Btrfs: add a sanity test for btrfs_split_item

While looking at somebodys corruption I became completely convinced that
btrfs_split_item was broken, so I wrote this test to verify that it was working
as it was supposed to. Thankfully it appears to be working as intended, so just
add this test to make sure nobody breaks it in the future. Thanks,

Signed-off-by: Josef Bacik <[e-mail]>
Signed-off-by: Chris Mason <[e-mail]>

fs/btrfs/Makefile

···
 btrfs-$(CONFIG_BTRFS_FS_POSIX_ACL) += acl.o
 btrfs-$(CONFIG_BTRFS_FS_CHECK_INTEGRITY) += check-integrity.o
 
-btrfs-$(CONFIG_BTRFS_FS_RUN_SANITY_TESTS) += tests/free-space-tests.o
+btrfs-$(CONFIG_BTRFS_FS_RUN_SANITY_TESTS) += tests/free-space-tests.o \
+	tests/extent-buffer-tests.o

fs/btrfs/ctree.h

···
 	int ref_cows;
 	int track_dirty;
 	int in_radix;
-
+#ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
+	int dummy_root;
+#endif
 	u64 defrag_trans_start;
 	struct btrfs_key defrag_progress;
 	struct btrfs_key defrag_max;

fs/btrfs/disk-io.c

···
 	atomic_set(&root->refs, 1);
 	root->log_transid = 0;
 	root->last_log_commit = 0;
-	extent_io_tree_init(&root->dirty_log_pages,
-			     fs_info->btree_inode->i_mapping);
+	if (fs_info)
+		extent_io_tree_init(&root->dirty_log_pages,
+				     fs_info->btree_inode->i_mapping);
 
 	memset(&root->root_key, 0, sizeof(root->root_key));
 	memset(&root->root_item, 0, sizeof(root->root_item));
 	memset(&root->defrag_progress, 0, sizeof(root->defrag_progress));
 	memset(&root->root_kobj, 0, sizeof(root->root_kobj));
-	root->defrag_trans_start = fs_info->generation;
+	if (fs_info)
+		root->defrag_trans_start = fs_info->generation;
+	else
+		root->defrag_trans_start = 0;
 	init_completion(&root->kobj_unregister);
 	root->defrag_running = 0;
 	root->root_key.objectid = objectid;
···
 		root->fs_info = fs_info;
 	return root;
 }
+
+#ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
+/* Should only be used by the testing infrastructure */
+struct btrfs_root *btrfs_alloc_dummy_root(void)
+{
+	struct btrfs_root *root;
+
+	root = btrfs_alloc_root(NULL);
+	if (!root)
+		return ERR_PTR(-ENOMEM);
+	__setup_root(4096, 4096, 4096, 4096, root, NULL, 1);
+	root->dummy_root = 1;
+
+	return root;
+}
+#endif
 
 struct btrfs_root *btrfs_create_tree(struct btrfs_trans_handle *trans,
 				     struct btrfs_fs_info *fs_info,
···
 
 void btrfs_mark_buffer_dirty(struct extent_buffer *buf)
 {
-	struct btrfs_root *root = BTRFS_I(buf->pages[0]->mapping->host)->root;
+	struct btrfs_root *root;
 	u64 transid = btrfs_header_generation(buf);
 	int was_dirty;
 
+#ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
+	/*
+	 * This is a fast path so only do this check if we have sanity tests
+	 * enabled.  Normal people shouldn't be marking dummy buffers as dirty
+	 * outside of the sanity tests.
+	 */
+	if (unlikely(test_bit(EXTENT_BUFFER_DUMMY, &buf->bflags)))
+		return;
+#endif
+	root = BTRFS_I(buf->pages[0]->mapping->host)->root;
 	btrfs_assert_tree_locked(buf);
 	if (transid != root->fs_info->generation)
 		WARN(1, KERN_CRIT "btrfs transid mismatch buffer %llu, "

fs/btrfs/disk-io.h

···
 				 struct btrfs_root *root);
 void btrfs_free_fs_root(struct btrfs_root *root);
 
+#ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
+struct btrfs_root *btrfs_alloc_dummy_root(void);
+#endif
+
 /*
  * This function is used to grab the root, and avoid it is freed when we
  * access it. But it doesn't ensure that the tree is not dropped.

