From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mta0.migadu.com (out-220.mta0.migadu.com [91.218.175.220]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1AB303403F4 for ; Mon, 14 Sep 2026 03:09:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.220 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789355366; cv=none; b=T0sNNDhT9gP7mBzQ6/p3SvpjDm3gi0BFZBOgA8L/U1nkbs/BOODPkmMFwghKU+ogrB+gO6kgCDVY67P05SEWN7hK6X3RAVPNvnWsyxBJ+W8+AcGTPBvnYtqJrb6d7qiaBT4ILW680c+AGWhb4mmQWcl7Umfz1ZXfioShkqGx304= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789355366; c=relaxed/simple; bh=m+foVBAoalhqLlq2Og+IWuwZmX9gvSN2FL3MD01und4=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=E1kp53rs+KEK+EcMWys3klxKvYYX0b/rN+VHSeAuOtvmz5LjyGak6yszeKUtK/3PbO6HodnS0KL8+HSprb94/NoAg3O9g0Ek4ayor39l/fhI5nsAvCWhGlwrNwdQNhdvjVr6e+5WWMtYoewlS7SDQvBbz2WfM+8z9hgs6vHdTBQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=XMm5I/3W; arc=none smtp.client-ip=91.218.175.220 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="XMm5I/3W" X-Envelope-To: linux-kernel@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=m+foVBAoalhqLlq2Og+IWuwZmX9gvSN2FL3MD01und4=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1789355355; v=1; x=1789960155; b=XMm5I/3WfwV828PwC0hisoEi0O+4sNAvlHcX6SGKGQSYvbvuRNCg4cf+v0dJ9YDn0UCzV5V8 f4Kvd1b1SNl7KeAZqntkIJXPNF+Kjbc7DZFO2Ze5yhHO9LVcCqghfLh/w10zoXjJFQlT0n08JJY PWbhP/ADe60L18QKKEERwHYs= X-Envelope-To: linux-kernel@vger.kernel.org Received: by smtp.migadu.com with ESMTPS id ab92a83b59a5437d; Mon, 14 Sep 2026 03:09:15 +0000 X-Mizu-Trace-ID: ab92a83b59a5437d X-Migadu-Flow: FLOW_OUT Message-ID: Date: Mon, 14 Sep 2026 11:09:08 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] mm: shmem: ignore sysfs configs for shmem forced collapse To: Baolin Wang , akpm@linux-foundation.org, hughd@google.com, david@kernel.org Cc: ziy@nvidia.com, liam@infradead.org, nico.pache@linux.dev, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, lance.yang@linux.dev, usama.arif@linux.dev, kas@kernel.org, ljs@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <063f655b4d6c4234f3aa27ed6ecab10283ecb880.1789351825.git.baolin.wang@linux.alibaba.com> From: Qi Zheng In-Reply-To: <063f655b4d6c4234f3aa27ed6ecab10283ecb880.1789351825.git.baolin.wang@linux.alibaba.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 9/14/26 10:12 AM, Baolin Wang wrote: > According to Documentation/mm/transhuge.rst, MADV_COLLAPSE is expected to > ignore any THP or mTHP interface settings. > > However, after commit 26c7d8413aaf ("mm: thp: support "THPeligible" semantics > for mTHP with anonymous shmem"), performing MADV_COLLAPSE on shmem will > depend on /sys/.../hugepages-2048kB/shmem_enabled being set to "inherit" > (although that is the default), which can cause MADV_COLLAPSE to fail > unexpectedly. > > Fix this by returning the result of shmem_huge_global_enabled() directly > when MADV_COLLAPSE is requested, allowing PMD-order collapse while ignoring > shmem THP/mTHP settings. > > Fixes: 26c7d8413aaf ("mm: thp: support "THPeligible" semantics for mTHP with anonymous shmem") > Reported-by: Kiryl Shutsemau (Meta) > Closes: https://lore.kernel.org/all/20260908125105.1510704-7-kirill@shutemov.name/ > Reviewed-by: Kiryl Shutsemau (Meta) > Acked-by: Zi Yan > Reviewed-by: Lance Yang > Signed-off-by: Baolin Wang > --- > Changes from v1: > - Use the correct fixes tag (per Kiryl). > - Collect reviewed tags from Kiryl, Zi and Lance. Thanks. > --- > mm/shmem.c | 7 +++++-- > 1 file changed, 5 insertions(+), 2 deletions(-) Acked-by: Qi Zheng Thanks, Qi > > diff --git a/mm/shmem.c b/mm/shmem.c > index c92ed17dbc4a..b572c60f2af8 100644 > --- a/mm/shmem.c > +++ b/mm/shmem.c > @@ -2049,8 +2049,11 @@ unsigned long shmem_allowable_huge_orders(struct inode *inode, > > global_orders = shmem_huge_global_enabled(inode, index, write_end, > shmem_huge_force, vma, vm_flags); > - /* Tmpfs huge pages allocation */ > - if (!vma || !vma_is_anon_shmem(vma)) > + /* > + * Tmpfs huge pages allocation or forced collapse ignores > + * sysfs configs. > + */ > + if (!vma || !vma_is_anon_shmem(vma) || shmem_huge_force) > return global_orders; > > /*