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dm cache: improve efficiency of quiescing flag management 

Make the quiescing flag an atomic_t and stop protecting it with a spin
lock.

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This commit is contained in:
Joe Thornber 2013-10-30 17:29:30 +00:00 committed by Mike Snitzer
parent 66cb1910df
commit 238f8363b6
1 changed files with 5 additions and 22 deletions
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27
drivers/md/dm-cache-target.c
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@ -149,6 +149,7 @@ struct cache {
atomic_t nr_migrations;
wait_queue_head_t quiescing_wait;
atomic_t quiescing;
atomic_t quiescing_ack;
/*
@ -189,7 +190,6 @@ struct cache {
bool need_tick_bio:1;
bool sized:1;
bool quiescing:1;
bool commit_requested:1;
bool loaded_mappings:1;
bool loaded_discards:1;
@ -1353,14 +1353,7 @@ static void writeback_some_dirty_blocks(struct cache *cache)
*--------------------------------------------------------------*/
static bool is_quiescing(struct cache *cache)
{
int r;
unsigned long flags;
spin_lock_irqsave(&cache->lock, flags);
r = cache->quiescing;
spin_unlock_irqrestore(&cache->lock, flags);
return r;
return atomic_read(&cache->quiescing);
}
static void ack_quiescing(struct cache *cache)
@ -1378,23 +1371,13 @@ static void wait_for_quiescing_ack(struct cache *cache)
static void start_quiescing(struct cache *cache)
{
unsigned long flags;
spin_lock_irqsave(&cache->lock, flags);
cache->quiescing = true;
spin_unlock_irqrestore(&cache->lock, flags);
atomic_inc(&cache->quiescing);
wait_for_quiescing_ack(cache);
}
static void stop_quiescing(struct cache *cache)
{
unsigned long flags;
spin_lock_irqsave(&cache->lock, flags);
cache->quiescing = false;
spin_unlock_irqrestore(&cache->lock, flags);
atomic_set(&cache->quiescing, 0);
atomic_set(&cache->quiescing_ack, 0);
}
@ -2030,6 +2013,7 @@ static int cache_create(struct cache_args *ca, struct cache **result)
init_waitqueue_head(&cache->migration_wait);
init_waitqueue_head(&cache->quiescing_wait);
atomic_set(&cache->quiescing, 0);
atomic_set(&cache->quiescing_ack, 0);
r = -ENOMEM;
@ -2091,7 +2075,6 @@ static int cache_create(struct cache_args *ca, struct cache **result)
cache->need_tick_bio = true;
cache->sized = false;
cache->quiescing = false;
cache->commit_requested = false;
cache->loaded_mappings = false;
cache->loaded_discards = false;