dm: add reserved_bio_based_ios module parameter

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

The default value is RESERVED_BIO_BASED_IOS (16).  The maximum allowed
value is RESERVED_MAX_IOS (1024).

Export dm_get_reserved_bio_based_ios() for use by DM targets and core
code.  Switch to sizing dm-io's mempool and bioset using DM core's
configurable 'reserved_bio_based_ios'.

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

1 files changed, 3 insertions, 4 deletions

diff --git a/drivers/md/dm-io.c b/drivers/md/dm-io.c
index ea49834377c8..2a20986a2fec 100644
--- a/drivers/md/dm-io.c
+++ b/drivers/md/dm-io.c
@@ -19,8 +19,6 @@
 #define DM_MSG_PREFIX "io"
 
 #define DM_IO_MAX_REGIONS       BITS_PER_LONG
-#define MIN_IOS         16
-#define MIN_BIOS        16
 
 struct dm_io_client {
         mempool_t *pool;
@@ -50,16 +48,17 @@ static struct kmem_cache *_dm_io_cache;
 struct dm_io_client *dm_io_client_create(void)
 {
         struct dm_io_client *client;
+        unsigned min_ios = dm_get_reserved_bio_based_ios();
 
         client = kmalloc(sizeof(*client), GFP_KERNEL);
         if (!client)
                 return ERR_PTR(-ENOMEM);
 
-        client->pool = mempool_create_slab_pool(MIN_IOS, _dm_io_cache);
+        client->pool = mempool_create_slab_pool(min_ios, _dm_io_cache);
         if (!client->pool)
                 goto bad;
 
-        client->bios = bioset_create(MIN_BIOS, 0);
+        client->bios = bioset_create(min_ios, 0);
         if (!client->bios)
                 goto bad;