[BLOCK] reimplement handling of barrier request

Reimplement handling of barrier requests.

* Flexible handling to deal with various capabilities of
  target devices.
* Retry support for falling back.
* Tagged queues which don't support ordered tag can do ordered.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jens Axboe <axboe@suse.de>

2 files changed, 301 insertions, 167 deletions

diff --git a/block/elevator.c b/block/elevator.c
index 85a11cee7d1c..39dcccc82ada 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -304,15 +304,7 @@ void elv_requeue_request(request_queue_t *q, struct request *rq)
 
         rq->flags &= ~REQ_STARTED;
 
-        /*
-         * if this is the flush, requeue the original instead and drop the flush
-         */
-        if (rq->flags & REQ_BAR_FLUSH) {
-                clear_bit(QUEUE_FLAG_FLUSH, &q->queue_flags);
-                rq = rq->end_io_data;
-        }
-
-        __elv_add_request(q, rq, ELEVATOR_INSERT_FRONT, 0);
+        __elv_add_request(q, rq, ELEVATOR_INSERT_REQUEUE, 0);
 }
 
 static void elv_drain_elevator(request_queue_t *q)
@@ -332,8 +324,19 @@ static void elv_drain_elevator(request_queue_t *q)
 void __elv_add_request(request_queue_t *q, struct request *rq, int where,
                        int plug)
 {
+        struct list_head *pos;
+        unsigned ordseq;
+
+        if (q->ordcolor)
+                rq->flags |= REQ_ORDERED_COLOR;
+
         if (rq->flags & (REQ_SOFTBARRIER | REQ_HARDBARRIER)) {
                 /*
+                 * toggle ordered color
+                 */
+                q->ordcolor ^= 1;
+
+                /*
                  * barriers implicitly indicate back insertion
                  */
                 if (where == ELEVATOR_INSERT_SORT)
@@ -393,6 +396,30 @@ void __elv_add_request(request_queue_t *q, struct request *rq, int where,
                 q->elevator->ops->elevator_add_req_fn(q, rq);
                 break;
 
+        case ELEVATOR_INSERT_REQUEUE:
+                /*
+                 * If ordered flush isn't in progress, we do front
+                 * insertion; otherwise, requests should be requeued
+                 * in ordseq order.
+                 */
+                rq->flags |= REQ_SOFTBARRIER;
+
+                if (q->ordseq == 0) {
+                        list_add(&rq->queuelist, &q->queue_head);
+                        break;
+                }
+
+                ordseq = blk_ordered_req_seq(rq);
+
+                list_for_each(pos, &q->queue_head) {
+                        struct request *pos_rq = list_entry_rq(pos);
+                        if (ordseq <= blk_ordered_req_seq(pos_rq))
+                                break;
+                }
+
+                list_add_tail(&rq->queuelist, pos);
+                break;
+
         default:
                 printk(KERN_ERR "%s: bad insertion point %d\n",
                        __FUNCTION__, where);
@@ -422,25 +449,16 @@ static inline struct request *__elv_next_request(request_queue_t *q)
 {
         struct request *rq;
 
-        if (unlikely(list_empty(&q->queue_head) &&
-                     !q->elevator->ops->elevator_dispatch_fn(q, 0)))
-                return NULL;
-
-        rq = list_entry_rq(q->queue_head.next);
-
-        /*
-         * if this is a barrier write and the device has to issue a
-         * flush sequence to support it, check how far we are
-         */
-        if (blk_fs_request(rq) && blk_barrier_rq(rq)) {
-                BUG_ON(q->ordered == QUEUE_ORDERED_NONE);
+        while (1) {
+                while (!list_empty(&q->queue_head)) {
+                        rq = list_entry_rq(q->queue_head.next);
+                        if (blk_do_ordered(q, &rq))
+                                return rq;
+                }
 
