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b=iDvBnehmRwrVXOGnplb24UwMW47ZtquKrCHal2FynT4Ad3Mp9Q9J40uXtQF2rdiR3 YzxegO2k2fBKjorOE+WtZaQYhoQ4F2LOttuwuKK6pYUtm+fr4WTNW/lzNet2rY/tZU O/tzrKzPt1fZwl1WEbUwTA4lFu6elBajsb3v31UFjGCXmjKYAKpXdPw9hQH2SQDEtA xttATGDDDmfwxcI+m+fZKaEaVEpZh2jrtQjt3r2Fievnbm6TU8osdgLZmqQgZGfsmj 3gphpztxGPo2dBezI0az/vtMF5mJSkLEKmRVBO7zYMn3m9wqKENvMG5/8nXBFJH6Ah LBBeMPB856YJw== 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 v1.1 02/14] mm/damon/core: do not use region out of a loop in damon_set_regions() Date: Wed, 20 May 2026 20:53:36 -0700 Message-ID: <20260521035349.87565-3-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260521035349.87565-1-sj@kernel.org> References: <20260521035349.87565-1-sj@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Queue-Id: 39D55C0004 X-Stat-Signature: m4ghsu1ihatu86g34imapfrbszw1fa1w X-Rspamd-Server: rspam06 X-HE-Tag: 1779335641-372886 X-HE-Meta: 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 +VaW9wNZ +tY8qS61w7DUh0W/vvW5vEtBsZOfdRsoMhNYOthOiMoXKxi4ziWD7z3pKaEktRplfGFLUDKBPM+p/nSHn07GFBHQnqGjXMMLDfmVV8KFhsx/YSU/mJYMc4sF2T3R7TLturUq6FuoWW9YdHwvt3Mok2Ri+uqRiRADWp6awZmjMSngtza8Bc5p7Pykv5f6Vx7zPbPTdO7yHHGvyGIOCWdN6Da1uBt3qSmpCIcfsMQ0F3yZlb2NTELwDVE0mcOFDDW1Y3NLWFybcNYtr6wqX7LN5Ti/1eA== 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