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=1794092411; b=KykbWwqlRChVoLv62GM+kgyt3lH1RVwIPyxc5U+nYkzy6W1Ax53CijTVvyZOU1TH9+AZ m4rEskLZNSpyjJmmSFTu/CBpXeg1+A/2mVUlTwvJHJytYxDiteRfqN4fD+bqt/mwuMIpG IQ/QGkgq5oH4OCOVyIqTmCnVQ1xkubrbdMSqtiLkhfFGlwMDeMrqDgyZSlEEUeoXL93il c0Bowq8C3HjwaK1Uu7NwCzaU+3A9BULCrTGr6btyfZ1NpBLVUp/VXoWVCK+OL/od5VHD3 dqa6v7esn0FSiEU0ZX4Nm2bYoF1GHbXdWKCqZzXUUj4lCjSeQljkWPhaUzqgS9Gd4cw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794092411; 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=2nPedpe9fvXNxnCnfL0oF2XIPr3VRkJl9pVL7wPawBk=; b=YpYlEe35ve+1AAvnzIPwQWlcagW5XDBB2iDjlXv4RFM6jZkElef/CaD+L0LJJ8gpLICV 4y1ZEFfHAJ6I26Gn0OBWGE2yA0OLekS+mbGF3X47nbg6vn1KHv0qC+CEAKdTGdrlfWHbH nx4JwfDYWsokBPTGg0/UAFfszrRG3z6UFwlXh9pfiIHqCpx9uGf/whrY3/Aaz2HYAQC9e xBGjCLHHVJd9D47UoqL8KZXWUVFtD9PlVinNOOPp/zvLV16PwiVzsHeCP2yEO4Bo8qIYd 6YoBy3rhyipOpyuyq8Rpo/qUVcI02pMP+PfxwdiUHUCQTSa+VCZLTPRlGWfRnNIRV+g== 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=Ne2+iWZT; 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 9FEE1606A32C for ; Sat, 7 Nov 2026 23:00:10 +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=Ne2+iWZT Received: by smtp.kernel.org (Postfix) with ESMTPSA id 31EC51F0089F; Sat, 7 Nov 2026 23:00:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794092410; bh=2nPedpe9fvXNxnCnfL0oF2XIPr3VRkJl9pVL7wPawBk=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=Ne2+iWZTrSTy58Ahwlyxyb0R9k5m1UmL7ars3odDrkX2sDT9klY0gUPSfNaYiyW1/ WhRvS2QRDgdBfvPQR+e+yNnX2GC9eLj8HRJWE8Tn+9s+nv3o8Wpt8r+EPKhBp/iODH kJDI/m5MKooUAXTmph9rDYBeJy4rtHz6NA82UTAAw3yF2JeLNt5p5O+gwbmCTa3jen rQqGk8BByLRlqIjPfIM0ABpvsRGbAzUPK5CnO/V2blMmgP0J3B/58TUdyAmrCOOJMt UonnMEb+6Rx9dVPtfR1Q6vLoFV7bxyJtwDzptaHEQra1J3lnBE6+POQ7ZgvekNfaR6 dZjomrnvy/Deg== 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 6.1.y 1/2] mm/damon/core: skip applying scheme if region split for quota fails Date: Sat, 7 Nov 2026 15:00:02 -0800 Message-ID: <20261107230003.340646-1-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 22:56:53 +0000 sashiko-bot@kernel.org wrote: > Thank you for your contribution! Sashiko AI review found 1 potential > issue to consider: > - [Low] mm/damon: inflated tried stats in damon_do_apply_schemes() on > split failure > -- > > commit 2d405ecddea503227b3b4138fe63cbeb95dc50b9 > Author: SJ Park > > mm/damon/core: skip applying scheme if region split for quota fails > > This commit changes damon_split_region_at() to return an error on memory > allocation failure and skips applying the DAMOS scheme in > damon_do_apply_schemes() when splitting a region to fit within the 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 f0da5cb2b88a0..9206737d05ae7 100644 > > --- a/mm/damon/core.c > > +++ b/mm/damon/core.c > > [ ... ] > > > @@ -810,7 +810,8 @@ static void damon_do_apply_schemes(struct damon_ctx *c, > > 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; > > [Severity: Low] > Does jumping to update_stat here inflate s->stat.nr_tried and > s->stat.sz_tried when damon_split_region_at() fails? > > Unlike the !sz path right above, sz holds the non-zero remaining quota > when damon_split_region_at() is called, and update_stat unconditionally > accounts it: > > mm/damon/core.c:damon_do_apply_schemes() { > ... > update_stat: > s->stat.nr_tried++; > s->stat.sz_tried += sz; > ... > } > > Because c->ops.apply_scheme() is skipped and quota->charged_sz is not > advanced, any subsequent matching regions in the same pass that also fail > to split will repeatedly add sz to s->stat.sz_tried. Good finding, but the user impact is trivial. Same behavior exists in the mainline, too. Hence no blocker for this patch. > > -- > Sashiko AI review ยท https://sashiko.dev/#/patchset/20261107224800.340250-1-sj@kernel.org?part=1 > Thanks, SJ