Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752398AbdGaP3u (ORCPT ); Mon, 31 Jul 2017 11:29:50 -0400 Received: from mail.kernel.org ([198.145.29.99]:34528 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752045AbdGaP3t (ORCPT ); Mon, 31 Jul 2017 11:29:49 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0BAE222B66 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=jlayton@kernel.org From: Jeff Layton To: Jan Kara , Andrew Morton , Al Viro Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Marcelo Tosatti Subject: [PATCH] mm: remove optimizations based on i_size in mapping writeback waits Date: Mon, 31 Jul 2017 11:29:46 -0400 Message-Id: <20170731152946.13976-1-jlayton@kernel.org> X-Mailer: git-send-email 2.13.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3824 Lines: 106 From: Jeff Layton Marcelo added this i_size based optimization with a patch in 2004 (commit 765dad09b4ac in the linux-history tree): commit 765dad09b4ac101a32d87af2bb793c3060497d3c Author: Marcelo Tosatti Date: Tue Sep 7 17:51:17 2004 -0700 small wait_on_page_writeback_range() optimization filemap_fdatawait() calls wait_on_page_writeback_range() with -1 as "end" parameter. This is not needed since we know the EOF from the inode. Use that instead. There may be races here, particularly with clustered or network filesystems. Block devices always have an i_size of 0 as well, which makes using this with a blockdev inode sort of pointless. It also seems like a bit of a layering violation since we're operating on an address_space here, not an inode. Finally, it's also questionable whether this optimization really helps on workloads that we care about. Should we be optimizing for writeback vs. truncate races in a codepath where we expect to wait anyway? It doesn't seem worth the risk. Remove this optimization from the filemap_fdatawait codepaths. This means that filemap_fdatawait becomes a trivial wrapper around filemap_fdatawait_range. Signed-off-by: Jeff Layton --- include/linux/fs.h | 9 +++++++-- mm/filemap.c | 30 +----------------------------- 2 files changed, 8 insertions(+), 31 deletions(-) diff --git a/include/linux/fs.h b/include/linux/fs.h index af592ca3d509..656e04c6983e 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -2538,10 +2538,15 @@ extern int invalidate_inode_pages2_range(struct address_space *mapping, extern int write_inode_now(struct inode *, int); extern int filemap_fdatawrite(struct address_space *); extern int filemap_flush(struct address_space *); -extern int filemap_fdatawait(struct address_space *); -extern int filemap_fdatawait_keep_errors(struct address_space *mapping); extern int filemap_fdatawait_range(struct address_space *, loff_t lstart, loff_t lend); +extern int filemap_fdatawait_keep_errors(struct address_space *mapping); + +static inline int filemap_fdatawait(struct address_space *mapping) +{ + return filemap_fdatawait_range(mapping, 0, LLONG_MAX); +} + extern bool filemap_range_has_page(struct address_space *, loff_t lstart, loff_t lend); extern int __must_check file_fdatawait_range(struct file *file, loff_t lstart, diff --git a/mm/filemap.c b/mm/filemap.c index 394bb5e96f87..85dfe3bee324 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -512,39 +512,11 @@ EXPORT_SYMBOL(file_fdatawait_range); */ int filemap_fdatawait_keep_errors(struct address_space *mapping) { - loff_t i_size = i_size_read(mapping->host); - - if (i_size == 0) - return 0; - - __filemap_fdatawait_range(mapping, 0, i_size - 1); + __filemap_fdatawait_range(mapping, 0, LLONG_MAX); return filemap_check_and_keep_errors(mapping); } EXPORT_SYMBOL(filemap_fdatawait_keep_errors); -/** - * filemap_fdatawait - wait for all under-writeback pages to complete - * @mapping: address space structure to wait for - * - * Walk the list of under-writeback pages of the given address space - * and wait for all of them. Check error status of the address space - * and return it. - * - * Since the error status of the address space is cleared by this function, - * callers are responsible for checking the return value and handling and/or - * reporting the error. - */ -int filemap_fdatawait(struct address_space *mapping) -{ - loff_t i_size = i_size_read(mapping->host); - - if (i_size == 0) - return 0; - - return filemap_fdatawait_range(mapping, 0, i_size - 1); -} -EXPORT_SYMBOL(filemap_fdatawait); - static bool mapping_needs_writeback(struct address_space *mapping) { return (!dax_mapping(mapping) && mapping->nrpages) || -- 2.13.3