From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A43A813CF82 for ; Sat, 3 Oct 2026 13:22:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791033751; cv=none; b=d5I9mi8BroBgTrNJgJD57OgZO99vPHNaP0IHplTylDX4s48Wqc8g8boyuP3Za/yZ02FEG2hzA8C9805+iotaDTZv5enIlQSGSfcXQ5zdnCDBX3co0ixpJwZbicWBG8pfEWGyIhz5IIMOAenbCC36EqVunZXfbzWEtr/mt2wstSA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791033751; c=relaxed/simple; bh=04tSFBx2p5DNAGkEFm2eIouoabdQFvCDqfBF+k2tjTc=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=OOtyOm49UigxFyuigDDm1AwC/5/KcKOUHZphpeuYv7qD26BWAYTJOVgu6Y+m6WR2qll3a5n6/E6h98ax3y4SRgUmTc2fPx7U/k+wJmaLvE08Ewqdj988QnoBKK/ZqkrytvVBFnow8qCFAzg/3m4AlTu89pbzHriNuSyilS9B4yo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=vr0uz4AC; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="vr0uz4AC" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C0E3B1F0089B; Sat, 3 Oct 2026 13:22:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1791033750; bh=U0tenhTAGWjCMyCVahGCzn2AQlkdRiUOcn2ZLt+H9MA=; h=Subject:To:Cc:From:Date; b=vr0uz4ACWTcgLeLsP8eG6fGA4R41a3D+g47W1jjEMAU8DRE4Sn1htwkwVgLYeDrFh FDtJoESI1QlRf1ilS6cm/67UceCACtAIQc02wINtIpAXHIT3wwrmQd60bEYaB9N1iv HnQO9pSK1aDsTeVLtmrJj5hWm23tlAbP4GWZ62PY= Subject: FAILED: patch "[PATCH] mm/damon/core: don't skip damos_adjust_quota() while esz is" failed to apply to 6.1-stable tree To: sj@kernel.org,akpm@linux-foundation.org,kunwu.chan@gmail.com,stable@vger.kernel.org Cc: From: Date: Sat, 03 Oct 2026 15:22:19 +0200 Message-ID: <2026100319-silent-lark-6245@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit The patch below does not apply to the 6.1-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 . 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-6.1.y git checkout FETCH_HEAD git cherry-pick -x 52ae167ce16609c7e6fffef588b3c2c26de2db19 # git commit -s git send-email --to '' --in-reply-to '2026100319-silent-lark-6245@gregkh' --subject-prefix 'PATCH 6.1.y' 'HEAD^..' Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 52ae167ce16609c7e6fffef588b3c2c26de2db19 Mon Sep 17 00:00:00 2001 From: SJ Park Date: Wed, 16 Sep 2026 06:50:19 -0700 Subject: [PATCH] mm/damon/core: don't skip damos_adjust_quota() while esz is not zero DAMOS could unexpectedly stop working when a user disables quota using the online parameters commit feature. Fix it by correcting a wrong quota unset check in damos_adjust_quota(). DAMON users could disable all quotas by unsetting time and size quotas, and removing all quota goals. The intention of disabling quotas would be making DAMOS run at full speed. When such quota disabled setup is detected, damos_adjust_quota() skips all its work. The skipped works include effective size quota (damos_quota->esz) updates and charged quota amount (damos_quota->charged_sz) resets. The intention is to avoid doing unnecessary work when quotas are disabled. However, users could do the setup while effective size quota is non-zero, by doing the disabling with the online DAMON parameters commit feature. In this case, because the effective size quota exists, DAMOS will keep working with the quota until it is fully charged. After the effective quota is fully charged, the charged quota amount (damos_quota->charged_sz) cannot be reset because damos_adjust_quota() skips it. Then, DAMOS stops working until the quota is newly set or DAMON is entirely restarted. The problem happens because damos_adjust_quota() assumes the user setup for disabling quota immediately disabled it. In reality, the quota is still working until the effective size quota is also updated to zero. Other logic for catching that uses damos_quota_is_set(), which understands the fact and therefore checks the effective size quota in addition to the user setup. Fix the issue by using damos_quota_is_set() in damos_adjust_quota() to determine if its works should be skipped. The user impact is a non-deterministic and unexpected DAMOS stop behavior. That is, users would disable quotas using the online parameters commit feature, expecting DAMOS will run at full speed. However, depending on the timing, the setup can be updated while the effective size quota is non-zero. Due to the above mentioned internal mechanism, DAMOS stops working instead of running at full speed. It is unexpected behavior. It is also non-deterministic because sometimes the setup is done when the effective size quota is zero, depending on the timing. It doesn't cause critical issues like crashes or leaks. Users can simply set a reasonable quota again, or restart DAMON. But definitely it is an unexpected and non-deterministic behavior that makes it difficult to reliably use. Also investigating the root cause of the behavior would be quite difficult. Link: https://lore.kernel.org/20260916135020.86483-1-sj@kernel.org Fixes: da87878010e5 ("mm/damon/sysfs: support online inputs update") Signed-off-by: SJ Park Signed-off-by: Andrew Morton Reviewed-by: Kunwu Chan Cc: # 5.19.x diff --git a/mm/damon/core.c b/mm/damon/core.c index 1764620903f2..ab3c4d754964 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -3147,7 +3147,7 @@ static void damos_adjust_quota(struct damon_ctx *c, struct damos *s) unsigned long cumulated_sz, cached_esz; unsigned int score, max_score = 0; - if (!quota->ms && !quota->sz && list_empty("a->goals)) + if (!damos_quota_is_set(quota)) return; /* First charge window */