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    Subject[PATCH 06/41] block: misc cleanups in barrier code
    Date
    Make the following cleanups in preparation of barrier/flush update.

    * blk_do_ordered() declaration is moved from include/linux/blkdev.h to
    block/blk.h.

    * blk_do_ordered() now returns pointer to struct request, with %NULL
    meaning "try the next request" and ERR_PTR(-EAGAIN) "try again
    later". The third case will be dropped with further changes.

    * In the initialization of proxy barrier request, data direction is
    already set by init_request_from_bio(). Drop unnecessary explicit
    REQ_WRITE setting and move init_request_from_bio() above REQ_FUA
    flag setting.

    * add_request() is collapsed into __make_request().

    These changes don't make any functional difference.

    Signed-off-by: Tejun Heo <tj@kernel.org>
    ---
    block/blk-barrier.c | 32 ++++++++++++++------------------
    block/blk-core.c | 21 ++++-----------------
    block/blk.h | 7 +++++--
    include/linux/blkdev.h | 1 -
    4 files changed, 23 insertions(+), 38 deletions(-)

    diff --git a/block/blk-barrier.c b/block/blk-barrier.c
    index ed0aba5..f1be85b 100644
    --- a/block/blk-barrier.c
    +++ b/block/blk-barrier.c
    @@ -110,9 +110,9 @@ static void queue_flush(struct request_queue *q, unsigned which)
    elv_insert(q, rq, ELEVATOR_INSERT_FRONT);
    }

    -static inline bool start_ordered(struct request_queue *q, struct request **rqp)
    +static inline struct request *start_ordered(struct request_queue *q,
    + struct request *rq)
    {
    - struct request *rq = *rqp;
    unsigned skip = 0;

    q->orderr = 0;
    @@ -149,11 +149,9 @@ static inline bool start_ordered(struct request_queue *q, struct request **rqp)

    /* initialize proxy request and queue it */
    blk_rq_init(q, rq);
    - if (bio_data_dir(q->orig_bar_rq->bio) == WRITE)
    - rq->cmd_flags |= REQ_WRITE;
    + init_request_from_bio(rq, q->orig_bar_rq->bio);
    if (q->ordered & QUEUE_ORDERED_DO_FUA)
    rq->cmd_flags |= REQ_FUA;
    - init_request_from_bio(rq, q->orig_bar_rq->bio);
    rq->end_io = bar_end_io;

    elv_insert(q, rq, ELEVATOR_INSERT_FRONT);
    @@ -171,27 +169,26 @@ static inline bool start_ordered(struct request_queue *q, struct request **rqp)
    else
    skip |= QUEUE_ORDSEQ_DRAIN;

    - *rqp = rq;
    -
    /*
    * Complete skipped sequences. If whole sequence is complete,
    - * return false to tell elevator that this request is gone.
    + * return %NULL to tell elevator that this request is gone.
    */
    - return !blk_ordered_complete_seq(q, skip, 0);
    + if (blk_ordered_complete_seq(q, skip, 0))
    + rq = NULL;
    + return rq;
    }

    -bool blk_do_ordered(struct request_queue *q, struct request **rqp)
    +struct request *blk_do_ordered(struct request_queue *q, struct request *rq)
    {
    - struct request *rq = *rqp;
    const int is_barrier = rq->cmd_type == REQ_TYPE_FS &&
    (rq->cmd_flags & REQ_HARDBARRIER);

    if (!q->ordseq) {
    if (!is_barrier)
    - return true;
    + return rq;

    if (q->next_ordered != QUEUE_ORDERED_NONE)
    - return start_ordered(q, rqp);
    + return start_ordered(q, rq);
    else {
    /*
    * Queue ordering not supported. Terminate
    @@ -199,8 +196,7 @@ bool blk_do_ordered(struct request_queue *q, struct request **rqp)
    */
    blk_dequeue_request(rq);
    __blk_end_request_all(rq, -EOPNOTSUPP);
    - *rqp = NULL;
    - return false;
    + return NULL;
    }
    }

