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, 41 insertions, 18 deletions

diff --git a/drivers/mtd/ubi/kapi.c b/drivers/mtd/ubi/kapi.c
index 780c273ff452..4ec3a33b2577 100644
--- a/drivers/mtd/ubi/kapi.c
+++ b/drivers/mtd/ubi/kapi.c
@@ -30,23 +30,27 @@
  * @ubi_num: UBI device number
  * @di: the information is stored here
  *
- * This function returns %0 in case of success and a %-ENODEV if there is no
- * such UBI device.
+ * This function returns %0 in case of success, %-EINVAL if the UBI device
+ * number is invalid, and %-ENODEV if there is no such UBI device.
  */
 int ubi_get_device_info(int ubi_num, struct ubi_device_info *di)
 {
-        const struct ubi_device *ubi;
+        struct ubi_device *ubi;
 
-        if (ubi_num < 0 || ubi_num >= UBI_MAX_DEVICES ||
-            !ubi_devices[ubi_num])
+        if (ubi_num < 0 || ubi_num >= UBI_MAX_DEVICES)
+                return -EINVAL;
+
+        ubi = ubi_get_device(ubi_num);
+        if (!ubi)
                 return -ENODEV;
 
-        ubi = ubi_devices[ubi_num];
         di->ubi_num = ubi->ubi_num;
         di->leb_size = ubi->leb_size;
         di->min_io_size = ubi->min_io_size;
         di->ro_mode = ubi->ro_mode;
         di->cdev = ubi->cdev.dev;
+
+        ubi_put_device(ubi);
         return 0;
 }
 EXPORT_SYMBOL_GPL(ubi_get_device_info);
@@ -111,16 +115,23 @@ struct ubi_volume_desc *ubi_open_volume(int ubi_num, int vol_id, int mode)
             mode != UBI_EXCLUSIVE)
                 return ERR_PTR(-EINVAL);
 
-        ubi = ubi_devices[ubi_num];
+        /*
+         * First of all, we have to get the UBI device to prevent its removal.
+         */
+        ubi = ubi_get_device(ubi_num);
         if (!ubi)
                 return ERR_PTR(-ENODEV);
 
-        if (vol_id < 0 || vol_id >= ubi->vtbl_slots)
-                return ERR_PTR(-EINVAL);
+        if (vol_id < 0 || vol_id >= ubi->vtbl_slots) {
+                err = -EINVAL;
+                goto out_put_ubi;
+        }
 
         desc = kmalloc(sizeof(struct ubi_volume_desc), GFP_KERNEL);
-        if (!desc)
-                return ERR_PTR(-ENOMEM);
+        if (!desc) {
+                err = -ENOMEM;
+                goto out_put_ubi;
+        }
 
         err = -ENODEV;
         if (!try_module_get(THIS_MODULE))
@@ -188,6 +199,8 @@ out_unlock:
         module_put(THIS_MODULE);
 out_free:
         kfree(desc);
+out_put_ubi:
+        ubi_put_device(ubi);
         return ERR_PTR(err);
 }
 EXPORT_SYMBOL_GPL(ubi_open_volume);
@@ -205,6 +218,7 @@ struct ubi_volume_desc *ubi_open_volume_nm(int ubi_num, const char *name,
 {
         int i, vol_id = -1, len;
         struct ubi_device *ubi;
+        struct ubi_volume_desc *ret;
 
         dbg_msg("open volume %s, mode %d", name, mode);
 
@@ -218,7 +232,7 @@ struct ubi_volume_desc *ubi_open_volume_nm(int ubi_num, const char *name,
         if (ubi_num < 0 || ubi_num >= UBI_MAX_DEVICES)
                 return ERR_PTR(-EINVAL);
 
-        ubi = ubi_devices[ubi_num];
+        ubi = ubi_get_device(ubi_num);
         if (!ubi)
                 return ERR_PTR(-ENODEV);
 
@@ -234,10 +248,17 @@ struct ubi_volume_desc *ubi_open_volume_nm(int ubi_num, const char *name,
         }
         spin_unlock(&ubi->volumes_lock);
 
-        if (vol_id < 0)
-                return ERR_PTR(-ENODEV);
+        if (vol_id >= 0)
+                ret = ubi_open_volume(ubi_num, vol_id, mode);
+        else
+                ret = ERR_PTR(-ENODEV);
 
-        return ubi_open_volume(ubi_num, vol_id, mode);
+        /*
+         * We should put the UBI device even in case of success, because
+         * 'ubi_open_volume()' took a reference as well.
+         */
+        ubi_put_device(ubi);
+        return ret;
 }
 EXPORT_SYMBOL_GPL(ubi_open_volume_nm);
 
@@ -248,10 +269,11 @@ EXPORT_SYMBOL_GPL(ubi_open_volume_nm);
 void ubi_close_volume(struct ubi_volume_desc *desc)
 {
         struct ubi_volume *vol = desc->vol;
+        struct ubi_device *ubi = vol->ubi;
 
         dbg_msg("close volume %d, mode %d", vol->vol_id, desc->mode);
 
-        spin_lock(&vol->ubi->volumes_lock);
+        spin_lock(&ubi->volumes_lock);
         switch (desc->mode) {
         case UBI_READONLY:
                 vol->readers -= 1;
@@ -263,10 +285,11 @@ void ubi_close_volume(struct ubi_volume_desc *desc)
                 vol->exclusive = 0;
         }
         vol->ref_count -= 1;
-        spin_unlock(&vol->ubi->volumes_lock);
+        spin_unlock(&ubi->volumes_lock);
 
-        put_device(&vol->dev);
         kfree(desc);
+        put_device(&vol->dev);
+        ubi_put_device(ubi);
         module_put(THIS_MODULE);
 }
 EXPORT_SYMBOL_GPL(ubi_close_volume);