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Mon, 02 Nov 2026 16:43:42 -0800 (PST) Received: from [127.0.1.1] ([23.254.208.9]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-36a428ecb61sm36846013eec.10.2026.11.02.16.43.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 02 Nov 2026 16:43:42 -0800 (PST) From: Qiliang Yuan Date: Mon, 02 Nov 2026 19:43:37 -0500 Subject: [PATCH v2] mm/filemap: clear page cache marks once when removing a folio X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20261102-bug-mm-filemap-init-marks-once-v2-1-985753b11173@gmail.com> X-B4-Tracking: v=1; b=H4sIADgu6WoC/42NQQ6CMBAAv0L27JoWYgVP/MNwaOsCG2lLWiQaw t+tvMDjzGFmg0SRKcGt2CDSyomDz1CeCrCj9gMhPzJDKUolRSXQvAZ0DnueyOkZ2fOCTsdnwuA toakrq7RWV6MN5Mgcqef3Mbh3mUdOS4if47fKn/07vUqUqJqmri69VaoR7eA0T2cbHHT7vn8Bw qJ4xcwAAAA= To: "Matthew Wilcox (Oracle)" , Jan Kara , Andrew Morton Cc: linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Qiliang Yuan X-Mailer: b4 0.13.0 xas_store() clears the marks of an entry before it replaces the entry with NULL. page_cache_delete() calls xas_init_marks() after xas_store() whether it stored a shadow entry or NULL, so a folio removed without a shadow, as POSIX_FADV_DONTNEED and drop_caches do, has its marks cleared twice. With 4K folios that is about 6% of the time it takes to drop clean page cache. Call xas_init_marks() only after storing a shadow entry, whose marks xas_store() leaves alone. Dropping 8 GiB of 4K folios, median of five runs, averaged over two boots of each kernel, in a 32 vCPU VM: before after POSIX_FADV_DONTNEED 1517 ms 1423 ms drop_caches 1515 ms 1422 ms Signed-off-by: Qiliang Yuan Reviewed-by: Jan Kara --- V1 -> V2: - Explain the condition in a comment (Jan Kara) - Add Reviewed-by from Jan - Rebase on v7.4-rc1 v1: https://lore.kernel.org/r/20261030-bug-mm-filemap-init-marks-once-v1-1-699835fc6690@gmail.com --- mm/filemap.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/mm/filemap.c b/mm/filemap.c index b74bc1e5015c6..c2effedf975a2 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -140,7 +140,9 @@ static void page_cache_delete(struct address_space *mapping, VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio); xas_store(&xas, shadow); - xas_init_marks(&xas); + /* If xas_store() didn't clear marks, do it now */ + if (shadow) + xas_init_marks(&xas); folio->mapping = NULL; /* Leave folio->index set: truncation lookup relies upon it */ --- base-commit: 6628e7d4c6b25c8d18f1345e3a20d21829aae7e4 change-id: 20261030-bug-mm-filemap-init-marks-once-b83c6aa67bab Best regards, -- Qiliang Yuan