059df350f8..23ce3ceba0a9 100644
--- a/fs/btrfs/disk-io.h
+++ b/fs/btrfs/disk-io.h
@@ -68,6 +68,7 @@ struct btrfs_root *btrfs_read_fs_root(struct btrfs_root *tree_root,
 int btrfs_init_fs_root(struct btrfs_root *root);
 int btrfs_insert_fs_root(struct btrfs_fs_info *fs_info,
 			 struct btrfs_root *root);
+void btrfs_free_fs_roots(struct btrfs_fs_info *fs_info);
 
 struct btrfs_root *btrfs_get_fs_root(struct btrfs_fs_info *fs_info,
 				     struct btrfs_key *key,
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 343eb10230a1..ddf16bfb9270 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -2992,6 +2992,10 @@ static int __btrfs_mod_ref(struct btrfs_trans_handle *trans,
 	int (*process_func)(struct btrfs_trans_handle *, struct btrfs_root *,
 			    u64, u64, u64, u64, u64, u64, int);
 
+#ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
+	if (unlikely(test_bit(BTRFS_ROOT_DUMMY_ROOT, &root->state)))
+		return 0;
+#endif
 	ref_root = btrfs_header_owner(buf);
 	nritems = btrfs_header_nritems(buf);
 	level = btrfs_header_level(buf);
@@ -6151,6 +6155,10 @@ int btrfs_free_extent(struct btrfs_trans_handle *trans, struct btrfs_root *root,
 	int ret;
 	struct btrfs_fs_info *fs_info = root->fs_info;
 
+#ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
+	if (unlikely(test_bit(BTRFS_ROOT_DUMMY_ROOT, &root->state)))
+		return 0;
+#endif
 	add_pinned_bytes(root->fs_info, num_bytes, owner, root_objectid);
 
 	/*
@@ -7157,6 +7165,15 @@ struct extent_buffer *btrfs_alloc_free_block(struct btrfs_trans_handle *trans,
 	bool skinny_metadata = btrfs_fs_incompat(root->fs_info,
 						 SKINNY_METADATA);
 
+#ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
+	if (unlikely(test_bit(BTRFS_ROOT_DUMMY_ROOT, &root->state))) {
+		buf = btrfs_init_new_buffer(trans, root, root->alloc_bytenr,
+					    blocksize, level);
+		if (!IS_ERR(buf))
+			root->alloc_bytenr += blocksize;
+		return buf;
+	}
+#endif
 	block_rsv = use_block_rsv(trans, root, blocksize);
 	if (IS_ERR(block_rsv))
 		return ERR_CAST(block_rsv);
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index a55580f4e611..8285ed0464fa 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -4549,6 +4549,53 @@ struct extent_buffer *find_extent_buffer(struct btrfs_fs_info *fs_info,
 	return NULL;
 }
 
+#ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
+struct extent_buffer *alloc_test_extent_buffer(struct btrfs_fs_info *fs_info,
+					       u64 start, unsigned long len)
+{
+	struct extent_buffer *eb, *exists = NULL;
+	int ret;
+
+	eb = find_extent_buffer(fs_info, start);
+	if (eb)
+		return eb;
+	eb = alloc_dummy_extent_buffer(start, len);
+	if (!eb)
+		return NULL;
+	eb->fs_info = fs_info;
+again:
+	ret = radix_tree_preload(GFP_NOFS & ~__GFP_HIGHMEM);
+	if (ret)
+		goto free_eb;
+	spin_lock(&fs_info->buffer_lock);
+	ret = radix_tree_insert(&fs_info->buffer_radix,
+				start >> PAGE_CACHE_SHIFT, eb);
+	spin_unlock(&fs_info->buffer_lock);
+	radix_tree_preload_end();
+	if (ret == -EEXIST) {
+		exists = find_extent_buffer(fs_info, start);
+		if (exists)
+			goto free_eb;
+		else
+			goto again;
+	}
+	check_buffer_tree_ref(eb);
+	set_bit(EXTENT_BUFFER_IN_TREE, &eb->bflags);
+
+	/*
+	 * We will free dummy extent buffer's if they come into
+	 * free_extent_buffer with a ref count of 2, but if we are using this we
+	 * want the buffers to stay in memory until we're done with them, so
+	 * bump the ref count again.
+	 */
+	atomic_inc(&eb->refs);
+	return eb;
+free_eb:
+	btrfs_release_extent_buffer(eb);
+	return exists;
+}
+#endif
+
 struct extent_buffer *alloc_extent_buffer(struct btrfs_fs_info *fs_info,
 					  u64 start, unsigned long len)
 {
diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
index c488b45237bf..8b63f2d46518 100644
--- a/fs/btrfs/extent_io.h
+++ b/fs/btrfs/extent_io.h
@@ -350,5 +350,7 @@ noinline u64 find_lock_delalloc_range(struct inode *inode,
 				      struct extent_io_tree *tree,
 				      struct page *locked_page, u64 *start,
 				      u64 *end, u64 max_bytes);
+struct extent_buffer *alloc_test_extent_buffer(struct btrfs_fs_info *fs_info,
+					       u64 start, unsigned long len);
 #endif
 #endif
diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
index 09b8cc83965c..73f706c9a342 100644
--- a/fs/btrfs/qgroup.c
+++ b/fs/btrfs/qgroup.c
@@ -246,6 +246,21 @@ static int del_relation_rb(struct btrfs_fs_info *fs_info,
 	return -ENOENT;
 }
 
