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dm thin: use per thin device deferred bio lists
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The thin-pool previously only had a single deferred_bios list that would
collect bios for all thin devices in the pool.  Split this per-pool
deferred_bios list out to per-thin deferred_bios_list -- doing so
enables increased parallelism when processing deferred bios.  And now
that each thin device has it's own deferred_bios_list we can sort all
bios in the list using logical sector.  The requeue code in error
handling path is also cleaner as a side-effect.

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Acked-by: Joe Thornber <ejt@redhat.com>
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Mike Snitzer committed Mar 31, 2014
1 parent 760fe67 commit c140e1c
Showing 1 changed file with 104 additions and 61 deletions.
165 changes: 104 additions & 61 deletions drivers/md/dm-thin.c
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Original file line number Diff line number Diff line change
Expand Up @@ -12,6 +12,7 @@
#include <linux/dm-io.h>
#include <linux/dm-kcopyd.h>
#include <linux/list.h>
#include <linux/rculist.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/slab.h>
Expand Down Expand Up @@ -178,12 +179,10 @@ struct pool {
unsigned ref_count;

spinlock_t lock;
struct bio_list deferred_bios;
struct bio_list deferred_flush_bios;
struct list_head prepared_mappings;
struct list_head prepared_discards;

struct bio_list retry_on_resume_list;
struct list_head active_thins;

struct dm_deferred_set *shared_read_ds;
struct dm_deferred_set *all_io_ds;
Expand Down Expand Up @@ -220,13 +219,17 @@ struct pool_c {
* Target context for a thin.
*/
struct thin_c {
struct list_head list;
struct dm_dev *pool_dev;
struct dm_dev *origin_dev;
dm_thin_id dev_id;

struct pool *pool;
struct dm_thin_device *td;
bool requeue_mode:1;
spinlock_t lock;
struct bio_list deferred_bio_list;
struct bio_list retry_on_resume_list;
};

/*----------------------------------------------------------------*/
Expand Down Expand Up @@ -287,9 +290,9 @@ static void cell_defer_no_holder_no_free(struct thin_c *tc,
struct pool *pool = tc->pool;
unsigned long flags;

spin_lock_irqsave(&pool->lock, flags);
dm_cell_release_no_holder(pool->prison, cell, &pool->deferred_bios);
spin_unlock_irqrestore(&pool->lock, flags);
spin_lock_irqsave(&tc->lock, flags);
dm_cell_release_no_holder(pool->prison, cell, &tc->deferred_bio_list);
spin_unlock_irqrestore(&tc->lock, flags);

wake_worker(pool);
}
Expand Down Expand Up @@ -378,46 +381,48 @@ static void requeue_bio_list(struct thin_c *tc, struct bio_list *master)

bio_list_init(&bios);

spin_lock_irqsave(&tc->pool->lock, flags);
spin_lock_irqsave(&tc->lock, flags);
bio_list_merge(&bios, master);
bio_list_init(master);
spin_unlock_irqrestore(&tc->pool->lock, flags);
spin_unlock_irqrestore(&tc->lock, flags);

while ((bio = bio_list_pop(&bios))) {
struct dm_thin_endio_hook *h = dm_per_bio_data(bio, sizeof(struct dm_thin_endio_hook));

if (h->tc == tc)
bio_endio(bio, DM_ENDIO_REQUEUE);
else
bio_list_add(master, bio);
}
while ((bio = bio_list_pop(&bios)))
bio_endio(bio, DM_ENDIO_REQUEUE);
}

static void requeue_io(struct thin_c *tc)
{
struct pool *pool = tc->pool;

requeue_bio_list(tc, &pool->deferred_bios);
requeue_bio_list(tc, &pool->retry_on_resume_list);
requeue_bio_list(tc, &tc->deferred_bio_list);
requeue_bio_list(tc, &tc->retry_on_resume_list);
}

static void error_retry_list(struct pool *pool)
static void error_thin_retry_list(struct thin_c *tc)
{
struct bio *bio;
unsigned long flags;
struct bio_list bios;

bio_list_init(&bios);

spin_lock_irqsave(&pool->lock, flags);
bio_list_merge(&bios, &pool->retry_on_resume_list);
bio_list_init(&pool->retry_on_resume_list);
spin_unlock_irqrestore(&pool->lock, flags);
spin_lock_irqsave(&tc->lock, flags);
bio_list_merge(&bios, &tc->retry_on_resume_list);
bio_list_init(&tc->retry_on_resume_list);
spin_unlock_irqrestore(&tc->lock, flags);

while ((bio = bio_list_pop(&bios)))
bio_io_error(bio);
}

static void error_retry_list(struct pool *pool)
{
struct thin_c *tc;

rcu_read_lock();
list_for_each_entry_rcu(tc, &pool->active_thins, list)
error_thin_retry_list(tc);
rcu_read_unlock();
}

