Instead of changing the page's tag solely in order to obtain a pointer with a match-all tag and then changing it back again, just convert the pointer that we get from kmap_atomic() into one with a match-all tag before passing it to clear_page(). On a certain microarchitecture, this has been observed to cause a measurable improvement in microbenchmark performance, presumably as a result of being able to avoid the atomic operations on the page tag. Signed-off-by: Peter Collingbourne <pcc@xxxxxxxxxx> Link: https://linux-review.googlesource.com/id/I0249822cc29097ca7a04ad48e8eb14871f80e711 --- v2: - switched to kmap_local_page() include/linux/highmem.h | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-) diff --git a/include/linux/highmem.h b/include/linux/highmem.h index 44242268f53b..212fd081b227 100644 --- a/include/linux/highmem.h +++ b/include/linux/highmem.h @@ -245,12 +245,10 @@ static inline void clear_highpage(struct page *page) static inline void clear_highpage_kasan_tagged(struct page *page) { - u8 tag; + void *kaddr = kmap_local_page(page); - tag = page_kasan_tag(page); - page_kasan_tag_reset(page); - clear_highpage(page); - page_kasan_tag_set(page, tag); + clear_page(kasan_reset_tag(kaddr)); + kunmap_local(kaddr); } #ifndef __HAVE_ARCH_TAG_CLEAR_HIGHPAGE -- 2.39.2.637.g21b0678d19-goog
