Re: [syzbot] [jfs?] INFO: task hung in txBegin

[Edward Adam Davis]

with sb rwsem lock to order syncfs and wb worker

#syz test: upstream 50736169ecc8

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 92a5b8283528..660a1ac8912f 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -2123,8 +2123,12 @@ static long wb_writeback(struct bdi_writeback *wb,
 			queue_io(wb, work, dirtied_before);
 			queued = true;
 		}
-		if (work->sb)
+		if (work->sb) {
+			printk("sb: %p, %s\n", work->sb, __func__);
+			down_write(&work->sb->s_umount);
 			progress = writeback_sb_inodes(work->sb, wb, work);
+			up_write(&work->sb->s_umount);
+		}
 		else
 			progress = __writeback_inodes_wb(wb, work);
 		trace_writeback_written(wb, work);
diff --git a/fs/sync.c b/fs/sync.c
index dc725914e1ed..111c3c29b139 100644
--- a/fs/sync.c
+++ b/fs/sync.c
@@ -51,6 +51,7 @@ int sync_filesystem(struct super_block *sb)
 	 * methods call sync_dirty_buffer() and thus effectively write one block
 	 * at a time.
 	 */
+	printk("sb: %p, %s\n", sb, __func__);
 	writeback_inodes_sb(sb, WB_REASON_SYNC);
 	if (sb->s_op->sync_fs) {
 		ret = sb->s_op->sync_fs(sb, 0);