/*
* This section of code contains the logic for processing a thin device's IO.
* Much of the code depends on pool object resources (lists, workqueues, etc)
Expand Down Expand Up @@ -608,9 +613,9 @@ static void cell_defer(struct thin_c *tc, struct dm_bio_prison_cell *cell)
struct pool *pool = tc->pool;
unsigned long flags;

spin_lock_irqsave(&pool->lock, flags);
cell_release(pool, cell, &pool->deferred_bios);
spin_unlock_irqrestore(&tc->pool->lock, flags);
spin_lock_irqsave(&tc->lock, flags);
cell_release(pool, cell, &tc->deferred_bio_list);
spin_unlock_irqrestore(&tc->lock, flags);

wake_worker(pool);
}
Expand All @@ -623,9 +628,9 @@ static void cell_defer_no_holder(struct thin_c *tc, struct dm_bio_prison_cell *c
struct pool *pool = tc->pool;
unsigned long flags;

spin_lock_irqsave(&pool->lock, flags);
cell_release_no_holder(pool, cell, &pool->deferred_bios);
spin_unlock_irqrestore(&pool->lock, flags);
spin_lock_irqsave(&tc->lock, flags);
cell_release_no_holder(pool, cell, &tc->deferred_bio_list);
spin_unlock_irqrestore(&tc->lock, flags);

wake_worker(pool);
}
Expand Down Expand Up @@ -1001,12 +1006,11 @@ static void retry_on_resume(struct bio *bio)
{
struct dm_thin_endio_hook *h = dm_per_bio_data(bio, sizeof(struct dm_thin_endio_hook));
struct thin_c *tc = h->tc;
struct pool *pool = tc->pool;
unsigned long flags;

spin_lock_irqsave(&pool->lock, flags);
bio_list_add(&pool->retry_on_resume_list, bio);
spin_unlock_irqrestore(&pool->lock, flags);
spin_lock_irqsave(&tc->lock, flags);
bio_list_add(&tc->retry_on_resume_list, bio);
spin_unlock_irqrestore(&tc->lock, flags);
}

static bool should_error_unserviceable_bio(struct pool *pool)
Expand Down Expand Up @@ -1363,38 +1367,36 @@ static int need_commit_due_to_time(struct pool *pool)
jiffies > pool->last_commit_jiffies + COMMIT_PERIOD;
}

static void process_deferred_bios(struct pool *pool)
static void process_thin_deferred_bios(struct thin_c *tc)
{
struct pool *pool = tc->pool;
unsigned long flags;
struct bio *bio;
struct bio_list bios;

if (tc->requeue_mode) {
requeue_bio_list(tc, &tc->deferred_bio_list);
return;
}

bio_list_init(&bios);

spin_lock_irqsave(&pool->lock, flags);
bio_list_merge(&bios, &pool->deferred_bios);
bio_list_init(&pool->deferred_bios);
spin_unlock_irqrestore(&pool->lock, flags);
spin_lock_irqsave(&tc->lock, flags);
bio_list_merge(&bios, &tc->deferred_bio_list);
bio_list_init(&tc->deferred_bio_list);
spin_unlock_irqrestore(&tc->lock, flags);

while ((bio = bio_list_pop(&bios))) {
struct dm_thin_endio_hook *h = dm_per_bio_data(bio, sizeof(struct dm_thin_endio_hook));
struct thin_c *tc = h->tc;

if (tc->requeue_mode) {
bio_endio(bio, DM_ENDIO_REQUEUE);
continue;
}

/*
* If we've got no free new_mapping structs, and processing
* this bio might require one, we pause until there are some
* prepared mappings to process.
*/
if (ensure_next_mapping(pool)) {
spin_lock_irqsave(&pool->lock, flags);
bio_list_add(&pool->deferred_bios, bio);
bio_list_merge(&pool->deferred_bios, &bios);
spin_unlock_irqrestore(&pool->lock, flags);
spin_lock_irqsave(&tc->lock, flags);
bio_list_add(&tc->deferred_bio_list, bio);
bio_list_merge(&tc->deferred_bio_list, &bios);
spin_unlock_irqrestore(&tc->lock, flags);
break;
}

