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b=LkusKe2FMzJBDbjcyry/6L7Ye17EKtbUrBNtIWUra74cYtqsGpoMI1PdIeeRkUdEL r987uAJiH9MyvCSbP98srQXmYFaUswDAUdc/hsiDePQU3Y29gfH9Fj7oXiZTARPOW6 In1y/bOdVU6eyO3IRSF0OyfhXWg+YUQuhC+/uTw7zUgrBuE+Pq9uS3TQqmqXZkvtWC AucarmJsSQLIo84mQyoUlunXNC4Ybinv2sVSsDY1Z2B6o9dJNcGhGIc6rd1bNh82jV 4XH4xoGZAK4gkqph6/Cp4QC+cVo65fR7fhiSNCZxaeiLZfivlcm7GwCPDxrUMnBUU0 KXOiOI6k92L6A== From: SJ Park To: Cc: SJ Park , stable@vger.kernel.org, Andrew Morton , damon@lists.linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [RFC PATCH v1.1 1/9] mm/damon/core: skip applying scheme if region split for quota fails Date: Sun, 2 Aug 2026 09:26:22 -0700 Message-ID: <20260802162631.90304-2-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260802162631.90304-1-sj@kernel.org> References: <20260802162631.90304-1-sj@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 94298A0003 X-Stat-Signature: mkoba5u3kmqy5nzx43s53qjw11tagozw X-Rspam-User: X-HE-Tag: 1785688001-948317 X-HE-Meta: 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 s34bwiD9 QqRPABbP2hqnaYemybc8YtykBTe20ltnuforPSBmEosb9D3keM9RY65AJnQQtJA5dQHIU++wfs6XTPOrKYdVLGHhH0p6kwugDXn2KgWhXBzicSScEizkRKzg4pDXU5F7XyYq7jbAG1bMulupDcUSsZ0sgw1kx/yv78ylPmnU8jDMQgC0IkrHXzcCdblT4SZw84UyKscJfv/uSuZxbAwrWYEZoBDxR5DdwVB8eAftXNF9JEGE= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: damos_apply_scheme() splits a region and apply the action to the subregion if it is needed for not violating the quota. The split operation (damon_split_region_at()) could fail for allocation failure. In the case, the quota could be violated. From the user's perspective, DAMOS becomes more aggressive than expected under the extreme situation. Handle the failure. The user impact is not critical. The failure of damon_split_region_at() is unlikely since it is arguably too small to fail. Also DAMOS being aggressive is limited to the single region. Users can set min_nr_regions to set the maximum size of each region. If it is reasonably set, the transient overhead shouldn't be critical. The issue was discovered [1] by Sashiko. [1] https://lore.kernel.org/20260718171523.87547-1-sj@kernel.org Fixes: 2b8a248d5873 ("mm/damon/schemes: implement size quota for schemes application speed control") Cc: # 5.16.x Signed-off-by: SJ Park --- mm/damon/core.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/mm/damon/core.c b/mm/damon/core.c index 644daf5a16560..e2900d0c984c9 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -2613,7 +2613,8 @@ static void damos_apply_scheme(struct damon_ctx *c, struct damon_target *t, c->min_region_sz); 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_core_filter_out(c, t, r, s)) return; -- 2.47.3