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md/raid5: add simple plugging infrastructure.
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md/raid5 uses the plugging infrastructure provided by the block layer
and 'struct request_queue'.  However when we plug raid5 under dm there
is no request queue so we cannot use that.

So create a similar infrastructure that is much lighter weight and use
it for raid5.

Signed-off-by: NeilBrown <neilb@suse.de>
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NeilBrown committed Jul 26, 2010
1 parent 11d8a6e commit 2ac8740
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Showing 4 changed files with 93 additions and 14 deletions.
45 changes: 45 additions & 0 deletions drivers/md/md.c
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Original file line number Diff line number Diff line change
Expand Up @@ -386,6 +386,51 @@ void md_barrier_request(mddev_t *mddev, struct bio *bio)
}
EXPORT_SYMBOL(md_barrier_request);

/* Support for plugging.
* This mirrors the plugging support in request_queue, but does not
* require having a whole queue
*/
static void plugger_work(struct work_struct *work)
{
struct plug_handle *plug =
container_of(work, struct plug_handle, unplug_work);
plug->unplug_fn(plug);
}
static void plugger_timeout(unsigned long data)
{
struct plug_handle *plug = (void *)data;
kblockd_schedule_work(NULL, &plug->unplug_work);
}
void plugger_init(struct plug_handle *plug,
void (*unplug_fn)(struct plug_handle *))
{
plug->unplug_flag = 0;
plug->unplug_fn = unplug_fn;
init_timer(&plug->unplug_timer);
plug->unplug_timer.function = plugger_timeout;
plug->unplug_timer.data = (unsigned long)plug;
INIT_WORK(&plug->unplug_work, plugger_work);
}
EXPORT_SYMBOL_GPL(plugger_init);

void plugger_set_plug(struct plug_handle *plug)
{
if (!test_and_set_bit(PLUGGED_FLAG, &plug->unplug_flag))
mod_timer(&plug->unplug_timer, jiffies + msecs_to_jiffies(3)+1);
}
EXPORT_SYMBOL_GPL(plugger_set_plug);

int plugger_remove_plug(struct plug_handle *plug)
{
if (test_and_clear_bit(PLUGGED_FLAG, &plug->unplug_flag)) {
del_timer(&plug->unplug_timer);
return 1;
} else
return 0;
}
EXPORT_SYMBOL_GPL(plugger_remove_plug);


static inline mddev_t *mddev_get(mddev_t *mddev)
{
atomic_inc(&mddev->active);
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20 changes: 20 additions & 0 deletions drivers/md/md.h
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Original file line number Diff line number Diff line change
Expand Up @@ -29,6 +29,26 @@
typedef struct mddev_s mddev_t;
typedef struct mdk_rdev_s mdk_rdev_t;

/* generic plugging support - like that provided with request_queue,
* but does not require a request_queue
*/
struct plug_handle {
void (*unplug_fn)(struct plug_handle *);
struct timer_list unplug_timer;
struct work_struct unplug_work;
unsigned long unplug_flag;
};
#define PLUGGED_FLAG 1
void plugger_init(struct plug_handle *plug,
void (*unplug_fn)(struct plug_handle *));
void plugger_set_plug(struct plug_handle *plug);
int plugger_remove_plug(struct plug_handle *plug);
static inline void plugger_flush(struct plug_handle *plug)
{
del_timer_sync(&plug->unplug_timer);
cancel_work_sync(&plug->unplug_work);
}

/*
* MD's 'extended' device
*/
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39 changes: 25 additions & 14 deletions drivers/md/raid5.c
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Original file line number Diff line number Diff line change
Expand Up @@ -201,11 +201,11 @@ static void __release_stripe(raid5_conf_t *conf, struct stripe_head *sh)
if (test_bit(STRIPE_HANDLE, &sh->state)) {
if (test_bit(STRIPE_DELAYED, &sh->state)) {
list_add_tail(&sh->lru, &conf->delayed_list);
blk_plug_device(conf->mddev->queue);
plugger_set_plug(&conf->plug);
} else if (test_bit(STRIPE_BIT_DELAY, &sh->state) &&
sh->bm_seq - conf->seq_write > 0) {
list_add_tail(&sh->lru, &conf->bitmap_list);
blk_plug_device(conf->mddev->queue);
plugger_set_plug(&conf->plug);
} else {
clear_bit(STRIPE_BIT_DELAY, &sh->state);
list_add_tail(&sh->lru, &conf->handle_list);
Expand Down Expand Up @@ -434,7 +434,7 @@ static int has_failed(raid5_conf_t *conf)
}

