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authorJens Axboe <jens.axboe@oracle.com>2009-09-15 20:04:57 +0200
committerJens Axboe <jens.axboe@oracle.com>2009-09-16 15:18:52 +0200
commit8010c3b6349b407f8f11b3f4d7e9f94cb00fe528 (patch)
treeeecf594bec286f582c0b9709a87a0edb82dc034b /fs
parentce5f8e7795195edb6f84f74aa9d72e739df38486 (diff)
downloadlinux-linaro-stable-8010c3b6349b407f8f11b3f4d7e9f94cb00fe528.tar.gz
writeback: add comments to bdi_work structure
And document its retriever, get_next_work_item(). Acked-by: Jan Kara <jack@suse.cz> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Diffstat (limited to 'fs')
-rw-r--r--fs/fs-writeback.c18
1 files changed, 11 insertions, 7 deletions
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 5887328b5a06..55f0d4e51b59 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -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)