From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E6A44C32793 for ; Wed, 18 Jan 2023 18:16:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230376AbjARSQg (ORCPT ); Wed, 18 Jan 2023 13:16:36 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40672 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231201AbjARSQQ (ORCPT ); Wed, 18 Jan 2023 13:16:16 -0500 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 92D3D55290 for ; Wed, 18 Jan 2023 10:15:27 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1674065726; 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=rgtBVwEo115pa/wHlq8zXkWV41DjF6dYWeawMxXfPU8=; b=go2M2ci34qXOSojIymxoFOOCoBI0nh9KqMhDbnzfZJE/G7p1PR/iWelZNeAGo1ORW0DB72 TO5Ze9VCpj2K6Pc1B52q8pCoKSkkl7DdU2atSe0xmItx4GiEiBCUri0FRdZefO2LlLIok1 iMRQCFhhiKilL2Pdf+mzEeSMlGtPBDA= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-398-Lo7GEuZjOV-TWbeD26myVA-1; Wed, 18 Jan 2023 13:15:20 -0500 X-MC-Unique: Lo7GEuZjOV-TWbeD26myVA-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 79F3B280558D; Wed, 18 Jan 2023 18:15:17 +0000 (UTC) Received: from segfault.boston.devel.redhat.com (segfault.boston.devel.redhat.com [10.19.60.26]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 50BCB1121315; Wed, 18 Jan 2023 18:15:17 +0000 (UTC) From: Jeff Moyer To: Kent Overstreet Cc: linux-kernel@vger.kernel.org, linux-aio@kvack.org, linux-fsdevel@vger.kernel.org, fmdefrancesco@gmail.com Subject: Re: [PATCH 1/2] fs/aio: Use kmap_local() instead of kmap() References: <20230118152603.28301-1-kent.overstreet@linux.dev> X-PGP-KeyID: 1F78E1B4 X-PGP-CertKey: F6FE 280D 8293 F72C 65FD 5A58 1FF8 A7CA 1F78 E1B4 Date: Wed, 18 Jan 2023 13:19:13 -0500 In-Reply-To: <20230118152603.28301-1-kent.overstreet@linux.dev> (Kent Overstreet's message of "Wed, 18 Jan 2023 10:26:02 -0500") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 3.1 on 10.11.54.3 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, Kent, Kent Overstreet writes: > Originally, we used kmap() instead of kmap_atomic() for reading events > out of the completion ringbuffer because we're using copy_to_user(), > which can fault. > > Now that kmap_local() is a thing, use that instead. This has already been proposed as part of a more comprehensive patch: https://lore.kernel.org/linux-fsdevel/20230109175629.9482-1-fmdefrancesco@gmail.com/ Would you be willing to review that one? Thanks! Jeff > > Signed-off-by: Kent Overstreet > Cc: Benjamin LaHaise Cc: linux-aio@kvack.org > Cc: linux-fsdevel@vger.kernel.org > --- > fs/aio.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/fs/aio.c b/fs/aio.c > index 5b2ff20ad3..3f795ed2a2 100644 > --- a/fs/aio.c > +++ b/fs/aio.c > @@ -1246,10 +1246,10 @@ static long aio_read_events_ring(struct kioctx *ctx, > avail = min(avail, nr - ret); > avail = min_t(long, avail, AIO_EVENTS_PER_PAGE - pos); > > - ev = kmap(page); > + ev = kmap_local_page(page); > copy_ret = copy_to_user(event + ret, ev + pos, > sizeof(*ev) * avail); > - kunmap(page); > + kunmap_local(ev); > > if (unlikely(copy_ret)) { > ret = -EFAULT;