Subject: Re: [PATCH next v2 11/11] minmax: min() and max() don't need to return constant expressions

From: kernel test robot <[email-masked]>
Date: Mon, 26 Feb 2024 17:42:13 +0800

Hi David,

kernel test robot noticed the following build warnings:

[auto build test WARNING on drm-misc/drm-misc-next]
[also build test WARNING on linux/master mkl-can-next/testing kdave/for-next akpm-mm/mm-nonmm-unstable linus/master v6.8-rc6]
[cannot apply to next-20240223 dtor-input/next dtor-input/for-linus axboe-block/for-next horms-ipvs/master next-20240223]
[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/David-Laight/minmax-Put-all-the-clamp-definitions-together/20240226-005902
base:   git://anongit.freedesktop.org/drm/drm-misc drm-misc-next
patch link:    https://lore.kernel.org/r/a18dcae310f74dcb9c6fc01d5bdc0568%40AcuMS.aculab.com
patch subject: [PATCH next v2 11/11] minmax: min() and max() don't need to return constant expressions
config: i386-buildonly-randconfig-001-20240226 (https://download.01.org/0day-ci/archive/20240226/[email-masked]/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/20240226/[email-masked]/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 <[email-masked]>
| Closes: https://lore.kernel.org/oe-kbuild-all/[email-masked]/

All warnings (new ones prefixed by >>):

>> arch/x86/mm/pgtable.c:437:14: warning: variable length array used [-Wvla]
     437 |         pmd_t *pmds[MAX_PREALLOCATED_PMDS];
         |                     ^~~~~~~~~~~~~~~~~~~~~
   arch/x86/mm/pgtable.c:180:31: note: expanded from macro 'MAX_PREALLOCATED_PMDS'
     180 | #define MAX_PREALLOCATED_PMDS   MAX_UNSHARED_PTRS_PER_PGD
         |                                 ^~~~~~~~~~~~~~~~~~~~~~~~~
   arch/x86/mm/pgtable.c:113:2: note: expanded from macro 'MAX_UNSHARED_PTRS_PER_PGD'
     113 |         max_t(size_t, KERNEL_PGD_BOUNDARY, PTRS_PER_PGD)
         |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   include/linux/minmax.h:152:27: note: expanded from macro 'max_t'
     152 | #define max_t(type, x, y)       __careful_cmp(max, (type)(x), (type)(y), __COUNTER__)
         |                                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   include/linux/minmax.h:62:2: note: expanded from macro '__careful_cmp'
      59 | #define __careful_cmp(op, x, y, uniq) ({        \
         |                                       ~~~~~~~~~~~
      60 |         _Static_assert(__types_ok(x, y),        \
         |         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      61 |                 #op "(" #x ", " #y ") signedness error, fix types or consider u" #op "() before " #op "_t()"); \
         |                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      62 |         __cmp_once(op, x, y, uniq); })
         |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   include/linux/minmax.h:57:2: note: expanded from macro '__cmp_once'
      57 |         __cmp(op, __x_##uniq, __y_##uniq); })
         |         ^
   include/linux/minmax.h:52:26: note: expanded from macro '__cmp'
      52 | #define __cmp(op, x, y) ((x) __cmp_op_##op (y) ? (x) : (y))
         |                          ^
   1 warning generated.

