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 X-Spam-Level: X-Spam-Status: No, score=-5.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A6730C19437 for ; Tue, 8 Dec 2020 14:15:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8431023A33 for ; Tue, 8 Dec 2020 14:15:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729813AbgLHOPY (ORCPT ); Tue, 8 Dec 2020 09:15:24 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:42331 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729379AbgLHOPX (ORCPT ); Tue, 8 Dec 2020 09:15:23 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1607436837; 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=tffr6g9iDgmcI1vdIiaVq+38gJQDylZk+4muqW+tsNE=; b=PYPRxxRSdfplv5X8EEkbvHRzLxpQozQ/FPoppOBP5D/81FAR9/eUOu/c4Lv9CYnt/9C2RE V6FNERbX9+IM1sVOntnpE99gUw0o4YBjSDARTrHNmW2SMJiTl8qQBkyBnX3iet6LZ6ql56 +w/v5SuFcWqzGmj2PuGmBVbGts7Q2iM= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-386-_6Jn5BKhNzC6LVuO_YUIoQ-1; Tue, 08 Dec 2020 09:13:53 -0500 X-MC-Unique: _6Jn5BKhNzC6LVuO_YUIoQ-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 9DADC19611AE; Tue, 8 Dec 2020 14:13:51 +0000 (UTC) Received: from warthog.procyon.org.uk (ovpn-116-67.rdu2.redhat.com [10.10.116.67]) by smtp.corp.redhat.com (Postfix) with ESMTP id 5E13960BE2; Tue, 8 Dec 2020 14:13:49 +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: <2F96670A-58DC-43A6-A20E-696803F0BFBA@oracle.com> <160518586534.2277919.14475638653680231924.stgit@warthog.procyon.org.uk> <118876.1607093975@warthog.procyon.org.uk> <955415.1607433903@warthog.procyon.org.uk> To: Ard Biesheuvel Cc: dhowells@redhat.com, Chuck Lever , Bruce Fields , CIFS , Linux NFS Mailing List , Herbert Xu , "open list:BPF JIT for MIPS (32-BIT AND 64-BIT)" , Linux Kernel Mailing List , Trond Myklebust , Linux Crypto Mailing List , linux-fsdevel@vger.kernel.org, linux-afs@lists.infradead.org Subject: Re: Why the auxiliary cipher in gss_krb5_crypto.c? MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <960648.1607436828.1@warthog.procyon.org.uk> Date: Tue, 08 Dec 2020 14:13:48 +0000 Message-ID: <960649.1607436828@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Ard Biesheuvel wrote: > Apparently, it is permitted for gss_krb5_cts_crypt() to do a > kmalloc(GFP_NOFS) in the context from where gss_krb5_aes_encrypt() is > being invoked, and so I don't see why it wouldn't be possible to > simply kmalloc() a scatterlist[] of the appropriate size, populate it > with all the pages, bufs and whatever else gets passed into the > skcipher, and pass it into the skcipher in one go. I never said it wasn't possible. But doing a pair of order-1 allocations from there might have a significant detrimental effect on performance - in which case Trond and co. will say "no". Remember: to crypt 1MiB of data on a 64-bit machine requires 2 x minimum 8KiB scatterlist arrays. That's assuming the pages in the middle are contiguous, which might not be the case for a direct I/O read/write. So for the DIO case, it could be involve an order-2 allocation (or chaining of single pages). David