-                if (q->ordered == QUEUE_ORDERED_FLUSH &&
-                    !blk_barrier_preflush(rq))
-                        rq = blk_start_pre_flush(q, rq);
+                if (!q->elevator->ops->elevator_dispatch_fn(q, 0))
+                        return NULL;
         }
-
-        return rq;
 }
 
 struct request *elv_next_request(request_queue_t *q)
@@ -593,7 +611,21 @@ void elv_completed_request(request_queue_t *q, struct request *rq)
          * request is released from the driver, io must be done
          */
         if (blk_account_rq(rq)) {
+                struct request *first_rq = list_entry_rq(q->queue_head.next);
+
                 q->in_flight--;
+
+                /*
+                 * Check if the queue is waiting for fs requests to be
+                 * drained for flush sequence.
+                 */
+                if (q->ordseq && q->in_flight == 0 &&
+                    blk_ordered_cur_seq(q) == QUEUE_ORDSEQ_DRAIN &&
+                    blk_ordered_req_seq(first_rq) > QUEUE_ORDSEQ_DRAIN) {
+                        blk_ordered_complete_seq(q, QUEUE_ORDSEQ_DRAIN, 0);
+                        q->request_fn(q);
+                }
+
                 if (blk_sorted_rq(rq) && e->ops->elevator_completed_req_fn)
                         e->ops->elevator_completed_req_fn(q, rq);
         }
diff --git a/block/ll_rw_blk.c b/block/ll_rw_blk.c
index 65c4efc02adf..91d3b4828c49 100644
--- a/block/ll_rw_blk.c
+++ b/block/ll_rw_blk.c
@@ -290,8 +290,8 @@ static inline void rq_init(request_queue_t *q, struct request *rq)
 
 /**
  * blk_queue_ordered - does this queue support ordered writes
- * @q:     the request queue
- * @flag:  see below
+ * @q:        the request queue
+ * @ordered:  one of QUEUE_ORDERED_*
  *
  * Description:
  *   For journalled file systems, doing ordered writes on a commit
@@ -300,28 +300,30 @@ static inline void rq_init(request_queue_t *q, struct request *rq)
  *   feature should call this function and indicate so.
  *
  **/
-void blk_queue_ordered(request_queue_t *q, int flag)
-{
-        switch (flag) {
-                case QUEUE_ORDERED_NONE:
-                        if (q->flush_rq)
-                                kmem_cache_free(request_cachep, q->flush_rq);
-                        q->flush_rq = NULL;
-                        q->ordered = flag;
-                        break;
-                case QUEUE_ORDERED_TAG:
-                        q->ordered = flag;
-                        break;
-                case QUEUE_ORDERED_FLUSH:
-                        q->ordered = flag;
-                        if (!q->flush_rq)
-                                q->flush_rq = kmem_cache_alloc(request_cachep,
-                                                                GFP_KERNEL);
-                        break;
-                default:
-                        printk("blk_queue_ordered: bad value %d\n", flag);
-                        break;
+int blk_queue_ordered(request_queue_t *q, unsigned ordered,
+                      prepare_flush_fn *prepare_flush_fn)
+{
+        if (ordered & (QUEUE_ORDERED_PREFLUSH | QUEUE_ORDERED_POSTFLUSH) &&
+            prepare_flush_fn == NULL) {
+                printk(KERN_ERR "blk_queue_ordered: prepare_flush_fn required\n");
+                return -EINVAL;
+        }
+
+        if (ordered != QUEUE_ORDERED_NONE &&
+            ordered != QUEUE_ORDERED_DRAIN &&
+            ordered != QUEUE_ORDERED_DRAIN_FLUSH &&
+            ordered != QUEUE_ORDERED_DRAIN_FUA &&
+            ordered != QUEUE_ORDERED_TAG &&
+            ordered != QUEUE_ORDERED_TAG_FLUSH &&
+            ordered != QUEUE_ORDERED_TAG_FUA) {
+                printk(KERN_ERR "blk_queue_ordered: bad value %d\n", ordered);
+                return -EINVAL;
         }
+
+        q->next_ordered = ordered;
+        q->prepare_flush_fn = prepare_flush_fn;
+
+        return 0;
 }
 
