[akpm-mm:mm-unstable 260/261] mm/hugetlb_vmemmap.c:110:17: error: call to undeclared function 'sparse_decode_mem_map'; ISO C99 and later do not support implicit function declarations

[kernel test robot <lkp@xxxxxxxxx>]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-unstable
head:   882be1ed6b1b5073fc88552181b99bd2b9c0031f
commit: 10a76873547090b69a8c47788065a24696b152c3 [260/261] mm: memory_hotplug: make hugetlb_optimize_vmemmap compatible with memmap_on_memory
config: x86_64-randconfig-a013-20220620 (https://download.01.org/0day-ci/archive/20220620/202206200857.ZpTFxNAY-lkp@xxxxxxxxx/config)
compiler: clang version 15.0.0 (https://github.com/llvm/llvm-project af6d2a0b6825e71965f3e2701a63c239fa0ad70f)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git/commit/?id=10a76873547090b69a8c47788065a24696b152c3
        git remote add akpm-mm https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git
        git fetch --no-tags akpm-mm mm-unstable
        git checkout 10a76873547090b69a8c47788065a24696b152c3
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash

If you fix the issue, kindly add following tag where applicable
Reported-by: kernel test robot <lkp@xxxxxxxxx>

All error/warnings (new ones prefixed by >>):

>> mm/hugetlb_vmemmap.c:110:17: error: call to undeclared function 'sparse_decode_mem_map'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
           vmemmap_page = sparse_decode_mem_map(ms->section_mem_map,
                          ^
>> mm/hugetlb_vmemmap.c:110:15: warning: incompatible integer to pointer conversion assigning to 'struct page *' from 'int' [-Wint-conversion]
           vmemmap_page = sparse_decode_mem_map(ms->section_mem_map,
                        ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   1 warning and 1 error generated.


vim +/sparse_decode_mem_map +110 mm/hugetlb_vmemmap.c

    98	
    99	static unsigned int vmemmap_optimizable_pages(struct hstate *h,
   100						      struct page *head)
   101	{
   102		struct mem_section *ms;
   103		struct page *vmemmap_page;
   104		unsigned long pfn = page_to_pfn(head);
   105	
   106		if (READ_ONCE(vmemmap_optimize_mode) == VMEMMAP_OPTIMIZE_OFF)
   107			return 0;
   108	
   109		ms = __pfn_to_section(pfn);
 > 110		vmemmap_page = sparse_decode_mem_map(ms->section_mem_map,
   111						     pfn_to_section_nr(pfn));
   112		/*
   113		 * Only the vmemmap pages' vmemmap may be marked as VmemmapSelfHosted.
   114		 *
   115		 * Due to HugeTLB alignment requirements, and the vmemmap pages being
   116		 * at the start of the hotplugged memory region. Checking any vmemmap
   117		 * page's vmemmap is fine.
   118		 *
   119		 * [      hotplugged memory     ]
   120		 * [ vmemmap ][  usable memory  ]
   121		 *   ^   |      |            |
   122		 *   +---+      |            |
   123		 *     ^        |            |
   124		 *     +--------+            |
   125		 *         ^                 |
   126		 *         +-----------------+
   127		 */
   128		if (PageVmemmapSelfHosted(vmemmap_page))
   129			return 0;
   130	
   131		return hugetlb_optimize_vmemmap_pages(h);
   132	}
   133	

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