From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794049489; b=2UfoSeQQg1mr5a2Yx5CVNUnnzhoO4UNAh6uHdFG9to9AEPSUvM/6c5/rUUKgkNIneH38 eEnqQSlIb9hJEhx2KJ3iTY/p9lfQspJ6i8v9E1KM7D6KsmGLv0dJL4iDXnaym6MkFY+w5 U0dJFA16Qd3UoJzZn7oaX3V/RhyE95Ddk74HyCwaTdMJVVFAGLU3sJ8A0lTRcHo9aBw71 yBrZR6LCIZJUtcp/dfmvv4+jmeWYIdzlyttuhuvQWi8XdxJybJ7T9RRAELzAQStt+VtWi 3N7Pqza/WGNVMhzZ6f5ZLiLuD8AQGuk5eGg9OkUEBCmoRohDP8gWOZVOWhwVJ/SSFIQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794049489; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: MIME-Version:Content-Type:Content-Transfer-Encoding; bh=sFdS9ERHuuyZA/Px+2YIWGRxL6VeI9hSMRDJrLXJcGA=; b=sljywMD1M/HtxWzBnF/YGjMukFj0EhZmnC5lr8bXRv9MAX1DEieX+53UaDIH9SKueIUG rTOmwZJKg27Gwm7rVdwKisEJeKoT4KVOmpfydRury5UMSOWon6I/vOhMjfpdrGkBYBI36 TjK1YFiFJd6zHMk1mLYyFl1jiZi0zLhDWhJzE/YaWKsc4jD/sLvgecLci2HEZU8vth3e+ Ccx7Ouox+A4pvcO35SAzOIHIZ7iaOmxtOhVcv3FXVQqvFz808rZuZpuVaHtS1bFWU6lJy nfEsINWUmR4Pkkdj/J7BL/ZzGFt4f3abmEGPWwVfVuwbcjZLPoCrWDMKStR+yV0TVTg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=DEe1O6mJ; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 80340606A32C for ; Sat, 7 Nov 2026 11:04:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=DEe1O6mJ Received: by smtp.kernel.org (Postfix) with ESMTPSA id 681ED1F0089F; Sat, 7 Nov 2026 11:04:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794049489; bh=sFdS9ERHuuyZA/Px+2YIWGRxL6VeI9hSMRDJrLXJcGA=; h=From:To:Cc:Subject:Date; b=DEe1O6mJyittxFdlrRyKkUcWCLcBwoEQ/7LtvBrmhC1SAl20ClGWh9xL62pDBEEQR aOFRPEiENbqxcH9URGWaA7W3ZyncUdf4pxLIwqUZ94XX+CG7mXIQbN8+XLf2rBoJAR M5XAjEqcs+jp4w6r5+UpUVhBGmmqKvKmrf6FDDXuiXodV39ZOjvdZWPDoFLf9KFO2F f/ZFSdVKsrH/WAf86783MZ42HhBTmlXEreQ8YI+R6md0JDy1K9YZX1BYjT/dI4V9JC lQ+JxRIgydHd1dva/bx5uYZQgOEeyJVs5jkm4zP4bEWNWL2PLGp9qgsOipYdigWDE3 MbJxiqJZqHfSw== From: Sasha Levin To: gourry@gourry.net, akpm@linux-foundation.org, sashiko-bot@kernel.org, ljs@kernel.org, david@kernel.org, jannh@google.com, liam@infradead.org, vbabka@kernel.org Cc: stable@vger.kernel.org Subject: FAILED: patch "[PATCH] mm/madvise: use folio_trylock() in the cold/pageout PMD split" failed to apply to 5.15-stable tree Date: Sat, 7 Nov 2026 06:04:47 -0500 Message-ID: <20261107060446-failed-5.15-5a6c9cf117fc@kernel.org> X-Mailer: git-send-email 2.53.0 X-Mailing-List: stable@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: 8bit The patch below does not apply to the 5.15-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y git checkout FETCH_HEAD git cherry-pick -x 5a6c9cf117fca3c38a98fb2a2d5549795c8b0b73 # git commit -s git send-email --to '' --in-reply-to '20261107060446-failed-5.15-5a6c9cf117fc@kernel.org' --subject-prefix 'PATCH 5.15.y' 'HEAD^..' Thanks, Sasha ------------------ original commit in Linus's tree ------------------ >From 5a6c9cf117fca3c38a98fb2a2d5549795c8b0b73 Mon Sep 17 00:00:00 2001 From: Gregory Price Date: Sat, 12 Sep 2026 07:05:40 -0400 Subject: [PATCH] mm/madvise: use folio_trylock() in the cold/pageout PMD split MADV_COLD or MADV_PAGEOUT over part of a PMD splits the THP in madvise_cold_or_pageout_pte_range(). Two threads doing that to the same THP create spurious failures. CPU0 CPU1 ---- ---- folio_get() spin_unlock(ptl) folio_lock() folio_get() spin_unlock(ptl) folio_lock() <- blocks, keeps its ref split_folio() folio_expected_ref_count(folio) != folio_ref_count(folio) - 1 -EAGAIN CPU1 cannot drop its reference until it gets the lock CPU0 holds, so CPU0's split always fails. folio_trylock() makes CPU1 leave without ever taking a reference. The PTE branch of this same function already does this, as do madvise_free_pte_range() and madvise_free_huge_pmd(). Reproducer: 400 rounds of eight threads calling MADV_COLD on half of each of eight THPs, re-formed with MADV_COLLAPSE between rounds. From /proc/vmstat: thp_split_page thp_split_page_failed before 3186 860 after 3200 0 The short before count is rounds where every thread failed and the advice was dropped for that THP entirely. On failure the walker returns 0 and nothing retries. The PMD path becomes best effort when the folio lock is held elsewhere - same as the PTE path. Link: https://lore.kernel.org/20260912110540.3203010-1-gourry@gourry.net Signed-off-by: Gregory Price (Meta) Signed-off-by: Andrew Morton Reported-by: sashiko-bot Closes: https://sashiko.dev/#/patchset/20260817220810.1175596-1-gourry%40gourry.net Acked-by: Lorenzo Stoakes (ARM) Acked-by: David Hildenbrand (Arm) Assisted-by: LLM Cc: Jann Horn Cc: Liam R. Howlett Cc: Vlastimil Babka Cc: --- mm/madvise.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/mm/madvise.c b/mm/madvise.c index 8943ae1811449..bef4de4425f29 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -417,9 +417,10 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd, if (next - addr != HPAGE_PMD_SIZE) { int err; + if (!folio_trylock(folio)) + goto huge_unlock; folio_get(folio); spin_unlock(ptl); - folio_lock(folio); err = split_folio(folio); folio_unlock(folio); folio_put(folio); -- 2.53.0