Re: [PATCH] mm: don't be stuck to rmap lock on reclaim path

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

Hi Minchan,

I love your patch! Perhaps something to improve:

[auto build test WARNING on hnaz-mm/master]

url:    https://github.com/intel-lab-lkp/linux/commits/Minchan-Kim/mm-don-t-be-stuck-to-rmap-lock-on-reclaim-path/20220504-010625
base:   https://github.com/hnaz/linux-mm master
config: x86_64-randconfig-a013 (https://download.01.org/0day-ci/archive/20220504/202205041057.a78ABZ95-lkp@intel.com/config)
compiler: gcc-11 (Debian 11.2.0-20) 11.2.0
reproduce (this is a W=1 build):
        # https://github.com/intel-lab-lkp/linux/commit/0e190ce022ef259d63eb2cf50110b292ba17c79c
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Minchan-Kim/mm-don-t-be-stuck-to-rmap-lock-on-reclaim-path/20220504-010625
        git checkout 0e190ce022ef259d63eb2cf50110b292ba17c79c
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash

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

All warnings (new ones prefixed by >>):

   mm/page_idle.c: In function 'page_idle_clear_pte_refs':
>> mm/page_idle.c:106:26: warning: passing argument 2 of 'rmap_walk' discards 'const' qualifier from pointer target type [-Wdiscarded-qualifiers]
     106 |         rmap_walk(folio, &rwc);
         |                          ^~~~
   In file included from mm/page_idle.c:11:
   include/linux/rmap.h:403:63: note: expected 'struct rmap_walk_control *' but argument is of type 'const struct rmap_walk_control *'
     403 | void rmap_walk(struct folio *folio, struct rmap_walk_control *rwc);
         |                                     ~~~~~~~~~~~~~~~~~~~~~~~~~~^~~


vim +106 mm/page_idle.c

33c3fc71c8cfa3 Vladimir Davydov        2015-09-09   85  
33c3fc71c8cfa3 Vladimir Davydov        2015-09-09   86  static void page_idle_clear_pte_refs(struct page *page)
33c3fc71c8cfa3 Vladimir Davydov        2015-09-09   87  {
4aed23a2f8aaaa Matthew Wilcox (Oracle  2022-01-29   88) 	struct folio *folio = page_folio(page);
33c3fc71c8cfa3 Vladimir Davydov        2015-09-09   89  	/*
33c3fc71c8cfa3 Vladimir Davydov        2015-09-09   90  	 * Since rwc.arg is unused, rwc is effectively immutable, so we
33c3fc71c8cfa3 Vladimir Davydov        2015-09-09   91  	 * can make it static const to save some cycles and stack.
33c3fc71c8cfa3 Vladimir Davydov        2015-09-09   92  	 */
33c3fc71c8cfa3 Vladimir Davydov        2015-09-09   93  	static const struct rmap_walk_control rwc = {
33c3fc71c8cfa3 Vladimir Davydov        2015-09-09   94  		.rmap_one = page_idle_clear_pte_refs_one,
2f031c6f042cb8 Matthew Wilcox (Oracle  2022-01-29   95) 		.anon_lock = folio_lock_anon_vma_read,
33c3fc71c8cfa3 Vladimir Davydov        2015-09-09   96  	};
33c3fc71c8cfa3 Vladimir Davydov        2015-09-09   97  	bool need_lock;
33c3fc71c8cfa3 Vladimir Davydov        2015-09-09   98  
4aed23a2f8aaaa Matthew Wilcox (Oracle  2022-01-29   99) 	if (!folio_mapped(folio) || !folio_raw_mapping(folio))
33c3fc71c8cfa3 Vladimir Davydov        2015-09-09  100  		return;
33c3fc71c8cfa3 Vladimir Davydov        2015-09-09  101  
4aed23a2f8aaaa Matthew Wilcox (Oracle  2022-01-29  102) 	need_lock = !folio_test_anon(folio) || folio_test_ksm(folio);
4aed23a2f8aaaa Matthew Wilcox (Oracle  2022-01-29  103) 	if (need_lock && !folio_trylock(folio))
33c3fc71c8cfa3 Vladimir Davydov        2015-09-09  104  		return;
33c3fc71c8cfa3 Vladimir Davydov        2015-09-09  105  
84fbbe21894bb9 Matthew Wilcox (Oracle  2022-01-29 @106) 	rmap_walk(folio, &rwc);
33c3fc71c8cfa3 Vladimir Davydov        2015-09-09  107  
33c3fc71c8cfa3 Vladimir Davydov        2015-09-09  108  	if (need_lock)
4aed23a2f8aaaa Matthew Wilcox (Oracle  2022-01-29  109) 		folio_unlock(folio);
33c3fc71c8cfa3 Vladimir Davydov        2015-09-09  110  }
33c3fc71c8cfa3 Vladimir Davydov        2015-09-09  111  

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