linux-kernel - [PATCH 5/6] fs-writeback: move nr_pages == 0 logic to one location

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Date:   Tue, 19 Sep 2017 13:53:06 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-mm@...ck.org
Cc:     hannes@...xchg.org, clm@...com, jack@...e.cz,
        Jens Axboe <axboe@...nel.dk>
Subject: [PATCH 5/6] fs-writeback: move nr_pages == 0 logic to one location

Now that we have no external callers of wb_start_writeback(),
we can move the nr_pages == 0 logic into that function.

Signed-off-by: Jens Axboe <axboe@...nel.dk>
---
 fs/fs-writeback.c | 34 +++++++++++++++++-----------------
 1 file changed, 17 insertions(+), 17 deletions(-)

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 7564347914f8..a9a86644cb9f 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -933,6 +933,17 @@ static void bdi_split_work_to_wbs(struct backing_dev_info *bdi,
 
 #endif	/* CONFIG_CGROUP_WRITEBACK */
 
+/*
+ * Add in the number of potentially dirty inodes, because each inode
+ * write can dirty pagecache in the underlying blockdev.
+ */
+static unsigned long get_nr_dirty_pages(void)
+{
+	return global_node_page_state(NR_FILE_DIRTY) +
+		global_node_page_state(NR_UNSTABLE_NFS) +
+		get_nr_dirty_inodes();
+}
+
 static void wb_start_writeback(struct bdi_writeback *wb, long nr_pages,
 			       bool range_cyclic, enum wb_reason reason)
 {
@@ -942,6 +953,12 @@ static void wb_start_writeback(struct bdi_writeback *wb, long nr_pages,
 		return;
 
 	/*
+	 * If someone asked for zero pages, we write out the WORLD
+	 */
+	if (!nr_pages)
+		nr_pages = get_nr_dirty_pages();
+
+	/*
 	 * This is WB_SYNC_NONE writeback, so if allocation fails just
 	 * wakeup the thread for old dirty data writeback
 	 */
@@ -1814,17 +1831,6 @@ static struct wb_writeback_work *get_next_work_item(struct bdi_writeback *wb)
 	return work;
 }
 
-/*
- * Add in the number of potentially dirty inodes, because each inode
- * write can dirty pagecache in the underlying blockdev.
- */
-static unsigned long get_nr_dirty_pages(void)
-{
-	return global_node_page_state(NR_FILE_DIRTY) +
-		global_node_page_state(NR_UNSTABLE_NFS) +
-		get_nr_dirty_inodes();
-}
-
 static long wb_check_background_flush(struct bdi_writeback *wb)
 {
 	if (wb_over_bg_thresh(wb)) {
@@ -1966,9 +1972,6 @@ static void __wakeup_flusher_threads_bdi(struct backing_dev_info *bdi,
 void wakeup_flusher_threads_bdi(struct backing_dev_info *bdi, long nr_pages,
 				enum wb_reason reason)
 {
-	if (!nr_pages)
-		nr_pages = get_nr_dirty_pages();
-
 	rcu_read_lock();
 	__wakeup_flusher_threads_bdi(bdi, nr_pages, reason);
 	rcu_read_unlock();
@@ -1988,9 +1991,6 @@ void wakeup_flusher_threads(long nr_pages, enum wb_reason reason)
 	if (blk_needs_flush_plug(current))
 		blk_schedule_flush_plug(current);
 
-	if (!nr_pages)
-		nr_pages = get_nr_dirty_pages();
-
 	rcu_read_lock();
 	list_for_each_entry_rcu(bdi, &bdi_list, bdi_list)
 		__wakeup_flusher_threads_bdi(bdi, nr_pages, reason);
-- 
2.7.4