+#ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
+int btrfs_verify_qgroup_counts(struct btrfs_fs_info *fs_info, u64 qgroupid,
+			       u64 rfer, u64 excl)
+{
+	struct btrfs_qgroup *qgroup;
+
+	qgroup = find_qgroup_rb(fs_info, qgroupid);
+	if (!qgroup)
+		return -EINVAL;
+	if (qgroup->rfer != rfer || qgroup->excl != excl)
+		return -EINVAL;
+	return 0;
+}
+#endif
+
 /*
  * The full config is read in one go, only called from open_ctree()
  * It doesn't use any locking, as at this point we're still single-threaded
@@ -524,6 +539,10 @@ static int add_qgroup_item(struct btrfs_trans_handle *trans,
 	struct extent_buffer *leaf;
 	struct btrfs_key key;
 
+#ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
+	if (unlikely(test_bit(BTRFS_ROOT_DUMMY_ROOT, &quota_root->state)))
+		return 0;
+#endif
 	path = btrfs_alloc_path();
 	if (!path)
 		return -ENOMEM;
@@ -673,6 +692,10 @@ static int update_qgroup_info_item(struct btrfs_trans_handle *trans,
 	int ret;
 	int slot;
 
+#ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
+	if (unlikely(test_bit(BTRFS_ROOT_DUMMY_ROOT, &root->state)))
+		return 0;
+#endif
 	key.objectid = 0;
 	key.type = BTRFS_QGROUP_INFO_KEY;
 	key.offset = qgroup->qgroupid;
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 8f7c03db1f8d..d80a2786f563 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -1895,6 +1895,9 @@ static int btrfs_run_sanity_tests(void)
 	if (ret)
 		goto out;
 	ret = btrfs_test_inodes();
+	if (ret)
+		goto out;
+	ret = btrfs_test_qgroups();
 out:
 	btrfs_destroy_test_fs();
 	return ret;
diff --git a/fs/btrfs/tests/btrfs-tests.c b/fs/btrfs/tests/btrfs-tests.c
index 757ef00a75a4..a5dcacb5df9c 100644
--- a/fs/btrfs/tests/btrfs-tests.c
+++ b/fs/btrfs/tests/btrfs-tests.c
@@ -21,6 +21,9 @@
 #include <linux/magic.h>
 #include "btrfs-tests.h"
 #include "../ctree.h"
+#include "../volumes.h"
+#include "../disk-io.h"
+#include "../qgroup.h"
 
 static struct vfsmount *test_mnt = NULL;
 
