Re: [PATCH 3/6] mm/folio, mm/mlock: Don't batch folios in per-CPU LRU caches on isolated CPUs

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

Hi Matthew,

kernel test robot noticed the following build errors:

[auto build test ERROR on akpm-mm/mm-everything]

url:    https://github.com/intel-lab-lkp/linux/commits/Matthew-Ruffell/sched-isolation-Consider-nohz_full-CPUs-isolated-in-cpu_is_isolated-again/20261103-205935
base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
patch link:    https://lore.kernel.org/r/20261103075940.110308-4-matthew.ruffell%40canonical.com
patch subject: [PATCH 3/6] mm/folio, mm/mlock: Don't batch folios in per-CPU LRU caches on isolated CPUs
config: um-allnoconfig (https://download.01.org/0day-ci/archive/20261103/202611032053.I3Ud8d11-lkp@intel.com/config)
compiler: clang version 17.0.6 (https://github.com/llvm/llvm-project 6009708b4367171ccdbf4b5905cb6a803753fe18)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20261103/202611032053.I3Ud8d11-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/202611032053.I3Ud8d11-lkp@intel.com/

All errors (new ones prefixed by >>):

>> mm/folio.c:293:6: error: call to undeclared function 'lru_batching_bypassed'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
     293 |         if (lru_batching_bypassed())
         |             ^
   1 error generated.


vim +/lru_batching_bypassed +293 mm/folio.c

   280	
   281	static void __folio_batch_add_and_move(struct folio_batch __percpu *fbatch,
   282			struct folio *folio, move_fn_t move_fn, bool disable_irq)
   283	{
   284		unsigned long flags;
   285	
   286		folio_get(folio);
   287	
   288		if (disable_irq)
   289			local_lock_irqsave(&cpu_fbatches.lock_irq, flags);
   290		else
   291			local_lock(&cpu_fbatches.lock);
   292	
 > 293		if (lru_batching_bypassed())
   294			folio_move_lru_now(folio, move_fn);
   295		else if (!folio_batch_add(this_cpu_ptr(fbatch), folio) ||
   296				!folio_may_be_lru_cached(folio) || lru_cache_disabled())
   297			folio_batch_move_lru(this_cpu_ptr(fbatch), move_fn);
   298	
   299		if (disable_irq)
   300			local_unlock_irqrestore(&cpu_fbatches.lock_irq, flags);
   301		else
   302			local_unlock(&cpu_fbatches.lock);
   303	}
   304	

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