Re: [PATCH 3/3] nfsd: split nfsd_mutex into one mutex per net-namespace.

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

Hi NeilBrown,

kernel test robot noticed the following build warnings:

[auto build test WARNING on brauner-vfs/vfs.all]
[also build test WARNING on trondmy-nfs/linux-next linus/master v6.16-rc2 next-20250619]
[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#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/NeilBrown/nfsd-provide-proper-locking-for-all-write_-function/20250619-053514
base:   https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git vfs.all
patch link:    https://lore.kernel.org/r/20250618213347.425503-4-neil%40brown.name
patch subject: [PATCH 3/3] nfsd: split nfsd_mutex into one mutex per net-namespace.
config: x86_64-kexec (https://download.01.org/0day-ci/archive/20250619/202506192052.L9tj28RJ-lkp@intel.com/config)
compiler: clang version 20.1.2 (https://github.com/llvm/llvm-project 58df0ef89dd64126512e4ee27b4ac3fd8ddf6247)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250619/202506192052.L9tj28RJ-lkp@intel.com/reproduce)

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@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202506192052.L9tj28RJ-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> fs/nfsd/nfsctl.c:1891:14: warning: variable 'nn' is uninitialized when used here [-Wuninitialized]
    1891 |         mutex_lock(&nn->nfsd_info.mutex);
         |                     ^~
   fs/nfsd/nfsctl.c:1877:21: note: initialize the variable 'nn' to silence this warning
    1877 |         struct nfsd_net *nn;
         |                            ^
         |                             = NULL
   1 warning generated.


vim +/nn +1891 fs/nfsd/nfsctl.c

  1867	
  1868	/**
  1869	 * nfsd_nl_version_get_doit - get the enabled status for all supported nfs versions
  1870	 * @skb: reply buffer
  1871	 * @info: netlink metadata and command arguments
  1872	 *
  1873	 * Return 0 on success or a negative errno.
  1874	 */
  1875	int nfsd_nl_version_get_doit(struct sk_buff *skb, struct genl_info *info)
  1876	{
  1877		struct nfsd_net *nn;
  1878		int i, err;
  1879		void *hdr;
  1880	
  1881		skb = genlmsg_new(GENLMSG_DEFAULT_SIZE, GFP_KERNEL);
  1882		if (!skb)
  1883			return -ENOMEM;
  1884	
  1885		hdr = genlmsg_iput(skb, info);
  1886		if (!hdr) {
  1887			err = -EMSGSIZE;
  1888			goto err_free_msg;
  1889		}
  1890	
> 1891		mutex_lock(&nn->nfsd_info.mutex);
  1892		nn = net_generic(genl_info_net(info), nfsd_net_id);
  1893	
  1894		for (i = 2; i <= 4; i++) {
  1895			int j;
  1896	
  1897			for (j = 0; j <= NFSD_SUPPORTED_MINOR_VERSION; j++) {
  1898				struct nlattr *attr;
  1899	
  1900				/* Don't record any versions the kernel doesn't have
  1901				 * compiled in
  1902				 */
  1903				if (!nfsd_support_version(i))
  1904					continue;
  1905	
  1906				/* NFSv{2,3} does not support minor numbers */
  1907				if (i < 4 && j)
  1908					continue;
  1909	
  1910				attr = nla_nest_start(skb,
  1911						      NFSD_A_SERVER_PROTO_VERSION);
  1912				if (!attr) {
  1913					err = -EINVAL;
  1914					goto err_nfsd_unlock;
  1915				}
  1916	
  1917				if (nla_put_u32(skb, NFSD_A_VERSION_MAJOR, i) ||
  1918				    nla_put_u32(skb, NFSD_A_VERSION_MINOR, j)) {
  1919					err = -EINVAL;
  1920					goto err_nfsd_unlock;
  1921				}
  1922	
  1923				/* Set the enabled flag if the version is enabled */
  1924				if (nfsd_vers(nn, i, NFSD_TEST) &&
  1925				    (i < 4 || nfsd_minorversion(nn, j, NFSD_TEST)) &&
  1926				    nla_put_flag(skb, NFSD_A_VERSION_ENABLED)) {
  1927					err = -EINVAL;
  1928					goto err_nfsd_unlock;
  1929				}
  1930	
  1931				nla_nest_end(skb, attr);
  1932			}
  1933		}
  1934	
  1935		mutex_unlock(&nn->nfsd_info.mutex);
  1936		genlmsg_end(skb, hdr);
  1937	
  1938		return genlmsg_reply(skb, info);
  1939	
  1940	err_nfsd_unlock:
  1941		mutex_unlock(&nn->nfsd_info.mutex);
  1942	err_free_msg:
  1943		nlmsg_free(skb);
  1944	
  1945		return err;
  1946	}
  1947	

-- 
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