@@ -72,3 +75,97 @@ void btrfs_destroy_test_fs(void)
 	kern_unmount(test_mnt);
 	unregister_filesystem(&test_type);
 }
+
+struct btrfs_fs_info *btrfs_alloc_dummy_fs_info(void)
+{
+	struct btrfs_fs_info *fs_info = kzalloc(sizeof(struct btrfs_fs_info),
+						GFP_NOFS);
+
+	if (!fs_info)
+		return fs_info;
+	fs_info->fs_devices = kzalloc(sizeof(struct btrfs_fs_devices),
+				      GFP_NOFS);
+	if (!fs_info->fs_devices) {
+		kfree(fs_info);
+		return NULL;
+	}
+	fs_info->super_copy = kzalloc(sizeof(struct btrfs_super_block),
+				      GFP_NOFS);
+	if (!fs_info->super_copy) {
+		kfree(fs_info->fs_devices);
+		kfree(fs_info);
+		return NULL;
+	}
+
+	if (init_srcu_struct(&fs_info->subvol_srcu)) {
+		kfree(fs_info->fs_devices);
+		kfree(fs_info->super_copy);
+		kfree(fs_info);
+		return NULL;
+	}
+
+	spin_lock_init(&fs_info->buffer_lock);
+	spin_lock_init(&fs_info->qgroup_lock);
+	spin_lock_init(&fs_info->qgroup_op_lock);
+	spin_lock_init(&fs_info->super_lock);
+	spin_lock_init(&fs_info->fs_roots_radix_lock);
+	spin_lock_init(&fs_info->tree_mod_seq_lock);
+	mutex_init(&fs_info->qgroup_ioctl_lock);
+	mutex_init(&fs_info->qgroup_rescan_lock);
+	rwlock_init(&fs_info->tree_mod_log_lock);
+	fs_info->running_transaction = NULL;
+	fs_info->qgroup_tree = RB_ROOT;
+	fs_info->qgroup_ulist = NULL;
+	atomic64_set(&fs_info->tree_mod_seq, 0);
+	INIT_LIST_HEAD(&fs_info->dirty_qgroups);
+	INIT_LIST_HEAD(&fs_info->dead_roots);
+	INIT_LIST_HEAD(&fs_info->tree_mod_seq_list);
+	INIT_RADIX_TREE(&fs_info->buffer_radix, GFP_ATOMIC);
+	INIT_RADIX_TREE(&fs_info->fs_roots_radix, GFP_ATOMIC);
+	return fs_info;
+}
+
+static void btrfs_free_dummy_fs_info(struct btrfs_fs_info *fs_info)
+{
+	struct radix_tree_iter iter;
+	void **slot;
+
+	spin_lock(&fs_info->buffer_lock);
+restart:
+	radix_tree_for_each_slot(slot, &fs_info->buffer_radix, &iter, 0) {
+		struct extent_buffer *eb;
+
+		eb = radix_tree_deref_slot(slot);
+		if (!eb)
+			continue;
+		/* Shouldn't happen but that kind of thinking creates CVE's */
+		if (radix_tree_exception(eb)) {
+			if (radix_tree_deref_retry(eb))
+				goto restart;
+			continue;
+		}
+		spin_unlock(&fs_info->buffer_lock);
+		free_extent_buffer_stale(eb);
+		spin_lock(&fs_info->buffer_lock);
+	}
+	spin_unlock(&fs_info->buffer_lock);
+
+	btrfs_free_qgroup_config(fs_info);
+	btrfs_free_fs_roots(fs_info);
+	cleanup_srcu_struct(&fs_info->subvol_srcu);
+	kfree(fs_info->super_copy);
+	kfree(fs_info->fs_devices);
+	kfree(fs_info);
+}
+
+void btrfs_free_dummy_root(struct btrfs_root *root)
+{
+	if (!root)
+		return;
+	if (root->node)
+		free_extent_buffer(root->node);
+	if (root->fs_info)
+		btrfs_free_dummy_fs_info(root->fs_info);
+	kfree(root);
+}
+
diff --git a/fs/btrfs/tests/btrfs-tests.h b/fs/btrfs/tests/btrfs-tests.h
index 312560a9123d..fd3954224480 100644
--- a/fs/btrfs/tests/btrfs-tests.h
+++ b/fs/btrfs/tests/btrfs-tests.h
@@ -23,13 +23,18 @@
 
 #define test_msg(fmt, ...) pr_info("BTRFS: selftest: " fmt, ##__VA_ARGS__)
 
