dm: add reserved_rq_based_ios module parameter

Allow user to change the number of IOs that are reserved by
request-based DM's mempools by writing to this file:
/sys/module/dm_mod/parameters/reserved_rq_based_ios

The default value is RESERVED_REQUEST_BASED_IOS (256).  The maximum
allowed value is RESERVED_MAX_IOS (1024).

Export dm_get_reserved_rq_based_ios() for use by DM targets and core
code.  Switch to sizing dm-mpath's mempool using DM core's configurable
'reserved_rq_based_ios'.

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Frank Mayhar <fmayhar@google.com>
Acked-by: Mikulas Patocka <mpatocka@redhat.com>

1 files changed, 3 insertions, 3 deletions

diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
index e08be94959fd..de570a558764 100644
--- a/drivers/md/dm-mpath.c
+++ b/drivers/md/dm-mpath.c
@@ -7,6 +7,7 @@
 
 #include <linux/device-mapper.h>
 
+#include "dm.h"
 #include "dm-path-selector.h"
 #include "dm-uevent.h"
 
@@ -116,8 +117,6 @@ struct dm_mpath_io {
 
 typedef int (*action_fn) (struct pgpath *pgpath);
 
-#define MIN_IOS 256     /* Mempool size */
-
 static struct kmem_cache *_mpio_cache;
 
 static struct workqueue_struct *kmultipathd, *kmpath_handlerd;
@@ -190,6 +189,7 @@ static void free_priority_group(struct priority_group *pg,
 static struct multipath *alloc_multipath(struct dm_target *ti)
 {
         struct multipath *m;
+        unsigned min_ios = dm_get_reserved_rq_based_ios();
 
         m = kzalloc(sizeof(*m), GFP_KERNEL);
         if (m) {
@@ -202,7 +202,7 @@ 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);
+                m->mpio_pool = mempool_create_slab_pool(min_ios, _mpio_cache);
                 if (!m->mpio_pool) {
                         kfree(m);
                         return NULL;