From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 70BB321D3F4 for ; Sun, 3 May 2026 12:41:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777812069; cv=none; b=B19Vomx/wf9uoHJN0PODLnOOlWT2ZJgJfX+1/QQXRu7TjjNZBPAzP5RIyi3qTdpb5EvRG4X2EiL/8ulrF4Zzun+5n4xx1LPFJUO91+ekk+KvOH0/Y4iDWA5baug+Q88KolG3vxTqJLVZChsTBLq5i3behpvgQNoNiA9K7Hs13Wo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777812069; c=relaxed/simple; bh=EseE2dvo3wAcClAtK08ti6hWrKsbWnknzVS4vlRMuNA=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=WoKlQpDQzDVuAbvSzjrm+xcg59HRDimCFC5OUu42A0dvr+hNYN9UaWA6l1zUUB+lhnDBiwTv1dRK7yt+dUyWe70+01wLfpTrDndvrw/K5FqR25LbzRgx1CzbBo/eYMBp8H0T667gk2NgTcIJ2RO/ebTI3Xunwp1P4IrPnIW+WMo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=ktfCmoYZ; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="ktfCmoYZ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C7F5EC2BCB4; Sun, 3 May 2026 12:41:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1777812069; bh=EseE2dvo3wAcClAtK08ti6hWrKsbWnknzVS4vlRMuNA=; h=Subject:To:Cc:From:Date:From; b=ktfCmoYZyKUGw6OFE4RM0ghUhdIzPjS63iEn5YudvVEDFnzozTebMpgVuyohx/MPc ztrci7uHu6Yo6y3uX4ZUL7jeCIOfWE5QyWlKLEz7Ix1fk+CnZ4OG2PdoB7AvA2JeCV 3EbFZsQLXhg69oSJSGyLC4gWIOcyui3X1kakyPxk= Subject: FAILED: patch "[PATCH] mm/damon/core: disallow time-quota setting zero esz" failed to apply to 6.18-stable tree To: sj@kernel.org,akpm@linux-foundation.org,stable@vger.kernel.org Cc: From: Date: Sun, 03 May 2026 14:41:06 +0200 Message-ID: <2026050306-june-passerby-c0a0@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 6.18-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 . 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 8bbde987c2b84f80da0853f739f0a920386f8b99 # git commit -s git send-email --to '' --in-reply-to '2026050306-june-passerby-c0a0@gregkh' --subject-prefix 'PATCH 6.18.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 8bbde987c2b84f80da0853f739f0a920386f8b99 Mon Sep 17 00:00:00 2001 From: SeongJae Park Date: Mon, 6 Apr 2026 17:31:52 -0700 Subject: [PATCH] mm/damon/core: disallow time-quota setting zero esz When the throughput of a DAMOS scheme is very slow, DAMOS time quota can make the effective size quota smaller than damon_ctx->min_region_sz. In the case, damos_apply_scheme() will skip applying the action, because the action is tried at region level, which requires >=min_region_sz size. That is, the quota is effectively exceeded for the quota charge window. Because no action will be applied, the total_charged_sz and total_charged_ns are also not updated. damos_set_effective_quota() will try to update the effective size quota before starting the next charge window. However, because the total_charged_sz and total_charged_ns have not updated, the throughput and effective size quota are also not changed. Since effective size quota can only be decreased, other effective size quota update factors including DAMOS quota goals and size quota cannot make any change, either. As a result, the scheme is unexpectedly deactivated until the user notices and mitigates the situation. The users can mitigate this situation by changing the time quota online or re-install the scheme. While the mitigation is somewhat straightforward, finding the situation would be challenging, because DAMON is not providing good observabilities for that. Even if such observability is provided, doing the additional monitoring and the mitigation is somewhat cumbersome and not aligned to the intention of the time quota. The time quota was intended to help reduce the user's administration overhead. Fix the problem by setting time quota-modified effective size quota be at least min_region_sz always. The issue was discovered [1] by sashiko. Link: https://lore.kernel.org/20260407003153.79589-1-sj@kernel.org Link: https://lore.kernel.org/20260405192504.110014-1-sj@kernel.org [1] Fixes: 1cd243030059 ("mm/damon/schemes: implement time quota") Signed-off-by: SeongJae Park Cc: # 5.16.x Signed-off-by: Andrew Morton diff --git a/mm/damon/core.c b/mm/damon/core.c index 3e1890d64d06..3703f62a876b 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -2228,7 +2228,8 @@ static unsigned long damos_quota_score(struct damos_quota *quota) /* * Called only if quota->ms, or quota->sz are set, or quota->goals is not empty */ -static void damos_set_effective_quota(struct damos_quota *quota) +static void damos_set_effective_quota(struct damos_quota *quota, + struct damon_ctx *ctx) { unsigned long throughput; unsigned long esz = ULONG_MAX; @@ -2254,6 +2255,7 @@ static void damos_set_effective_quota(struct damos_quota *quota) else throughput = PAGE_SIZE * 1024; esz = min(throughput * quota->ms, esz); + esz = max(ctx->min_region_sz, esz); } if (quota->sz && quota->sz < esz) @@ -2290,7 +2292,7 @@ static void damos_adjust_quota(struct damon_ctx *c, struct damos *s) /* First charge window */ if (!quota->total_charged_sz && !quota->charged_from) { quota->charged_from = jiffies; - damos_set_effective_quota(quota); + damos_set_effective_quota(quota, c); } /* New charge window starts */ @@ -2303,7 +2305,7 @@ static void damos_adjust_quota(struct damon_ctx *c, struct damos *s) quota->charged_sz = 0; if (trace_damos_esz_enabled()) cached_esz = quota->esz; - damos_set_effective_quota(quota); + damos_set_effective_quota(quota, c); if (trace_damos_esz_enabled() && quota->esz != cached_esz) damos_trace_esz(c, s, quota); }