From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 73A6A1CACE1 for ; Fri, 4 Oct 2024 16:57:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728061023; cv=none; b=KU2XFMPVbF3uXHPU2JDXvHmPtUvZ7AiP2uly7ITJaPmrS9udlAzD5xpKhkiojeulJtOW2h9GGUbNTr7r6LBWfdLlBCR/zGImKU6AnWX/Hco+C9VST3X0Vzqi8b+JQBS3sJqQB1bx3wXP+bOY/P6oNFiShFUTgiPEAjRtyM3vOfE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728061023; c=relaxed/simple; bh=LC5opBzsfMWT+Woxf6ql+szBwJm4lOK2uFmK2/got7M=; h=From:In-Reply-To:References:To:Cc:Subject:MIME-Version: Content-Type:Date:Message-ID; b=gs+23ipueNX5dwHQhES/HhK9QStJjWXYaZ8zQegmMPpUQ+OwXVUNKkITgbE5VzJn7TKUhx+xLT1LFQf3SFi3fOvtVQ4RvsQWhCkDxaQ/eKJf6rlEkI8iut92vb6JVk3mZvZoHvhj2UX/0+0xhltlukwtEdX5c8ctv9b401HiUW0= 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=OUi85u3A; arc=none smtp.client-ip=170.10.133.124 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="OUi85u3A" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1728061021; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=EpJ30SXry5ywItaI0zm3pCFPe4HCY3tu4N9t4xI5rt8=; b=OUi85u3AOibRI+zLvCspJAyfae3KhXEGUtXs//2+E/68OMwhpqpZoeTzKpQA8FTzkZZ9oq ZfmZsIP8Fd7S1soAmSs6vecCEgvXL4LD64T1gyFzVklVCc8jyd8KDQIbk8z4LC3KFEJGjs /S/CRTaO5Vwrr/tTRCDi51s9x6xrHCY= Received: from mx-prod-mc-04.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-472-QZcaDm-GPOmeyaH_zzULWg-1; Fri, 04 Oct 2024 12:56:58 -0400 X-MC-Unique: QZcaDm-GPOmeyaH_zzULWg-1 Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.12]) (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 mx-prod-mc-04.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 62DC019560BF; Fri, 4 Oct 2024 16:56:56 +0000 (UTC) Received: from warthog.procyon.org.uk (unknown [10.42.28.145]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 4435B19560AE; Fri, 4 Oct 2024 16:56:53 +0000 (UTC) Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: <20241004153025.1867858-1-ming.lei@redhat.com> References: <20241004153025.1867858-1-ming.lei@redhat.com> To: Ming Lei Cc: dhowells@redhat.com, Jens Axboe , Alexander Viro , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] lib/iov_iter.c: extract virt-contiguous pages in iov_iter_extract_bvec_pages Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <3855841.1728061012.1@warthog.procyon.org.uk> Date: Fri, 04 Oct 2024 17:56:52 +0100 Message-ID: <3855842.1728061012@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 Ming Lei wrote: > All iov_iter_bvec() users only want to extract virt-contiguous pages from > iov_iter_extract_pages() instead physical-contiguous pages. What do you mean by "virt-contiguous"? Virtual according to what mapping? The reason for physical contiguity is that you can pass a set of physical contiguous pages as a single DMA descriptor. Therefore, at some point, you might end up screwing up skb_splice_from_iter(). Currently, that's limited to a PAGE_SIZE per fragment, but hopefully that will be fixed at some point. David