>From 2e3d6f21ffa990780e9b25e11be31a6e0da13c79 Mon Sep 17 00:00:00 2001 From: Jan Kara Date: Fri, 12 Jul 2013 17:30:07 +0200 Subject: [PATCH] writeback: Fix occasional slow sync(1) In case when system contains no dirty pages, wakeup_flusher_threads() will submit WB_SYNC_NONE writeback for 0 pages so wb_writeback() exits immediately without doing anything. Thus sync(1) will write all the dirty inodes from a WB_SYNC_ALL writeback pass which is slow. Fix the problem by using get_nr_dirty_pages() in wakeup_flusher_threads() instead of calculating number of dirty pages manually. That function also takes number of dirty inodes into account. CC: stable@vger.kernel.org Reported-by: Paul Taysom Signed-off-by: Jan Kara --- fs/fs-writeback.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index a85ac4e..d0d70a8 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -1055,10 +1055,8 @@ void wakeup_flusher_threads(long nr_pages, enum wb_reason reason) { struct backing_dev_info *bdi; - if (!nr_pages) { - nr_pages = global_page_state(NR_FILE_DIRTY) + - global_page_state(NR_UNSTABLE_NFS); - } + if (!nr_pages) + nr_pages = get_nr_dirty_pages(); rcu_read_lock(); list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) { -- 1.8.1.4