Re: [PATCH v4 13/13] x86/folio_zero_user: Add multi-page clearing

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

Hi Ankur,

kernel test robot noticed the following build warnings:

[auto build test WARNING on perf-tools-next/perf-tools-next]
[also build test WARNING on tip/perf/core perf-tools/perf-tools linus/master v6.16-rc2 next-20250616]
[cannot apply to acme/perf/core]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Ankur-Arora/perf-bench-mem-Remove-repetition-around-time-measurement/20250616-132651
base:   https://git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-next.git perf-tools-next
patch link:    https://lore.kernel.org/r/20250616052223.723982-14-ankur.a.arora%40oracle.com
patch subject: [PATCH v4 13/13] x86/folio_zero_user: Add multi-page clearing
config: x86_64-buildonly-randconfig-003-20250616 (https://download.01.org/0day-ci/archive/20250616/202506161939.YrEAfTPY-lkp@intel.com/config)
compiler: clang version 20.1.2 (https://github.com/llvm/llvm-project 58df0ef89dd64126512e4ee27b4ac3fd8ddf6247)
rustc: rustc 1.78.0 (9b00956e5 2024-04-29)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250616/202506161939.YrEAfTPY-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/202506161939.YrEAfTPY-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> arch/x86/mm/memory.c:61:6: warning: no previous prototype for function 'folio_zero_user' [-Wmissing-prototypes]
      61 | void folio_zero_user(struct folio *folio, unsigned long addr_hint)
         |      ^
   arch/x86/mm/memory.c:61:1: note: declare 'static' if the function is not intended to be used outside of this translation unit
      61 | void folio_zero_user(struct folio *folio, unsigned long addr_hint)
         | ^
         | static 
   1 warning generated.


vim +/folio_zero_user +61 arch/x86/mm/memory.c

    39	
    40	/*
    41	 * folio_zero_user() - multi-page clearing.
    42	 *
    43	 * @folio: hugepage folio
    44	 * @addr_hint: faulting address (if any)
    45	 *
    46	 * Overrides common code folio_zero_user(). This version takes advantage of
    47	 * the fact that string instructions in clear_pages() are more performant
    48	 * on larger extents compared to the usual page-at-a-time clearing.
    49	 *
    50	 * Clearing of 2MB pages is split in three parts: pages in the immediate
    51	 * locality of the faulting page, and its left, right regions; with the local
    52	 * neighbourhood cleared last in order to keep cache lines of the target
    53	 * region hot.
    54	 *
    55	 * For GB pages, there is no expectation of cache locality so just do a
    56	 * straight zero.
    57	 *
    58	 * Note that the folio is fully allocated already so we don't do any exception
    59	 * handling.
    60	 */
  > 61	void folio_zero_user(struct folio *folio, unsigned long addr_hint)

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