From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794047533; b=qE+QcP1aVCWD1fNbeqJeq/QX5Nr0eHbOccrWphVt/HiKL+U3LCUYta8ljum/bPibcqwX yjbBR9xb2zmr0pOauu90EwlrVIa/0lnkZsS3co6J1LrTw1VtRul6Fs8FK6bLJJKTWaDoV KYWh4bvWfN27DMGxIxIarD9yeGvOMTEv02IM5J0XxWAsP/HChCTxB8tau+F0Deasarb7n 0ClE9RL94P/p81DbdAkBvReCLwNPQfXGzzIePMUhUQnhXhlvcAirm42TmADvWU0TKI/X7 unW8TfoWdxUtqijFai0P0jeankAvgZXZViWTKIU7Y5nXWgbo6/IIHfKpfJ0L3M9uOtQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794047533; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: MIME-Version:Content-Type:Content-Transfer-Encoding; bh=TBM6dIapub0MswAC4p16FtbvE5vtVUkAlv+Ot9bV4iM=; b=A2wAP0vX3mg0MZ/eS1LZmlmCoYdBI8nRfDZHGp1xkW6QGU9/GQg6MkV96dhktuSPc6uY zZQO21ue0XzwB55u5BoJbMxtg3GjQMbhg4QYh+ppoAB9JYgjfsh9MZ93U/MrqDQtbVcE9 L82OjwoNjFo0BkOJadz8N9NbIXCfyidWKTYr+jWYMcBaFvPYnxoFFTwdqfMRULbyluLol 4dPzk5mQ90KTqg4q2PXvv23NY2nirkagKWJX+KRFMshTF0/CvgYFL6hwtvdPizqBk5llJ cFLJSrbON1ghSeTrO65DIARdVKsyJxwTiS1pAnmtP14C8n3G3HyWBJQeoL+jF1zaFbQ== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=XQ9HXf7x; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1D6B2606D80A for ; Sat, 7 Nov 2026 10:32:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=XQ9HXf7x Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3BBA31F008A1; Sat, 7 Nov 2026 10:32:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794047532; bh=TBM6dIapub0MswAC4p16FtbvE5vtVUkAlv+Ot9bV4iM=; h=From:To:Cc:Subject:Date; b=XQ9HXf7xId5Z5aPhKFB7Uh2aUMgV5Tbf8+uMKVoN3+iY3HSx84f8bAo+stZnv48Kf qd5MnylLEd4JoOSQ1s1V2Yl6t/JdcDvsr5nSVUfmpLGQKUfatUCpjvSVnullhFvVUk g15gJC1Yld8PZOvguQL/AfWhfR15og/7jnuszf+wIhQbG23RP07a2Z1NqqkoURYl5D 5X5L9RiUUAMM0RV7ir5Qc/5daMHMt/SdWPrdBpPpi1l1Jmo3z7kpdCsh+zexMqzLiL 70K5qG6J8wsIg1HNQ2ks8HtZD18LGiRUWg3vbwEI87bbUSCP3N1ZfBmFMATqY/HWx7 v3jvmx/LtOw1A== From: Sasha Levin To: sj@kernel.org, akpm@linux-foundation.org, usamaarif642@gmail.com Cc: stable@vger.kernel.org Subject: FAILED: patch "[PATCH] mm/damon/core: skip applying scheme if region split for quota fails" failed to apply to 6.6-stable tree Date: Sat, 7 Nov 2026 05:32:11 -0500 Message-ID: <20261107053211-failed-6.6-90c2fa6adfed@kernel.org> X-Mailer: git-send-email 2.53.0 X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The patch below does not apply to the 6.6-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-6.6.y git checkout FETCH_HEAD git cherry-pick -x 90c2fa6adfed7abe0935506a43cdff3a05c1fff0 # git commit -s git send-email --to '' --in-reply-to '20261107053211-failed-6.6-90c2fa6adfed@kernel.org' --subject-prefix 'PATCH 6.6.y' 'HEAD^..' Thanks, Sasha ------------------ original commit in Linus's tree ------------------ >From 90c2fa6adfed7abe0935506a43cdff3a05c1fff0 Mon Sep 17 00:00:00 2001 From: SJ Park Date: Tue, 1 Sep 2026 06:18:42 -0700 Subject: [PATCH] mm/damon/core: skip applying scheme if region split for quota fails Patch series "mm/damon: fix DAMOS bugs in core, paddr and vaddr". Fix misc bugs of DAMOS. Patch 1 makes DAMOS less stress memory allocator under extreme situation. Patches 2 and 3 fix wrong folios walking in DAMON_PADDR. Patches 4 and 5 fix wrong folios walking in DAMON_VADDR. Patches 6-8 handle extreme and unlikely memory situations that can cause divide by zero and underflow. All bugs are discovered by Sashiko. This patch (of 8): damos_apply_scheme() splits a region and apply the action to the subregion if it is needed for not violating the quota. The split operation (damon_split_region_at()) could fail for allocation failure. In the case, the quota could be violated. From the user's perspective, DAMOS becomes more aggressive than expected under the extreme situation. Handle the failure. The user impact is not critical. The failure of damon_split_region_at() is unlikely since it is arguably too small to fail. Also DAMOS being aggressive is limited to the single region. Users can set min_nr_regions to set the maximum size of each region. If it is reasonably set, the transient overhead shouldn't be critical. The issue was discovered [1] by Sashiko. Link: https://lore.kernel.org/20260901131850.98037-1-sj@kernel.org Link: https://lore.kernel.org/20260901131850.98037-2-sj@kernel.org Link: https://lore.kernel.org/20260718171523.87547-1-sj@kernel.org [1] Fixes: 2b8a248d5873 ("mm/damon/schemes: implement size quota for schemes application speed control") Signed-off-by: SJ Park Signed-off-by: Andrew Morton Cc: Usama Arif Cc: # 5.16.x --- mm/damon/core.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/mm/damon/core.c b/mm/damon/core.c index d63d4c6fd3ffd..53952d16ebd88 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -2607,7 +2607,8 @@ static void damos_apply_scheme(struct damon_ctx *c, struct damon_target *t, c->min_region_sz); if (!sz) goto update_stat; - damon_split_region_at(t, r, sz); + if (damon_split_region_at(t, r, sz)) + goto update_stat; } if (damos_core_filter_out(c, t, r, s)) return; -- 2.53.0