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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 D59A7C282C2 for ; Thu, 7 Feb 2019 22:38:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AC0DC21916 for ; Thu, 7 Feb 2019 22:38:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726742AbfBGWih (ORCPT ); Thu, 7 Feb 2019 17:38:37 -0500 Received: from mx1.redhat.com ([209.132.183.28]:43956 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726650AbfBGWig (ORCPT ); Thu, 7 Feb 2019 17:38:36 -0500 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id AC602C01DE0D; Thu, 7 Feb 2019 22:38:36 +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 B415D87CF; Thu, 7 Feb 2019 22:38:35 +0000 (UTC) From: Jeff Moyer To: Jens Axboe Cc: linux-aio@kvack.org, linux-block@vger.kernel.org, linux-api@vger.kernel.org, hch@lst.de, avi@scylladb.com, jannh@google.com, viro@ZenIV.linux.org.uk Subject: Re: [PATCH 12/18] io_uring: add support for pre-mapped user IO buffers References: <20190207195552.22770-1-axboe@kernel.dk> <20190207195552.22770-13-axboe@kernel.dk> X-PGP-KeyID: 1F78E1B4 X-PGP-CertKey: F6FE 280D 8293 F72C 65FD 5A58 1FF8 A7CA 1F78 E1B4 Date: Thu, 07 Feb 2019 17:38:34 -0500 In-Reply-To: <20190207195552.22770-13-axboe@kernel.dk> (Jens Axboe's message of "Thu, 7 Feb 2019 12:55:46 -0700") 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 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.31]); Thu, 07 Feb 2019 22:38:36 +0000 (UTC) Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org Hi, Jens, Jens Axboe writes: > For now, buffers must not be file backed. If file backed buffers are > passed in, the registration will fail with -1/EOPNOTSUPP. This > restriction may be relaxed in the future. [...] > + down_write(¤t->mm->mmap_sem); > + pret = get_user_pages_longterm(ubuf, nr_pages, FOLL_WRITE, > + pages, vmas); > + if (pret == nr_pages) { > + /* don't support file backed memory */ > + for (j = 0; j < nr_pages; j++) { > + struct vm_area_struct *vma = vmas[j]; > + > + if (vma->vm_file) { > + ret = -EOPNOTSUPP; > + break; > + } > + } Unfortunately, this suffers the same problem as FOLL_ANON. Huge pages are backed by hugetlbfs, and vma->vm_file will be filled in. I guess you could check is_file_hugepages(vma->vm_file): if (vma->vm_file && !is_file_hugepages(vma->vm_file)) { ret = -EOPNOTSUPP; break; } That works for me. -Jeff