Expand All @@ -1403,6 +1405,19 @@ static void process_deferred_bios(struct pool *pool)
else
pool->process_bio(tc, bio);
}
}

static void process_deferred_bios(struct pool *pool)
{
unsigned long flags;
struct bio *bio;
struct bio_list bios;
struct thin_c *tc;

rcu_read_lock();
list_for_each_entry_rcu(tc, &pool->active_thins, list)
process_thin_deferred_bios(tc);
rcu_read_unlock();

/*
* If there are any deferred flush bios, we must commit
Expand Down Expand Up @@ -1634,9 +1649,9 @@ static void thin_defer_bio(struct thin_c *tc, struct bio *bio)
unsigned long flags;
struct pool *pool = tc->pool;

spin_lock_irqsave(&pool->lock, flags);
bio_list_add(&pool->deferred_bios, bio);
spin_unlock_irqrestore(&pool->lock, flags);
spin_lock_irqsave(&tc->lock, flags);
bio_list_add(&tc->deferred_bio_list, bio);
spin_unlock_irqrestore(&tc->lock, flags);

wake_worker(pool);
}
Expand Down Expand Up @@ -1767,10 +1782,19 @@ static int pool_is_congested(struct dm_target_callbacks *cb, int bdi_bits)
return bdi_congested(&q->backing_dev_info, bdi_bits);
}

static void __requeue_bios(struct pool *pool)
static void requeue_bios(struct pool *pool)
{
bio_list_merge(&pool->deferred_bios, &pool->retry_on_resume_list);
bio_list_init(&pool->retry_on_resume_list);
unsigned long flags;
struct thin_c *tc;

rcu_read_lock();
list_for_each_entry_rcu(tc, &pool->active_thins, list) {
spin_lock_irqsave(&tc->lock, flags);
bio_list_merge(&tc->deferred_bio_list, &tc->retry_on_resume_list);
bio_list_init(&tc->retry_on_resume_list);
spin_unlock_irqrestore(&tc->lock, flags);
}
rcu_read_unlock();
}

/*----------------------------------------------------------------
Expand Down Expand Up @@ -1951,12 +1975,11 @@ static struct pool *pool_create(struct mapped_device *pool_md,
INIT_WORK(&pool->worker, do_worker);
INIT_DELAYED_WORK(&pool->waker, do_waker);
spin_lock_init(&pool->lock);
bio_list_init(&pool->deferred_bios);
bio_list_init(&pool->deferred_flush_bios);
INIT_LIST_HEAD(&pool->prepared_mappings);
INIT_LIST_HEAD(&pool->prepared_discards);
INIT_LIST_HEAD(&pool->active_thins);
pool->low_water_triggered = false;
bio_list_init(&pool->retry_on_resume_list);

pool->shared_read_ds = dm_deferred_set_create();
if (!pool->shared_read_ds) {
Expand Down Expand Up @@ -2501,8 +2524,8 @@ static void pool_resume(struct dm_target *ti)

spin_lock_irqsave(&pool->lock, flags);
pool->low_water_triggered = false;
__requeue_bios(pool);
spin_unlock_irqrestore(&pool->lock, flags);
requeue_bios(pool);

do_waker(&pool->waker.work);
}
Expand Down Expand Up @@ -2962,6 +2985,12 @@ static struct target_type pool_target = {
static void thin_dtr(struct dm_target *ti)
{
struct thin_c *tc = ti->private;
unsigned long flags;

spin_lock_irqsave(&tc->pool->lock, flags);
list_del_rcu(&tc->list);
spin_unlock_irqrestore(&tc->pool->lock, flags);
synchronize_rcu();

mutex_lock(&dm_thin_pool_table.mutex);

Expand Down Expand Up @@ -3008,6 +3037,9 @@ static int thin_ctr(struct dm_target *ti, unsigned argc, char **argv)
r = -ENOMEM;
goto out_unlock;
}
spin_lock_init(&tc->lock);
bio_list_init(&tc->deferred_bio_list);
bio_list_init(&tc->retry_on_resume_list);

if (argc == 3) {
r = dm_get_device(ti, argv[2], FMODE_READ, &origin_dev);
Expand Down Expand Up @@ -3079,6 +3111,17 @@ static int thin_ctr(struct dm_target *ti, unsigned argc, char **argv)

mutex_unlock(&dm_thin_pool_table.mutex);

spin_lock(&tc->pool->lock);
list_add_tail_rcu(&tc->list, &tc->pool->active_thins);
spin_unlock(&tc->pool->lock);
/*
* This synchronize_rcu() call is needed here otherwise we risk a
* wake_worker() call finding no bios to process (because the newly
* added tc isn't yet visible). So this reduces latency since we
* aren't then dependent on the periodic commit to wake_worker().
*/
synchronize_rcu();

return 0;

bad_target_max_io_len:
Expand Down

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