Commit 467a8fc9 authored Oct 31, 2024 by SeongJae Park Committed by Wen Zhiwei Jan 15, 2025

mm/damon/core: handle zero schemes apply interval

stable inclusion
from stable-v6.6.63
commit 6cba27abb6695b1facdd58a6480c611e3b41f1cb
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/IBI1RP

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6cba27abb6695b1facdd58a6480c611e3b41f1cb

--------------------------------

commit 8e7bde615f634a82a44b1f3d293c049fd3ef9ca9 upstream.

DAMON's logics to determine if this is the time to apply damos schemes
assumes next_apply_sis is always set larger than current
passed_sample_intervals.  And therefore assume continuously incrementing
passed_sample_intervals will make it reaches to the next_apply_sis in
future.  The logic hence does apply the scheme and update next_apply_sis
only if passed_sample_intervals is same to next_apply_sis.

If Schemes apply interval is set as zero, however, next_apply_sis is set
same to current passed_sample_intervals, respectively.  And
passed_sample_intervals is incremented before doing the next_apply_sis
check.  Hence, next_apply_sis becomes larger than next_apply_sis, and the
logic says it is not the time to apply schemes and update next_apply_sis.
In other words, DAMON stops applying schemes until passed_sample_intervals
overflows.

Based on the documents and the common sense, a reasonable behavior for
such inputs would be applying the schemes for every sampling interval.
Handle the case by removing the assumption.

Link: https://lkml.kernel.org/r/20241031183757.49610-3-sj@kernel.org


Fixes: 42f994b71404 ("mm/damon/core: implement scheme-specific apply interval")
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: <stable@vger.kernel.org>	[6.7.x]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Wen Zhiwei <wenzhiwei@kylinos.cn>

parent 366f8f3b

mm/damon/core.c

+4 −4

Original line number	Diff line number	Diff line
		@@ -989,7 +989,7 @@ static void damon_do_apply_schemes(struct damon_ctx *c,
		damon_for_each_scheme(s, c) {
		struct damos_quota *quota = &s->quota;

		if (c->passed_sample_intervals != s->next_apply_sis)
		if (c->passed_sample_intervals < s->next_apply_sis)
		continue;

		if (!s->wmarks.activated)
		@@ -1089,7 +1089,7 @@ static void kdamond_apply_schemes(struct damon_ctx *c)
		bool has_schemes_to_apply = false;

		damon_for_each_scheme(s, c) {
		if (c->passed_sample_intervals != s->next_apply_sis)
		if (c->passed_sample_intervals < s->next_apply_sis)
		continue;

		if (!s->wmarks.activated)
		@@ -1109,9 +1109,9 @@ static void kdamond_apply_schemes(struct damon_ctx *c)
		}

		damon_for_each_scheme(s, c) {
		if (c->passed_sample_intervals != s->next_apply_sis)
		if (c->passed_sample_intervals < s->next_apply_sis)
		continue;
		s->next_apply_sis +=
		s->next_apply_sis = c->passed_sample_intervals +
		(s->apply_interval_us ? s->apply_interval_us :
		c->attrs.aggr_interval) / sample_interval;
		}