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 <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>

1 files changed, 34 insertions, 4 deletions

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index f724397b396b..db2095486a4f 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1229,14 +1229,18 @@ static void __setup_root(u32 nodesize, u32 leafsize, u32 sectorsize,
         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;
@@ -1253,6 +1257,22 @@ static struct btrfs_root *btrfs_alloc_root(struct btrfs_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,
                                      u64 objectid)
@@ -3670,10 +3690,20 @@ int btrfs_set_buffer_uptodate(struct extent_buffer *buf)
 
 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, "