From 83d5e5b0af907d46d241a86d9e44003b3f0accbd Mon Sep 17 00:00:00 2001 From: Mikulas Patocka Date: Wed, 10 Jul 2013 23:41:18 +0100 Subject: dm: optimize use SRCU and RCU This patch removes "io_lock" and "map_lock" in struct mapped_device and "holders" in struct dm_table and replaces these mechanisms with sleepable-rcu. Previously, the code would call "dm_get_live_table" and "dm_table_put" to get and release table. Now, the code is changed to call "dm_get_live_table" and "dm_put_live_table". dm_get_live_table locks sleepable-rcu and dm_put_live_table unlocks it. dm_get_live_table_fast/dm_put_live_table_fast can be used instead of dm_get_live_table/dm_put_live_table. These *_fast functions use non-sleepable RCU, so the caller must not block between them. If the code changes active or inactive dm table, it must call dm_sync_table before destroying the old table. Signed-off-by: Mikulas Patocka Signed-off-by: Jun'ichi Nomura Signed-off-by: Alasdair G Kergon --- drivers/md/dm-table.c | 35 ----------------------------------- 1 file changed, 35 deletions(-) (limited to 'drivers/md/dm-table.c') diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c index 1ff252ab7d46..f221812b7dbc 100644 --- a/drivers/md/dm-table.c +++ b/drivers/md/dm-table.c @@ -26,22 +26,8 @@ #define KEYS_PER_NODE (NODE_SIZE / sizeof(sector_t)) #define CHILDREN_PER_NODE (KEYS_PER_NODE + 1) -/* - * The table has always exactly one reference from either mapped_device->map - * or hash_cell->new_map. This reference is not counted in table->holders. - * A pair of dm_create_table/dm_destroy_table functions is used for table - * creation/destruction. - * - * Temporary references from the other code increase table->holders. A pair - * of dm_table_get/dm_table_put functions is used to manipulate it. - * - * When the table is about to be destroyed, we wait for table->holders to - * drop to zero. - */ - struct dm_table { struct mapped_device *md; - atomic_t holders; unsigned type; /* btree table */ @@ -208,7 +194,6 @@ int dm_table_create(struct dm_table **result, fmode_t mode, INIT_LIST_HEAD(&t->devices); INIT_LIST_HEAD(&t->target_callbacks); - atomic_set(&t->holders, 0); if (!num_targets) num_targets = KEYS_PER_NODE; @@ -246,10 +231,6 @@ void dm_table_destroy(struct dm_table *t) if (!t) return; - while (atomic_read(&t->holders)) - msleep(1); - smp_mb(); - /* free the indexes */ if (t->depth >= 2) vfree(t->index[t->depth - 2]); @@ -274,22 +255,6 @@ void dm_table_destroy(struct dm_table *t) kfree(t); } -void dm_table_get(struct dm_table *t) -{ - atomic_inc(&t->holders); -} -EXPORT_SYMBOL(dm_table_get); - -void dm_table_put(struct dm_table *t) -{ - if (!t) - return; - - smp_mb__before_atomic_dec(); - atomic_dec(&t->holders); -} -EXPORT_SYMBOL(dm_table_put); - /* * Checks to see if we need to extend highs or targets. */ -- cgit v1.2.3