dm mpath: use blk-mq pdu for per-request 'struct dm_mpath_io'

Allow the multipath target to avoid making small allocations for each
'struct dm_mpath_io' that is needed for each request.

Signed-off-by: Mike Snitzer <snitzer@redhat.com>

diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
index 3ddaa11584ef80bea8416f25cf99619cef307461..021ea3944f4a9f1d85fd60631ff5503ddc77ec1c 100644 (file)
--- a/drivers/md/dm-mpath.c
+++ b/drivers/md/dm-mpath.c
@@ -181,10 +181,9 @@ static void free_priority_group(struct priority_group *pg,
        kfree(pg);
 }
 
-static struct multipath *alloc_multipath(struct dm_target *ti)
+static struct multipath *alloc_multipath(struct dm_target *ti, bool use_blk_mq)
 {
        struct multipath *m;
-       unsigned min_ios = dm_get_reserved_rq_based_ios();
 
        m = kzalloc(sizeof(*m), GFP_KERNEL);
        if (m) {
@@ -195,11 +194,18 @@ static struct multipath *alloc_multipath(struct dm_target *ti)
                INIT_WORK(&m->trigger_event, trigger_event);
                init_waitqueue_head(&m->pg_init_wait);
                mutex_init(&m->work_mutex);
-               m->mpio_pool = mempool_create_slab_pool(min_ios, _mpio_cache);
-               if (!m->mpio_pool) {
-                       kfree(m);
-                       return NULL;
+
+               m->mpio_pool = NULL;
+               if (!use_blk_mq) {
+                       unsigned min_ios = dm_get_reserved_rq_based_ios();
+
+                       m->mpio_pool = mempool_create_slab_pool(min_ios, _mpio_cache);
+                       if (!m->mpio_pool) {
+                               kfree(m);
+                               return NULL;
+                       }
                }
+
                m->ti = ti;
                ti->private = m;
        }
@@ -226,6 +232,13 @@ static int set_mapinfo(struct multipath *m, union map_info *info)
 {
        struct dm_mpath_io *mpio;
 
+       if (!m->mpio_pool) {
+               /* Use blk-mq pdu memory requested via per_io_data_size */
+               mpio = info->ptr;
+               memset(mpio, 0, sizeof(*mpio));
+               return mpio;
+       }
+
        mpio = mempool_alloc(m->mpio_pool, GFP_ATOMIC);
        if (!mpio)
                return -ENOMEM;
@@ -238,10 +251,13 @@ static int set_mapinfo(struct multipath *m, union map_info *info)
 
 static void clear_mapinfo(struct multipath *m, union map_info *info)
 {
-       struct dm_mpath_io *mpio = info->ptr;
+       /* Only needed for non blk-mq */
+       if (m->mpio_pool) {
+               struct dm_mpath_io *mpio = info->ptr;
 
-       info->ptr = NULL;
-       mempool_free(mpio, m->mpio_pool);
+               info->ptr = NULL;
+               mempool_free(mpio, m->mpio_pool);
+       }
 }
 
 /*-----------------------------------------------
@@ -428,7 +444,6 @@ static int __multipath_map(struct dm_target *ti, struct request *clone,
                                           rq_data_dir(rq), GFP_ATOMIC);
                if (IS_ERR(*__clone)) {
                        /* ENOMEM, requeue */
-                       clear_mapinfo(m, map_context);
                        return r;
                }
                (*__clone)->bio = (*__clone)->biotail = NULL;
@@ -820,11 +835,12 @@ static int multipath_ctr(struct dm_target *ti, unsigned int argc,
        struct dm_arg_set as;
        unsigned pg_count = 0;
        unsigned next_pg_num;
+       bool use_blk_mq = dm_use_blk_mq(dm_table_get_md(ti->table));
 
        as.argc = argc;
        as.argv = argv;
 
-       m = alloc_multipath(ti);
+       m = alloc_multipath(ti, use_blk_mq);
        if (!m) {
                ti->error = "can't allocate multipath";
                return -EINVAL;
@@ -880,6 +896,8 @@ static int multipath_ctr(struct dm_target *ti, unsigned int argc,
        ti->num_flush_bios = 1;
        ti->num_discard_bios = 1;
        ti->num_write_same_bios = 1;
+       if (use_blk_mq)
+               ti->per_io_data_size = sizeof(struct dm_mpath_io);
 
        return 0;