+struct btrfs_root;
+
 int btrfs_test_free_space_cache(void);
 int btrfs_test_extent_buffer_operations(void);
 int btrfs_test_extent_io(void);
 int btrfs_test_inodes(void);
+int btrfs_test_qgroups(void);
 int btrfs_init_test_fs(void);
 void btrfs_destroy_test_fs(void);
 struct inode *btrfs_new_test_inode(void);
+struct btrfs_fs_info *btrfs_alloc_dummy_fs_info(void);
+void btrfs_free_dummy_root(struct btrfs_root *root);
 #else
 static inline int btrfs_test_free_space_cache(void)
 {
@@ -54,6 +59,10 @@ static inline int btrfs_test_inodes(void)
 {
 	return 0;
 }
+static inline int btrfs_test_qgroups(void)
+{
+	return 0;
+}
 #endif
 
 #endif
diff --git a/fs/btrfs/tests/inode-tests.c b/fs/btrfs/tests/inode-tests.c
index 397d1f99a8eb..3ae0f5b8bb80 100644
--- a/fs/btrfs/tests/inode-tests.c
+++ b/fs/btrfs/tests/inode-tests.c
@@ -23,33 +23,6 @@
 #include "../extent_io.h"
 #include "../volumes.h"
 
-static struct btrfs_fs_info *alloc_dummy_fs_info(void)
-{
-	struct btrfs_fs_info *fs_info = kzalloc(sizeof(struct btrfs_fs_info),
-						GFP_NOFS);
-	if (!fs_info)
-		return fs_info;
-	fs_info->fs_devices = kzalloc(sizeof(struct btrfs_fs_devices),
-				      GFP_NOFS);
-	if (!fs_info->fs_devices) {
-		kfree(fs_info);
-		return NULL;
-	}
-	return fs_info;
-}
-static void free_dummy_root(struct btrfs_root *root)
-{
-	if (!root)
-		return;
-	if (root->fs_info) {
-		kfree(root->fs_info->fs_devices);
-		kfree(root->fs_info);
-	}
-	if (root->node)
-		free_extent_buffer(root->node);
-	kfree(root);
-}
-
 static void insert_extent(struct btrfs_root *root, u64 start, u64 len,
 			  u64 ram_bytes, u64 offset, u64 disk_bytenr,
 			  u64 disk_len, u32 type, u8 compression, int slot)
@@ -276,7 +249,7 @@ static noinline int test_btrfs_get_extent(void)
 	 * We do this since btrfs_get_extent wants to assign em->bdev to
 	 * root->fs_info->fs_devices->latest_bdev.
 	 */
-	root->fs_info = alloc_dummy_fs_info();
+	root->fs_info = btrfs_alloc_dummy_fs_info();
 	if (!root->fs_info) {
 		test_msg("Couldn't allocate dummy fs info\n");
 		goto out;
@@ -837,7 +810,7 @@ out:
 	if (!IS_ERR(em))
 		free_extent_map(em);
 	iput(inode);
-	free_dummy_root(root);
+	btrfs_free_dummy_root(root);
 	return ret;
 }
 
@@ -864,7 +837,7 @@ static int test_hole_first(void)
 		goto out;
 	}
 
-	root->fs_info = alloc_dummy_fs_info();
+	root->fs_info = btrfs_alloc_dummy_fs_info();
 	if (!root->fs_info) {
 		test_msg("Couldn't allocate dummy fs info\n");
 		goto out;
@@ -934,7 +907,7 @@ out:
 	if (!IS_ERR(em))
 		free_extent_map(em);
 	iput(inode);
-	free_dummy_root(root);
+	btrfs_free_dummy_root(root);
 	return ret;
 }
 
