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Wed, 03 Jun 2026 19:38:38 -0700 (PDT) From: Wandun Chen To: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev Cc: akpm@linux-foundation.org, vbabka@kernel.org, surenb@google.com, mhocko@suse.com, jackmanb@google.com, hannes@cmpxchg.org, ziy@nvidia.com, rostedt@goodmis.org, mhiramat@kernel.org, mathieu.desnoyers@efficios.com, david@kernel.org, ljs@kernel.org, liam@infradead.org, rppt@kernel.org, bigeasy@linutronix.de, clrkwllms@kernel.org, Alexander.Krabler@kuka.com Subject: [RFC PATCH 1/3] mm/compaction: skip isolate mlocked folios when compact_unevictable_allowed=0 Date: Thu, 4 Jun 2026 10:38:10 +0800 Message-ID: <20260604023812.3700316-2-chenwandun1@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260604023812.3700316-1-chenwandun1@gmail.com> References: <20260604023812.3700316-1-chenwandun1@gmail.com> Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Wandun Chen compact_unevictable_allowed is default 0 under PREEMPT_RT, isolate_migratepages_block() skips folios with PG_unevictable set. However, mlock_folio() sets PG_mlocked immediately but defers PG_unevictable to mlock_folio_batch(), result in a folio with PG_mlocked=1 but PG_unevictable=0. Compaction will isolate such a folio. Fix by checking folio_test_mlocked() together with the existing folio_test_unevictable() check. A similar issue has been reported by Alexander Krabler on a 6.12-rt aarch64 system. Vlastimil suggested to check the mlocked flag [1]. Reported-by: Alexander Krabler Closes: https://lore.kernel.org/all/DU0PR01MB10385345F7153F334100981888259A@DU0PR01MB10385.eurprd01.prod.exchangelabs.com/ Suggested-by: Vlastimil Babka Signed-off-by: Wandun Chen Link: https://lore.kernel.org/all/33275585-f2db-4779-89f0-3ae24b455a67@suse.cz/ [1] --- mm/compaction.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/mm/compaction.c b/mm/compaction.c index b776f35ad020..7e07b792bcb5 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -1116,7 +1116,8 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, is_unevictable = folio_test_unevictable(folio); /* Compaction might skip unevictable pages but CMA takes them */ - if (!(mode & ISOLATE_UNEVICTABLE) && is_unevictable) + if (!(mode & ISOLATE_UNEVICTABLE) && + (is_unevictable || folio_test_mlocked(folio))) goto isolate_fail_put; /* -- 2.43.0