UBI: harmonize the update of ubi->beb_rsvd_pebs

Currently, there are several locations where an attempt to reserve more
PEBs for bad PEB handling is made, with the same code being duplicated.

Harmonize it by introducing 'ubi_update_reserved()'.

Also, improve the debug message issued, making it more descriptive.

Artem: amended the patch a little.

Signed-off-by: Shmulik Ladkani <shmulik.ladkani@gmail.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@linux.intel.com>
diff --git a/drivers/mtd/ubi/misc.c b/drivers/mtd/ubi/misc.c
index b57134d..8bbfb44 100644
--- a/drivers/mtd/ubi/misc.c
+++ b/drivers/mtd/ubi/misc.c
@@ -92,6 +92,29 @@
 }
 
 /**
+ * ubi_update_reserved - update bad eraseblock handling accounting data.
+ * @ubi: UBI device description object
+ *
+ * This function calculates the gap between current number of PEBs reserved for
+ * bad eraseblock handling and the required level of PEBs that must be
+ * reserved, and if necessary, reserves more PEBs to fill that gap, according
+ * to availability. Should be called with ubi->volumes_lock held.
+ */
+void ubi_update_reserved(struct ubi_device *ubi)
+{
+	int need = ubi->beb_rsvd_level - ubi->beb_rsvd_pebs;
+
+	if (need <= 0 || ubi->avail_pebs == 0)
+		return;
+
+	need = min_t(int, need, ubi->avail_pebs);
+	ubi->avail_pebs -= need;
+	ubi->rsvd_pebs += need;
+	ubi->beb_rsvd_pebs += need;
+	ubi_msg("reserved more %d PEBs for bad PEB handling", need);
+}
+
+/**
  * ubi_calculate_reserved - calculate how many PEBs must be reserved for bad
  * eraseblock handling.
  * @ubi: UBI device description object