diff --git a/fs/btrfs/tests/qgroup-tests.c b/fs/btrfs/tests/qgroup-tests.c
new file mode 100644
index 000000000000..fa691b754aaf
--- /dev/null
+++ b/fs/btrfs/tests/qgroup-tests.c
@@ -0,0 +1,468 @@
+/*
+ * Copyright (C) 2013 Facebook.  All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License v2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public
+ * License along with this program; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 021110-1307, USA.
+ */
+
+#include "btrfs-tests.h"
+#include "../ctree.h"
+#include "../transaction.h"
+#include "../disk-io.h"
+#include "../qgroup.h"
+
+static void init_dummy_trans(struct btrfs_trans_handle *trans)
+{
+	memset(trans, 0, sizeof(*trans));
+	trans->transid = 1;
+	INIT_LIST_HEAD(&trans->qgroup_ref_list);
+	trans->type = __TRANS_DUMMY;
+}
+
+static int insert_normal_tree_ref(struct btrfs_root *root, u64 bytenr,
+				  u64 num_bytes, u64 parent, u64 root_objectid)
+{
+	struct btrfs_trans_handle trans;
+	struct btrfs_extent_item *item;
+	struct btrfs_extent_inline_ref *iref;
+	struct btrfs_tree_block_info *block_info;
+	struct btrfs_path *path;
+	struct extent_buffer *leaf;
+	struct btrfs_key ins;
+	u32 size = sizeof(*item) + sizeof(*iref) + sizeof(*block_info);
+	int ret;
+
+	init_dummy_trans(&trans);
+
+	ins.objectid = bytenr;
+	ins.type = BTRFS_EXTENT_ITEM_KEY;
+	ins.offset = num_bytes;
+
+	path = btrfs_alloc_path();
+	if (!path) {
+		test_msg("Couldn't allocate path\n");
+		return -ENOMEM;
+	}
+
+	path->leave_spinning = 1;
+	ret = btrfs_insert_empty_item(&trans, root, path, &ins, size);
+	if (ret) {
+		test_msg("Couldn't insert ref %d\n", ret);
+		btrfs_free_path(path);
+		return ret;
+	}
+
+	leaf = path->nodes[0];
+	item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_extent_item);
+	btrfs_set_extent_refs(leaf, item, 1);
+	btrfs_set_extent_generation(leaf, item, 1);
+	btrfs_set_extent_flags(leaf, item, BTRFS_EXTENT_FLAG_TREE_BLOCK);
+	block_info = (struct btrfs_tree_block_info *)(item + 1);
+	btrfs_set_tree_block_level(leaf, block_info, 1);
+	iref = (struct btrfs_extent_inline_ref *)(block_info + 1);
+	if (parent > 0) {
+		btrfs_set_extent_inline_ref_type(leaf, iref,
+						 BTRFS_SHARED_BLOCK_REF_KEY);
+		btrfs_set_extent_inline_ref_offset(leaf, iref, parent);
+	} else {
+		btrfs_set_extent_inline_ref_type(leaf, iref, BTRFS_TREE_BLOCK_REF_KEY);
+		btrfs_set_extent_inline_ref_offset(leaf, iref, root_objectid);
+	}
+	btrfs_free_path(path);
+	return 0;
+}
+
+static int add_tree_ref(struct btrfs_root *root, u64 bytenr, u64 num_bytes,
+			u64 parent, u64 root_objectid)
+{
+	struct btrfs_trans_handle trans;
+	struct btrfs_extent_item *item;
+	struct btrfs_path *path;
+	struct btrfs_key key;
+	u64 refs;
+	int ret;
+
+	init_dummy_trans(&trans);
+
+	key.objectid = bytenr;
+	key.type = BTRFS_EXTENT_ITEM_KEY;
+	key.offset = num_bytes;
+
+	path = btrfs_alloc_path();
+	if (!path) {
+		test_msg("Couldn't allocate path\n");
+		return -ENOMEM;
+	}
+
+	path->leave_spinning = 1;
+	ret = btrfs_search_slot(&trans, root, &key, path, 0, 1);
+	if (ret) {
+		test_msg("Couldn't find extent ref\n");
