From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kara Subject: [PATCH] fs: Make sync_file_range(2) use WB_SYNC_NONE writeback Date: Sat, 24 Oct 2015 21:28:17 +0200 Message-ID: <1445714897-26342-1-git-send-email-jack@suse.com> Cc: Andrew Morton , Andres Freund , Al Viro , Jan Kara To: linux-fsdevel@vger.kernel.org Return-path: Received: from mx2.suse.de ([195.135.220.15]:59573 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750728AbbJYEOs (ORCPT ); Sun, 25 Oct 2015 00:14:48 -0400 Sender: linux-fsdevel-owner@vger.kernel.org List-ID: sync_file_range(2) is documented to issue writeback only for pages that are not currently being written. After all the system call has been created for userspace to be able to issue background writeout and so waiting for in-flight IO is undesirable there. However commit ee53a891f474 (mm: do_sync_mapping_range integrity fix) switched do_sync_mapping_range() and thus sync_file_range() to issue writeback in WB_SYNC_ALL mode since do_sync_mapping_range() was used by other code relying on WB_SYNC_ALL semantics. These days do_sync_mapping_range() went away and we can switch sync_file_range(2) back to issuing WB_SYNC_NONE writeback. That should help PostgreSQL avoid large latency spikes when flushing data in the background. Reported-by: Andres Freund Signed-off-by: Jan Kara --- fs/sync.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/fs/sync.c b/fs/sync.c index fbc98ee62044..ef60e812d771 100644 --- a/fs/sync.c +++ b/fs/sync.c @@ -343,7 +343,8 @@ SYSCALL_DEFINE4(sync_file_range, int, fd, loff_t, offset, loff_t, nbytes, } if (flags & SYNC_FILE_RANGE_WRITE) { - ret = filemap_fdatawrite_range(mapping, offset, endbyte); + ret = __filemap_fdatawrite_range(mapping, offset, endbyte, + WB_SYNC_NONE); if (ret < 0) goto out_put; } -- 2.1.4