[PATCH v2 2/6] fs/writeback: bail out if there is no more inodes for IO and queued once

[Kemeng Shi <shikemeng@huaweicloud.com>]

For case there is no more inodes for IO in io list from last wb_writeback,
We may bail out early even there is inode in dirty list should be written
back. Only bail out when we queued once to avoid missing dirtied inode.

This is from code reading...

Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 fs/fs-writeback.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 4e6166e07eaf..6fa623277d75 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -2076,6 +2076,7 @@ static long wb_writeback(struct bdi_writeback *wb,
 	struct inode *inode;
 	long progress;
 	struct blk_plug plug;
+	bool queued = false;
 
 	blk_start_plug(&plug);
 	for (;;) {
@@ -2118,8 +2119,10 @@ static long wb_writeback(struct bdi_writeback *wb,
 			dirtied_before = jiffies;
 
 		trace_writeback_start(wb, work);
-		if (list_empty(&wb->b_io))
+		if (list_empty(&wb->b_io)) {
 			queue_io(wb, work, dirtied_before);
+			queued = true;
+		}
 		if (work->sb)
 			progress = writeback_sb_inodes(work->sb, wb, work);
 		else
@@ -2142,7 +2145,7 @@ static long wb_writeback(struct bdi_writeback *wb,
 		/*
 		 * No more inodes for IO, bail
 		 */
-		if (list_empty(&wb->b_more_io)) {
+		if (list_empty(&wb->b_more_io) && queued) {
 			spin_unlock(&wb->list_lock);
 			break;
 		}
-- 
2.30.0