+		btrfs_free_path(path);
+		return ret;
+	}
+
+	item = btrfs_item_ptr(path->nodes[0], path->slots[0],
+			      struct btrfs_extent_item);
+	refs = btrfs_extent_refs(path->nodes[0], item);
+	btrfs_set_extent_refs(path->nodes[0], item, refs + 1);
+	btrfs_release_path(path);
+
+	key.objectid = bytenr;
+	if (parent) {
+		key.type = BTRFS_SHARED_BLOCK_REF_KEY;
+		key.offset = parent;
+	} else {
+		key.type = BTRFS_TREE_BLOCK_REF_KEY;
+		key.offset = root_objectid;
+	}
+
+	ret = btrfs_insert_empty_item(&trans, root, path, &key, 0);
+	if (ret)
+		test_msg("Failed to insert backref\n");
+	btrfs_free_path(path);
+	return ret;
+}
+
+static int remove_extent_item(struct btrfs_root *root, u64 bytenr,
+			      u64 num_bytes)
+{
+	struct btrfs_trans_handle trans;
+	struct btrfs_key key;
+	struct btrfs_path *path;
+	int ret;
+
+	init_dummy_trans(&trans);
+
+	key.objectid = bytenr;
+	key.type = BTRFS_EXTENT_ITEM_KEY;
+	key.offset = num_bytes;
+
+	path = btrfs_alloc_path();
+	if (!path) {
+		test_msg("Couldn't allocate path\n");
+		return -ENOMEM;
+	}
+	path->leave_spinning = 1;
+
+	ret = btrfs_search_slot(&trans, root, &key, path, -1, 1);
+	if (ret) {
+		test_msg("Didn't find our key %d\n", ret);
+		btrfs_free_path(path);
+		return ret;
+	}
+	btrfs_del_item(&trans, root, path);
+	btrfs_free_path(path);
+	return 0;
+}
+
+static int remove_extent_ref(struct btrfs_root *root, u64 bytenr,
+			     u64 num_bytes, u64 parent, u64 root_objectid)
+{
+	struct btrfs_trans_handle trans;
+	struct btrfs_extent_item *item;
+	struct btrfs_path *path;
+	struct btrfs_key key;
+	u64 refs;
+	int ret;
+
+	init_dummy_trans(&trans);
+
+	key.objectid = bytenr;
+	key.type = BTRFS_EXTENT_ITEM_KEY;
+	key.offset = num_bytes;
+
+	path = btrfs_alloc_path();
+	if (!path) {
+		test_msg("Couldn't allocate path\n");
+		return -ENOMEM;
+	}
+
+	path->leave_spinning = 1;
+	ret = btrfs_search_slot(&trans, root, &key, path, 0, 1);
+	if (ret) {
+		test_msg("Couldn't find extent ref\n");
+		btrfs_free_path(path);
+		return ret;
+	}
+
+	item = btrfs_item_ptr(path->nodes[0], path->slots[0],
+			      struct btrfs_extent_item);
+	refs = btrfs_extent_refs(path->nodes[0], item);
+	btrfs_set_extent_refs(path->nodes[0], item, refs - 1);
+	btrfs_release_path(path);
+
+	key.objectid = bytenr;
+	if (parent) {
+		key.type = BTRFS_SHARED_BLOCK_REF_KEY;
+		key.offset = parent;
+	} else {
+		key.type = BTRFS_TREE_BLOCK_REF_KEY;
+		key.offset = root_objectid;
+	}
+
+	ret = btrfs_search_slot(&trans, root, &key, path, -1, 1);
+	if (ret) {
+		test_msg("Couldn't find backref %d\n", ret);
+		btrfs_free_path(path);
+		return ret;
+	}
+	btrfs_del_item(&trans, root, path);
+	btrfs_free_path(path);
+	return ret;
+}
+
+static int test_no_shared_qgroup(struct btrfs_root *root)
+{
+	struct btrfs_trans_handle trans;
+	struct btrfs_fs_info *fs_info = root->fs_info;
+	int ret;
+
+	init_dummy_trans(&trans);
+
+	test_msg("Qgroup basic add\n");
+	ret = btrfs_create_qgroup(NULL, fs_info, 5, NULL);
+	if (ret) {
+		test_msg("Couldn't create a qgroup %d\n", ret);
+		return ret;
+	}
+
+	ret = btrfs_qgroup_record_ref(&trans, fs_info, 5, 4096, 4096,
