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authorMikulas Patocka <mpatocka@redhat.com>2013-07-10 23:41:18 +0100
committerAlasdair G Kergon <agk@redhat.com>2013-07-10 23:41:18 +0100
commit83d5e5b0af907d46d241a86d9e44003b3f0accbd (patch)
tree46349d07c2090da15c250af3bac40833eb96e9f0 /drivers/md/dm-table.c
parent2480945cd44b50ba8b1646544eec2db21f064f12 (diff)
downloadlinux-83d5e5b0af907d46d241a86d9e44003b3f0accbd.tar.bz2
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 <mpatocka@redhat.com> Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Diffstat (limited to 'drivers/md/dm-table.c')
-rw-r--r--drivers/md/dm-table.c35
1 files changed, 0 insertions, 35 deletions
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.
*/