Btrfs: init relocate extent_io_tree with a mapping

Dave reported a NULL pointer deref.  This is caused because he thought he'd be
smart and add sanity checks to the extent_io bit operations, but he didn't
expect a tree to have a NULL mapping.  To fix this we just need to init the
relocation's processed_blocks with the btree_inode->i_mapping.  Thanks,

Reported-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>

1 files changed, 5 insertions, 4 deletions

diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index 395b82031a42..4febca4fc2de 100644
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -4082,7 +4082,7 @@ out:
         return inode;
 }
 
-static struct reloc_control *alloc_reloc_control(void)
+static struct reloc_control *alloc_reloc_control(struct btrfs_fs_info *fs_info)
 {
         struct reloc_control *rc;
 
@@ -4093,7 +4093,8 @@ static struct reloc_control *alloc_reloc_control(void)
         INIT_LIST_HEAD(&rc->reloc_roots);
         backref_cache_init(&rc->backref_cache);
         mapping_tree_init(&rc->reloc_root_tree);
-        extent_io_tree_init(&rc->processed_blocks, NULL);
+        extent_io_tree_init(&rc->processed_blocks,
+                            fs_info->btree_inode->i_mapping);
         return rc;
 }
 
@@ -4110,7 +4111,7 @@ int btrfs_relocate_block_group(struct btrfs_root *extent_root, u64 group_start)
         int rw = 0;
         int err = 0;
 
-        rc = alloc_reloc_control();
+        rc = alloc_reloc_control(fs_info);
         if (!rc)
                 return -ENOMEM;
 
@@ -4311,7 +4312,7 @@ int btrfs_recover_relocation(struct btrfs_root *root)
         if (list_empty(&reloc_roots))
                 goto out;
 
-        rc = alloc_reloc_control();
+        rc = alloc_reloc_control(root->fs_info);
         if (!rc) {
                 err = -ENOMEM;
                 goto out;