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@xxxxxxxxxxxxxxx
Reported-by: Paul Taysom <taysom@xxxxxxxxxxxx>
Signed-off-by: Jan Kara <jack@xxxxxxx>
---
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
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