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=-9.0 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 BA11FC43381 for ; Thu, 28 Feb 2019 21:36:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7D57C218AE for ; Thu, 28 Feb 2019 21:36:49 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=kernel-dk.20150623.gappssmtp.com header.i=@kernel-dk.20150623.gappssmtp.com header.b="STqJ3kBH" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730072AbfB1Vgs (ORCPT ); Thu, 28 Feb 2019 16:36:48 -0500 Received: from mail-io1-f67.google.com ([209.85.166.67]:38585 "EHLO mail-io1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727775AbfB1Vgs (ORCPT ); Thu, 28 Feb 2019 16:36:48 -0500 Received: by mail-io1-f67.google.com with SMTP id p18so17893130ioh.5 for ; Thu, 28 Feb 2019 13:36:48 -0800 (PST) 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=s4r3IKeU2bKeb+yed6nB7uqZH66NYELE7D70Un3HupY=; b=STqJ3kBHRxEAk8qedva5PRItvR1R+NQDSADuYDHancWggYhYWDguaLEU5DLUtM11Nf iCu5GUZYsQsxSc5K+qZP8+A5YoHihMk4Gg16NLB5tjtJkkBMhMsNXFu1ZWTgLBu7Y6Wc 56cc4osrPR9KV5PW5g/ZcqtGuMbnfOQpE2ZmsELh0U1JisIicRTA11lYpUD0b1dN1t+L 1nsZiSz9+F9XckQg1F1m5eAJicaRCMzOfNdX5JoFoKTZ+/N47IAODY8T/bjRKrIHdMX3 Y5sfeRtg069r9BVeDPwyXIjFAAZ7F6c8u5O+UKXShh2pDdcalMSTK/Jm+AZYox2yO3D7 vI4A== 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=s4r3IKeU2bKeb+yed6nB7uqZH66NYELE7D70Un3HupY=; b=Ifec8KSf15rUbJcJn03SeLAery7JT+7FxBfPDt6D0HoUt0bs4MWGruRMelYNGftKAb 0HrggPagusWDI9g8m16eXXNKcjNqu++Zxe/azy8Ws2Stp2nCwYJC+H94EsIBdsi5hSNC 4K5ya1dtrvMlviuOMhQ2zCLHn/nJ4UIPOT/hB0eSsiVWpLVGv89Agyz6HzaIR/AwdyeJ IjIV6EeJdcX3MY3GHVmjT/JEYwJNwC/B+/HdRhfpETO79NOKJ3dCjyy7jL2iflwRknqI DIqTcoJfYj6NP/hsH813N8VepljtdDXY4SYg2XiDC8a64NFTu+PJZycL67df2KbQ/Zgx fmtg== X-Gm-Message-State: APjAAAVx8gI9fxSCo+xsUiC+2ERMtPm0FYboo9cTG1hFr8l8HLkOw3Un I/JQ0NG5qCosRxElAbtZvs4XJw== X-Google-Smtp-Source: APXvYqw/5hYeaYZke66pd7zSDw4jxeTOXXbaJK5YZdJIvpINHTK+O0OhBguWyH4RBX0O48U34+rodQ== X-Received: by 2002:a6b:b5c7:: with SMTP id e190mr943982iof.26.1551389807582; Thu, 28 Feb 2019 13:36:47 -0800 (PST) Received: from x1.localdomain ([216.160.245.98]) by smtp.gmail.com with ESMTPSA id m79sm1376311itm.25.2019.02.28.13.36.45 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 28 Feb 2019 13:36:46 -0800 (PST) From: Jens Axboe To: linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org Cc: hch@lst.de, viro@ZenIV.linux.org.uk, Jens Axboe Subject: [PATCH 1/2] iov_iter: add ITER_BVEC_FLAG_NO_REF flag Date: Thu, 28 Feb 2019 14:36:41 -0700 Message-Id: <20190228213642.306-2-axboe@kernel.dk> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20190228213642.306-1-axboe@kernel.dk> References: <20190228213642.306-1-axboe@kernel.dk> Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org 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 f2df45bd61c3..6bdf280a7fb9 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -869,6 +869,9 @@ 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. * -- 2.17.1