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    Subject[PATCH 11/11] writeback: add comments to bdi_work structure
    Date
    And document its retriever, get_next_work_item().

    Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
    ---
    fs/fs-writeback.c | 18 +++++++++++-------
    1 files changed, 11 insertions(+), 7 deletions(-)

    diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
    index 3de93a9..6e199ef 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)
    --
    1.6.4.1.207.g68ea


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