+				      BTRFS_QGROUP_OPER_ADD_EXCL, 0);
+	if (ret) {
+		test_msg("Couldn't add space to a qgroup %d\n", ret);
+		return ret;
+	}
+
+	ret = insert_normal_tree_ref(root, 4096, 4096, 0, 5);
+	if (ret)
+		return ret;
+
+	ret = btrfs_delayed_qgroup_accounting(&trans, fs_info);
+	if (ret) {
+		test_msg("Delayed qgroup accounting failed %d\n", ret);
+		return ret;
+	}
+
+	if (btrfs_verify_qgroup_counts(fs_info, 5, 4096, 4096)) {
+		test_msg("Qgroup counts didn't match expected values\n");
+		return -EINVAL;
+	}
+
+	ret = remove_extent_item(root, 4096, 4096);
+	if (ret)
+		return -EINVAL;
+
+	ret = btrfs_qgroup_record_ref(&trans, fs_info, 5, 4096, 4096,
+				      BTRFS_QGROUP_OPER_SUB_EXCL, 0);
+	if (ret) {
+		test_msg("Couldn't remove space from the qgroup %d\n", ret);
+		return -EINVAL;
+	}
+
+	ret = btrfs_delayed_qgroup_accounting(&trans, fs_info);
+	if (ret) {
+		test_msg("Qgroup accounting failed %d\n", ret);
+		return -EINVAL;
+	}
+
+	if (btrfs_verify_qgroup_counts(fs_info, 5, 0, 0)) {
+		test_msg("Qgroup counts didn't match expected values\n");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+/*
+ * Add a ref for two different roots to make sure the shared value comes out
+ * right, also remove one of the roots and make sure the exclusive count is
+ * adjusted properly.
+ */
+static int test_multiple_refs(struct btrfs_root *root)
+{
+	struct btrfs_trans_handle trans;
+	struct btrfs_fs_info *fs_info = root->fs_info;
+	int ret;
+
+	init_dummy_trans(&trans);
+
+	test_msg("Qgroup multiple refs test\n");
+
+	/* We have 5 created already from the previous test */
+	ret = btrfs_create_qgroup(NULL, fs_info, 256, NULL);
+	if (ret) {
+		test_msg("Couldn't create a qgroup %d\n", ret);
+		return ret;
+	}
+
+	ret = insert_normal_tree_ref(root, 4096, 4096, 0, 5);
+	if (ret)
+		return ret;
+
+	ret = btrfs_qgroup_record_ref(&trans, fs_info, 5, 4096, 4096,
+				      BTRFS_QGROUP_OPER_ADD_EXCL, 0);
+	if (ret) {
+		test_msg("Couldn't add space to a qgroup %d\n", ret);
+		return ret;
+	}
+
+	ret = btrfs_delayed_qgroup_accounting(&trans, fs_info);
+	if (ret) {
+		test_msg("Delayed qgroup accounting failed %d\n", ret);
+		return ret;
+	}
+
+	if (btrfs_verify_qgroup_counts(fs_info, 5, 4096, 4096)) {
+		test_msg("Qgroup counts didn't match expected values\n");
+		return -EINVAL;
+	}
+
+	ret = add_tree_ref(root, 4096, 4096, 0, 256);
+	if (ret)
+		return ret;
+
+	ret = btrfs_qgroup_record_ref(&trans, fs_info, 256, 4096, 4096,
+				      BTRFS_QGROUP_OPER_ADD_SHARED, 0);
+	if (ret) {
+		test_msg("Qgroup record ref failed %d\n", ret);
+		return ret;
+	}
+
+	ret = btrfs_delayed_qgroup_accounting(&trans, fs_info);
+	if (ret) {
+		test_msg("Qgroup accounting failed %d\n", ret);
+		return ret;
+	}
+
+	if (btrfs_verify_qgroup_counts(fs_info, 5, 4096, 0)) {
+		test_msg("Qgroup counts didn't match expected values\n");
+		return -EINVAL;
+	}
+
+	if (btrfs_verify_qgroup_counts(fs_info, 256, 4096, 0)) {
+		test_msg("Qgroup counts didn't match expected values\n");
+		return -EINVAL;
+	}
+
+	ret = remove_extent_ref(root, 4096, 4096, 0, 256);
