linux-kernel - Re: [PATCH mm-new v3 3/3] mm/khugepaged: merge PTE scanning logic into a new helper

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Message-Id: <20251008180744.008424134fbc29e9616899ad@linux-foundation.org>
Date: Wed, 8 Oct 2025 18:07:44 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: Lance Yang <lance.yang@...ux.dev>
Cc: david@...hat.com, lorenzo.stoakes@...cle.com, ziy@...dia.com,
 baolin.wang@...ux.alibaba.com, Liam.Howlett@...cle.com, npache@...hat.com,
 ryan.roberts@....com, dev.jain@....com, baohua@...nel.org,
 ioworker0@...il.com, richard.weiyang@...il.com,
 linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH mm-new v3 3/3] mm/khugepaged: merge PTE scanning logic
 into a new helper

On Wed,  8 Oct 2025 12:37:48 +0800 Lance Yang <lance.yang@...ux.dev> wrote:

> +		if (!cc->is_khugepaged ||
> +		    *unmapped <= khugepaged_max_ptes_swap) {
> +			/*
> +			 * Always be strict with uffd-wp enabled swap
> +			 * entries. Please see comment below for
> +			 * pte_uffd_wp().
> +			 */
> +			if (pte_swp_uffd_wp(pte)) {
> +				*scan_result = SCAN_PTE_UFFD_WP;
> +				return PTE_CHECK_FAIL;
> +			}
> +			return PTE_CHECK_CONTINUE;
> +		} else {
> +			*scan_result = SCAN_EXCEED_SWAP_PTE;
> +			count_vm_event(THP_SCAN_EXCEED_SWAP_PTE);
> +			return PTE_CHECK_FAIL;
> +		}

I'm inclined to agree with checkpatch here.

WARNING: else is not generally useful after a break or return
#81: FILE: mm/khugepaged.c:574:
+			return PTE_CHECK_CONTINUE;
+		} else {

did you see this and disagree or did you forget to run checkpatch?

--- a/mm/khugepaged.c~mm-khugepaged-merge-pte-scanning-logic-into-a-new-helper-checkpatch-fixes
+++ a/mm/khugepaged.c
@@ -571,11 +571,10 @@ static inline int thp_collapse_check_pte
 		    (!cc->is_khugepaged ||
 		     *none_or_zero <= khugepaged_max_ptes_none)) {
 			return PTE_CHECK_CONTINUE;
-		} else {
-			*scan_result = SCAN_EXCEED_NONE_PTE;
-			count_vm_event(THP_SCAN_EXCEED_NONE_PTE);
-			return PTE_CHECK_FAIL;
 		}
+		*scan_result = SCAN_EXCEED_NONE_PTE;
+		count_vm_event(THP_SCAN_EXCEED_NONE_PTE);
+		return PTE_CHECK_FAIL;
 	} else if (!pte_present(pte)) {
 		if (!unmapped) {
 			*scan_result = SCAN_PTE_NON_PRESENT;
@@ -600,11 +599,10 @@ static inline int thp_collapse_check_pte
 				return PTE_CHECK_FAIL;
 			}
 			return PTE_CHECK_CONTINUE;
-		} else {
-			*scan_result = SCAN_EXCEED_SWAP_PTE;
-			count_vm_event(THP_SCAN_EXCEED_SWAP_PTE);
-			return PTE_CHECK_FAIL;
 		}
+		*scan_result = SCAN_EXCEED_SWAP_PTE;
+		count_vm_event(THP_SCAN_EXCEED_SWAP_PTE);
+		return PTE_CHECK_FAIL;
 	} else if (pte_uffd_wp(pte)) {
 		/*
 		 * Don't collapse the page if any of the small PTEs are
_