Re: [PATCH] mm: migrate: handle freed page at the first place

[kbuild test robot]

Hi Yang,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on mmotm/master]
[also build test WARNING on v5.4-rc7 next-20191112]
[if your patch is applied to the wrong git tree, please drop us a note to help
improve the system. BTW, we also suggest to use '--base' option to specify the
base tree in git format-patch, please see https://stackoverflow.com/a/37406982]

url:    https://github.com/0day-ci/linux/commits/Yang-Shi/mm-migrate-handle-freed-page-at-the-first-place/20191113-044923
base:   git://git.cmpxchg.org/linux-mmotm.git master
config: x86_64-rhel-7.6-kasan (attached as .config)
compiler: gcc-7 (Debian 7.4.0-14) 7.4.0
reproduce:
        # save the attached .config to linux build tree
        make ARCH=x86_64 

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

Note: it may well be a FALSE warning. FWIW you are at least aware of it now.
http://gcc.gnu.org/wiki/Better_Uninitialized_Warnings

All warnings (new ones prefixed by >>):

   In file included from include/asm-generic/bug.h:5:0,
                    from arch/x86/include/asm/bug.h:83,
                    from include/linux/bug.h:5,
                    from include/linux/mmdebug.h:5,
                    from include/linux/mm.h:9,
                    from include/linux/migrate.h:5,
                    from mm/migrate.c:16:
   mm/migrate.c: In function 'migrate_pages':
>> include/linux/compiler.h:188:26: warning: 'newpage' may be used uninitialized in this function [-Wmaybe-uninitialized]
     case 8: *(__u64 *)res = *(volatile __u64 *)p; break;  \
                             ^
   mm/migrate.c:1170:15: note: 'newpage' was declared here
     struct page *newpage;
                  ^~~~~~~

vim +/newpage +188 include/linux/compiler.h

230fa253df6352 Christian Borntraeger 2014-11-25  181  
d976441f44bc5d Andrey Ryabinin       2015-10-19  182  #define __READ_ONCE_SIZE						\
d976441f44bc5d Andrey Ryabinin       2015-10-19  183  ({									\
d976441f44bc5d Andrey Ryabinin       2015-10-19  184  	switch (size) {							\
d976441f44bc5d Andrey Ryabinin       2015-10-19  185  	case 1: *(__u8 *)res = *(volatile __u8 *)p; break;		\
d976441f44bc5d Andrey Ryabinin       2015-10-19  186  	case 2: *(__u16 *)res = *(volatile __u16 *)p; break;		\
d976441f44bc5d Andrey Ryabinin       2015-10-19  187  	case 4: *(__u32 *)res = *(volatile __u32 *)p; break;		\
d976441f44bc5d Andrey Ryabinin       2015-10-19 @188  	case 8: *(__u64 *)res = *(volatile __u64 *)p; break;		\
d976441f44bc5d Andrey Ryabinin       2015-10-19  189  	default:							\
d976441f44bc5d Andrey Ryabinin       2015-10-19  190  		barrier();						\
d976441f44bc5d Andrey Ryabinin       2015-10-19  191  		__builtin_memcpy((void *)res, (const void *)p, size);	\
d976441f44bc5d Andrey Ryabinin       2015-10-19  192  		barrier();						\
d976441f44bc5d Andrey Ryabinin       2015-10-19  193  	}								\
d976441f44bc5d Andrey Ryabinin       2015-10-19  194  })
d976441f44bc5d Andrey Ryabinin       2015-10-19  195  

:::::: The code at line 188 was first introduced by commit
:::::: d976441f44bc5d48635d081d277aa76556ffbf8b compiler, atomics, kasan: Provide READ_ONCE_NOCHECK()

:::::: TO: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
:::::: CC: Ingo Molnar <mingo@xxxxxxxxxx>

---
0-DAY kernel test infrastructure                 Open Source Technology Center
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