linux-kernel - fs/dcache.c:2788:24-43: WARNING: atomic_dec_and_test variation before object free at line 2789.

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Message-ID: <202502070322.IsdN65Ea-lkp@intel.com>
Date: Fri, 7 Feb 2025 03:44:40 +0800
From: kernel test robot <lkp@...el.com>
To: Al Viro <viro@...iv.linux.org.uk>
Cc: oe-kbuild-all@...ts.linux.dev, linux-kernel@...r.kernel.org,
	Jeff Layton <jlayton@...nel.org>, Jan Kara <jack@...e.cz>
Subject: fs/dcache.c:2788:24-43: WARNING: atomic_dec_and_test variation
 before object free at line 2789.

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   92514ef226f511f2ca1fb1b8752966097518edc0
commit: 95a4ccbbe596b45264af5e3a019cb920c05ccffd dissolve external_name.u into separate members
date:   10 days ago
config: alpha-randconfig-r053-20250206 (https://download.01.org/0day-ci/archive/20250207/202502070322.IsdN65Ea-lkp@intel.com/config)
compiler: alpha-linux-gcc (GCC) 14.2.0

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@...el.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202502070322.IsdN65Ea-lkp@intel.com/

cocci warnings: (new ones prefixed by >>)
>> fs/dcache.c:2788:24-43: WARNING: atomic_dec_and_test variation before object free at line 2789.
   fs/dcache.c:407:13-32: WARNING: atomic_dec_and_test variation before object free at line 408.
   fs/dcache.c:407:13-32: WARNING: atomic_dec_and_test variation before object free at line 416.
   fs/dcache.c:368:15-34: WARNING: atomic_dec_and_test variation before object free at line 369.

vim +2788 fs/dcache.c

  2774	
  2775	static void copy_name(struct dentry *dentry, struct dentry *target)
  2776	{
  2777		struct external_name *old_name = NULL;
  2778		if (unlikely(dname_external(dentry)))
  2779			old_name = external_name(dentry);
  2780		if (unlikely(dname_external(target))) {
  2781			atomic_inc(&external_name(target)->count);
  2782			dentry->d_name = target->d_name;
  2783		} else {
  2784			dentry->d_shortname = target->d_shortname;
  2785			dentry->d_name.name = dentry->d_shortname.string;
  2786			dentry->d_name.hash_len = target->d_name.hash_len;
  2787		}
> 2788		if (old_name && likely(atomic_dec_and_test(&old_name->count)))
> 2789			kfree_rcu(old_name, head);
  2790	}
  2791	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki