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dm: submit stacked requests in irq enabled context

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Switch to having request-based DM enqueue all prep'ed requests into work
processed by another thread.  This allows request-based DM to invoke
block APIs that assume interrupt enabled context (e.g. blk_get_request)
and is a prerequisite for adding blk-mq support to request-based DM.

The new kernel thread is only initialized for request-based DM devices.

multipath_map() is now always in irq enabled context so change multipath
spinlock (m->lock) locking to always disable interrupts.

Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This commit is contained in:
Keith Busch 2014-10-17 17:46:36 -06:00 committed by Mike Snitzer
parent 1ae49ea2cf
commit 2eb6e1e3aa
2 changed files with 47 additions and 19 deletions
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20
drivers/md/dm-mpath.c
View File

@ -384,12 +384,11 @@ static int multipath_map(struct dm_target *ti, struct request *clone,
struct multipath *m = (struct multipath *) ti->private;
int r = DM_MAPIO_REQUEUE;
size_t nr_bytes = blk_rq_bytes(clone);
unsigned long flags;
struct pgpath *pgpath;
struct block_device *bdev;
struct dm_mpath_io *mpio;
spin_lock_irqsave(&m->lock, flags);
spin_lock_irq(&m->lock);
/* Do we need to select a new pgpath? */
if (!m->current_pgpath ||
@ -411,21 +410,26 @@ static int multipath_map(struct dm_target *ti, struct request *clone,
/* ENOMEM, requeue */
goto out_unlock;
bdev = pgpath->path.dev->bdev;
clone->q = bdev_get_queue(bdev);
clone->rq_disk = bdev->bd_disk;
clone->cmd_flags |= REQ_FAILFAST_TRANSPORT;
mpio = map_context->ptr;
mpio->pgpath = pgpath;
mpio->nr_bytes = nr_bytes;
bdev = pgpath->path.dev->bdev;
clone->q = bdev_get_queue(bdev);
clone->rq_disk = bdev->bd_disk;
clone->cmd_flags |= REQ_FAILFAST_TRANSPORT;
spin_unlock_irq(&m->lock);
if (pgpath->pg->ps.type->start_io)
pgpath->pg->ps.type->start_io(&pgpath->pg->ps,
&pgpath->path,
nr_bytes);
r = DM_MAPIO_REMAPPED;
return DM_MAPIO_REMAPPED;
out_unlock:
spin_unlock_irqrestore(&m->lock, flags);
spin_unlock_irq(&m->lock);
return r;
}

46
drivers/md/dm.c
View File

@ -20,6 +20,7 @@
#include <linux/hdreg.h>
#include <linux/delay.h>
#include <linux/wait.h>
#include <linux/kthread.h>
#include <trace/events/block.h>
@ -79,6 +80,7 @@ struct dm_rq_target_io {
struct mapped_device *md;
struct dm_target *ti;
struct request *orig, *clone;
struct kthread_work work;
int error;
union map_info info;
};
@ -208,6 +210,9 @@ struct mapped_device {
struct bio flush_bio;
struct dm_stats stats;
struct kthread_worker kworker;
struct task_struct *kworker_task;
};
/*
@ -1773,6 +1778,8 @@ static struct request *__clone_rq(struct request *rq, struct mapped_device *md,
return clone;
}
static void map_tio_request(struct kthread_work *work);
static struct request *clone_rq(struct request *rq, struct mapped_device *md,
gfp_t gfp_mask)
{
@ -1789,6 +1796,7 @@ static struct request *clone_rq(struct request *rq, struct mapped_device *md,
tio->orig = rq;
tio->error = 0;
memset(&tio->info, 0, sizeof(tio->info));
init_kthread_work(&tio->work, map_tio_request);
clone = __clone_rq(rq, md, tio, GFP_ATOMIC);
if (!clone) {
@ -1833,7 +1841,6 @@ static int map_request(struct dm_target *ti, struct request *clone,
int r, requeued = 0;
struct dm_rq_target_io *tio = clone->end_io_data;
tio->ti = ti;
r = ti->type->map_rq(ti, clone, &tio->info);
switch (r) {
case DM_MAPIO_SUBMITTED:
@ -1864,6 +1871,13 @@ static int map_request(struct dm_target *ti, struct request *clone,
return requeued;
}
static void map_tio_request(struct kthread_work *work)
{
struct dm_rq_target_io *tio = container_of(work, struct dm_rq_target_io, work);
map_request(tio->ti, tio->clone, tio->md);
}
static struct request *dm_start_request(struct mapped_device *md, struct request *orig)
{
struct request *clone;
@ -1895,6 +1909,7 @@ static void dm_request_fn(struct request_queue *q)
struct dm_table *map = dm_get_live_table(md, &srcu_idx);
struct dm_target *ti;
struct request *rq, *clone;
struct dm_rq_target_io *tio;
sector_t pos;
/*
@ -1930,20 +1945,15 @@ static void dm_request_fn(struct request_queue *q)
clone = dm_start_request(md, rq);
spin_unlock(q->queue_lock);
if (map_request(ti, clone, md))
goto requeued;
tio = rq->special;
/* Establish tio->ti before queuing work (map_tio_request) */
tio->ti = ti;
queue_kthread_work(&md->kworker, &tio->work);
BUG_ON(!irqs_disabled());
spin_lock(q->queue_lock);
}
goto out;
requeued:
BUG_ON(!irqs_disabled());
spin_lock(q->queue_lock);
delay_and_out:
blk_delay_queue(q, HZ / 10);
out:
@ -2129,6 +2139,7 @@ static struct mapped_device *alloc_dev(int minor)
INIT_WORK(&md->work, dm_wq_work);
init_waitqueue_head(&md->eventq);
init_completion(&md->kobj_holder.completion);
md->kworker_task = NULL;
md->disk->major = _major;
md->disk->first_minor = minor;
@ -2189,6 +2200,9 @@ static void free_dev(struct mapped_device *md)
unlock_fs(md);
bdput(md->bdev);
destroy_workqueue(md->wq);
if (md->kworker_task)
kthread_stop(md->kworker_task);
if (md->io_pool)
mempool_destroy(md->io_pool);
if (md->rq_pool)
@ -2484,6 +2498,11 @@ static int dm_init_request_based_queue(struct mapped_device *md)
blk_queue_prep_rq(md->queue, dm_prep_fn);
blk_queue_lld_busy(md->queue, dm_lld_busy);
/* Also initialize the request-based DM worker thread */
init_kthread_worker(&md->kworker);
md->kworker_task = kthread_run(kthread_worker_fn, &md->kworker,
"kdmwork-%s", dm_device_name(md));
elv_register_queue(md->queue);
return 1;
@ -2574,6 +2593,9 @@ static void __dm_destroy(struct mapped_device *md, bool wait)
set_bit(DMF_FREEING, &md->flags);
spin_unlock(&_minor_lock);
if (dm_request_based(md))
flush_kthread_worker(&md->kworker);
if (!dm_suspended_md(md)) {
dm_table_presuspend_targets(map);
dm_table_postsuspend_targets(map);
@ -2817,8 +2839,10 @@ static int __dm_suspend(struct mapped_device *md, struct dm_table *map,
* Stop md->queue before flushing md->wq in case request-based
* dm defers requests to md->wq from md->queue.
*/
if (dm_request_based(md))
if (dm_request_based(md)) {
stop_queue(md->queue);
flush_kthread_worker(&md->kworker);
}
flush_workqueue(md->wq);