From patchwork Thu Mar 14 20:44:33 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jens Axboe X-Patchwork-Id: 10853575 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 4ACC36C2 for ; Thu, 14 Mar 2019 20:44:54 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 3BD0E2A650 for ; Thu, 14 Mar 2019 20:44:54 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 305362A654; Thu, 14 Mar 2019 20:44:54 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.9 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id D24B72A650 for ; Thu, 14 Mar 2019 20:44:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727933AbfCNUow (ORCPT ); Thu, 14 Mar 2019 16:44:52 -0400 Received: from mail-it1-f193.google.com ([209.85.166.193]:38067 "EHLO mail-it1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727912AbfCNUow (ORCPT ); Thu, 14 Mar 2019 16:44:52 -0400 Received: by mail-it1-f193.google.com with SMTP id k193so7345629ita.3 for ; Thu, 14 Mar 2019 13:44:51 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20150623.gappssmtp.com; s=20150623; h=from:to:cc:subject:date:message-id:in-reply-to:references; bh=G1Jr4tdYvPOZT9iN+F+fcErmHVHIuOwHcm6qKgjAwBo=; b=mK0amnxSw+2w7/yYNc0Fn3k7i/v89nbwzu9S/duk9WFSE2unT65ayI4ziOSA0daRZj 5EyuCl5km3boOh0/Hzeq9kycjMPvvVsidcoJPQXFjp+2CdqY2Ucul0kPcihjIWCIQBdq g/WRJqnikUxfxEf1/xQey94oIDFkVBHZN8vYc62c5N0Th+7dnynkkG+IvoXGKChBwEWg zRUvSWXNOgr/tCi5PiXR9FCFvRRWXrBc3KmEUnXTGyDv93SWd6ByOShVVO02JR9v4TMD rvdT+XUoWdW9lW3U64HXakV5At0rnlVyc9P1PBaxm0K9uhZLYtQFwyN7K+UKfQTWlg9f lEcQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references; bh=G1Jr4tdYvPOZT9iN+F+fcErmHVHIuOwHcm6qKgjAwBo=; b=ngarTRYquVPs8fQClNO2NzC3UDwyt/t1Ejtb3PB1NMIsODD08VoCJTspFRuF94O+RE c8hK3/0oyOoU6BrNcmPqYXqvSF1vGhcdI310Mr6F5Jq2/pNNLf/hbH0wf4IXeTejWJfC xNz9qckwiHqkFqLccQiErA9VVG2pUgAheFoIYWuOL9LK0La4Rqx50rCe8gIMARqvLQPt dgsEH+oSm1vvZlaE9x5rthTQqazhQjvL1je6qeNXyxeHLhBfI4kP3DnU28IrFMPleqvG 1QiUoq4jcrqqo6FZ3DoBpX+QbbUAXwIoc9SWlr2RJOZj5rhxxsakoIJnKkxcdVt6Qj5l qJNg== X-Gm-Message-State: APjAAAUu0GxPJx1OmOY11iGVWW/fq71veNBOmpYKQdff7yMqvGVW0lVE MQezOottSONZcvOGm8efxBXpWJHd228eKw== X-Google-Smtp-Source: APXvYqzt+rpMkTwzHoW03akfTRgMxucZclVWsAIApuPMV1CmRFtFmFbx+ypa4YpGHxFc8uJxgXNlKg== X-Received: by 2002:a05:660c:6c3:: with SMTP id z3mr291942itk.83.1552596290372; Thu, 14 Mar 2019 13:44:50 -0700 (PDT) Received: from x1.thefacebook.com ([216.160.245.98]) by smtp.gmail.com with ESMTPSA id w19sm1820538ita.33.2019.03.14.13.44.48 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 14 Mar 2019 13:44:49 -0700 (PDT) From: Jens Axboe To: linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org Cc: viro@ZenIV.linux.org.uk, Jens Axboe Subject: [PATCH 6/8] iov_iter: add ITER_BVEC_FLAG_NO_REF flag Date: Thu, 14 Mar 2019 14:44:33 -0600 Message-Id: <20190314204435.7692-7-axboe@kernel.dk> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20190314204435.7692-1-axboe@kernel.dk> References: <20190314204435.7692-1-axboe@kernel.dk> Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP For ITER_BVEC, if we're holding on to kernel pages, the caller doesn't need to grab a reference to the bvec pages, and drop that same reference on IO completion. This is essentially safe for any ITER_BVEC, but some use cases end up reusing pages and uncondtionally dropping a page reference on completion. And example of that is sendfile(2), that ends up being a splice_in + splice_out on the pipe pages. Add a flag that tells us it's fine to not grab a page reference to the bvec pages, since that caller knows not to drop a reference when it's done with the pages. Signed-off-by: Jens Axboe --- fs/io_uring.c | 3 +++ include/linux/uio.h | 24 +++++++++++++++++++----- 2 files changed, 22 insertions(+), 5 deletions(-) diff --git a/fs/io_uring.c b/fs/io_uring.c index 46cf38b8d863..b89f91ab6e32 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -850,6 +850,9 @@ static int io_import_fixed(struct io_ring_ctx *ctx, int rw, iov_iter_bvec(iter, rw, imu->bvec, imu->nr_bvecs, offset + len); if (offset) iov_iter_advance(iter, offset); + + /* don't drop a reference to these pages */ + iter->type |= ITER_BVEC_FLAG_NO_REF; return 0; } diff --git a/include/linux/uio.h b/include/linux/uio.h index ecf584f6b82d..4e926641fa80 100644 --- a/include/linux/uio.h +++ b/include/linux/uio.h @@ -23,14 +23,23 @@ struct kvec { }; enum iter_type { - ITER_IOVEC = 0, - ITER_KVEC = 2, - ITER_BVEC = 4, - ITER_PIPE = 8, - ITER_DISCARD = 16, + /* set if ITER_BVEC doesn't hold a bv_page ref */ + ITER_BVEC_FLAG_NO_REF = 2, + + /* iter types */ + ITER_IOVEC = 4, + ITER_KVEC = 8, + ITER_BVEC = 16, + ITER_PIPE = 32, + ITER_DISCARD = 64, }; struct iov_iter { + /* + * Bit 0 is the read/write bit, set if we're writing. + * Bit 1 is the BVEC_FLAG_NO_REF bit, set if type is a bvec and + * the caller isn't expecting to drop a page reference when done. + */ unsigned int type; size_t iov_offset; size_t count; @@ -84,6 +93,11 @@ static inline unsigned char iov_iter_rw(const struct iov_iter *i) return i->type & (READ | WRITE); } +static inline bool iov_iter_bvec_no_ref(const struct iov_iter *i) +{ + return (i->type & ITER_BVEC_FLAG_NO_REF) != 0; +} + /* * Total number of bytes covered by an iovec. *