Btrfs: fail to mount if we have problems reading the block groups

We don't actually check the return value of btrfs_read_block_groups, so we can
possibly succeed to mount, but then fail to say read the superblock xattr for
selinux which will cause the vfs code to deactivate the super.

This is a problem because in find_free_extent we just assume that we
will find the right space_info for the allocation we want.  But if we
failed to read the block groups, we won't have setup any space_info's,
and we'll hit a NULL pointer deref in find_free_extent.

This patch fixes that problem by checking the return value of
btrfs_read_block_groups, and failing out properly.  I've also added a
check in find_free_extent so if for some reason we don't find an
appropriate space_info, we just return -ENOSPC.

Signed-off-by: Josef Bacik <josef@redhat.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 8 insertions, 3 deletions

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 11d0ad30e203..5ae1c0fcfce0 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1922,7 +1922,11 @@ struct btrfs_root *open_ctree(struct super_block *sb,
 
         csum_root->track_dirty = 1;
 
-        btrfs_read_block_groups(extent_root);
+        ret = btrfs_read_block_groups(extent_root);
+        if (ret) {
+                printk(KERN_ERR "Failed to read block groups: %d\n", ret);
+                goto fail_block_groups;
+        }
 
         fs_info->generation = generation;
         fs_info->last_trans_committed = generation;
@@ -1932,7 +1936,7 @@ struct btrfs_root *open_ctree(struct super_block *sb,
         fs_info->cleaner_kthread = kthread_run(cleaner_kthread, tree_root,
                                                "btrfs-cleaner");
         if (IS_ERR(fs_info->cleaner_kthread))
-                goto fail_csum_root;
+                goto fail_block_groups;
 
         fs_info->transaction_kthread = kthread_run(transaction_kthread,
                                                    tree_root,
@@ -2020,7 +2024,8 @@ fail_cleaner:
         filemap_write_and_wait(fs_info->btree_inode->i_mapping);
         invalidate_inode_pages2(fs_info->btree_inode->i_mapping);
 
-fail_csum_root:
+fail_block_groups:
+        btrfs_free_block_groups(fs_info);
         free_extent_buffer(csum_root->node);
         free_extent_buffer(csum_root->commit_root);
 fail_dev_root: