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b=Jeb/k8ECSQYxRI6pMowOh6vnr6v2+UOutb5+7NMmpN8FF1IXZJpsjUuTQ9yd2SvSq 5Ag7I03DN6djHqW2oGpkQZXli+vphAS5DiYacQptubs5ef09jxEkGFgiymJqWZBncz 9tPZte19BmEfU7f9nnGBfD+35oHbSe2O+HSDpgHH6J0AocP9YcvoFXKlwLRL+WrM2k WARX6EZRiFghYcrWO+oIaogBGaOEhXqF6VY/PUnMhboG3444EjP/YT1YyUcE4DA1OJ owN7iJszrl0AaSTlrb/LoFVzShHxxKa060kCKlomnzzS7kVMvcPjUvwjwHhZzzzkg1 HY9i5KvXSAbJA== From: SeongJae Park To: Cc: SeongJae Park , Andrew Morton , damon@lists.linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [RFC PATCH 02/14] mm/damon/core: do not use region out of a loop in damon_set_regions() Date: Tue, 19 May 2026 23:28:34 -0700 Message-ID: <20260520062858.167011-3-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260520062858.167011-1-sj@kernel.org> References: <20260520062858.167011-1-sj@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Stat-Signature: ch5t8ty67qryfpzendptutsq58rajjqj X-Rspamd-Queue-Id: 3719414000F X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1779258549-782504 X-HE-Meta: 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 HddfE0L1 45kcpL3hp4j+2kR0f/JY0BN8rj/Bg3SmwoTsQn77Jyf3bXy17fr3pWX//YGo7E646z/0oRUuEPIPiRAsW7S8sRPaWDIlmngZKDgmu9QuC8I4z58zgqQiSfdS++LX8dpz2J4KRqfrNTBF1GDBHhQVsRRyPpAgWmqNsgETw6px+m7EhZhoiq8n/RlA6obgNY2YBVCnDZ53QtHeweT2BMuNlRRo6G+5uzhmXm5p132/zSPgG5v2zet8NzZm/vIjx/GzWmrINX+I8WEH4DL1OcFtPe9olMQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: damon_set_regions() assumes the DAMON region iterator is referencing the last region after the region iteration loop is completed. The code is indeed implemented in the way, but that is not a documented safe behavior. Hence it is unreliable and difficult to read. Cleanup the code to avoid the case. No behavioral change is intended. Signed-off-by: SeongJae Park --- mm/damon/core.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/mm/damon/core.c b/mm/damon/core.c index 40946a7f6f549..e8cf3632115e5 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -374,6 +374,7 @@ int damon_set_regions(struct damon_target *t, struct damon_addr_range *ranges, for (i = 0; i < nr_ranges; i++) { struct damon_region *first = NULL, *last, *newr; struct damon_addr_range *range; + bool insert_before_r = false; range = &ranges[i]; /* Get the first/last regions intersecting with the range */ @@ -383,8 +384,10 @@ int damon_set_regions(struct damon_target *t, struct damon_addr_range *ranges, first = r; last = r; } - if (r->ar.start >= range->end) + if (r->ar.start >= range->end) { + insert_before_r = true; break; + } } if (!first) { /* no region intersects with this range */ @@ -394,7 +397,11 @@ int damon_set_regions(struct damon_target *t, struct damon_addr_range *ranges, ALIGN(range->end, min_region_sz)); if (!newr) return -ENOMEM; - damon_insert_region(newr, damon_prev_region(r), r, t); + if (insert_before_r) + damon_insert_region(newr, damon_prev_region(r), + r, t); + else + damon_add_region(newr, t); } else { /* resize intersecting regions to fit in this range */ first->ar.start = ALIGN_DOWN(range->start, -- 2.47.3