fs/btrfs/super.c

···
 
 static int btrfs_run_sanity_tests(void)
 {
-	return btrfs_test_free_space_cache();
+	int ret;
+
+	ret = btrfs_test_free_space_cache();
+	if (ret)
+		return ret;
+	return btrfs_test_extent_buffer_operations();
 }
 
 static int __init init_btrfs_fs(void)

fs/btrfs/tests/btrfs-tests.h

···
 #define test_msg(fmt, ...) pr_info("btrfs: selftest: " fmt, ##__VA_ARGS__)
 
 int btrfs_test_free_space_cache(void);
+int btrfs_test_extent_buffer_operations(void);
 #else
 static inline int btrfs_test_free_space_cache(void)
+{
+	return 0;
+}
+static inline int btrfs_test_extent_buffer_operations(void)
 {
 	return 0;
 }

fs/btrfs/tests/extent-buffer-tests.c

···
+/*
+ * Copyright (C) 2013 Fusion IO.  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 <linux/slab.h>
+#include "btrfs-tests.h"
+#include "../ctree.h"
+#include "../extent_io.h"
+#include "../disk-io.h"
+
+static int test_btrfs_split_item(void)
+{
+	struct btrfs_path *path;
+	struct btrfs_root *root;
+	struct extent_buffer *eb;
+	struct btrfs_item *item;
+	char *value = "mary had a little lamb";
+	char *split1 = "mary had a little";
+	char *split2 = " lamb";
+	char *split3 = "mary";
+	char *split4 = " had a little";
+	char buf[32];
+	struct btrfs_key key;
+	u32 value_len = strlen(value);
+	int ret = 0;
+
+	test_msg("Running btrfs_split_item tests\n");
+
+	root = btrfs_alloc_dummy_root();
+	if (IS_ERR(root)) {
+		test_msg("Could not allocate root\n");
+		return PTR_ERR(root);
+	}
+
+	path = btrfs_alloc_path();
+	if (!path) {
+		test_msg("Could not allocate path\n");
+		kfree(root);
+		return -ENOMEM;
+	}
+
+	path->nodes[0] = eb = alloc_dummy_extent_buffer(0, 4096);
+	if (!eb) {
+		test_msg("Could not allocate dummy buffer\n");
+		ret = -ENOMEM;
+		goto out;
+	}
+	path->slots[0] = 0;
+
+	key.objectid = 0;
+	key.type = BTRFS_EXTENT_CSUM_KEY;
+	key.offset = 0;
+
+	setup_items_for_insert(root, path, &key, &value_len, value_len,
+			       value_len + sizeof(struct btrfs_item), 1);
+	item = btrfs_item_nr(0);
+	write_extent_buffer(eb, value, btrfs_item_ptr_offset(eb, 0),
+			    value_len);
+
+	key.offset = 3;
+
+	/*
+	 * Passing NULL trans here should be safe because we have plenty of
+	 * space in this leaf to split the item without having to split the
+	 * leaf.
+	 */
+	ret = btrfs_split_item(NULL, root, path, &key, 17);
+	if (ret) {
+		test_msg("Split item failed %d\n", ret);
+		goto out;
+	}
+
+	/*
+	 * Read the first slot, it should have the original key and contain only
+	 * 'mary had a little'
+	 */
+	btrfs_item_key_to_cpu(eb, &key, 0);
+	if (key.objectid != 0 || key.type != BTRFS_EXTENT_CSUM_KEY ||
+	    key.offset != 0) {
+		test_msg("Invalid key at slot 0\n");
+		ret = -EINVAL;
+		goto out;
+	}
+
+	item = btrfs_item_nr(0);
+	if (btrfs_item_size(eb, item) != strlen(split1)) {
+		test_msg("Invalid len in the first split\n");
+		ret = -EINVAL;
+		goto out;
+	}
+
+	read_extent_buffer(eb, buf, btrfs_item_ptr_offset(eb, 0),
+			   strlen(split1));
+	if (memcmp(buf, split1, strlen(split1))) {
+		test_msg("Data in the buffer doesn't match what it should "
