FAILED: patch "[PATCH] mm/damon/core: trace esz at first setup" failed to apply to 6.18-stable tree

The patch below does not apply to the 6.18-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.18.y
git checkout FETCH_HEAD
git cherry-pick -x 7e6cc35f5283eab81a14231a64ecd640b690c48c
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026072016-imprison-unknown-9cd4@gregkh' --subject-prefix 'PATCH 6.18.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 7e6cc35f5283eab81a14231a64ecd640b690c48c Mon Sep 17 00:00:00 2001
From: SeongJae Park <[email protected]>
Date: Wed, 20 May 2026 08:03:10 -0700
Subject: [PATCH] mm/damon/core: trace esz at first setup

DAMON traces effective size quota from the second update, only if a change has been made by the update. Tracing only changed updates was an intentional decision to avoid unnecessary same value tracing. Always skipping the first value is just an unintended mistake.

The mistake makes the tracepoint based investigation incomplete, because the first effective size quota is never traced. It is not a big issue when the 'consist' quota tuner is used, because it keeps changing the quota in the usual setup.

However, when the 'temporal' tuner is used, the quota value is not changed before the goal achievement status is completely changed. For example, if the DAMOS scheme is started with an under-achieved goal, the quota is set to the maximum value, and kept the same value until the goal is achieved. Because DAMON skips the first value, the user cannot know what effective quota the current scheme is using. Only after the goal is achieved, the effective quota is changed to zero, and traced.

Unconditionally trace the initial quota value to fix this problem.

Note that the 'temporal' quota tuner was introduced by commit af738a6a00c1 ("mm/damon/core: introduce DAMOS_QUOTA_GOAL_TUNER_TEMPORAL"), which was added to 7.1-rc1. But even with the 'consist' quota tuner, the tracing is unintentionally incomplete. Hence this commit marks the introduction of the trace event as the broken commit.

index b33920873871..265d51ade25b 100644
@@ -2899,6 +2899,8 @@ static void damos_adjust_quota(struct damon_ctx *c, struct damos *s)
 	if (!quota->total_charged_sz && !quota->charged_from) {
 		quota->charged_from = jiffies;
 		damos_set_effective_quota(c, s);
+		if (trace_damos_esz_enabled())
+			damos_trace_esz(c, s, quota);
 	}
 
 	/* New charge window starts */

From: SeongJae Park <[email protected]>

DAMON traces effective size quota from the second update, only if a change has been made by the update. Tracing only changed updates was an intentional decision to avoid unnecessary same value tracing. Always skipping the first value is just an unintended mistake.

The mistake makes the tracepoint based investigation incomplete, because the first effective size quota is never traced. It is not a big issue when the 'consist' quota tuner is used, because it keeps changing the quota in the usual setup.

However, when the 'temporal' tuner is used, the quota value is not changed before the goal achievement status is completely changed. For example, if the DAMOS scheme is started with an under-achieved goal, the quota is set to the maximum value, and kept the same value until the goal is achieved. Because DAMON skips the first value, the user cannot know what effective quota the current scheme is using. Only after the goal is achieved, the effective quota is changed to zero, and traced.

Unconditionally trace the initial quota value to fix this problem.

Note that the 'temporal' quota tuner was introduced by commit af738a6a00c1 ("mm/damon/core: introduce DAMOS_QUOTA_GOAL_TUNER_TEMPORAL"), which was added to 7.1-rc1. But even with the 'consist' quota tuner, the tracing is unintentionally incomplete. Hence this commit marks the introduction of the trace event as the broken commit.

---
 mm/damon/core.c | 2 ++
 1 file changed, 2 insertions(+)

index 2b7e0ee772f32..9fb96d55d13a7 100644
@@ -2237,6 +2237,8 @@ static void damos_adjust_quota(struct damon_ctx *c, struct damos *s)
 	if (!quota->total_charged_sz && !quota->charged_from) {
 		quota->charged_from = jiffies;
 		damos_set_effective_quota(quota, c);
+		if (trace_damos_esz_enabled())
+			damos_trace_esz(c, s, quota);
 	}
 
 	/* New charge window starts */

2.47.3