 EXPORT_SYMBOL(blk_queue_ordered);
@@ -346,167 +348,265 @@ EXPORT_SYMBOL(blk_queue_issue_flush_fn);
 /*
  * Cache flushing for ordered writes handling
  */
-static void blk_pre_flush_end_io(struct request *flush_rq, int error)
+inline unsigned blk_ordered_cur_seq(request_queue_t *q)
 {
-        struct request *rq = flush_rq->end_io_data;
-        request_queue_t *q = rq->q;
-
-        elv_completed_request(q, flush_rq);
-
-        rq->flags |= REQ_BAR_PREFLUSH;
-
-        if (!flush_rq->errors)
-                elv_requeue_request(q, rq);
-        else {
-                q->end_flush_fn(q, flush_rq);
-                clear_bit(QUEUE_FLAG_FLUSH, &q->queue_flags);
-                q->request_fn(q);
-        }
+        if (!q->ordseq)
+                return 0;
+        return 1 << ffz(q->ordseq);
 }
 
-static void blk_post_flush_end_io(struct request *flush_rq, int error)
+unsigned blk_ordered_req_seq(struct request *rq)
 {
-        struct request *rq = flush_rq->end_io_data;
         request_queue_t *q = rq->q;
 
-        elv_completed_request(q, flush_rq);
+        BUG_ON(q->ordseq == 0);
 
-        rq->flags |= REQ_BAR_POSTFLUSH;
+        if (rq == &q->pre_flush_rq)
+                return QUEUE_ORDSEQ_PREFLUSH;
+        if (rq == &q->bar_rq)
+                return QUEUE_ORDSEQ_BAR;
+        if (rq == &q->post_flush_rq)
+                return QUEUE_ORDSEQ_POSTFLUSH;
 
-        q->end_flush_fn(q, flush_rq);
-        clear_bit(QUEUE_FLAG_FLUSH, &q->queue_flags);
-        q->request_fn(q);
+        if ((rq->flags & REQ_ORDERED_COLOR) ==
+            (q->orig_bar_rq->flags & REQ_ORDERED_COLOR))
+                return QUEUE_ORDSEQ_DRAIN;
+        else
+                return QUEUE_ORDSEQ_DONE;
 }
 
-struct request *blk_start_pre_flush(request_queue_t *q, struct request *rq)
+void blk_ordered_complete_seq(request_queue_t *q, unsigned seq, int error)
 {
-        struct request *flush_rq = q->flush_rq;
-
-        BUG_ON(!blk_barrier_rq(rq));
+        struct request *rq;
+        int uptodate;
 
-        if (test_and_set_bit(QUEUE_FLAG_FLUSH, &q->queue_flags))
-                return NULL;
+        if (error && !q->orderr)
+                q->orderr = error;
 
-        rq_init(q, flush_rq);
-        flush_rq->elevator_private = NULL;
-        flush_rq->flags = REQ_BAR_FLUSH;
-        flush_rq->rq_disk = rq->rq_disk;
-        flush_rq->rl = NULL;
+        BUG_ON(q->ordseq & seq);
+        q->ordseq |= seq;
 
-        /*
-         * prepare_flush returns 0 if no flush is needed, just mark both
-         * pre and post flush as done in that case
-         */
-        if (!q->prepare_flush_fn(q, flush_rq)) {
-                rq->flags |= REQ_BAR_PREFLUSH | REQ_BAR_POSTFLUSH;
-                clear_bit(QUEUE_FLAG_FLUSH, &q->queue_flags);
-                return rq;
-        }
+        if (blk_ordered_cur_seq(q) != QUEUE_ORDSEQ_DONE)
+                return;
 
         /*
-         * some drivers dequeue requests right away, some only after io
-         * completion. make sure the request is dequeued.
+         * Okay, sequence complete.
          */
-        if (!list_empty(&rq->queuelist))
-                blkdev_dequeue_request(rq);
+        rq = q->orig_bar_rq;
+        uptodate = q->orderr ? q->orderr : 1;
 
-        flush_rq->end_io_data = rq;
-        flush_rq->end_io = blk_pre_flush_end_io;
+        q->ordseq = 0;
 
-        __elv_add_request(q, flush_rq, ELEVATOR_INSERT_FRONT, 0);
-        return flush_rq;
+        end_that_request_first(rq, uptodate, rq->hard_nr_sectors);
+        end_that_request_last(rq, uptodate);
 }
 
