Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965110AbbLOPnr (ORCPT ); Tue, 15 Dec 2015 10:43:47 -0500 Received: from mx1.redhat.com ([209.132.183.28]:60206 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932335AbbLOPnp (ORCPT ); Tue, 15 Dec 2015 10:43:45 -0500 From: Abhi Das To: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Cc: Abhi Das , Bob Peterson Subject: [RFC v2 PATCH] fs: __generic_file_splice_read retry lookup on AOP_TRUNCATED_PAGE Date: Tue, 15 Dec 2015 09:43:25 -0600 Message-Id: <1450194205-44587-1-git-send-email-adas@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2335 Lines: 70 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. This version fixes a return code issue pointed out by Bob Peterson. Signed-off-by: Abhi Das Cc: Bob Peterson --- fs/splice.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) diff --git a/fs/splice.c b/fs/splice.c index 801c21c..365cd2a 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)); @@ -439,14 +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) { error = 0; - + if (retries++ < 3) + goto retry_lookup; + } break; } } -- 2.4.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/