Re: [PATCH 3/3] btrfs: allow BTRFS_IOC_SNAP_DESTROY_V2 to remove ghost subvolume

[kernel test robot <lkp@intel.com>]

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Hi Qu,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on kdave/for-next]
[also build test WARNING on v5.13 next-20210628]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/Qu-Wenruo/btrfs-allow-BTRFS_IOC_SNAP_DESTROY_V2-to-remove-ghost-subvolume/20210628-181747
base:   https://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux.git for-next
config: x86_64-randconfig-a002-20210628 (attached as .config)
compiler: clang version 13.0.0 (https://github.com/llvm/llvm-project 4c92e31dd0f1bd152eda883af20ff7fbcaa14945)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # install x86_64 cross compiling tool for clang build
        # apt-get install binutils-x86-64-linux-gnu
        # https://github.com/0day-ci/linux/commit/391ab0041fef5776e7517ab363701d6f86d9406b
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Qu-Wenruo/btrfs-allow-BTRFS_IOC_SNAP_DESTROY_V2-to-remove-ghost-subvolume/20210628-181747
        git checkout 391ab0041fef5776e7517ab363701d6f86d9406b
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=x86_64 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All warnings (new ones prefixed by >>):

>> fs/btrfs/ioctl.c:2931:6: warning: variable 'ret' is used uninitialized whenever 'if' condition is true [-Wsometimes-uninitialized]
           if (test_bit(BTRFS_ROOT_ORPHAN_ITEM_INSERTED, &root->state))
               ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   fs/btrfs/ioctl.c:2967:9: note: uninitialized use occurs here
           return ret;
                  ^~~
   fs/btrfs/ioctl.c:2931:2: note: remove the 'if' if its condition is always false
           if (test_bit(BTRFS_ROOT_ORPHAN_ITEM_INSERTED, &root->state))
           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   fs/btrfs/ioctl.c:2911:9: note: initialize the variable 'ret' to silence this warning
           int ret;
                  ^
                   = 0
   1 warning generated.


vim +2931 fs/btrfs/ioctl.c

  2894	
  2895	/*
  2896	 * Special case that some subvolume has missing ORPHAN_ITEM, but its refs is
  2897	 * already 0 (without any ROOT_REF/BACKREF).
  2898	 * In that case such subvolume is only taking space while unable to be deleted.
  2899	 *
  2900	 * No reproducer to reproduce such corruption, but it won't hurt to cleanup them
  2901	 * as we can reuse existing code since we only need to insert an orphan item and
  2902	 * queue them to be deleted.
  2903	 */
  2904	static int __cold remove_ghost_subvol(struct btrfs_fs_info *fs_info,
  2905					      u64 rootid)
  2906	{
  2907		struct btrfs_trans_handle *trans;
  2908		struct btrfs_root *root;
  2909		struct btrfs_path *path;
  2910		struct btrfs_key key;
  2911		int ret;
  2912	
  2913		root = btrfs_get_fs_root(fs_info, rootid, false);
  2914		if (IS_ERR(root)) {
  2915			ret = PTR_ERR(root);
  2916			return ret;
  2917		}
  2918	
  2919		/* A ghost subvolume is already a problem, better to output a warning */
  2920		btrfs_warn(fs_info, "root %llu has no refs nor orphan item", rootid); 
  2921		if (btrfs_root_refs(&root->root_item) != 0) {
  2922			/* We get some strange root */
  2923			btrfs_warn(fs_info,
  2924				"root %llu has %u refs, but no proper root backref",
  2925				rootid, btrfs_root_refs(&root->root_item));
  2926			ret = -EUCLEAN;
  2927			goto out;
  2928		}
  2929	
  2930		/* Already has orphan inserted */
> 2931		if (test_bit(BTRFS_ROOT_ORPHAN_ITEM_INSERTED, &root->state))
  2932			goto out;
  2933	
  2934		path = btrfs_alloc_path();
  2935		if (!path) {
  2936			ret = -ENOMEM;
  2937			goto out;
  2938		}
  2939		key.objectid = BTRFS_ORPHAN_OBJECTID;
  2940		key.type = BTRFS_ORPHAN_ITEM_KEY;
  2941		key.offset = rootid;
  2942	
  2943		ret = btrfs_search_slot(NULL, fs_info->tree_root, &key, path, 0, 0);
  2944		btrfs_free_path(path);
  2945		/* Either error or there is already an orphan item */
  2946		if (ret <= 0)
  2947			goto out;
  2948	
  2949		trans = btrfs_start_transaction(fs_info->tree_root, 1);
  2950		if (IS_ERR(trans)) {
  2951			ret = PTR_ERR(trans);
  2952			goto out;
  2953		}
  2954	
  2955		ret = btrfs_insert_orphan_item(trans, fs_info->tree_root, rootid);
  2956		if (ret < 0 && ret != -EEXIST) {
  2957			btrfs_abort_transaction(trans, ret);
  2958			goto end_trans;
  2959		}
  2960		ret = 0;
  2961		btrfs_add_dead_root(root);
  2962	
  2963	end_trans:
  2964		btrfs_end_transaction(trans);
  2965	out:
  2966		btrfs_put_root(root);
  2967		return ret;
  2968	}
  2969	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

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