Hi Nadav,

I love your patch! Perhaps something to improve:

[auto build test WARNING on char-misc/char-misc-testing]
[also build test WARNING on v4.19-rc4 next-20180913]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Nadav-Amit/vmw_balloon-compaction-shrinker-64-bit-etc/20180918-152302
config: x86_64-randconfig-x007-201837 (attached as .config)
compiler: gcc-7 (Debian 7.3.0-1) 7.3.0
reproduce:
        # save the attached .config to linux build tree
        make ARCH=x86_64 

All warnings (new ones prefixed by >>):

   In file included from include/linux/export.h:45:0,
                    from include/linux/linkage.h:7,
                    from include/linux/kernel.h:7,
                    from drivers/misc/vmw_balloon.c:20:
   drivers/misc/vmw_balloon.c: In function 'vmballoon_change.isra.2':
   include/linux/compiler.h:358:38: error: call to '__compiletime_assert_659' declared with attribute error: BUILD_BUG failed
     _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
                                         ^
   include/linux/compiler.h:69:16: note: in definition of macro '__trace_if'
      ______r = !!(cond);     \
                   ^~~~
>> drivers/misc/vmw_balloon.c:659:2: note: in expansion of macro 'if'
     if (target < size && size - target < HPAGE_PMD_NR && target != 0)
     ^~
   include/linux/compiler.h:346:2: note: in expansion of macro '__compiletime_assert'
     __compiletime_assert(condition, msg, prefix, suffix)
     ^~~~~~~~~~~~~~~~~~~~
   include/linux/compiler.h:358:2: note: in expansion of macro '_compiletime_assert'
     _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
     ^~~~~~~~~~~~~~~~~~~
   include/linux/build_bug.h:45:37: note: in expansion of macro 'compiletime_assert'
    #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
                                        ^~~~~~~~~~~~~~~~~~
   include/linux/build_bug.h:79:21: note: in expansion of macro 'BUILD_BUG_ON_MSG'
    #define BUILD_BUG() BUILD_BUG_ON_MSG(1, "BUILD_BUG failed")
                        ^~~~~~~~~~~~~~~~
   include/linux/huge_mm.h:250:28: note: in expansion of macro 'BUILD_BUG'
    #define HPAGE_PMD_SHIFT ({ BUILD_BUG(); 0; })
                               ^~~~~~~~~
   include/linux/huge_mm.h:80:26: note: in expansion of macro 'HPAGE_PMD_SHIFT'
    #define HPAGE_PMD_ORDER (HPAGE_PMD_SHIFT-PAGE_SHIFT)
                             ^~~~~~~~~~~~~~~
   include/linux/huge_mm.h:81:26: note: in expansion of macro 'HPAGE_PMD_ORDER'
    #define HPAGE_PMD_NR (1<<HPAGE_PMD_ORDER)
                             ^~~~~~~~~~~~~~~
   drivers/misc/vmw_balloon.c:659:39: note: in expansion of macro 'HPAGE_PMD_NR'
     if (target < size && size - target < HPAGE_PMD_NR && target != 0)
                                          ^~~~~~~~~~~~
   In file included from include/linux/mm.h:10:0,
                    from drivers/misc/vmw_balloon.c:21:
   In function 'vmballoon_alloc_page',
       inlined from 'vmballoon_inflate' at drivers/misc/vmw_balloon.c:702:8,
       inlined from 'vmballoon_work' at drivers/misc/vmw_balloon.c:971:4:
   include/linux/compiler.h:358:38: error: call to '__compiletime_assert_389' declared with attribute error: BUILD_BUG failed
     _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
                                         ^
   include/linux/gfp.h:518:46: note: in definition of macro 'alloc_pages'
      alloc_pages_node(numa_node_id(), gfp_mask, order)
                                                 ^~~~~
   include/linux/compiler.h:346:2: note: in expansion of macro '__compiletime_assert'
     __compiletime_assert(condition, msg, prefix, suffix)
     ^~~~~~~~~~~~~~~~~~~~
   include/linux/compiler.h:358:2: note: in expansion of macro '_compiletime_assert'
     _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
     ^~~~~~~~~~~~~~~~~~~
   include/linux/build_bug.h:45:37: note: in expansion of macro 'compiletime_assert'
    #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
                                        ^~~~~~~~~~~~~~~~~~
   include/linux/build_bug.h:79:21: note: in expansion of macro 'BUILD_BUG_ON_MSG'
    #define BUILD_BUG() BUILD_BUG_ON_MSG(1, "BUILD_BUG failed")
                        ^~~~~~~~~~~~~~~~
   include/linux/huge_mm.h:250:28: note: in expansion of macro 'BUILD_BUG'
    #define HPAGE_PMD_SHIFT ({ BUILD_BUG(); 0; })
                               ^~~~~~~~~
   include/linux/huge_mm.h:80:26: note: in expansion of macro 'HPAGE_PMD_SHIFT'
    #define HPAGE_PMD_ORDER (HPAGE_PMD_SHIFT-PAGE_SHIFT)
                             ^~~~~~~~~~~~~~~
   drivers/misc/vmw_balloon.c:389:49: note: in expansion of macro 'HPAGE_PMD_ORDER'
      return alloc_pages(VMW_HUGE_PAGE_ALLOC_FLAGS, HPAGE_PMD_ORDER);
                                                    ^~~~~~~~~~~~~~~

vim +/if +659 drivers/misc/vmw_balloon.c

   634	
   635	/**
   636	 * vmballoon_change - retrieve the required balloon change
   637	 *
   638	 * @b: pointer for the balloon.
   639	 *
   640	 * Return: the required change for the balloon size. A positive number
   641	 * indicates inflation, a negative number indicates a deflation.
   642	 */
   643	static int64_t vmballoon_change(struct vmballoon *b)
   644	{
   645		int64_t size, target;
   646	
   647		size = b->size;
   648		target = b->target;
   649	
   650		/*
   651		 * We must cast first because of int sizes
   652		 * Otherwise we might get huge positives instead of negatives
   653		 */
   654	
   655		if (b->reset_required)
   656			return 0;
   657	
   658		/* consider a 2MB slack on deflate, unless the balloon is emptied */
 > 659		if (target < size && size - target < HPAGE_PMD_NR && target != 0)
   660			return 0;
   661	
   662		return target - size;
   663	}
   664	

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