Re: [PATCH] btrfs: fix a potential racy

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

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Hi,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on btrfs/next]
[also build test WARNING on v5.7-rc2 next-20200421]
[if your patch is applied to the wrong git tree, please drop us a note to help
improve the system. BTW, we also suggest to use '--base' option to specify the
base tree in git format-patch, please see https://stackoverflow.com/a/37406982]

url:    https://github.com/0day-ci/linux/commits/wu000273-umn-edu/btrfs-fix-a-potential-racy/20200421-072124
base:   https://git.kernel.org/pub/scm/linux/kernel/git/mason/linux-btrfs.git next
config: arm64-allmodconfig (attached as .config)
compiler: aarch64-linux-gcc (GCC) 9.3.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day GCC_VERSION=9.3.0 make.cross ARCH=arm64 

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

All warnings (new ones prefixed by >>):

   fs/btrfs/reada.c: In function 'reada_extent_put':
>> fs/btrfs/reada.c:509:3: warning: ISO C90 forbids mixed declarations and code [-Wdeclaration-after-statement]
     509 |   struct reada_zone *zone = re->zones[i];
         |   ^~~~~~

vim +509 fs/btrfs/reada.c

7414a03fbf9e75 Arne Jansen        2011-05-23  485  
7414a03fbf9e75 Arne Jansen        2011-05-23  486  static void reada_extent_put(struct btrfs_fs_info *fs_info,
7414a03fbf9e75 Arne Jansen        2011-05-23  487  			     struct reada_extent *re)
7414a03fbf9e75 Arne Jansen        2011-05-23  488  {
7414a03fbf9e75 Arne Jansen        2011-05-23  489  	int i;
09cbfeaf1a5a67 Kirill A. Shutemov 2016-04-01  490  	unsigned long index = re->logical >> PAGE_SHIFT;
7414a03fbf9e75 Arne Jansen        2011-05-23  491  
7414a03fbf9e75 Arne Jansen        2011-05-23  492  	spin_lock(&fs_info->reada_lock);
99621b44aa194e Al Viro            2012-08-29  493  	if (--re->refcnt) {
7414a03fbf9e75 Arne Jansen        2011-05-23  494  		spin_unlock(&fs_info->reada_lock);
7414a03fbf9e75 Arne Jansen        2011-05-23  495  		return;
7414a03fbf9e75 Arne Jansen        2011-05-23  496  	}
7414a03fbf9e75 Arne Jansen        2011-05-23  497  
7414a03fbf9e75 Arne Jansen        2011-05-23  498  	radix_tree_delete(&fs_info->reada_tree, index);
7414a03fbf9e75 Arne Jansen        2011-05-23  499  	for (i = 0; i < re->nzones; ++i) {
7414a03fbf9e75 Arne Jansen        2011-05-23  500  		struct reada_zone *zone = re->zones[i];
7414a03fbf9e75 Arne Jansen        2011-05-23  501  
7414a03fbf9e75 Arne Jansen        2011-05-23  502  		radix_tree_delete(&zone->device->reada_extents, index);
7414a03fbf9e75 Arne Jansen        2011-05-23  503  	}
7414a03fbf9e75 Arne Jansen        2011-05-23  504  
7414a03fbf9e75 Arne Jansen        2011-05-23  505  	spin_unlock(&fs_info->reada_lock);
7414a03fbf9e75 Arne Jansen        2011-05-23  506  
7414a03fbf9e75 Arne Jansen        2011-05-23  507  	for (i = 0; i < re->nzones; ++i) {
1255ee642bf9b0 Qiushi Wu          2020-04-18  508  		spin_lock(&fs_info->reada_lock);
7414a03fbf9e75 Arne Jansen        2011-05-23 @509  		struct reada_zone *zone = re->zones[i];
7414a03fbf9e75 Arne Jansen        2011-05-23  510  		kref_get(&zone->refcnt);
1255ee642bf9b0 Qiushi Wu          2020-04-18  511  		spin_unlock(&fs_info->reada_lock);
1255ee642bf9b0 Qiushi Wu          2020-04-18  512  
7414a03fbf9e75 Arne Jansen        2011-05-23  513  		spin_lock(&zone->lock);
7414a03fbf9e75 Arne Jansen        2011-05-23  514  		--zone->elems;
7414a03fbf9e75 Arne Jansen        2011-05-23  515  		if (zone->elems == 0) {
7414a03fbf9e75 Arne Jansen        2011-05-23  516  			/* no fs_info->reada_lock needed, as this can't be
7414a03fbf9e75 Arne Jansen        2011-05-23  517  			 * the last ref */
7414a03fbf9e75 Arne Jansen        2011-05-23  518  			kref_put(&zone->refcnt, reada_zone_release);
7414a03fbf9e75 Arne Jansen        2011-05-23  519  		}
7414a03fbf9e75 Arne Jansen        2011-05-23  520  		spin_unlock(&zone->lock);
7414a03fbf9e75 Arne Jansen        2011-05-23  521  
7414a03fbf9e75 Arne Jansen        2011-05-23  522  		spin_lock(&fs_info->reada_lock);
7414a03fbf9e75 Arne Jansen        2011-05-23  523  		kref_put(&zone->refcnt, reada_zone_release);
7414a03fbf9e75 Arne Jansen        2011-05-23  524  		spin_unlock(&fs_info->reada_lock);
7414a03fbf9e75 Arne Jansen        2011-05-23  525  	}
7414a03fbf9e75 Arne Jansen        2011-05-23  526  
7414a03fbf9e75 Arne Jansen        2011-05-23  527  	kfree(re);
7414a03fbf9e75 Arne Jansen        2011-05-23  528  }
7414a03fbf9e75 Arne Jansen        2011-05-23  529  

:::::: The code at line 509 was first introduced by commit
:::::: 7414a03fbf9e75fbbf2a3c16828cd862e572aa44 btrfs: initial readahead code and prototypes

:::::: TO: Arne Jansen <sensille@gmx.net>
:::::: CC: Arne Jansen <sensille@gmx.net>

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

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