-static void blk_start_post_flush(request_queue_t *q, struct request *rq)
+static void pre_flush_end_io(struct request *rq, int error)
 {
-        struct request *flush_rq = q->flush_rq;
+        elv_completed_request(rq->q, rq);
+        blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_PREFLUSH, error);
+}
 
-        BUG_ON(!blk_barrier_rq(rq));
+static void bar_end_io(struct request *rq, int error)
+{
+        elv_completed_request(rq->q, rq);
+        blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_BAR, error);
+}
 
-        rq_init(q, flush_rq);
-        flush_rq->elevator_private = NULL;
-        flush_rq->flags = REQ_BAR_FLUSH;
-        flush_rq->rq_disk = rq->rq_disk;
-        flush_rq->rl = NULL;
+static void post_flush_end_io(struct request *rq, int error)
+{
+        elv_completed_request(rq->q, rq);
+        blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_POSTFLUSH, error);
+}
 
-        if (q->prepare_flush_fn(q, flush_rq)) {
-                flush_rq->end_io_data = rq;
-                flush_rq->end_io = blk_post_flush_end_io;
+static void queue_flush(request_queue_t *q, unsigned which)
+{
+        struct request *rq;
+        rq_end_io_fn *end_io;
 
-                __elv_add_request(q, flush_rq, ELEVATOR_INSERT_FRONT, 0);
-                q->request_fn(q);
+        if (which == QUEUE_ORDERED_PREFLUSH) {
+                rq = &q->pre_flush_rq;
+                end_io = pre_flush_end_io;
+        } else {
+                rq = &q->post_flush_rq;
+                end_io = post_flush_end_io;
         }
+
+        rq_init(q, rq);
+        rq->flags = REQ_HARDBARRIER;
+        rq->elevator_private = NULL;
+        rq->rq_disk = q->bar_rq.rq_disk;
+        rq->rl = NULL;
+        rq->end_io = end_io;
+        q->prepare_flush_fn(q, rq);
+
+        __elv_add_request(q, rq, ELEVATOR_INSERT_FRONT, 0);
 }
 
-static inline int blk_check_end_barrier(request_queue_t *q, struct request *rq,
-                                        int sectors)
+static inline struct request *start_ordered(request_queue_t *q,
+                                            struct request *rq)
 {
-        if (sectors > rq->nr_sectors)
-                sectors = rq->nr_sectors;
+        q->bi_size = 0;
+        q->orderr = 0;
+        q->ordered = q->next_ordered;
+        q->ordseq |= QUEUE_ORDSEQ_STARTED;
+
+        /*
+         * Prep proxy barrier request.
+         */
+        blkdev_dequeue_request(rq);
+        q->orig_bar_rq = rq;
+        rq = &q->bar_rq;
+        rq_init(q, rq);
+        rq->flags = bio_data_dir(q->orig_bar_rq->bio);
+        rq->flags |= q->ordered & QUEUE_ORDERED_FUA ? REQ_FUA : 0;
+        rq->elevator_private = NULL;
+        rq->rl = NULL;
+        init_request_from_bio(rq, q->orig_bar_rq->bio);
+        rq->end_io = bar_end_io;
+
+        /*
+         * Queue ordered sequence.  As we stack them at the head, we
+         * need to queue in reverse order.  Note that we rely on that
+         * no fs request uses ELEVATOR_INSERT_FRONT and thus no fs
+         * request gets inbetween ordered sequence.
+         */
+        if (q->ordered & QUEUE_ORDERED_POSTFLUSH)
+                queue_flush(q, QUEUE_ORDERED_POSTFLUSH);
+        else
+                q->ordseq |= QUEUE_ORDSEQ_POSTFLUSH;
+
+        __elv_add_request(q, rq, ELEVATOR_INSERT_FRONT, 0);
+
+        if (q->ordered & QUEUE_ORDERED_PREFLUSH) {
+                queue_flush(q, QUEUE_ORDERED_PREFLUSH);
+                rq = &q->pre_flush_rq;
+        } else
+                q->ordseq |= QUEUE_ORDSEQ_PREFLUSH;
 
-        rq->nr_sectors -= sectors;
-        return rq->nr_sectors;
+        if ((q->ordered & QUEUE_ORDERED_TAG) || q->in_flight == 0)
+                q->ordseq |= QUEUE_ORDSEQ_DRAIN;
+        else
+                rq = NULL;
+
+        return rq;
 }
 
