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 7FBA13CE4B9; Sat, 10 Oct 2026 06:30:59 +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=1791613860; cv=none; b=EeTTVCAqxhozlfT8/UZyGUkNPQRu7fUnGu/KcjgW28/3iHnIsuwOyRv/NIgzWWDZCxTYLQ84YHWanb7ft5CpWSGotwnKS541D3uttwOhIxU7L/qnxk3Bw2keaksz6LWGq8MiO4CmOUrWhBHv/F+1aCqtNauOChQHYOBkYAd22zM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791613860; c=relaxed/simple; bh=h8X2muhUdACmOdoZASl/DFvmfI/hssIIHL/fX4jH2Fg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=XUStOP6qOpMH+alBDforXunyXigv2CzT3APTEAp/rpa8yM44DakkLAFFFJDYsd/c4MuumrWCd3y8UohyAVWWGxyY4dVNoZGCP/3OOBE+ZMnmFta2Os27baLhVaosQtT8RhXlPDweGihi9PSRb85yXWo9z/onT16ooRDkCPMwDv4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=na/YQiyq; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="na/YQiyq" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B6C341F00893; Sat, 10 Oct 2026 06:30:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1791613859; bh=j1dLtZeKKzHRznic0qP4ENsLiLP/MhUoxtlmVSeVJ3A=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=na/YQiyqF+nlJrw2g8bdII7e8JJgQYjJ7kMojwNMWr+rF0ebYZnB8J/IKC8RrB82x oLY1V8bxa2LLgF2T2ri0ClpW1+6sK7pI03+b5eZtDiEcj2XRKsNQHz21Yt4NtcA4sm y7jJOHnZDRvTbuRkPkle+RJseSwlD1WcErjpZt01VCAc5UDjG1IGU0PokkfKMvUta+ mmUaZzJuh36qpky1PsZnda4LKVQPlpXIPbpCLryoFBdmVjO4Mtq5UkjqU1pihZ7aAN a14puebgqV0G7T6etmUl2BYTNNBO2WjZYDa2lPkGh5eRuDOUtb6+PKokPCB+AJTAd9 PWuxIV8pQDHRA== From: SJ Park To: stable@vger.kernel.org Cc: damon@lists.linux.dev, Liew Rui Yan , SJ Park , Andrew Morton Subject: [PATCH 6.1.y v3 2/2] mm/damon/core: fix unconditionally skip last region Date: Fri, 9 Oct 2026 23:30:42 -0700 Message-ID: <20261010063042.8611-3-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20261010063042.8611-1-sj@kernel.org> References: <2026092949-surpass-thimble-02a8@gregkh> <20261010063042.8611-1-sj@kernel.org> Precedence: bulk X-Mailing-List: damon@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Liew Rui Yan Once quota set, the charge_{target,addr}_from unconditionally skips and resets at the last region of the tracked target, so the last region can be skipped even when it has not been processed. Example: 1. Target has 2 regions: R1 (0-100 bytes) and R2 (100-200 bytes). 2. Quota is configured to process only 100 bytes per window. 3. Window 1: Processes R1 (0-100). Quota is full. charge_{target, addr}_from is saved at (Target, 100). 4. Window 2: The loop reaches R2. Because R2 is damon_last_region(t), the old code unconditionally returns true, skipping R2 entirely and resetting the charge_{target,addr}_from. Result: R2 is permanently skipped even though it has never been processed. However, it is important to note that this is a very minor issue. This is because it is triggered only when the previous window saved/kept charge_{target,addr}_from, and in the next window, all regions except the last region were skipped by damos_skip_charged_region(). Fix this by only resetting the charge_{target,addr}_from when last region is reached, only skipping when it is applied or cannot split. Link: https://lore.kernel.org/20260908134739.96919-1-sj@kernel.org Fixes: 50585192bc2e ("mm/damon/schemes: skip already charged targets and regions") Signed-off-by: Liew Rui Yan Reviewed-by: SJ Park Signed-off-by: SJ Park Signed-off-by: Andrew Morton Cc: # v5.16.x (cherry picked from commit b3723b596b548c837a766aae3553c14a7b15af2b) Signed-off-by: SJ Park --- mm/damon/core.c | 25 +++++++++++++++---------- 1 file changed, 15 insertions(+), 10 deletions(-) diff --git a/mm/damon/core.c b/mm/damon/core.c index b5c85e648859..1b9fb00405cf 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -756,6 +756,7 @@ static void damon_do_apply_schemes(struct damon_ctx *c, unsigned long sz = damon_sz_region(r); struct timespec64 begin, end; unsigned long sz_applied = 0; + bool skip = false; if (!s->wmarks.activated) continue; @@ -768,14 +769,11 @@ static void damon_do_apply_schemes(struct damon_ctx *c, if (quota->charge_target_from) { if (t != quota->charge_target_from) continue; - if (r == damon_last_region(t)) { - quota->charge_target_from = NULL; - quota->charge_addr_from = 0; - continue; - } if (quota->charge_addr_from && - r->ar.end <= quota->charge_addr_from) - continue; + r->ar.end <= quota->charge_addr_from) { + skip = true; + goto clean_charge_from_skip; + } if (quota->charge_addr_from && r->ar.start < quota->charge_addr_from) { @@ -783,16 +781,23 @@ static void damon_do_apply_schemes(struct damon_ctx *c, r->ar.start, DAMON_MIN_REGION); if (!sz) { if (damon_sz_region(r) <= - DAMON_MIN_REGION) - continue; + DAMON_MIN_REGION) { + skip = true; + goto clean_charge_from_skip; + } sz = DAMON_MIN_REGION; } damon_split_region_at(t, r, sz); - continue; + skip = true; } + } +clean_charge_from_skip: + if (r == damon_last_region(t)) { quota->charge_target_from = NULL; quota->charge_addr_from = 0; } + if (skip) + continue; if (!damos_valid_target(c, t, r, s)) continue; -- 2.47.3