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=1794091059; b=Wuwr0mX0KrwaRfyWGYWV32VesKCk9gfrpWbvg+bOiTa+GJpRDuOKzjnCUZFdfP+UiD6E oeTPVrr89HU1IcvNd1yDhcM0FiiDn9Rpw8/Su3lgrgXNLpkGRA+Qj5HutJwQQpbTozfBg Atxf/U7/qQjI04i7F1WSsFK+9qWxcc/xKr2fSVq9Cmdmd4n1iDajAQorFv7ZtxDVj7mcA 9FO1nlKwdi/9Zw20W7UP9OXcsp/KziPcbHCJMZSSX4A7jkmifOKTIQ7ckoai6LLE4DIpL sCNG5/uBqpBno0w03HAeAIE07HTsMfLb0nhdQH9GfqabpEYxQ0m98L21Ll+wrMKSpfw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794091059; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Type: Content-Transfer-Encoding; bh=uTIW9ZNXo7IGqTDCIPcbW/4Ni86f8N+1UGLWhTVhaP8=; b=bqkDEJ1ngSIIpq2jyr2CfWrsFV3iWTW8oLacrfFQB01K1aO1666FbivI3O4KCVpfIl5u YyLT2xsOIldxN3kGrEGo4HqQQZmjnBYpKfXud83/oGj7xtywFrIKsgR0QPDDSg0Ecvaq5 Z3Koy0Q6qZv66LOGNwzwgKx698OfeGLJ1vLNDy/VZZ2zmvwyYTe38Lz8RgG0yzvO2jXDH Naf3SOkZ+08nGhMewCeCwN6K6mHDry2+XypFj0OsnSS68SMvdP884hG5XU5alNu7g0liq QthV7hSrTI9HD7TPkSczwfLI1G3mQkBwFEamI+Fd5QttpQ49qQx17FDUxFDVVYRWClw== 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=CIKJ08AS; 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 EF658606A326 for ; Sat, 7 Nov 2026 22:37:38 +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=CIKJ08AS Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5ACF71F0089F; Sat, 7 Nov 2026 22:37:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794091058; bh=uTIW9ZNXo7IGqTDCIPcbW/4Ni86f8N+1UGLWhTVhaP8=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=CIKJ08ASs6Z/18JYlAd7yBe6WatK4BqkdG/0IGe4R30w9gZQUdYrT2S8/9cYK2RSg scu5N709Ae8PvmqNXQWl3KxhUuiNoVanGaRRRUV2sF6m2v8FO8b+ugVxkLx05Wo0AH PcSyHi4UU/gSBbm/s+W2g8nruCmUBikifij8wpdKWBY/dXlAnMka1VMyssO5YaVG9P ZhZukBKtBCluRLYFjEbn9SUr6LlVx6GzZqx3Pur3jJCEnBTAR5/TenfHmO0gVLnEkJ 4uUKl+cLP6Yhry/nV/4w1IOEC5OXv4XohmtrgN3l4aAgu6PacUA+mX7yRBQBPC1E+S MnTathE26L9KQ== From: SJ Park To: sashiko-bot@kernel.org Cc: SJ Park , "Andrew Morton" , "Usama Arif" , damon@lists.linux.dev, linux-mm@kvack.org Subject: Re: [RFC PATCH 6.6.y 1/3] mm/damon/core: skip applying scheme if region split for quota fails Date: Sat, 7 Nov 2026 14:37:30 -0800 Message-ID: <20261107223731.331778-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: References: X-Mailing-List: damon@lists.linux.dev 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 On Sat, 07 Nov 2026 22:33:38 +0000 sashiko-bot@kernel.org wrote: > Thank you for your contribution! Sashiko AI review found 1 potential > issue to consider: > - [Medium] mm/damon: false tried stats on split failure in > damos_apply_scheme() > -- > > commit ae5a2312a946a6108ba6414ca8a1f6fb984dd078 > Author: SJ Park > > mm/damon/core: skip applying scheme if region split for quota fails > > This commit updates damon_split_region_at() to return an error code on > allocation failure and skips applying the DAMOS scheme in > damos_apply_scheme() when splitting a region to fit within the remaining > size quota fails. > > 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] > > > diff --git a/mm/damon/core.c b/mm/damon/core.c > > index b5b6d00d7a3b5..9d4a78deaa06a 100644 > > --- a/mm/damon/core.c > > +++ b/mm/damon/core.c > > [ ... ] > > > @@ -1004,7 +1004,8 @@ static void damos_apply_scheme(struct damon_ctx *c, struct damon_target *t, > > DAMON_MIN_REGION); > > 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_filter_out(c, t, r, s)) > > return; > > [Severity: Medium] > Does jumping to update_stat when damon_split_region_at() fails inflate > s->stat.nr_tried and s->stat.sz_tried? > > At this point sz is non-zero, so damos_update_stat(s, sz, sz_applied) > increments s->stat.nr_tried and adds the remaining quota size sz to > s->stat.sz_tried even though scheme application was skipped before > damos_filter_out() or c->ops.apply_scheme() ran. Because quota->charged_sz > is not updated either, every subsequent matching region in the same walk > that fails to split will add sz to s->stat.sz_tried again. Returning > directly instead of jumping to update_stat would avoid accounting the > skipped region as tried. Good finding, but no blocker. The user impact is trivial. Also same issue exists in the mainline. I will think about whether to fix it in mainline and backport to stable. > > -- > Sashiko AI review ยท https://sashiko.dev/#/patchset/20261107222202.331476-1-sj@kernel.org?part=1 > Thanks, SJ