Hi Waiman,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on linus/master]
[also build test ERROR on v4.18-rc4]
[cannot apply to next-20180713]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Waiman-Long/fs-dcache-Track-report-number-of-negative-dentries/20180714-161258
config: i386-tinyconfig (attached as .config)
compiler: gcc-7 (Debian 7.3.0-16) 7.3.0
reproduce:
        # save the attached .config to linux build tree
        make ARCH=i386 
:::::: branch date: 45 minutes ago
:::::: commit date: 45 minutes ago

Note: the linux-review/Waiman-Long/fs-dcache-Track-report-number-of-negative-dentries/20180714-161258 HEAD ca68ee513a450445b269248c2859302c8931a294 builds fine.
      It only hurts bisectibility.

All errors (new ones prefixed by >>):

   fs/dcache.c: In function 'neg_dentry_inc_slowpath':
>> fs/dcache.c:355:8: error: implicit declaration of function 'get_nr_dentry_neg'; did you mean 'neg_dentry_dec'? [-Werror=implicit-function-declaration]
     cnt = get_nr_dentry_neg();
           ^~~~~~~~~~~~~~~~~
           neg_dentry_dec
   cc1: some warnings being treated as errors

# https://github.com/0day-ci/linux/commit/2aa8bf4658af0dbc07ae9ea07d04937a347e3ef4
git remote add linux-review https://github.com/0day-ci/linux
git remote update linux-review
git checkout 2aa8bf4658af0dbc07ae9ea07d04937a347e3ef4
vim +355 fs/dcache.c

bcc9ba8b Waiman Long 2018-07-12  310  
bcc9ba8b Waiman Long 2018-07-12  311  static noinline void neg_dentry_inc_slowpath(struct dentry *dentry)
bcc9ba8b Waiman Long 2018-07-12  312  {
bcc9ba8b Waiman Long 2018-07-12  313  	long cnt = 0, *pcnt;
2aa8bf46 Waiman Long 2018-07-12  314  	unsigned long current_time;
bcc9ba8b Waiman Long 2018-07-12  315  
bcc9ba8b Waiman Long 2018-07-12  316  	/*
bcc9ba8b Waiman Long 2018-07-12  317  	 * Try to move some negative dentry quota from the global free
bcc9ba8b Waiman Long 2018-07-12  318  	 * pool to the percpu count to allow more negative dentries to
bcc9ba8b Waiman Long 2018-07-12  319  	 * be added to the LRU.
bcc9ba8b Waiman Long 2018-07-12  320  	 */
bcc9ba8b Waiman Long 2018-07-12  321  	pcnt = get_cpu_ptr(&nr_dentry_neg);
bcc9ba8b Waiman Long 2018-07-12  322  	if ((READ_ONCE(ndblk.nfree) > 0) &&
bcc9ba8b Waiman Long 2018-07-12  323  	    (*pcnt > neg_dentry_percpu_limit)) {
bcc9ba8b Waiman Long 2018-07-12  324  		cnt = __neg_dentry_nfree_dec(*pcnt - neg_dentry_percpu_limit);
bcc9ba8b Waiman Long 2018-07-12  325  		*pcnt -= cnt;
bcc9ba8b Waiman Long 2018-07-12  326  	}
bcc9ba8b Waiman Long 2018-07-12  327  	put_cpu_ptr(&nr_dentry_neg);
bcc9ba8b Waiman Long 2018-07-12  328  
2aa8bf46 Waiman Long 2018-07-12  329  	if (cnt)
2aa8bf46 Waiman Long 2018-07-12  330  		goto out;
2aa8bf46 Waiman Long 2018-07-12  331  
bcc9ba8b Waiman Long 2018-07-12  332  	/*
2aa8bf46 Waiman Long 2018-07-12  333  	 * Put out a warning every minute or so if there are just too many
2aa8bf46 Waiman Long 2018-07-12  334  	 * negative dentries.
bcc9ba8b Waiman Long 2018-07-12  335  	 */
2aa8bf46 Waiman Long 2018-07-12  336  	current_time = jiffies;
bcc9ba8b Waiman Long 2018-07-12  337  
2aa8bf46 Waiman Long 2018-07-12  338  	if (current_time < ndblk.warn_jiffies + NEG_WARN_PERIOD)
2aa8bf46 Waiman Long 2018-07-12  339  		goto out;
2aa8bf46 Waiman Long 2018-07-12  340  	/*
2aa8bf46 Waiman Long 2018-07-12  341  	 * Update the time in ndblk.warn_jiffies and print a warning
2aa8bf46 Waiman Long 2018-07-12  342  	 * if time update is successful.
2aa8bf46 Waiman Long 2018-07-12  343  	 */
2aa8bf46 Waiman Long 2018-07-12  344  	raw_spin_lock(&ndblk.nfree_lock);
2aa8bf46 Waiman Long 2018-07-12  345  	if (current_time < ndblk.warn_jiffies + NEG_WARN_PERIOD) {
2aa8bf46 Waiman Long 2018-07-12  346  		raw_spin_unlock(&ndblk.nfree_lock);
2aa8bf46 Waiman Long 2018-07-12  347  		goto out;
2aa8bf46 Waiman Long 2018-07-12  348  	}
2aa8bf46 Waiman Long 2018-07-12  349  	ndblk.warn_jiffies = current_time;
2aa8bf46 Waiman Long 2018-07-12  350  	raw_spin_unlock(&ndblk.nfree_lock);
2aa8bf46 Waiman Long 2018-07-12  351  
2aa8bf46 Waiman Long 2018-07-12  352  	/*
2aa8bf46 Waiman Long 2018-07-12  353  	 * Get the current negative dentry count & print a warning.
2aa8bf46 Waiman Long 2018-07-12  354  	 */
2aa8bf46 Waiman Long 2018-07-12 @355  	cnt = get_nr_dentry_neg();
2aa8bf46 Waiman Long 2018-07-12  356  	pr_warn("Warning: Too many negative dentries (%ld). "
2aa8bf46 Waiman Long 2018-07-12  357  		"This warning can be disabled by writing 0 to \"fs/neg-dentry-limit\" or increasing the limit.\n",
2aa8bf46 Waiman Long 2018-07-12  358  		cnt);
2aa8bf46 Waiman Long 2018-07-12  359  out:
2aa8bf46 Waiman Long 2018-07-12  360  	return;
bcc9ba8b Waiman Long 2018-07-12  361  }
bcc9ba8b Waiman Long 2018-07-12  362  

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