Re: [PATCH v2 2/2] mm/mglru: make retry logic explicit in isolate_folios()

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

On Thu, Sep 3, 2026 at 9:27 AM Baoquan He <baoquan.he@linux.dev> wrote:
>
[...]
>
> Thanks, Barry. These number is very convincing. The retry for swappiness
> 0 is worthy. Then the patchset feels like doing two things: refactoring
> the for() loop; improving the eviction for swappiness 0/201 by adding a
> retry and this also makes them be consistent with (1, 200). While the
> cover letter subject, patch 1 and patch 2 feels like it's not easy to
> match them to the corresponding part. Maybe merging them to one patch,
> or rearranging them? Just personal opinion.
>

Hi Baoquan,

Thanks very much for your suggestions and review.
We have two patches:

1. `mm/mglru: make type fallback logic explicit in isolate_folios()`
2. `mm/mglru: make retry logic explicit in isolate_folios()`

One handles fallback, while the other handles retry. I think this
separation makes the logic clearer. Could we keep the current
separation?

But we may really need Andrew's kind help to squash the change
you found below:


From 1fb8046662a8b23be1b87a21cc9964e9ff9e1eb0 Mon Sep 17 00:00:00 2001
From: "Barry Song (Xiaomi)" <baohua@kernel.org>
Date: Thu, 3 Sep 2026 14:48:52 +0800
Subject: [PATCH] mm: revert slight behavior change for swappiness 1-200

Baoquan's review found that we unexpectedly introduced a slight behavior
change for swappiness 1-200. We could now have a case like:

1. First scan -> `scanned != 0`
2. Second scan -> `scanned = 0`
3. Type fallback

Step 3 was impossible before. Let's remove this possibility.

Reported-by: Baoquan He <baoquan.he@linux.dev>
Closes: https://lore.kernel.org/linux-mm/apfZQE1X6zGAsBb_@fedora/
Signed-off-by: Barry Song (Xiaomi) <baohua@kernel.org>
---
 mm/vmscan.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index bf2786c7247d..ba7adf36e69f 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -4939,7 +4939,7 @@ static int isolate_folios(unsigned long nr_to_scan, struct lruvec *lruvec,
 	 * We are running out of the current reclaim type. Fall back to
 	 * the other type if allowed.
 	 */
-	if (!scanned && type_fallback_allowed) {
+	if (!scanned && !tried && type_fallback_allowed) {
 		type = !type;
 		tried = true;
 		type_fallback_allowed = false;
-- 
2.39.3 (Apple Git-146)