[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>
diff --git a/block/elevator.c b/block/elevator.c
index 85a11ce..39dcccc 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -304,15 +304,7 @@
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 @@
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 @@
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 @@
{
struct request *rq;
- if (unlikely(list_empty(&q->queue_head) &&
- !q->elevator->ops->elevator_dispatch_fn(q, 0)))
- return NULL;
+ 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 = 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);
-
- 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 @@
* 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 65c4efc..91d3b48 100644
--- a/block/ll_rw_blk.c
+++ b/block/ll_rw_blk.c
@@ -290,8 +290,8 @@
/**
* 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 @@
* feature should call this function and indicate so.
*
**/
-void blk_queue_ordered(request_queue_t *q, int flag)
+int blk_queue_ordered(request_queue_t *q, unsigned ordered,
+ prepare_flush_fn *prepare_flush_fn)
{
- 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;
+ 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 @@
/*
* 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;
+ if (!q->ordseq)
+ return 0;
+ return 1 << ffz(q->ordseq);
+}
+
+unsigned blk_ordered_req_seq(struct request *rq)
+{
request_queue_t *q = rq->q;
- elv_completed_request(q, flush_rq);
+ BUG_ON(q->ordseq == 0);
- rq->flags |= REQ_BAR_PREFLUSH;
+ 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;
- 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 ((rq->flags & REQ_ORDERED_COLOR) ==
+ (q->orig_bar_rq->flags & REQ_ORDERED_COLOR))
+ return QUEUE_ORDSEQ_DRAIN;
+ else
+ return QUEUE_ORDSEQ_DONE;
}
-static void blk_post_flush_end_io(struct request *flush_rq, int error)
+void blk_ordered_complete_seq(request_queue_t *q, unsigned seq, int error)
{
- struct request *rq = flush_rq->end_io_data;
- request_queue_t *q = rq->q;
+ struct request *rq;
+ int uptodate;
- elv_completed_request(q, flush_rq);
+ if (error && !q->orderr)
+ q->orderr = error;
- rq->flags |= REQ_BAR_POSTFLUSH;
+ BUG_ON(q->ordseq & seq);
+ q->ordseq |= seq;
- q->end_flush_fn(q, flush_rq);
- clear_bit(QUEUE_FLAG_FLUSH, &q->queue_flags);
- q->request_fn(q);
-}
-
-struct request *blk_start_pre_flush(request_queue_t *q, struct request *rq)
-{
- struct request *flush_rq = q->flush_rq;
-
- BUG_ON(!blk_barrier_rq(rq));
-
- if (test_and_set_bit(QUEUE_FLAG_FLUSH, &q->queue_flags))
- return NULL;
-
- 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;
+ if (blk_ordered_cur_seq(q) != QUEUE_ORDSEQ_DONE)
+ return;
/*
- * prepare_flush returns 0 if no flush is needed, just mark both
- * pre and post flush as done in that case
+ * Okay, sequence complete.
*/
- 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;
+ rq = q->orig_bar_rq;
+ uptodate = q->orderr ? q->orderr : 1;
+
+ q->ordseq = 0;
+
+ end_that_request_first(rq, uptodate, rq->hard_nr_sectors);
+ end_that_request_last(rq, uptodate);
+}
+
+static void pre_flush_end_io(struct request *rq, int error)
+{
+ elv_completed_request(rq->q, rq);
+ blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_PREFLUSH, error);
+}
+
+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);
+}
+
+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);
+}
+
+static void queue_flush(request_queue_t *q, unsigned which)
+{
+ struct request *rq;
+ rq_end_io_fn *end_io;
+
+ 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 struct request *start_ordered(request_queue_t *q,
+ struct request *rq)
+{
+ q->bi_size = 0;
+ q->orderr = 0;
+ q->ordered = q->next_ordered;
+ q->ordseq |= QUEUE_ORDSEQ_STARTED;
+
/*
- * some drivers dequeue requests right away, some only after io
- * completion. make sure the request is dequeued.
+ * Prep proxy barrier request.
*/
- if (!list_empty(&rq->queuelist))
- blkdev_dequeue_request(rq);
+ 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;
- flush_rq->end_io_data = rq;
- flush_rq->end_io = blk_pre_flush_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, flush_rq, ELEVATOR_INSERT_FRONT, 0);
- return flush_rq;
+ __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;
+
+ if ((q->ordered & QUEUE_ORDERED_TAG) || q->in_flight == 0)
+ q->ordseq |= QUEUE_ORDSEQ_DRAIN;
+ else
+ rq = NULL;
+
+ return rq;
}
-static void blk_start_post_flush(request_queue_t *q, struct request *rq)
+int blk_do_ordered(request_queue_t *q, struct request **rqp)
{
- struct request *flush_rq = q->flush_rq;
+ struct request *rq = *rqp, *allowed_rq;
+ int is_barrier = blk_fs_request(rq) && blk_barrier_rq(rq);
- BUG_ON(!blk_barrier_rq(rq));
+ if (!q->ordseq) {
+ if (!is_barrier)
+ return 1;
- 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;
-
- if (q->prepare_flush_fn(q, flush_rq)) {
- flush_rq->end_io_data = rq;
- flush_rq->end_io = blk_post_flush_end_io;
-
- __elv_add_request(q, flush_rq, ELEVATOR_INSERT_FRONT, 0);
- q->request_fn(q);
+ 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;
+ }
}
-}
-static inline int blk_check_end_barrier(request_queue_t *q, struct request *rq,
- int sectors)
-{
- if (sectors > rq->nr_sectors)
- sectors = rq->nr_sectors;
-
- rq->nr_sectors -= sectors;
- return rq->nr_sectors;
-}
-
-static int __blk_complete_barrier_rq(request_queue_t *q, struct request *rq,
- int sectors, int queue_locked)
-{
- 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;
-
- if (!blk_check_end_barrier(q, rq, sectors)) {
- unsigned long flags = 0;
-
- if (!queue_locked)
- spin_lock_irqsave(q->queue_lock, flags);
-
- blk_start_post_flush(q, rq);
-
- if (!queue_locked)
- spin_unlock_irqrestore(q->queue_lock, flags);
+ if (q->ordered & QUEUE_ORDERED_TAG) {
+ if (is_barrier && rq != &q->bar_rq)
+ *rqp = NULL;
+ return 1;
}
+ 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);
-}
-EXPORT_SYMBOL(blk_complete_barrier_rq);
+ request_queue_t *q = bio->bi_private;
+ struct bio_vec *bvec;
+ int i;
-/**
- * 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)
-{
- return __blk_complete_barrier_rq(q, rq, sectors, 1);
+ /*
+ * 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_locked);
+
+static inline int ordered_bio_endio(struct request *rq, struct bio *bio,
+ unsigned int nbytes, int error)
+{
+ 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;
+}
/**
* blk_queue_bounce_limit - set bounce buffer limit for queue
@@ -1047,6 +1147,7 @@
"REQ_SORTED",
"REQ_SOFTBARRIER",
"REQ_HARDBARRIER",
+ "REQ_FUA",
"REQ_CMD",
"REQ_NOMERGE",
"REQ_STARTED",
@@ -1066,6 +1167,7 @@
"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 @@
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 @@
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 @@
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 @@
* 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;
