+ samples-damon-fix-damon-sample-mtier-for-start-failure.patch added to mm-hotfixes-unstable branch

+ samples-damon-fix-damon-sample-mtier-for-start-failure.patch added to mm-hotfixes-unstable branch

[Andrew Morton]

The patch titled
     Subject: samples/damon: fix damon sample mtier for start failure
has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
     samples-damon-fix-damon-sample-mtier-for-start-failure.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/samples-damon-fix-damon-sample-mtier-for-start-failure.patch

This patch will later appear in the mm-hotfixes-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Honggyu Kim <honggyu.kim@sk.com>
Subject: samples/damon: fix damon sample mtier for start failure
Date: Wed, 2 Jul 2025 09:02:03 +0900

The damon_sample_mtier_start() can fail so we must reset the "enable"
parameter to "false" again for proper rollback.

In such cases, setting Y to "enable" then N triggers the similar crash
with mtier because damon sample start failed but the "enable" stays as Y.

Link: https://lkml.kernel.org/r/20250702000205.1921-4-honggyu.kim@sk.com
Fixes: 82a08bde3cf7 ("samples/damon: implement a DAMON module for memory tiering")
Signed-off-by: Honggyu Kim <honggyu.kim@sk.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 samples/damon/mtier.c |    8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

--- a/samples/damon/mtier.c~samples-damon-fix-damon-sample-mtier-for-start-failure
+++ a/samples/damon/mtier.c
@@ -164,8 +164,12 @@ static int damon_sample_mtier_enable_sto
 	if (enable == enabled)
 		return 0;
 
-	if (enable)
-		return damon_sample_mtier_start();
+	if (enable) {
+		err = damon_sample_mtier_start();
+		if (err)
+			enable = false;
+		return err;
+	}
 	damon_sample_mtier_stop();
 	return 0;
 }
_

Patches currently in -mm which might be from honggyu.kim@sk.com are

samples-damon-fix-damon-sample-prcl-for-start-failure.patch
samples-damon-fix-damon-sample-wsse-for-start-failure.patch
samples-damon-fix-damon-sample-mtier-for-start-failure.patch
mm-damon-fix-divide-by-zero-in-damon_get_intervals_score.patch