mm/mmap: leave adjust_next as virtual address instead of page frame number

Instead of converting adjust_next between bytes and pages number, let's
just store the virtual address into adjust_next.

Also, this patch fixes one typo in the comment of vma_adjust_trans_huge().

[vbabka@suse.cz: changelog tweak]

Signed-off-by: Wei Yang <richard.weiyang@linux.alibaba.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Link: http://lkml.kernel.org/r/20200828081031.11306-1-richard.weiyang@linux.alibaba.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index ec0f0cc..65c289c 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2306,13 +2306,13 @@ void vma_adjust_trans_huge(struct vm_area_struct *vma,
 
 	/*
 	 * If we're also updating the vma->vm_next->vm_start, if the new
-	 * vm_next->vm_start isn't page aligned and it could previously
+	 * vm_next->vm_start isn't hpage aligned and it could previously
 	 * contain an hugepage: check if we need to split an huge pmd.
 	 */
 	if (adjust_next > 0) {
 		struct vm_area_struct *next = vma->vm_next;
 		unsigned long nstart = next->vm_start;
-		nstart += adjust_next << PAGE_SHIFT;
+		nstart += adjust_next;
 		if (nstart & ~HPAGE_PMD_MASK &&
 		    (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
 		    (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)