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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-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 9ACB3100003 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-Stat-Signature: a4xy1nem8caamssuocjoejd3xwgom9eg X-HE-Tag: 1794091059-734904 X-HE-Meta: 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 A4Z5Yfki Ia9OtYPkE3w311B6gFb3xtFjAxe+cYgsOOP8X+dYKssF9v0SYRS/wygaLrUGmFUegSdkv6xrfC8gd9rwxhi0kdyqhrVJuAWuJeXYssTTANJO1X6BLVbPNlbpNX3vm6HA9dardfvY4KFzi7g2T3mnSisJI3eaWVcLNjXOiCt+oqrHBVa+qooHQl6dIKqhLDNJbYVwgeC0+zlvWGvlHRj0di4tZjH2ZxhqJreUYdEm56xfO9Gla50UEQ23TCb6fBGgvZG6o4+E5tDSDv5+VX9QVkpPsYe5fkgURp6lu7IrouYDgq24jSq15pfaCkZD6P1ve4UTA 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 22:33:38 +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