Commit 797e7dbb authored by Tejun Heo's avatar Tejun Heo Committed by Jens Axboe
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[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: default avatarTejun Heo <htejun@gmail.com>
Signed-off-by: default avatarJens Axboe <axboe@suse.de>
parent 52d9e675
......@@ -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)
......@@ -332,7 +324,18 @@ 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
*/
......@@ -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);
}
......
......@@ -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;
......
......@@ -207,6 +207,7 @@ enum rq_flag_bits {
__REQ_SORTED, /* elevator knows about this request */
__REQ_SOFTBARRIER, /* may not be passed by ioscheduler */
__REQ_HARDBARRIER, /* may not be passed by drive either */
__REQ_FUA, /* forced unit access */
__REQ_CMD, /* is a regular fs rw request */
__REQ_NOMERGE, /* don't touch this for merging */
__REQ_STARTED, /* drive already may have started this one */
......@@ -230,9 +231,7 @@ enum rq_flag_bits {