UBI: add UBI devices reference counting

This is one more step on the way to "removable" UBI devices. It
adds reference counting for UBI devices. Every time a volume on
this device is opened - the device's refcount is increased. It
is also increased if someone is reading any sysfs file of this
UBI device or of one of its volumes.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>

1 files changed, 9 insertions, 5 deletions

diff --git a/drivers/mtd/ubi/vmt.c b/drivers/mtd/ubi/vmt.c
index 3ed63dc37386..42d3dd70f2d0 100644
--- a/drivers/mtd/ubi/vmt.c
+++ b/drivers/mtd/ubi/vmt.c
@@ -71,11 +71,16 @@ static ssize_t vol_attribute_show(struct device *dev,
 {
         int ret;
         struct ubi_volume *vol = container_of(dev, struct ubi_volume, dev);
-        struct ubi_device *ubi = vol->ubi;
+        struct ubi_device *ubi;
+
+        ubi = ubi_get_device(vol->ubi->ubi_num);
+        if (!ubi)
+                return -ENODEV;
 
         spin_lock(&ubi->volumes_lock);
         if (!ubi->volumes[vol->vol_id]) {
                 spin_unlock(&ubi->volumes_lock);
+                ubi_put_device(ubi);
                 return -ENODEV;
         }
         /* Take a reference to prevent volume removal */
@@ -108,10 +113,12 @@ static ssize_t vol_attribute_show(struct device *dev,
                 /* This must be a bug */
                 ret = -EINVAL;
 
+        /* We've done the operation, drop volume and UBI device references */
         spin_lock(&ubi->volumes_lock);
         vol->ref_count -= 1;
         ubi_assert(vol->ref_count >= 0);
         spin_unlock(&ubi->volumes_lock);
+        ubi_put_device(ubi);
         return ret;
 }
 
@@ -260,6 +267,7 @@ int ubi_create_volume(struct ubi_device *ubi, struct ubi_mkvol_req *req)
         }
         ubi->avail_pebs -= vol->reserved_pebs;
         ubi->rsvd_pebs += vol->reserved_pebs;
+        spin_unlock(&ubi->volumes_lock);
 
         vol->vol_id    = vol_id;
         vol->alignment = req->alignment;
@@ -267,9 +275,7 @@ int ubi_create_volume(struct ubi_device *ubi, struct ubi_mkvol_req *req)
         vol->vol_type  = req->vol_type;
         vol->name_len  = req->name_len;
         memcpy(vol->name, req->name, vol->name_len + 1);
-        vol->exclusive = 1;
         vol->ubi = ubi;
-        spin_unlock(&ubi->volumes_lock);
 
         /*
          * Finish all pending erases because there may be some LEBs belonging
@@ -350,8 +356,6 @@ int ubi_create_volume(struct ubi_device *ubi, struct ubi_mkvol_req *req)
                 goto out_sysfs;
 
         spin_lock(&ubi->volumes_lock);
-        ubi->vol_count += 1;
-        vol->exclusive = 0;
         ubi->volumes[vol_id] = vol;
         spin_unlock(&ubi->volumes_lock);