Re: [PATCH 2/2] mm/gup: fix a misnamed "write" argument: should be "flags"

From: John Hubbard
Date: Mon Oct 14 2019 - 02:45:42 EST

On 10/13/19 11:12 PM, kbuild test robot wrote:
Hi John,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on linus/master]
[cannot apply to v5.4-rc3 next-20191011]
[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/John-Hubbard/gup-c-gup_benchmark-c-trivial-fixes-before-the-storm/20191014-114158
config: powerpc-defconfig (attached as .config)
compiler: powerpc64-linux-gcc (GCC) 7.4.0
reproduce:
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# save the attached .config to linux build tree
GCC_VERSION=7.4.0 make.cross ARCH=powerpc

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

All errors (new ones prefixed by >>):

mm/gup.c: In function 'gup_hugepte':
mm/gup.c:1990:33: error: 'write' undeclared (first use in this function); did you mean 'writeq'?
if (!pte_access_permitted(pte, write))
^~~~~
writeq
mm/gup.c:1990:33: note: each undeclared identifier is reported only once for each function it appears in


OK, so this shows that my cross-compiler test scripts are faulty lately,
sorry I missed this.

But more importantly, the above missed case is an example of when "write" really
means "write", as opposed to meaning flags.

Please put this patch on hold or drop it, until we hear from the authors as to how
they would like to resolve this. I suspect it will end up as something like:

bool write = (flags & FOLL_WRITE);

...perhaps?


thanks,
--
John Hubbard
NVIDIA


vim +1990 mm/gup.c

cbd34da7dc9afd Christoph Hellwig 2019-07-11 1974
cbd34da7dc9afd Christoph Hellwig 2019-07-11 1975 static int gup_hugepte(pte_t *ptep, unsigned long sz, unsigned long addr,
cc492e4c15e804 John Hubbard 2019-10-13 1976 unsigned long end, int flags, struct page **pages,
cc492e4c15e804 John Hubbard 2019-10-13 1977 int *nr)
cbd34da7dc9afd Christoph Hellwig 2019-07-11 1978 {
cbd34da7dc9afd Christoph Hellwig 2019-07-11 1979 unsigned long pte_end;
cbd34da7dc9afd Christoph Hellwig 2019-07-11 1980 struct page *head, *page;
cbd34da7dc9afd Christoph Hellwig 2019-07-11 1981 pte_t pte;
cbd34da7dc9afd Christoph Hellwig 2019-07-11 1982 int refs;
cbd34da7dc9afd Christoph Hellwig 2019-07-11 1983
cbd34da7dc9afd Christoph Hellwig 2019-07-11 1984 pte_end = (addr + sz) & ~(sz-1);
cbd34da7dc9afd Christoph Hellwig 2019-07-11 1985 if (pte_end < end)
cbd34da7dc9afd Christoph Hellwig 2019-07-11 1986 end = pte_end;
cbd34da7dc9afd Christoph Hellwig 2019-07-11 1987
cbd34da7dc9afd Christoph Hellwig 2019-07-11 1988 pte = READ_ONCE(*ptep);
cbd34da7dc9afd Christoph Hellwig 2019-07-11 1989
cbd34da7dc9afd Christoph Hellwig 2019-07-11 @1990 if (!pte_access_permitted(pte, write))
cbd34da7dc9afd Christoph Hellwig 2019-07-11 1991 return 0;
cbd34da7dc9afd Christoph Hellwig 2019-07-11 1992
cbd34da7dc9afd Christoph Hellwig 2019-07-11 1993 /* hugepages are never "special" */
cbd34da7dc9afd Christoph Hellwig 2019-07-11 1994 VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
cbd34da7dc9afd Christoph Hellwig 2019-07-11 1995
cbd34da7dc9afd Christoph Hellwig 2019-07-11 1996 refs = 0;
cbd34da7dc9afd Christoph Hellwig 2019-07-11 1997 head = pte_page(pte);
cbd34da7dc9afd Christoph Hellwig 2019-07-11 1998
cbd34da7dc9afd Christoph Hellwig 2019-07-11 1999 page = head + ((addr & (sz-1)) >> PAGE_SHIFT);
cbd34da7dc9afd Christoph Hellwig 2019-07-11 2000 do {
cbd34da7dc9afd Christoph Hellwig 2019-07-11 2001 VM_BUG_ON(compound_head(page) != head);
cbd34da7dc9afd Christoph Hellwig 2019-07-11 2002 pages[*nr] = page;
cbd34da7dc9afd Christoph Hellwig 2019-07-11 2003 (*nr)++;
cbd34da7dc9afd Christoph Hellwig 2019-07-11 2004 page++;
cbd34da7dc9afd Christoph Hellwig 2019-07-11 2005 refs++;
cbd34da7dc9afd Christoph Hellwig 2019-07-11 2006 } while (addr += PAGE_SIZE, addr != end);
cbd34da7dc9afd Christoph Hellwig 2019-07-11 2007
01a369160bbea4 Christoph Hellwig 2019-07-11 2008 head = try_get_compound_head(head, refs);
01a369160bbea4 Christoph Hellwig 2019-07-11 2009 if (!head) {
cbd34da7dc9afd Christoph Hellwig 2019-07-11 2010 *nr -= refs;
cbd34da7dc9afd Christoph Hellwig 2019-07-11 2011 return 0;
cbd34da7dc9afd Christoph Hellwig 2019-07-11 2012 }
cbd34da7dc9afd Christoph Hellwig 2019-07-11 2013
cbd34da7dc9afd Christoph Hellwig 2019-07-11 2014 if (unlikely(pte_val(pte) != pte_val(*ptep))) {
cbd34da7dc9afd Christoph Hellwig 2019-07-11 2015 /* Could be optimized better */
cbd34da7dc9afd Christoph Hellwig 2019-07-11 2016 *nr -= refs;
cbd34da7dc9afd Christoph Hellwig 2019-07-11 2017 while (refs--)
cbd34da7dc9afd Christoph Hellwig 2019-07-11 2018 put_page(head);
cbd34da7dc9afd Christoph Hellwig 2019-07-11 2019 return 0;
cbd34da7dc9afd Christoph Hellwig 2019-07-11 2020 }
cbd34da7dc9afd Christoph Hellwig 2019-07-11 2021
520b4a4496f12b Christoph Hellwig 2019-07-11 2022 SetPageReferenced(head);
cbd34da7dc9afd Christoph Hellwig 2019-07-11 2023 return 1;
cbd34da7dc9afd Christoph Hellwig 2019-07-11 2024 }
cbd34da7dc9afd Christoph Hellwig 2019-07-11 2025

:::::: The code at line 1990 was first introduced by commit
:::::: cbd34da7dc9afd521e0bea5e7d12701f4a9da7c7 mm: move the powerpc hugepd code to mm/gup.c

:::::: TO: Christoph Hellwig <hch@xxxxxx>
:::::: CC: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>

---
0-DAY kernel test infrastructure Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all Intel Corporation