[RFC PATCH 4/8] mm/vmalloc: Eliminate page table zigzag for huge vmalloc mappings

["Barry Song (Xiaomi)" <baohua@kernel.org>]

For vmalloc() allocations with VM_ALLOW_HUGE_VMAP, we no longer
need to iterate over pages one by one, which would otherwise lead to
zigzag page table mappings.

The code is now unified with the PAGE_SHIFT case by simply
calling vmap_small_pages_range_noflush().

Signed-off-by: Barry Song (Xiaomi) <baohua@kernel.org>
---
 mm/vmalloc.c | 22 ++++------------------
 1 file changed, 4 insertions(+), 18 deletions(-)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 5bf072297536..eba436386929 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -689,27 +689,13 @@ static int vmap_small_pages_range_noflush(unsigned long addr, unsigned long end,
 int __vmap_pages_range_noflush(unsigned long addr, unsigned long end,
 		pgprot_t prot, struct page **pages, unsigned int page_shift)
 {
-	unsigned int i, nr = (end - addr) >> PAGE_SHIFT;
-
 	WARN_ON(page_shift < PAGE_SHIFT);
 
-	if (!IS_ENABLED(CONFIG_HAVE_ARCH_HUGE_VMALLOC) ||
-			page_shift == PAGE_SHIFT)
-		return vmap_small_pages_range_noflush(addr, end, prot, pages, PAGE_SHIFT);
-
-	for (i = 0; i < nr; i += 1U << (page_shift - PAGE_SHIFT)) {
-		int err;
-
-		err = vmap_range_noflush(addr, addr + (1UL << page_shift),
-					page_to_phys(pages[i]), prot,
-					page_shift);
-		if (err)
-			return err;
+	if (!IS_ENABLED(CONFIG_HAVE_ARCH_HUGE_VMALLOC))
+		page_shift = PAGE_SHIFT;
 
-		addr += 1UL << page_shift;
-	}
-
-	return 0;
+	return vmap_small_pages_range_noflush(addr, end, prot, pages,
+			min(page_shift, PMD_SHIFT));
 }
 
 int vmap_pages_range_noflush(unsigned long addr, unsigned long end,
-- 
2.39.3 (Apple Git-146)