From patchwork Tue Apr 9 19:22:50 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Hildenbrand X-Patchwork-Id: 13623106 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 39895157E81 for ; Tue, 9 Apr 2024 19:25:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1712690704; cv=none; b=sheh9KD8nwc46r5Yv3drDPrcPIO0tA1dGVzUvavszWZvpDxjqVNpEnBzt53JYxdUDEpKSP5QBJ95asKdmkzgU6MbsacONy8OCCu2TbXNdLNZqqHSCTiq5JEUq7rQTQfmORZzR2T4Vt2pSVhMOAvDyj3Sxm59m2pr2v17drRWWVs= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1712690704; c=relaxed/simple; bh=FAIHwezgBzib8qVcIz1KMdTokmMBm7CLgJNhlG06JSY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=hny19y4wJWd5bFw6ox4jwO2cbW6SNB/UglF5Lwb5QUVs0Dsj3Jn66H+r1iTQwkeB5Yj7Jz/fSwchapUrZjo5qArseIeW9e1pI8tEMq25CAWkQO29u5v4V3/6SD4gH8kP1pPSAxhffYEEIQf6aIWqsNKoCicX53SaLWulTaWlXHA= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=Mj8euJmy; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Mj8euJmy" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1712690702; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=6rnCGH1F82LpMt5YjVvPZTK3t5BGo8uUqDhbNYCO1mM=; b=Mj8euJmyRbkqnGtXpMHf65w26Z9md3rt3ifAm+BoSVIrjYQjF6/TWfFWxPaOn/O3w2vUo6 AenTeskHeiXKQMCTVVBG861ko4x+M35IMY9vNL5kIr91Fg82VeXT4va2j8p22Jr6YxvXmj 3Vi/Slmvart/Rh0cNZgL2NHKU7Zq9AM= Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-195-HVcby02FNvy6GQIyoWw54g-1; Tue, 09 Apr 2024 15:24:57 -0400 X-MC-Unique: HVcby02FNvy6GQIyoWw54g-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.rdu2.redhat.com [10.11.54.2]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 6D86429AA392; Tue, 9 Apr 2024 19:24:56 +0000 (UTC) Received: from t14s.redhat.com (unknown [10.39.192.106]) by smtp.corp.redhat.com (Postfix) with ESMTP id 0A40740B497A; Tue, 9 Apr 2024 19:24:42 +0000 (UTC) From: David Hildenbrand To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, linux-doc@vger.kernel.org, cgroups@vger.kernel.org, linux-sh@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, David Hildenbrand , Andrew Morton , "Matthew Wilcox (Oracle)" , Peter Xu , Ryan Roberts , Yin Fengwei , Yang Shi , Zi Yan , Jonathan Corbet , Hugh Dickins , Yoshinori Sato , Rich Felker , John Paul Adrian Glaubitz , Chris Zankel , Max Filippov , Muchun Song , Miaohe Lin , Naoya Horiguchi , Richard Chang Subject: [PATCH v1 07/18] mm/memory: use folio_mapcount() in zap_present_folio_ptes() Date: Tue, 9 Apr 2024 21:22:50 +0200 Message-ID: <20240409192301.907377-8-david@redhat.com> In-Reply-To: <20240409192301.907377-1-david@redhat.com> References: <20240409192301.907377-1-david@redhat.com> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.2 We want to limit the use of page_mapcount() to the places where it is absolutely necessary. In zap_present_folio_ptes(), let's simply check the folio mapcount(). If there is some issue, it will underflow at some point either way when unmapping. As indicated already in commit 10ebac4f95e7 ("mm/memory: optimize unmap/zap with PTE-mapped THP"), we already documented "If we ever have a cheap folio_mapcount(), we might just want to check for underflows there.". There is no change for small folios. For large folios, we'll now catch more underflows when batch-unmapping, because instead of only testing the mapcount of the first subpage, we'll test if the folio mapcount underflows. Signed-off-by: David Hildenbrand --- mm/memory.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index 78422d1c7381..178492efb4af 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1502,8 +1502,7 @@ static __always_inline void zap_present_folio_ptes(struct mmu_gather *tlb, if (!delay_rmap) { folio_remove_rmap_ptes(folio, page, nr, vma); - /* Only sanity-check the first page in a batch. */ - if (unlikely(page_mapcount(page) < 0)) + if (unlikely(folio_mapcount(folio) < 0)) print_bad_pte(vma, addr, ptent, page); }