|
@@ -49,15 +49,15 @@ struct wb_writeback_args {
|
|
|
* Work items for the bdi_writeback threads
|
|
|
*/
|
|
|
struct bdi_work {
|
|
|
- struct list_head list;
|
|
|
- struct rcu_head rcu_head;
|
|
|
+ struct list_head list; /* pending work list */
|
|
|
+ struct rcu_head rcu_head; /* for RCU free/clear of work */
|
|
|
|
|
|
- unsigned long seen;
|
|
|
- atomic_t pending;
|
|
|
+ unsigned long seen; /* threads that have seen this work */
|
|
|
+ atomic_t pending; /* number of threads still to do work */
|
|
|
|
|
|
- struct wb_writeback_args args;
|
|
|
+ struct wb_writeback_args args; /* writeback arguments */
|
|
|
|
|
|
- unsigned long state;
|
|
|
+ unsigned long state; /* flag bits, see WS_* */
|
|
|
};
|
|
|
|
|
|
enum {
|
|
@@ -758,7 +758,11 @@ static long wb_writeback(struct bdi_writeback *wb,
|
|
|
|
|
|
/*
|
|
|
* Return the next bdi_work struct that hasn't been processed by this
|
|
|
- * wb thread yet
|
|
|
+ * wb thread yet. ->seen is initially set for each thread that exists
|
|
|
+ * for this device, when a thread first notices a piece of work it
|
|
|
+ * clears its bit. Depending on writeback type, the thread will notify
|
|
|
+ * completion on either receiving the work (WB_SYNC_NONE) or after
|
|
|
+ * it is done (WB_SYNC_ALL).
|
|
|
*/
|
|
|
static struct bdi_work *get_next_work_item(struct backing_dev_info *bdi,
|
|
|
struct bdi_writeback *wb)
|