From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 54C9D3242B2 for ; Fri, 19 Dec 2025 12:03:45 +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=1766145826; cv=none; b=ksi5LopQf+vPydLyHcNqvO9ADBtiArwdHsXsLJWbUBUzu59cn3UUrGlQbx0ttuwgsv8MQiGPhQFFWCQnv3/Tv0dno5Mb4Xgb7296Vj2oUx05d+J+jzjSCiw2vEeasGVFZDn5Mbe/mcc2bNwSN8hUU8EYydQhChXvDTuaPcFsiTk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766145826; c=relaxed/simple; bh=YFvGT7PS5q3O7lga4AU1uPhY7KUKky+K5vEq8RBLbQo=; h=From:In-Reply-To:References:To:Cc:Subject:MIME-Version: Content-Type:Date:Message-ID; b=MhD2RFWlBhmbGpve4XQCiWeib2H8fw6iUeqIIvXzIApnLj/u/8lURe0y3qdXuP1j5hY48S09LFj1G6YDoqhYJ79drPQ7Xl0G4WA3J2zLfyXVKBXwz0y0DSwqaoEmqihXtc1m4OyY7RYOkFAjXtjz5juiOlRiku5mDDb4mmbtiNo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine 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=NwqVMQ05; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine 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="NwqVMQ05" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1766145824; 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=EYx76SgRqxLyI8UZcz48rb07fztIJOHbJHyqiMlG2Fk=; b=NwqVMQ05E6rgKpyqi7dF2FskSmsUreVNE31RKImoGGvS3fR3XgUIOsb28/d4sR5po/p+X8 vzu4S2vMV8iwrpiVUpfzhPFLCUhm7vZ8eBlXIYhOoSNTRFy4nDMo3OC6I+ZQVg5CeoeOwI 8m/wQtW2nI4bSeqOMk8jHq78wDWSlUo= Received: from mx-prod-mc-05.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-561-f8gBi4v-NUS77fblkdUBmA-1; Fri, 19 Dec 2025 07:03:39 -0500 X-MC-Unique: f8gBi4v-NUS77fblkdUBmA-1 X-Mimecast-MFC-AGG-ID: f8gBi4v-NUS77fblkdUBmA_1766145817 Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (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-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id CE8501955E75; Fri, 19 Dec 2025 12:03:36 +0000 (UTC) Received: from warthog.procyon.org.uk (unknown [10.42.28.5]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 620E11956056; Fri, 19 Dec 2025 12:03:33 +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: References: <20251210-virtio_trans_iter-v1-1-92eee6d8b6db@codewreck.org> To: Dominique Martinet Cc: dhowells@redhat.com, Christoph Hellwig , Eric Van Hensbergen , Latchesar Ionkov , Christian Schoenebeck , v9fs@lists.linux.dev, linux-kernel@vger.kernel.org, Matthew Wilcox , linux-fsdevel@vger.kernel.org, Chris Arges Subject: Re: [PATCH] 9p/virtio: restrict page pinning to user_backed_iter() iovec Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <815090.1766145812.1@warthog.procyon.org.uk> Date: Fri, 19 Dec 2025 12:03:32 +0000 Message-ID: <815091.1766145812@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 Dominique Martinet wrote: > FWIW I tried logging and saw ITER_BVEC, ITER_KVEC and ITER_FOLIOQ -- > O_DIRECT writes are seen as BVEC so I guess it's not as direct as I > expected them to be -- that code could very well be leftovers from > the switch to iov_iter back in 2015... ITER_FOLIOQ should only be seen from buffered I/O. For unbuffered/direct I/O, user-backed writes are extracted to ITER_BVEC; kernel-backed writes are sliced, but the original iter type comes down. For the moment. David