UBI: set correct gluebi device size

In case of static volumes, make emulated MTD device size to
be equivalent to data size, rather then volume size.

Reported-by: John Smith <john@arrows.demon.co.uk>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>

drivers/mtd/ubi/cdev.c

@@ -397,6 +397,7 @@ static ssize_t vol_cdev_write(struct file *file, const char __user *buf,
 			vol->corrupted = 1;
 		}
 		vol->checked = 1;
+		ubi_gluebi_updated(vol);
 		revoke_exclusive(desc, UBI_READWRITE);
 	}
 

drivers/mtd/ubi/gluebi.c

@@ -282,14 +282,22 @@ int ubi_create_gluebi(struct ubi_device *ubi, struct ubi_volume *vol)
 		mtd->flags = MTD_WRITEABLE;
 	mtd->writesize  = ubi->min_io_size;
 	mtd->owner      = THIS_MODULE;
-	mtd->size       = vol->usable_leb_size * vol->reserved_pebs;
 	mtd->erasesize  = vol->usable_leb_size;
 	mtd->read       = gluebi_read;
 	mtd->write      = gluebi_write;
 	mtd->erase      = gluebi_erase;
 	mtd->get_device = gluebi_get_device;
 	mtd->put_device = gluebi_put_device;
 
+	/*
+	 * In case of dynamic volume, MTD device size is just volume size. In
+	 * case of a static volume the size is equivalent to the amount of data
+	 * bytes, which is zero at this moment and will be changed after volume
+	 * update.
+	 */
+	if (vol->vol_type == UBI_DYNAMIC_VOLUME)
+		mtd->size = vol->usable_leb_size * vol->reserved_pebs;
+
 	if (add_mtd_device(mtd)) {
 		ubi_err("cannot not add MTD device\n");
 		kfree(mtd->name);
@@ -321,3 +329,20 @@ int ubi_destroy_gluebi(struct ubi_volume *vol)
 	kfree(mtd->name);
 	return 0;
 }
+
+/**
+ * ubi_gluebi_updated - UBI volume was updated notifier.
+ * @vol: volume description object
+ *
+ * This function is called every time an UBI volume is updated. This function
+ * does nothing if volume @vol is dynamic, and changes MTD device size if the
+ * volume is static. This is needed because static volumes cannot be read past
+ * data they contain.
+ */
+void ubi_gluebi_updated(struct ubi_volume *vol)
+{
+	struct mtd_info *mtd = &vol->gluebi_mtd;
+
+	if (vol->vol_type == UBI_STATIC_VOLUME)
+		mtd->size = vol->used_bytes;
+}

drivers/mtd/ubi/scan.c

@@ -55,7 +55,7 @@ static int paranoid_check_si(const struct ubi_device *ubi,
 static struct ubi_ec_hdr *ech;
 static struct ubi_vid_hdr *vidh;
 
-/*
+/**
  * add_to_list - add physical eraseblock to a list.
  * @si: scanning information
  * @pnum: physical eraseblock number to add

drivers/mtd/ubi/ubi.h

@@ -374,9 +374,11 @@ void ubi_calculate_reserved(struct ubi_device *ubi);
 #ifdef CONFIG_MTD_UBI_GLUEBI
 int ubi_create_gluebi(struct ubi_device *ubi, struct ubi_volume *vol);
 int ubi_destroy_gluebi(struct ubi_volume *vol);
+void ubi_gluebi_updated(struct ubi_volume *vol);
 #else
 #define ubi_create_gluebi(ubi, vol) 0
 #define ubi_destroy_gluebi(vol) 0
+#define ubi_gluebi_updated(vol)
 #endif
 
 /* eba.c */