[GIT PULL 17/18] lightnvm: pblk: add possibility to set write buffer size manually

["Matias Bjørling" <mb@lightnvm.io>]

From: Marcin Dziegielewski <marcin.dziegielewski@intel.com>

In some cases, users can want set write buffer size manually, e.g. to
adjust it to specific workload. This patch provides the possibility
to set write buffer size via module parameter feature.

Signed-off-by: Marcin Dziegielewski <marcin.dziegielewski@intel.com>
Signed-off-by: Igor Konopko <igor.j.konopko@intel.com>
Signed-off-by: Matias Bjørling <mb@lightnvm.io>
---
 drivers/lightnvm/pblk-init.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/drivers/lightnvm/pblk-init.c b/drivers/lightnvm/pblk-init.c
index d65d2f972ccf..c890493e0e49 100644
--- a/drivers/lightnvm/pblk-init.c
+++ b/drivers/lightnvm/pblk-init.c
@@ -20,6 +20,11 @@
 
 #include "pblk.h"
 
+unsigned int write_buffer_size;
+
+module_param(write_buffer_size, uint, 0644);
+MODULE_PARM_DESC(write_buffer_size, "number of entries in a write buffer");
+
 static struct kmem_cache *pblk_ws_cache, *pblk_rec_cache, *pblk_g_rq_cache,
 				*pblk_w_rq_cache;
 static DECLARE_RWSEM(pblk_lock);
@@ -172,10 +177,15 @@ static int pblk_rwb_init(struct pblk *pblk)
 	struct nvm_tgt_dev *dev = pblk->dev;
 	struct nvm_geo *geo = &dev->geo;
 	struct pblk_rb_entry *entries;
-	unsigned long nr_entries;
+	unsigned long nr_entries, buffer_size;
 	unsigned int power_size, power_seg_sz;
 
-	nr_entries = pblk_rb_calculate_size(pblk->pgs_in_buffer);
+	if (write_buffer_size && (write_buffer_size > pblk->pgs_in_buffer))
+		buffer_size = write_buffer_size;
+	else
+		buffer_size = pblk->pgs_in_buffer;
+
+	nr_entries = pblk_rb_calculate_size(buffer_size);
 
 	entries = vzalloc(nr_entries * sizeof(struct pblk_rb_entry));
 	if (!entries)
-- 
2.11.0