-static int __blk_complete_barrier_rq(request_queue_t *q, struct request *rq,
-                                     int sectors, int queue_locked)
+int blk_do_ordered(request_queue_t *q, struct request **rqp)
 {
-        if (q->ordered != QUEUE_ORDERED_FLUSH)
-                return 0;
-        if (!blk_fs_request(rq) || !blk_barrier_rq(rq))
-                return 0;
-        if (blk_barrier_postflush(rq))
-                return 0;
+        struct request *rq = *rqp, *allowed_rq;
+        int is_barrier = blk_fs_request(rq) && blk_barrier_rq(rq);
 
-        if (!blk_check_end_barrier(q, rq, sectors)) {
-                unsigned long flags = 0;
+        if (!q->ordseq) {
+                if (!is_barrier)
+                        return 1;
 
-                if (!queue_locked)
-                        spin_lock_irqsave(q->queue_lock, flags);
+                if (q->next_ordered != QUEUE_ORDERED_NONE) {
+                        *rqp = start_ordered(q, rq);
+                        return 1;
+                } else {
+                        /*
+                         * This can happen when the queue switches to
+                         * ORDERED_NONE while this request is on it.
+                         */
+                        blkdev_dequeue_request(rq);
+                        end_that_request_first(rq, -EOPNOTSUPP,
+                                               rq->hard_nr_sectors);
+                        end_that_request_last(rq, -EOPNOTSUPP);
+                        *rqp = NULL;
+                        return 0;
+                }
+        }
 
-                blk_start_post_flush(q, rq);
+        if (q->ordered & QUEUE_ORDERED_TAG) {
+                if (is_barrier && rq != &q->bar_rq)
+                        *rqp = NULL;
+                return 1;
+        }
 
-                if (!queue_locked)
-                        spin_unlock_irqrestore(q->queue_lock, flags);
+        switch (blk_ordered_cur_seq(q)) {
+        case QUEUE_ORDSEQ_PREFLUSH:
+                allowed_rq = &q->pre_flush_rq;
+                break;
+        case QUEUE_ORDSEQ_BAR:
+                allowed_rq = &q->bar_rq;
+                break;
+        case QUEUE_ORDSEQ_POSTFLUSH:
+                allowed_rq = &q->post_flush_rq;
+                break;
+        default:
+                allowed_rq = NULL;
+                break;
         }
 
+        if (rq != allowed_rq &&
+            (blk_fs_request(rq) || rq == &q->pre_flush_rq ||
+             rq == &q->post_flush_rq))
+                *rqp = NULL;
+
         return 1;
 }
 
-/**
- * blk_complete_barrier_rq - complete possible barrier request
- * @q:  the request queue for the device
- * @rq:  the request
- * @sectors:  number of sectors to complete
- *
- * Description:
- *   Used in driver end_io handling to determine whether to postpone
- *   completion of a barrier request until a post flush has been done. This
- *   is the unlocked variant, used if the caller doesn't already hold the
- *   queue lock.
- **/
-int blk_complete_barrier_rq(request_queue_t *q, struct request *rq, int sectors)
+static int flush_dry_bio_endio(struct bio *bio, unsigned int bytes, int error)
 {
-        return __blk_complete_barrier_rq(q, rq, sectors, 0);
+        request_queue_t *q = bio->bi_private;
+        struct bio_vec *bvec;
+        int i;
+
+        /*
+         * This is dry run, restore bio_sector and size.  We'll finish
+         * this request again with the original bi_end_io after an
+         * error occurs or post flush is complete.
+         */
+        q->bi_size += bytes;
+
+        if (bio->bi_size)
+                return 1;
+
+        /* Rewind bvec's */
+        bio->bi_idx = 0;
+        bio_for_each_segment(bvec, bio, i) {
+                bvec->bv_len += bvec->bv_offset;
+                bvec->bv_offset = 0;
+        }
+
+        /* Reset bio */
+        set_bit(BIO_UPTODATE, &bio->bi_flags);
+        bio->bi_size = q->bi_size;
+        bio->bi_sector -= (q->bi_size >> 9);
+        q->bi_size = 0;
+
+        return 0;
 }
-EXPORT_SYMBOL(blk_complete_barrier_rq);
 
