From patchwork Tue Dec 15 01:33:49 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Abhi Das X-Patchwork-Id: 7850671 Return-Path: X-Original-To: patchwork-linux-fsdevel@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork1.web.kernel.org (Postfix) with ESMTP id 63CCA9F32E for ; Tue, 15 Dec 2015 01:34:39 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 8F2CC20274 for ; Tue, 15 Dec 2015 01:34:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B7F7D20254 for ; Tue, 15 Dec 2015 01:34:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932929AbbLOBeJ (ORCPT ); Mon, 14 Dec 2015 20:34:09 -0500 Received: from mx1.redhat.com ([209.132.183.28]:48110 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932869AbbLOBeI (ORCPT ); Mon, 14 Dec 2015 20:34:08 -0500 Received: from int-mx14.intmail.prod.int.phx2.redhat.com (int-mx14.intmail.prod.int.phx2.redhat.com [10.5.11.27]) by mx1.redhat.com (Postfix) with ESMTPS id 77C1814CAA5; Tue, 15 Dec 2015 01:34:08 +0000 (UTC) Received: from radium.msp.redhat.com (radium.msp.redhat.com [10.15.80.88]) by int-mx14.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id tBF1Y7IG009809 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Mon, 14 Dec 2015 20:34:07 -0500 From: Abhi Das To: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Cc: swhiteho@redhat.com, Abhi Das Subject: [RFC PATCH] fs: __generic_file_splice_read retry lookup on AOP_TRUNCATED_PAGE Date: Mon, 14 Dec 2015 19:33:49 -0600 Message-Id: <1450143229-40537-1-git-send-email-adas@redhat.com> X-Scanned-By: MIMEDefang 2.68 on 10.5.11.27 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Spam-Status: No, score=-6.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, T_RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP During testing, I discovered that __generic_file_splice_read() returns 0 (EOF) when aops->readpage fails with AOP_TRUNCATED_PAGE on the first page of a single/multi-page splice read operation. This EOF return code causes the userspace test to (correctly) report a zero-length read error when it was expecting otherwise. The current strategy of returning a partial non-zero read when ->readpage returns AOP_TRUNCATED_PAGE works only when the failed page is not the first of the lot being processed. This patch attempts to retry lookup and call ->readpage again on pages that had previously failed with AOP_TRUNCATED_PAGE. With this patch, my tests pass and I haven't noticed any unwanted side effects. Signed-off-by: Abhi Das --- fs/splice.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) diff --git a/fs/splice.c b/fs/splice.c index 801c21c..c424d44 100644 --- a/fs/splice.c +++ b/fs/splice.c @@ -387,6 +387,7 @@ __generic_file_splice_read(struct file *in, loff_t *ppos, spd.nr_pages = 0; for (page_nr = 0; page_nr < nr_pages; page_nr++) { unsigned int this_len; + int retries = 0; if (!len) break; @@ -415,6 +416,7 @@ __generic_file_splice_read(struct file *in, loff_t *ppos, */ if (!page->mapping) { unlock_page(page); +retry_lookup: page = find_or_create_page(mapping, index, mapping_gfp_mask(mapping)); @@ -439,13 +441,13 @@ __generic_file_splice_read(struct file *in, loff_t *ppos, error = mapping->a_ops->readpage(in, page); if (unlikely(error)) { /* - * We really should re-lookup the page here, - * but it complicates things a lot. Instead - * lets just do what we already stored, and - * we'll get it the next time we are called. + * Re-lookup the page */ - if (error == AOP_TRUNCATED_PAGE) + if (error == AOP_TRUNCATED_PAGE) { + if (retries++ < 3) + goto retry_lookup; error = 0; + } break; }