mm: mmap: no need to call khugepaged_enter_vma() for stack

We avoid allocating THP for temporary stack, even though
khugepaged_enter_vma() is called for stack VMAs, it actualy returns
false.  So no need to call it in the first place at all.

Link: https://lkml.kernel.org/r/20231221065943.2803551-1-shy828301@gmail.comSigned-off-by: Yang Shi <yang@os.amperecomputing.com>
Reviewed-by: Yin Fengwei <fengwei.yin@intel.com>
Cc: Christopher Lameter <cl@linux.com>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: kernel test robot <oliver.sang@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/mmap.c

@@ -2051,7 +2051,6 @@ static int expand_upwards(struct vm_area_struct *vma, unsigned long address)
 		}
 	}
 	anon_vma_unlock_write(vma->anon_vma);
-	khugepaged_enter_vma(vma, vma->vm_flags);
 	mas_destroy(&mas);
 	validate_mm(mm);
 	return error;
@@ -2145,7 +2144,6 @@ int expand_downwards(struct vm_area_struct *vma, unsigned long address)
 		}
 	}
 	anon_vma_unlock_write(vma->anon_vma);
-	khugepaged_enter_vma(vma, vma->vm_flags);
 	mas_destroy(&mas);
 	validate_mm(mm);
 	return error;