Re: [PATCH 3/3] mm: thp: relocate flush_cache_range() in migrate_misplaced_transhuge_page()

[Andrea Arcangeli <aarcange@redhat.com>]

On Sun, Oct 14, 2018 at 05:58:27PM +0800, kbuild test robot wrote:
> Hi Andrea,
> 
> Thank you for the patch! Yet something to improve:
> 
> [auto build test ERROR on linux-sof-driver/master]
> [also build test ERROR on v4.19-rc7 next-20181012]
> [if your patch is applied to the wrong git tree, please drop us a note to help improve the system]
> 
> url:    https://github.com/0day-ci/linux/commits/Andrea-Arcangeli/mm-thp-fix-MADV_DONTNEED-vs-migrate_misplaced_transhuge_page-race-condition/20181014-143004
> base:   https://github.com/thesofproject/linux master
> config: arm64-defconfig (attached as .config)
> compiler: aarch64-linux-gnu-gcc (Debian 7.2.0-11) 7.2.0
> 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=7.2.0 make.cross ARCH=arm64 
> 
> All errors (new ones prefixed by >>):
> 
>    mm/migrate.c: In function 'migrate_misplaced_transhuge_page':
> >> mm/migrate.c:2054:32: error: 'end' undeclared (first use in this function); did you mean '_end'?
>      flush_cache_range(vma, start, end + HPAGE_PMD_SIZE);
>                                    ^~~
>                                    _end
>    mm/migrate.c:2054:32: note: each undeclared identifier is reported only once for each function it appears in

Nice non-x86 coverage. I intended converted "end" to "start +
HPAGE_PMD_SIZE" to delete the "end" variable purely to shut off a
warning about unused "end" var from gcc on x86, but the s/end/start/
was missed and it still build fine on x86 but not anymore on aarch64.

Anyway I'm waiting some feedback about the whole patchset, before
resending patch 3/3.

diff --git a/mm/migrate.c b/mm/migrate.c
index 9bf5fe9a1008..8afb41167641 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -2050,7 +2050,7 @@ int migrate_misplaced_transhuge_page(struct mm_struct *mm,
 	new_page->mapping = page->mapping;
 	new_page->index = page->index;
 	/* flush the cache before copying using the kernel virtual address */
-	flush_cache_range(vma, start, end + HPAGE_PMD_SIZE);
+	flush_cache_range(vma, start, start + HPAGE_PMD_SIZE);
 	migrate_page_copy(new_page, page);
 	WARN_ON(PageLRU(new_page));
 

Thanks!
Andrea