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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-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Stat-Signature: 4okazzbrwb3z7ms556quttheudu1zi8u X-Rspamd-Queue-Id: 64AFEC0004 X-Rspam-User: X-Rspamd-Server: rspam08 X-Spam-Status: No, score=-13.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS, USER_AGENT_GIT autolearn=ham autolearn_force=no version=4.0.1 X-HE-Tag: 1794092411-293918 X-HE-Meta: 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 1mcL+u86 /QDazeSz/MQiHBwybXNNxCcdU8sKyCZBT/Or1ckA6MgD2FLiXaZQBvMYeANKb8x1/sM0vmBxo/1L3fL7cmQX5EJiI+dDYUXTbcquXYKGfgUVOpW+rc1LVeAyh2PCSi9Ze+27KPreVvoQI+DJ7CZnsjt3cSZm8mmne47fax4uy5ICSh/MmLlMYan6BENcLbxXXZ4Tt1Ijar5EPtzuJwAhrtJLu64gFBPhQVM3LjOddjHljxlEBq2DURru2cZCw77UOqNTr9tEEoqenE6IR11h7cVp/5vKs1pYJjI2+Vd3D8oCxV1rX2sMO9sHeUyH7TxQvBf6OkenSgItFqZQ= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 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