Re: [PATCH v4 2/5] fuse: Call vfs_get_tree() for submounts

[kernel test robot]

Hi Greg,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on fuse/for-next]
[also build test WARNING on linux/master linus/master v5.13-rc2 next-20210521]
[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/Greg-Kurz/virtiofs-propagate-sync-to-file-server/20210522-210652
base:   https://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse.git for-next
config: nds32-randconfig-r011-20210522 (attached as .config)
compiler: nds32le-linux-gcc (GCC) 9.3.0
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
        # https://github.com/0day-ci/linux/commit/ee3cc45c5a2311efc82021bd5463271507bef828
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Greg-Kurz/virtiofs-propagate-sync-to-file-server/20210522-210652
        git checkout ee3cc45c5a2311efc82021bd5463271507bef828
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=nds32 

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

All warnings (new ones prefixed by >>):

   fs/fuse/dir.c: In function 'fuse_dentry_automount':
>> fs/fuse/dir.c:312:21: warning: variable 'fm' set but not used [-Wunused-but-set-variable]
     312 |  struct fuse_mount *fm;
         |                     ^~


vim +/fm +312 fs/fuse/dir.c

8fab010644363f Miklos Szeredi 2018-08-15  303  
bf109c64040f5b Max Reitz      2020-04-21  304  /*
bf109c64040f5b Max Reitz      2020-04-21  305   * Create a fuse_mount object with a new superblock (with path->dentry
bf109c64040f5b Max Reitz      2020-04-21  306   * as the root), and return that mount so it can be auto-mounted on
bf109c64040f5b Max Reitz      2020-04-21  307   * @path.
bf109c64040f5b Max Reitz      2020-04-21  308   */
bf109c64040f5b Max Reitz      2020-04-21  309  static struct vfsmount *fuse_dentry_automount(struct path *path)
bf109c64040f5b Max Reitz      2020-04-21  310  {
bf109c64040f5b Max Reitz      2020-04-21  311  	struct fs_context *fsc;
bf109c64040f5b Max Reitz      2020-04-21 @312  	struct fuse_mount *fm;
bf109c64040f5b Max Reitz      2020-04-21  313  	struct vfsmount *mnt;
bf109c64040f5b Max Reitz      2020-04-21  314  	struct fuse_inode *mp_fi = get_fuse_inode(d_inode(path->dentry));
bf109c64040f5b Max Reitz      2020-04-21  315  	int err;
bf109c64040f5b Max Reitz      2020-04-21  316  
bf109c64040f5b Max Reitz      2020-04-21  317  	fsc = fs_context_for_submount(path->mnt->mnt_sb->s_type, path->dentry);
bf109c64040f5b Max Reitz      2020-04-21  318  	if (IS_ERR(fsc)) {
bf109c64040f5b Max Reitz      2020-04-21  319  		err = PTR_ERR(fsc);
bf109c64040f5b Max Reitz      2020-04-21  320  		goto out;
bf109c64040f5b Max Reitz      2020-04-21  321  	}
bf109c64040f5b Max Reitz      2020-04-21  322  
ee3cc45c5a2311 Greg Kurz      2021-05-20  323  	/*
ee3cc45c5a2311 Greg Kurz      2021-05-20  324  	 * Hijack fsc->fs_private to pass the mount point inode to
ee3cc45c5a2311 Greg Kurz      2021-05-20  325  	 * fuse_get_tree_submount(). It *must* be NULLified afterwards
ee3cc45c5a2311 Greg Kurz      2021-05-20  326  	 * to avoid the inode pointer to be passed to kfree() when
ee3cc45c5a2311 Greg Kurz      2021-05-20  327  	 * the context gets freed.
ee3cc45c5a2311 Greg Kurz      2021-05-20  328  	 */
ee3cc45c5a2311 Greg Kurz      2021-05-20  329  	fsc->fs_private = mp_fi;
ee3cc45c5a2311 Greg Kurz      2021-05-20  330  	err = vfs_get_tree(fsc);
ee3cc45c5a2311 Greg Kurz      2021-05-20  331  	fsc->fs_private = NULL;
ee3cc45c5a2311 Greg Kurz      2021-05-20  332  	if (err)
bf109c64040f5b Max Reitz      2020-04-21  333  		goto out_put_fsc;
bf109c64040f5b Max Reitz      2020-04-21  334  
ee3cc45c5a2311 Greg Kurz      2021-05-20  335  	fm = get_fuse_mount_super(fsc->root->d_sb);
bf109c64040f5b Max Reitz      2020-04-21  336  
bf109c64040f5b Max Reitz      2020-04-21  337  	/* Create the submount */
bf109c64040f5b Max Reitz      2020-04-21  338  	mnt = vfs_create_mount(fsc);
bf109c64040f5b Max Reitz      2020-04-21  339  	if (IS_ERR(mnt)) {
bf109c64040f5b Max Reitz      2020-04-21  340  		err = PTR_ERR(mnt);
bf109c64040f5b Max Reitz      2020-04-21  341  		goto out_put_fsc;
bf109c64040f5b Max Reitz      2020-04-21  342  	}
bf109c64040f5b Max Reitz      2020-04-21  343  	mntget(mnt);
bf109c64040f5b Max Reitz      2020-04-21  344  	put_fs_context(fsc);
bf109c64040f5b Max Reitz      2020-04-21  345  	return mnt;
bf109c64040f5b Max Reitz      2020-04-21  346  
bf109c64040f5b Max Reitz      2020-04-21  347  out_put_fsc:
bf109c64040f5b Max Reitz      2020-04-21  348  	put_fs_context(fsc);
bf109c64040f5b Max Reitz      2020-04-21  349  out:
bf109c64040f5b Max Reitz      2020-04-21  350  	return ERR_PTR(err);
bf109c64040f5b Max Reitz      2020-04-21  351  }
bf109c64040f5b Max Reitz      2020-04-21  352  

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