+	if (ret)
+		return ret;
+
+	ret = btrfs_qgroup_record_ref(&trans, fs_info, 256, 4096, 4096,
+				      BTRFS_QGROUP_OPER_SUB_SHARED, 0);
+	if (ret) {
+		test_msg("Qgroup record ref failed %d\n", ret);
+		return ret;
+	}
+
+	ret = btrfs_delayed_qgroup_accounting(&trans, fs_info);
+	if (ret) {
+		test_msg("Qgroup accounting failed %d\n", ret);
+		return ret;
+	}
+
+	if (btrfs_verify_qgroup_counts(fs_info, 256, 0, 0)) {
+		test_msg("Qgroup counts didn't match expected values\n");
+		return -EINVAL;
+	}
+
+	if (btrfs_verify_qgroup_counts(fs_info, 5, 4096, 4096)) {
+		test_msg("Qgroup counts didn't match expected values\n");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+int btrfs_test_qgroups(void)
+{
+	struct btrfs_root *root;
+	struct btrfs_root *tmp_root;
+	int ret = 0;
+
+	root = btrfs_alloc_dummy_root();
+	if (IS_ERR(root)) {
+		test_msg("Couldn't allocate root\n");
+		return PTR_ERR(root);
+	}
+
+	root->fs_info = btrfs_alloc_dummy_fs_info();
+	if (!root->fs_info) {
+		test_msg("Couldn't allocate dummy fs info\n");
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	/*
+	 * Can't use bytenr 0, some things freak out
+	 * *cough*backref walking code*cough*
+	 */
+	root->node = alloc_test_extent_buffer(root->fs_info, 4096, 4096);
+	if (!root->node) {
+		test_msg("Couldn't allocate dummy buffer\n");
+		ret = -ENOMEM;
+		goto out;
+	}
+	root->alloc_bytenr += 8192;
+
+	tmp_root = btrfs_alloc_dummy_root();
+	if (IS_ERR(tmp_root)) {
+		test_msg("Couldn't allocate a fs root\n");
+		ret = PTR_ERR(tmp_root);
+		goto out;
+	}
+
+	tmp_root->root_key.objectid = 5;
+	root->fs_info->fs_root = tmp_root;
+	ret = btrfs_insert_fs_root(root->fs_info, tmp_root);
+	if (ret) {
+		test_msg("Couldn't insert fs root %d\n", ret);
+		goto out;
+	}
+
+	tmp_root = btrfs_alloc_dummy_root();
+	if (IS_ERR(tmp_root)) {
+		test_msg("Couldn't allocate a fs root\n");
+		ret = PTR_ERR(tmp_root);
+		goto out;
+	}
+
+	tmp_root->root_key.objectid = 256;
+	ret = btrfs_insert_fs_root(root->fs_info, tmp_root);
+	if (ret) {
+		test_msg("Couldn't insert fs root %d\n", ret);
+		goto out;
+	}
+
+	/* We are using this root as our extent root */
+	root->fs_info->extent_root = root;
+
+	/*
+	 * Some of the paths we test assume we have a filled out fs_info, so we
+	 * just need to addt he root in there so we don't panic.
+	 */
+	root->fs_info->tree_root = root;
+	root->fs_info->quota_root = root;
+	root->fs_info->quota_enabled = 1;
+
+	test_msg("Running qgroup tests\n");
+	ret = test_no_shared_qgroup(root);
+	if (ret)
+		goto out;
+	ret = test_multiple_refs(root);
+out:
+	btrfs_free_dummy_root(root);
+	return ret;
+}
diff --git a/fs/btrfs/transaction.h b/fs/btrfs/transaction.h
index b57b924e8e03..7dd558ed0716 100644
--- a/fs/btrfs/transaction.h
+++ b/fs/btrfs/transaction.h
@@ -69,6 +69,7 @@ struct btrfs_transaction {
 #define __TRANS_ATTACH		(1U << 10)
 #define __TRANS_JOIN		(1U << 11)
 #define __TRANS_JOIN_NOLOCK	(1U << 12)
+#define __TRANS_DUMMY		(1U << 13)
 
 #define TRANS_USERSPACE		(__TRANS_USERSPACE | __TRANS_FREEZABLE)
 #define TRANS_START		(__TRANS_START | __TRANS_FREEZABLE)