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=1794046129; b=gnVEusILicpaWdsAaQxFfe6LZ0HdPdvZ6f/87UnNveopfXDHlxqsTQ54YWuiVhvGOsG3 gLmf5iMQSbqNY9pjmPEe72/kgr5uEYHnxQ/r+YziG6ksrA4M4ZfdTYgqBBl2Dd39oLj1x M5JRjg3ty63OHKcMLq1cXDfmWikhtgeW6L3eRVSz9pyA1PovDHqg1J91Y9OOJhfDef/+n VVrPu5jOvLr28+CXJ6ZA4yLFrMu8KggkWtutmUWBkJityIdezwtoWeK6eYtQ2kCHK0Vyg 3C1hqBPaHTZHO2PiUVRAw7FCq633fWVkKhIIAdd2Zd3EAf7asc1ncWDYonfDphC/h5w== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794046129; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: MIME-Version:Content-Type:Content-Transfer-Encoding; bh=uM4fYsGnhBp0gzWMQuxYLiPU3BFIVzOujs+A+7jdiT8=; b=SMpI8AMoGHPhYKv7prJV3kMSRGUxg57YS4qUhYmk1lV40xHHCPKXRU4pVjD9OgO5E+dl nrljS6Fnvha+yd1W8pw5s8N+EYdzvmtkdVorjw8VLZKcTU9j7ZsloXnP7lDkleGrbA0jP 6KE5dwYg2sr/pbp0Hbh1kTys6WX0oNSeUhjrRi4gwTSxYz7VPzjodONuoIoxbkekkn0Y4 8zhEHTaPiDkldPSZO4/G2vBlo0lJRb2yLXDWtOeoB9NhQqkvgur9wsb3NzNwzP0AZG6qJ +0jtuQX71/3TUg+iPURV2meoLda0x1lvCmHoC7iCTqgdQLDnp/HxXP/8zB/QCLrIvbA== 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=df1IiO40; 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 0BA85606A326 for ; Sat, 7 Nov 2026 10:08:49 +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=df1IiO40 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 644121F0089F; Sat, 7 Nov 2026 10:08:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794046128; bh=uM4fYsGnhBp0gzWMQuxYLiPU3BFIVzOujs+A+7jdiT8=; h=From:To:Cc:Subject:Date; b=df1IiO40Jc37zulfHMS4Bx2Fw7/XqiOAEDk0etPv0TnxMQWURPg34FBZZ7zoIm8Ha jvtKxC0mdraA9wMdrX86F7KmvAe+s8EKhvRGQYCyk5h4jnc85/pp7P52G7ze6ZR8CV 6nGxm66UToHus7C6Xd4B0XHOeWki5E9EOXOkDG4qOEqX8qAb7hQzjwnK0La+qCJ6uG KyICp9YfVtPI9beY0OPAoo3TOUVc35rtonTykInKtYl7+4X5LabfxRvuse4E2VXPz/ wX7/MxOVEQVIuT4yUX2N8MsyLgy76Jp1So5IhtZq5OgTAyuazUPx/jJZ2Q0tXlPjKC 8GHTPlPTDrWTA== 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 6.18-stable tree Date: Sat, 7 Nov 2026 05:08:47 -0500 Message-ID: <20261107050847-failed-6.18-90c2fa6adfed@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 6.18-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 90c2fa6adfed7abe0935506a43cdff3a05c1fff0 # git commit -s git send-email --to '' --in-reply-to '20261107050847-failed-6.18-90c2fa6adfed@kernel.org' --subject-prefix 'PATCH 6.18.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