Re: [PATCH bpf-next v2 4/6] memcg: Add __GFP_TRYLOCK support.

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

Hi Alexei,

kernel test robot noticed the following build warnings:

[auto build test WARNING on bpf-next/master]

url:    https://github.com/intel-lab-lkp/linux/commits/Alexei-Starovoitov/mm-bpf-Introduce-__GFP_TRYLOCK-for-opportunistic-page-allocation/20241210-104250
base:   https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git master
patch link:    https://lore.kernel.org/r/20241210023936.46871-5-alexei.starovoitov%40gmail.com
patch subject: [PATCH bpf-next v2 4/6] memcg: Add __GFP_TRYLOCK support.
config: x86_64-buildonly-randconfig-001-20241210 (https://download.01.org/0day-ci/archive/20241212/202412120745.nnianRgw-lkp@intel.com/config)
compiler: gcc-12 (Debian 12.2.0-14) 12.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20241212/202412120745.nnianRgw-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/202412120745.nnianRgw-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> mm/memcontrol.c:1761: warning: Function parameter or struct member 'gfp_mask' not described in 'consume_stock'


vim +1761 mm/memcontrol.c

cdec2e4265dfa0 KAMEZAWA Hiroyuki         2009-12-15  1743  
56751146238723 Sebastian Andrzej Siewior 2022-03-22  1744  static struct obj_cgroup *drain_obj_stock(struct memcg_stock_pcp *stock);
bf4f059954dcb2 Roman Gushchin            2020-08-06  1745  static bool obj_stock_flush_required(struct memcg_stock_pcp *stock,
bf4f059954dcb2 Roman Gushchin            2020-08-06  1746  				     struct mem_cgroup *root_memcg);
bf4f059954dcb2 Roman Gushchin            2020-08-06  1747  
a0956d54492eb7 Suleiman Souhlal          2012-12-18  1748  /**
a0956d54492eb7 Suleiman Souhlal          2012-12-18  1749   * consume_stock: Try to consume stocked charge on this cpu.
a0956d54492eb7 Suleiman Souhlal          2012-12-18  1750   * @memcg: memcg to consume from.
a0956d54492eb7 Suleiman Souhlal          2012-12-18  1751   * @nr_pages: how many pages to charge.
a0956d54492eb7 Suleiman Souhlal          2012-12-18  1752   *
a0956d54492eb7 Suleiman Souhlal          2012-12-18  1753   * The charges will only happen if @memcg matches the current cpu's memcg
a0956d54492eb7 Suleiman Souhlal          2012-12-18  1754   * stock, and at least @nr_pages are available in that stock.  Failure to
a0956d54492eb7 Suleiman Souhlal          2012-12-18  1755   * service an allocation will refill the stock.
a0956d54492eb7 Suleiman Souhlal          2012-12-18  1756   *
a0956d54492eb7 Suleiman Souhlal          2012-12-18  1757   * returns true if successful, false otherwise.
cdec2e4265dfa0 KAMEZAWA Hiroyuki         2009-12-15  1758   */
c889f3c0bc9a18 Alexei Starovoitov        2024-12-09  1759  static bool consume_stock(struct mem_cgroup *memcg, unsigned int nr_pages,
c889f3c0bc9a18 Alexei Starovoitov        2024-12-09  1760  			  gfp_t gfp_mask)
cdec2e4265dfa0 KAMEZAWA Hiroyuki         2009-12-15 @1761  {
cdec2e4265dfa0 KAMEZAWA Hiroyuki         2009-12-15  1762  	struct memcg_stock_pcp *stock;
1872b3bcd5874b Breno Leitao              2024-05-01  1763  	unsigned int stock_pages;
db2ba40c277dc5 Johannes Weiner           2016-09-19  1764  	unsigned long flags;
3e32cb2e0a12b6 Johannes Weiner           2014-12-10  1765  	bool ret = false;
cdec2e4265dfa0 KAMEZAWA Hiroyuki         2009-12-15  1766  
a983b5ebee5720 Johannes Weiner           2018-01-31  1767  	if (nr_pages > MEMCG_CHARGE_BATCH)
3e32cb2e0a12b6 Johannes Weiner           2014-12-10  1768  		return ret;
a0956d54492eb7 Suleiman Souhlal          2012-12-18  1769  
c889f3c0bc9a18 Alexei Starovoitov        2024-12-09  1770  	if (!local_trylock_irqsave(&memcg_stock.stock_lock, flags)) {
c889f3c0bc9a18 Alexei Starovoitov        2024-12-09  1771  		if (gfp_mask & __GFP_TRYLOCK)
c889f3c0bc9a18 Alexei Starovoitov        2024-12-09  1772  			return ret;
56751146238723 Sebastian Andrzej Siewior 2022-03-22  1773  		local_lock_irqsave(&memcg_stock.stock_lock, flags);
c889f3c0bc9a18 Alexei Starovoitov        2024-12-09  1774  	}
db2ba40c277dc5 Johannes Weiner           2016-09-19  1775  
db2ba40c277dc5 Johannes Weiner           2016-09-19  1776  	stock = this_cpu_ptr(&memcg_stock);
1872b3bcd5874b Breno Leitao              2024-05-01  1777  	stock_pages = READ_ONCE(stock->nr_pages);
1872b3bcd5874b Breno Leitao              2024-05-01  1778  	if (memcg == READ_ONCE(stock->cached) && stock_pages >= nr_pages) {
1872b3bcd5874b Breno Leitao              2024-05-01  1779  		WRITE_ONCE(stock->nr_pages, stock_pages - nr_pages);
3e32cb2e0a12b6 Johannes Weiner           2014-12-10  1780  		ret = true;
3e32cb2e0a12b6 Johannes Weiner           2014-12-10  1781  	}
db2ba40c277dc5 Johannes Weiner           2016-09-19  1782  
56751146238723 Sebastian Andrzej Siewior 2022-03-22  1783  	local_unlock_irqrestore(&memcg_stock.stock_lock, flags);
db2ba40c277dc5 Johannes Weiner           2016-09-19  1784  
cdec2e4265dfa0 KAMEZAWA Hiroyuki         2009-12-15  1785  	return ret;
cdec2e4265dfa0 KAMEZAWA Hiroyuki         2009-12-15  1786  }
cdec2e4265dfa0 KAMEZAWA Hiroyuki         2009-12-15  1787  

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