    @@ -211,14 +207,14 @@ bool blk_do_ordered(struct request_queue *q, struct request **rqp)
    /* Special requests are not subject to ordering rules. */
    if (rq->cmd_type != REQ_TYPE_FS &&
    rq != &q->pre_flush_rq && rq != &q->post_flush_rq)
    - return true;
    + return rq;

    /* Ordered by draining. Wait for turn. */
    WARN_ON(blk_ordered_req_seq(rq) < blk_ordered_cur_seq(q));
    if (blk_ordered_req_seq(rq) > blk_ordered_cur_seq(q))
    - *rqp = NULL;
    + rq = ERR_PTR(-EAGAIN);

    - return true;
    + return rq;
    }

    static void bio_end_empty_barrier(struct bio *bio, int err)
    diff --git a/block/blk-core.c b/block/blk-core.c
    index f063541..f8d37a8 100644
    --- a/block/blk-core.c
    +++ b/block/blk-core.c
    @@ -1037,22 +1037,6 @@ void blk_insert_request(struct request_queue *q, struct request *rq,
    }
    EXPORT_SYMBOL(blk_insert_request);

    -/*
    - * add-request adds a request to the linked list.
    - * queue lock is held and interrupts disabled, as we muck with the
    - * request queue list.
    - */
    -static inline void add_request(struct request_queue *q, struct request *req)
    -{
    - drive_stat_acct(req, 1);
    -
    - /*
    - * elevator indicated where it wants this request to be
    - * inserted at elevator_merge time
    - */
    - __elv_add_request(q, req, ELEVATOR_INSERT_SORT, 0);
    -}
    -
    static void part_round_stats_single(int cpu, struct hd_struct *part,
    unsigned long now)
    {
    @@ -1316,7 +1300,10 @@ get_rq:
    req->cpu = blk_cpu_to_group(smp_processor_id());
    if (queue_should_plug(q) && elv_queue_empty(q))
    blk_plug_device(q);
    - add_request(q, req);
    +
    + /* insert the request into the elevator */
    + drive_stat_acct(req, 1);
    + __elv_add_request(q, req, ELEVATOR_INSERT_SORT, 0);
    out:
    if (unplug || !queue_should_plug(q))
    __generic_unplug_device(q);
    diff --git a/block/blk.h b/block/blk.h
    index 6e7dc87..874eb4e 100644
    --- a/block/blk.h
    +++ b/block/blk.h
    @@ -51,6 +51,8 @@ static inline void blk_clear_rq_complete(struct request *rq)
    */
    #define ELV_ON_HASH(rq) (!hlist_unhashed(&(rq)->hash))

    +struct request *blk_do_ordered(struct request_queue *q, struct request *rq);
    +
    static inline struct request *__elv_next_request(struct request_queue *q)
    {
    struct request *rq;
    @@ -58,8 +60,9 @@ static inline struct request *__elv_next_request(struct request_queue *q)
    while (1) {
    while (!list_empty(&q->queue_head)) {
    rq = list_entry_rq(q->queue_head.next);
    - if (blk_do_ordered(q, &rq))
    - return rq;
    + rq = blk_do_ordered(q, rq);
    + if (rq)
    + return !IS_ERR(rq) ? rq : NULL;
    }

    if (!q->elevator->ops->elevator_dispatch_fn(q, 0))
    diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
    index e97911d..996549d 100644
    --- a/include/linux/blkdev.h
    +++ b/include/linux/blkdev.h
    @@ -869,7 +869,6 @@ extern void blk_queue_rq_timed_out(struct request_queue *, rq_timed_out_fn *);
    extern void blk_queue_rq_timeout(struct request_queue *, unsigned int);
    extern void blk_queue_flush(struct request_queue *q, unsigned int flush);
    extern struct backing_dev_info *blk_get_backing_dev_info(struct block_device *bdev);
    -extern bool blk_do_ordered(struct request_queue *, struct request **);
    extern unsigned blk_ordered_cur_seq(struct request_queue *);
    extern unsigned blk_ordered_req_seq(struct request *);
    extern bool blk_ordered_complete_seq(struct request_queue *, unsigned, int);
    --
    1.7.1


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