-/**
- * blk_complete_barrier_rq_locked - complete possible barrier request
- * @q:  the request queue for the device
- * @rq:  the request
- * @sectors:  number of sectors to complete
- *
- * Description:
- *   See blk_complete_barrier_rq(). This variant must be used if the caller
- *   holds the queue lock.
- **/
-int blk_complete_barrier_rq_locked(request_queue_t *q, struct request *rq,
-                                   int sectors)
+static inline int ordered_bio_endio(struct request *rq, struct bio *bio,
+                                    unsigned int nbytes, int error)
 {
-        return __blk_complete_barrier_rq(q, rq, sectors, 1);
+        request_queue_t *q = rq->q;
+        bio_end_io_t *endio;
+        void *private;
+
+        if (&q->bar_rq != rq)
+                return 0;
+
+        /*
+         * Okay, this is the barrier request in progress, dry finish it.
+         */
+        if (error && !q->orderr)
+                q->orderr = error;
+
+        endio = bio->bi_end_io;
+        private = bio->bi_private;
+        bio->bi_end_io = flush_dry_bio_endio;
+        bio->bi_private = q;
+
+        bio_endio(bio, nbytes, error);
+
+        bio->bi_end_io = endio;
+        bio->bi_private = private;
+
+        return 1;
 }
-EXPORT_SYMBOL(blk_complete_barrier_rq_locked);
 
 /**
  * blk_queue_bounce_limit - set bounce buffer limit for queue
@@ -1047,6 +1147,7 @@ static const char * const rq_flags[] = {
         "REQ_SORTED",
         "REQ_SOFTBARRIER",
         "REQ_HARDBARRIER",
+        "REQ_FUA",
         "REQ_CMD",
         "REQ_NOMERGE",
         "REQ_STARTED",
@@ -1066,6 +1167,7 @@ static const char * const rq_flags[] = {
         "REQ_PM_SUSPEND",
         "REQ_PM_RESUME",
         "REQ_PM_SHUTDOWN",
+        "REQ_ORDERED_COLOR",
 };
 
 void blk_dump_rq_flags(struct request *rq, char *msg)
@@ -1643,8 +1745,6 @@ void blk_cleanup_queue(request_queue_t * q)
         if (q->queue_tags)
                 __blk_queue_free_tags(q);
 
-        blk_queue_ordered(q, QUEUE_ORDERED_NONE);
-
         kmem_cache_free(requestq_cachep, q);
 }
 
@@ -2714,7 +2814,7 @@ static int __make_request(request_queue_t *q, struct bio *bio)
         spin_lock_prefetch(q->queue_lock);
 
         barrier = bio_barrier(bio);
-        if (unlikely(barrier) && (q->ordered == QUEUE_ORDERED_NONE)) {
+        if (unlikely(barrier) && (q->next_ordered == QUEUE_ORDERED_NONE)) {
                 err = -EOPNOTSUPP;
                 goto end_io;
         }
@@ -3075,7 +3175,8 @@ static int __end_that_request_first(struct request *req, int uptodate,
                 if (nr_bytes >= bio->bi_size) {
                         req->bio = bio->bi_next;
                         nbytes = bio->bi_size;
-                        bio_endio(bio, nbytes, error);
+                        if (!ordered_bio_endio(req, bio, nbytes, error))
+                                bio_endio(bio, nbytes, error);
                         next_idx = 0;
                         bio_nbytes = 0;
                 } else {
@@ -3130,7 +3231,8 @@ static int __end_that_request_first(struct request *req, int uptodate,
          * if the request wasn't completed, update state
          */
         if (bio_nbytes) {
-                bio_endio(bio, bio_nbytes, error);
+                if (!ordered_bio_endio(req, bio, bio_nbytes, error))
+                        bio_endio(bio, bio_nbytes, error);
                 bio->bi_idx += next_idx;
                 bio_iovec(bio)->bv_offset += nr_bytes;
                 bio_iovec(bio)->bv_len -= nr_bytes;