+			 "in the first split have='%.*s' want '%s'\n",
+			 (int)strlen(split1), buf, split1);
+		ret = -EINVAL;
+		goto out;
+	}
+
+	btrfs_item_key_to_cpu(eb, &key, 1);
+	if (key.objectid != 0 || key.type != BTRFS_EXTENT_CSUM_KEY ||
+	    key.offset != 3) {
+		test_msg("Invalid key at slot 1\n");
+		ret = -EINVAL;
+		goto out;
+	}
+
+	item = btrfs_item_nr(1);
+	if (btrfs_item_size(eb, item) != strlen(split2)) {
+		test_msg("Invalid len in the second split\n");
+		ret = -EINVAL;
+		goto out;
+	}
+
+	read_extent_buffer(eb, buf, btrfs_item_ptr_offset(eb, 1),
+			   strlen(split2));
+	if (memcmp(buf, split2, strlen(split2))) {
+		test_msg("Data in the buffer doesn't match what it should "
+			 "in the second split\n");
+		ret = -EINVAL;
+		goto out;
+	}
+
+	key.offset = 1;
+	/* Do it again so we test memmoving the other items in the leaf */
+	ret = btrfs_split_item(NULL, root, path, &key, 4);
+	if (ret) {
+		test_msg("Second split item failed %d\n", ret);
+		goto out;
+	}
+
+	btrfs_item_key_to_cpu(eb, &key, 0);
+	if (key.objectid != 0 || key.type != BTRFS_EXTENT_CSUM_KEY ||
+	    key.offset != 0) {
+		test_msg("Invalid key at slot 0\n");
+		ret = -EINVAL;
+		goto out;
+	}
+
+	item = btrfs_item_nr(0);
+	if (btrfs_item_size(eb, item) != strlen(split3)) {
+		test_msg("Invalid len in the first split\n");
+		ret = -EINVAL;
+		goto out;
+	}
+
+	read_extent_buffer(eb, buf, btrfs_item_ptr_offset(eb, 0),
+			   strlen(split3));
+	if (memcmp(buf, split3, strlen(split3))) {
+		test_msg("Data in the buffer doesn't match what it should "
+			 "in the third split");
+		ret = -EINVAL;
+		goto out;
+	}
+
+	btrfs_item_key_to_cpu(eb, &key, 1);
+	if (key.objectid != 0 || key.type != BTRFS_EXTENT_CSUM_KEY ||
+	    key.offset != 1) {
+		test_msg("Invalid key at slot 1\n");
+		ret = -EINVAL;
+		goto out;
+	}
+
+	item = btrfs_item_nr(1);
+	if (btrfs_item_size(eb, item) != strlen(split4)) {
+		test_msg("Invalid len in the second split\n");
+		ret = -EINVAL;
+		goto out;
+	}
+
+	read_extent_buffer(eb, buf, btrfs_item_ptr_offset(eb, 1),
+			   strlen(split4));
+	if (memcmp(buf, split4, strlen(split4))) {
+		test_msg("Data in the buffer doesn't match what it should "
+			 "in the fourth split\n");
+		ret = -EINVAL;
+		goto out;
+	}
+
+	btrfs_item_key_to_cpu(eb, &key, 2);
+	if (key.objectid != 0 || key.type != BTRFS_EXTENT_CSUM_KEY ||
+	    key.offset != 3) {
+		test_msg("Invalid key at slot 2\n");
+		ret = -EINVAL;
+		goto out;
+	}
+
+	item = btrfs_item_nr(2);
+	if (btrfs_item_size(eb, item) != strlen(split2)) {
+		test_msg("Invalid len in the second split\n");
+		ret = -EINVAL;
+		goto out;
+	}
+
+	read_extent_buffer(eb, buf, btrfs_item_ptr_offset(eb, 2),
+			   strlen(split2));
+	if (memcmp(buf, split2, strlen(split2))) {
+		test_msg("Data in the buffer doesn't match what it should "
+			 "in the last chunk\n");
+		ret = -EINVAL;
+		goto out;
+	}
+out:
+	btrfs_free_path(path);
+	kfree(root);
+	return ret;
+}
+
+int btrfs_test_extent_buffer_operations(void)
+{
+	test_msg("Running extent buffer operation tests");
+	return test_btrfs_split_item();
+}