linux-kernel - [RFC PATCH 02/16] mm/madvise: split out populate behavior check logic

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Message-Id: <20250305181611.54484-3-sj@kernel.org>
Date: Wed,  5 Mar 2025 10:15:57 -0800
From: SeongJae Park <sj@...nel.org>
To: 
Cc: SeongJae Park <sj@...nel.org>,
	"Liam R. Howlett" <howlett@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	David Hildenbrand <david@...hat.com>,
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
	Shakeel Butt <shakeel.butt@...ux.dev>,
	Vlastimil Babka <vbabka@...e.cz>,
	kernel-team@...a.com,
	linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: [RFC PATCH 02/16] mm/madvise: split out populate behavior check logic

madvise_do_behavior() has a long open-coded 'behavior' check for
MADV_POPULATE_{READ,WRITE}.  It adds multiple layers[1] and make the
code arguably take longer time to read.  Like is_memory_failure(), split
out the check to a separate function.  This is not technically removing
the additional layer but discourage further extending the switch-case.
Also it makes madvise_do_behavior() code shorter and therefore easier to
read.

[1] https://lore.kernel.org/bd6d0bf1-c79e-46bd-a810-9791efb9ad73@lucifer.local

Signed-off-by: SeongJae Park <sj@...nel.org>
---
 mm/madvise.c | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/mm/madvise.c b/mm/madvise.c
index dbc8fec05cc6..4a91590656dc 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -1633,6 +1633,17 @@ static bool is_valid_madvise(unsigned long start, size_t len_in, int behavior)
 	return true;
 }
 
+static bool is_memory_populate(int behavior)
+{
+	switch (behavior) {
+	case MADV_POPULATE_READ:
+	case MADV_POPULATE_WRITE:
+		return true;
+	default:
+		return false;
+	}
+}
+
 static int madvise_do_behavior(struct mm_struct *mm,
 		unsigned long start, size_t len_in, size_t len, int behavior)
 {
@@ -1646,16 +1657,11 @@ static int madvise_do_behavior(struct mm_struct *mm,
 	end = start + len;
 
 	blk_start_plug(&plug);
-	switch (behavior) {
-	case MADV_POPULATE_READ:
-	case MADV_POPULATE_WRITE:
+	if (is_memory_populate(behavior))
 		error = madvise_populate(mm, start, end, behavior);
-		break;
-	default:
+	else
 		error = madvise_walk_vmas(mm, start, end, behavior,
 					  madvise_vma_behavior);
-		break;
-	}
 	blk_finish_plug(&plug);
 	return error;
 }
-- 
2.39.5