Re: [PATCH 4.4 20/43] mm/vmalloc: add interfaces to free unmapped page table

[Nathan Chancellor]

On Tue, Mar 27, 2018 at 08:40:56PM +0000, Kani, Toshi wrote:
> On Tue, 2018-03-27 at 13:31 -0700, Nathan Chancellor wrote:
> > On Tue, Mar 27, 2018 at 03:17:00PM -0500, Dan Rue wrote:
> > > On Tue, Mar 27, 2018 at 06:27:24PM +0200, Greg Kroah-Hartman wrote:
> > > > 4.4-stable review patch.  If anyone has any objections, please let me know.
> > > > 
>  :
> > > 
> > > This patch causes the following build error on 4.4 arm64:
> > > 
> > > $ make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- O=build-arm64 defconfig
> > > $ make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- O=build-arm64
> > > 
> > >   CC      arch/arm64/mm/mmu.o
> > > ../arch/arm64/mm/mmu.c:701:5: error: redefinition of âpud_free_pmd_pageâ
> > >  int pud_free_pmd_page(pud_t *pud)
> > >      ^~~~~~~~~~~~~~~~~
> > > In file included from ../arch/arm64/include/asm/pgtable.h:682:0,
> > >                  from ../include/linux/mm.h:55,
> > >                  from ../include/linux/mman.h:4,
> > >                  from ../arch/arm64/mm/mmu.c:25:
> > > ../include/asm-generic/pgtable.h:777:19: note: previous definition of âpud_free_pmd_pageâ was here
> > >  static inline int pud_free_pmd_page(pud_t *pud)
> > >                    ^~~~~~~~~~~~~~~~~
> > > ../arch/arm64/mm/mmu.c:706:5: error: redefinition of âpmd_free_pte_pageâ
> > >  int pmd_free_pte_page(pmd_t *pmd)
> > >      ^~~~~~~~~~~~~~~~~
> > > In file included from ../arch/arm64/include/asm/pgtable.h:682:0,
> > >                  from ../include/linux/mm.h:55,
> > >                  from ../include/linux/mman.h:4,
> > >                  from ../arch/arm64/mm/mmu.c:25:
> > > ../include/asm-generic/pgtable.h:781:19: note: previous definition of âpmd_free_pte_pageâ was here
> > >  static inline int pmd_free_pte_page(pmd_t *pmd)
> > >                    ^~~~~~~~~~~~~~~~~
> > > make[2]: *** [../scripts/Makefile.build:270: arch/arm64/mm/mmu.o] Error 1
> > > make[1]: *** [/home/drue/src/linux/4.4-rc/Makefile:969: arch/arm64/mm] Error 2
> > > make[1]: Leaving directory '/home/drue/src/linux/4.4-rc/build-arm64'
> > > make: *** [Makefile:152: sub-make] Error 2
> > > 
> > > 
> > 
> > Both of my arm64 devices built fine with this patch... It seems like
> > the only way to hit that error is if HAVE_ARCH_HUGE_VMAP isn't set,
> > which seems impossible since it is selected by ARM64...
> > 
> > Someone smarter than I might have more insight but this patch is
> > unchanged from upstream so I can only assume that this error would
> > manifest there as well.
> 
> It appears that HAVE_ARCH_HUGE_VMAP was introduced in 4.6 on arm64. 
> Hence the problem in 4.4.
> 
> Thanks,
> -Toshi
> 

Ah, thanks for the heads up, since I have 324420bf91f6 ("arm64: add
support for ioremap() block mappings") in my tree due to Linaro's
backport of it for their Linaro Stable Kernel, which serves as a base
for most Android kernels. My apologies for not digging deeper and sorry
for the noise!

Cheers!
Nathan