[linux-next:master 9018/9031] mm/migrate.c:2177:4: note: in expansion of macro 'ptep_get_and_clear'

[linux-next:master 9018/9031] mm/migrate.c:2177:4: note: in expansion of macro 'ptep_get_and_clear'

[kbuild test robot]

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tree:   https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
head:   f8c97bdb49832d2b0edaa0c05db873aa2f6101ff
commit: ceab27c72f70ce7759f0f1415b83ee6d37f54a42 [9018/9031] mm/migrate: migrate_vma() unmap page from vma while collecting pages
config: m32r-allyesconfig (attached as .config)
compiler: m32r-linux-gcc (GCC) 6.2.0
reproduce:
        wget https://raw.githubusercontent.com/01org/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        git checkout ceab27c72f70ce7759f0f1415b83ee6d37f54a42
        # save the attached .config to linux build tree
        make.cross ARCH=m32r 

All warnings (new ones prefixed by >>):

   mm/migrate.c: In function 'migrate_vma_collect_hole':
   mm/migrate.c:2104:22: warning: unused variable 'next' [-Wunused-variable]
     unsigned long addr, next;
                         ^~~~
   In file included from arch/m32r/include/asm/m32r.h:146:0,
                    from arch/m32r/include/asm/ptrace.h:15,
                    from arch/m32r/include/asm/processor.h:18,
                    from arch/m32r/include/asm/thread_info.h:14,
                    from include/linux/thread_info.h:37,
                    from include/asm-generic/preempt.h:4,
                    from ./arch/m32r/include/generated/asm/preempt.h:1,
                    from include/linux/preempt.h:80,
                    from include/linux/spinlock.h:50,
                    from include/linux/mmzone.h:7,
                    from include/linux/gfp.h:5,
                    from include/linux/mm.h:9,
                    from include/linux/migrate.h:4,
                    from mm/migrate.c:15:
   mm/migrate.c: In function 'migrate_vma_collect_pmd':
   arch/m32r/include/asm/page.h:39:18: warning: value computed is not used [-Wunused-value]
    #define __pte(x) ((pte_t) { (x) } )
                     ^
>> arch/m32r/include/asm/pgtable-2level.h:66:40: note: in expansion of macro '__pte'
    #define ptep_get_and_clear(mm,addr,xp) __pte(xchg(&(xp)->pte, 0))
                                           ^~~~~
>> mm/migrate.c:2177:4: note: in expansion of macro 'ptep_get_and_clear'
       ptep_get_and_clear(mm, addr, ptep);
       ^~~~~~~~~~~~~~~~~~

vim +/ptep_get_and_clear +2177 mm/migrate.c

  2161			 * can't be dropped from it).
  2162			 */
  2163			get_page(page);
  2164			migrate->cpages++;
  2165			mpfn = migrate_pfn(pfn) | MIGRATE_PFN_MIGRATE;
  2166			mpfn |= pte_write(pte) ? MIGRATE_PFN_WRITE : 0;
  2167	
  2168			/*
  2169			 * Optimize for the common case where page is only mapped once
  2170			 * in one process. If we can lock the page, then we can safely
  2171			 * set up a special migration page table entry now.
  2172			 */
  2173			if (trylock_page(page)) {
  2174				pte_t swp_pte;
  2175	
  2176				mpfn |= MIGRATE_PFN_LOCKED;
> 2177				ptep_get_and_clear(mm, addr, ptep);
  2178	
  2179				/* Setup special migration page table entry */
  2180				entry = make_migration_entry(page, pte_write(pte));
  2181				swp_pte = swp_entry_to_pte(entry);
  2182				if (pte_soft_dirty(pte))
  2183					swp_pte = pte_swp_mksoft_dirty(swp_pte);
  2184				set_pte_at(mm, addr, ptep, swp_pte);
  2185	

---
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