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 814962DEA6B; Fri, 9 Oct 2026 14:48:23 +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=1791557304; cv=none; b=AiOI/puXyHWsTpewuWa1XgU1epoatNxw3k+xQcyjxYe1DRz0VGEzphyhfE+Iyl1Ff++E0ipcWsnCBoJ4p3NJqDtgTx+fpR6XFshJ5JtsYQh273gLe72+J1fRmUnpZFdNjjquU3WuYPYIHjWWYzr1NzzYVw2cs/J0VaZLiY08PPU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791557304; c=relaxed/simple; bh=2uAx7LTaA7OCPN+u8CwE9eb5yLoL9fHv7LaiKUHovok=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Dzy0ixUoSIDFTexnhVqulI38OCJLFIvwlMQ2ou/EZUwUfJcz/Pyd/x/G1S2cG7u78QzxVk4dpKX0zpeh8VGTfD+6DRXclp8wVuXVQCJQBxramdINVKHuEw1TmoxupIXSqH4vOyAlC3pyraLSSC6bxraMRgxVwFLXxwIR4dL4BG0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Rn1rHP2s; 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="Rn1rHP2s" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0AD491F000FF; Fri, 9 Oct 2026 14:48:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1791557303; bh=CVT5PRt0dTyvufkIKuOFIFmWNz6TXrIoc0o4HWEvw1o=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=Rn1rHP2sVSpjnbWJyVJgbZwvIkeCiUd8N/aLuOx4+dE/LXBPqQSAtQkESYPsXQv+J 4s3DJizeXDpaRBgeGVhfrLqtMeXgrMl475JIRKwVUeT3jvW47BdcbBUJD6kR4MqjT4 OlST/Y1LmAcFbNlZchUu1rWxl4E9dLFGSbwlTTAegv/hS7/+nidFxKwDx5DeP0uNbC lXzl/nC8MgRND6P2jbWOuP8J5rsgRmkKhSKqEtxaPE99U9YKZiyQk4AmjkmgI9ivmb prQ69HbD6OsQot1v0OXuSWeALIHSy7IqE9hKRTMcLqBGCRp+A/mJrZzp17m23AtAJR qrbGrlMeSaKeQ== 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 v2 2/2] mm/damon/core: fix unconditionally skip last region Date: Fri, 9 Oct 2026 07:48:08 -0700 Message-ID: <20261009144808.18317-3-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20261009144808.18317-1-sj@kernel.org> References: <2026092949-surpass-thimble-02a8@gregkh> <20261009144808.18317-1-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 | 24 +++++++++++++++--------- 1 file changed, 15 insertions(+), 9 deletions(-) diff --git a/mm/damon/core.c b/mm/damon/core.c index c65d2cbeea6b..f2f6f125c09b 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) { @@ -783,17 +781,25 @@ 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); r = damon_next_region(r); sz = damon_sz_region(r); + skip = false; } + } +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