static void unplug_slaves(mddev_t *mddev);
static void raid5_unplug_device(struct request_queue *q);
static void raid5_unplug_device(raid5_conf_t *conf);

static struct stripe_head *
get_active_stripe(raid5_conf_t *conf, sector_t sector,
Expand Down Expand Up @@ -464,7 +464,7 @@ get_active_stripe(raid5_conf_t *conf, sector_t sector,
< (conf->max_nr_stripes *3/4)
|| !conf->inactive_blocked),
conf->device_lock,
raid5_unplug_device(conf->mddev->queue)
raid5_unplug_device(conf)
);
conf->inactive_blocked = 0;
} else
Expand Down Expand Up @@ -3618,7 +3618,7 @@ static void raid5_activate_delayed(raid5_conf_t *conf)
list_add_tail(&sh->lru, &conf->hold_list);
}
} else
blk_plug_device(conf->mddev->queue);
plugger_set_plug(&conf->plug);
}

static void activate_bit_delay(raid5_conf_t *conf)
Expand Down Expand Up @@ -3659,23 +3659,33 @@ static void unplug_slaves(mddev_t *mddev)
rcu_read_unlock();
}

static void raid5_unplug_device(struct request_queue *q)
static void raid5_unplug_device(raid5_conf_t *conf)
{
mddev_t *mddev = q->queuedata;
raid5_conf_t *conf = mddev->private;
unsigned long flags;

spin_lock_irqsave(&conf->device_lock, flags);

if (blk_remove_plug(q)) {
if (plugger_remove_plug(&conf->plug)) {
conf->seq_flush++;
raid5_activate_delayed(conf);
}
md_wakeup_thread(mddev->thread);
md_wakeup_thread(conf->mddev->thread);

spin_unlock_irqrestore(&conf->device_lock, flags);

unplug_slaves(mddev);
unplug_slaves(conf->mddev);
}

static void raid5_unplug(struct plug_handle *plug)
{
raid5_conf_t *conf = container_of(plug, raid5_conf_t, plug);
raid5_unplug_device(conf);
}

static void raid5_unplug_queue(struct request_queue *q)
{
mddev_t *mddev = q->queuedata;
raid5_unplug_device(mddev->private);
}

int md_raid5_congested(mddev_t *mddev, int bits)
Expand Down Expand Up @@ -4085,7 +4095,7 @@ static int make_request(mddev_t *mddev, struct bio * bi)
* add failed due to overlap. Flush everything
* and wait a while
*/
raid5_unplug_device(mddev->queue);
raid5_unplug_device(conf);
release_stripe(sh);
schedule();
goto retry;
Expand Down Expand Up @@ -5178,6 +5188,7 @@ static int run(mddev_t *mddev)
mdname(mddev));
md_set_array_sectors(mddev, raid5_size(mddev, 0, 0));

plugger_init(&conf->plug, raid5_unplug);
if (mddev->queue) {
/* read-ahead size must cover two whole stripes, which
* is 2 * (datadisks) * chunksize where 'n' is the
Expand All @@ -5197,7 +5208,7 @@ static int run(mddev_t *mddev)

mddev->queue->queue_lock = &conf->device_lock;

mddev->queue->unplug_fn = raid5_unplug_device;
mddev->queue->unplug_fn = raid5_unplug_queue;

chunk_size = mddev->chunk_sectors << 9;
blk_queue_io_min(mddev->queue, chunk_size);
Expand Down Expand Up @@ -5229,7 +5240,7 @@ static int stop(mddev_t *mddev)
mddev->thread = NULL;
if (mddev->queue)
mddev->queue->backing_dev_info.congested_fn = NULL;
blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
plugger_flush(&conf->plug); /* the unplug fn references 'conf'*/
free_conf(conf);
mddev->private = NULL;
mddev->to_remove = &raid5_attrs_group;
Expand Down
3 changes: 3 additions & 0 deletions drivers/md/raid5.h
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Original file line number Diff line number Diff line change
Expand Up @@ -398,6 +398,9 @@ struct raid5_private_data {
* (fresh device added).
* Cleared when a sync completes.
*/

struct plug_handle plug;

/* per cpu variables */
struct raid5_percpu {
struct page *spare_page; /* Used when checking P/Q in raid6 */
Expand Down

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