vim +437 arch/x86/mm/pgtable.c

1db491f77b6ed0 Fenghua Yu          2015-01-15  432  
d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25  433  pgd_t *pgd_alloc(struct mm_struct *mm)
1ec1fe73dfb711 Ingo Molnar         2008-03-19  434  {
d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25  435  	pgd_t *pgd;
184d47f0fd3651 Kees Cook           2018-10-08  436  	pmd_t *u_pmds[MAX_PREALLOCATED_USER_PMDS];
184d47f0fd3651 Kees Cook           2018-10-08 @437  	pmd_t *pmds[MAX_PREALLOCATED_PMDS];
1ec1fe73dfb711 Ingo Molnar         2008-03-19  438  
1db491f77b6ed0 Fenghua Yu          2015-01-15  439  	pgd = _pgd_alloc();
1ec1fe73dfb711 Ingo Molnar         2008-03-19  440  
d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25  441  	if (pgd == NULL)
d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25  442  		goto out;
4f76cd382213b2 Jeremy Fitzhardinge 2008-03-17  443  
d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25  444  	mm->pgd = pgd;
4f76cd382213b2 Jeremy Fitzhardinge 2008-03-17  445  
25226df4b9be7f Gustavo A. R. Silva 2022-09-21  446  	if (sizeof(pmds) != 0 &&
25226df4b9be7f Gustavo A. R. Silva 2022-09-21  447  			preallocate_pmds(mm, pmds, PREALLOCATED_PMDS) != 0)
d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25  448  		goto out_free_pgd;
d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25  449  
25226df4b9be7f Gustavo A. R. Silva 2022-09-21  450  	if (sizeof(u_pmds) != 0 &&
25226df4b9be7f Gustavo A. R. Silva 2022-09-21  451  			preallocate_pmds(mm, u_pmds, PREALLOCATED_USER_PMDS) != 0)
d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25  452  		goto out_free_pmds;
d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25  453  
f59dbe9ca6707e Joerg Roedel        2018-07-18  454  	if (paravirt_pgd_alloc(mm) != 0)
f59dbe9ca6707e Joerg Roedel        2018-07-18  455  		goto out_free_user_pmds;
f59dbe9ca6707e Joerg Roedel        2018-07-18  456  
d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25  457  	/*
d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25  458  	 * Make sure that pre-populating the pmds is atomic with
d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25  459  	 * respect to anything walking the pgd_list, so that they
d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25  460  	 * never see a partially populated pgd.
d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25  461  	 */
a79e53d85683c6 Andrea Arcangeli    2011-02-16  462  	spin_lock(&pgd_lock);
4f76cd382213b2 Jeremy Fitzhardinge 2008-03-17  463  
617d34d9e5d832 Jeremy Fitzhardinge 2010-09-21  464  	pgd_ctor(mm, pgd);
25226df4b9be7f Gustavo A. R. Silva 2022-09-21  465  	if (sizeof(pmds) != 0)
d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25  466  		pgd_prepopulate_pmd(mm, pgd, pmds);
25226df4b9be7f Gustavo A. R. Silva 2022-09-21  467  
25226df4b9be7f Gustavo A. R. Silva 2022-09-21  468  	if (sizeof(u_pmds) != 0)
f59dbe9ca6707e Joerg Roedel        2018-07-18  469  		pgd_prepopulate_user_pmd(mm, pgd, u_pmds);
4f76cd382213b2 Jeremy Fitzhardinge 2008-03-17  470  
a79e53d85683c6 Andrea Arcangeli    2011-02-16  471  	spin_unlock(&pgd_lock);
4f76cd382213b2 Jeremy Fitzhardinge 2008-03-17  472  
4f76cd382213b2 Jeremy Fitzhardinge 2008-03-17  473  	return pgd;
d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25  474  
f59dbe9ca6707e Joerg Roedel        2018-07-18  475  out_free_user_pmds:
25226df4b9be7f Gustavo A. R. Silva 2022-09-21  476  	if (sizeof(u_pmds) != 0)
f59dbe9ca6707e Joerg Roedel        2018-07-18  477  		free_pmds(mm, u_pmds, PREALLOCATED_USER_PMDS);
d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25  478  out_free_pmds:
25226df4b9be7f Gustavo A. R. Silva 2022-09-21  479  	if (sizeof(pmds) != 0)
f59dbe9ca6707e Joerg Roedel        2018-07-18  480  		free_pmds(mm, pmds, PREALLOCATED_PMDS);
d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25  481  out_free_pgd:
1db491f77b6ed0 Fenghua Yu          2015-01-15  482  	_pgd_free(pgd);
d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25  483  out:
d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25  484  	return NULL;
4f76cd382213b2 Jeremy Fitzhardinge 2008-03-17  485  }
4f76cd382213b2 Jeremy Fitzhardinge 2008-03-17  486  

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