UBI: allow direct user-space I/O

Introduce a new ioctl UBI_IOCSETPROP to set properties
on a volume. Also add the first property:
UBI_PROP_DIRECT_WRITE, this property is used to set the
ability to use direct writes in userspace

Signed-off-by: Sidney Amani <seed@uffs.org>
Signed-off-by: Corentin Chary <corentincj@iksaif.net>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>

drivers/mtd/ubi/Kconfig.debug

@@ -33,16 +33,6 @@ config MTD_UBI_DEBUG_DISABLE_BGT
 	  This option switches the background thread off by default. The thread
 	  may be also be enabled/disabled via UBI sysfs.
 
-config MTD_UBI_DEBUG_USERSPACE_IO
-	bool "Direct user-space write/erase support"
-	default n
-	depends on MTD_UBI_DEBUG
-	help
-	  By default, users cannot directly write and erase individual
-	  eraseblocks of dynamic volumes, and have to use update operation
-	  instead. This option enables this capability - it is very useful for
-	  debugging and testing.
-
 config MTD_UBI_DEBUG_EMULATE_BITFLIPS
 	bool "Emulate flash bit-flips"
 	depends on MTD_UBI_DEBUG

drivers/mtd/ubi/cdev.c

@@ -259,12 +259,9 @@ static ssize_t vol_cdev_read(struct file *file, __user char *buf, size_t count,
 	return err ? err : count_save - count;
 }
 
-#ifdef CONFIG_MTD_UBI_DEBUG_USERSPACE_IO
-
 /*
  * This function allows to directly write to dynamic UBI volumes, without
- * issuing the volume update operation. Available only as a debugging feature.
- * Very useful for testing UBI.
+ * issuing the volume update operation.
  */
 static ssize_t vol_cdev_direct_write(struct file *file, const char __user *buf,
 				     size_t count, loff_t *offp)
@@ -276,6 +273,9 @@ static ssize_t vol_cdev_direct_write(struct file *file, const char __user *buf,
 	size_t count_save = count;
 	char *tbuf;
 
+	if (!vol->direct_writes)
+		return -EPERM;
+
 	dbg_gen("requested: write %zd bytes to offset %lld of volume %u",
 		count, *offp, vol->vol_id);
 
@@ -339,10 +339,6 @@ static ssize_t vol_cdev_direct_write(struct file *file, const char __user *buf,
 	return err ? err : count_save - count;
 }
 
-#else
-#define vol_cdev_direct_write(file, buf, count, offp) (-EPERM)
-#endif /* CONFIG_MTD_UBI_DEBUG_USERSPACE_IO */
-
 static ssize_t vol_cdev_write(struct file *file, const char __user *buf,
 			      size_t count, loff_t *offp)
 {
@@ -552,6 +548,30 @@ static long vol_cdev_ioctl(struct file *file, unsigned int cmd,
 		break;
 	}
 
+	/* Set volume property command*/
+	case UBI_IOCSETPROP:
+	{
+		struct ubi_set_prop_req req;
+
+		err = copy_from_user(&req, argp,
+				sizeof(struct ubi_set_prop_req));
+		if (err) {
+			err = -EFAULT;
+			break;
+		}
+		switch (req.property) {
+		case UBI_PROP_DIRECT_WRITE:
+			mutex_lock(&ubi->volumes_mutex);
+			desc->vol->direct_writes = !!req.value;
+			mutex_unlock(&ubi->volumes_mutex);
+			break;
+		default:
+			err = -EINVAL;
+			break;
+		}
+		break;
+	}
+
 	default:
 		err = -ENOTTY;
 		break;

drivers/mtd/ubi/ubi.h

@@ -206,6 +206,7 @@ struct ubi_volume_desc;
  * @upd_marker: %1 if the update marker is set for this volume
  * @updating: %1 if the volume is being updated
  * @changing_leb: %1 if the atomic LEB change ioctl command is in progress
+ * @direct_writes: %1 if direct writes are enabled for this volume
  *
  * @gluebi_desc: gluebi UBI volume descriptor
  * @gluebi_refcount: reference count of the gluebi MTD device
@@ -253,6 +254,7 @@ struct ubi_volume {
 	unsigned int upd_marker:1;
 	unsigned int updating:1;
 	unsigned int changing_leb:1;
+	unsigned int direct_writes:1;
 
 #ifdef CONFIG_MTD_UBI_GLUEBI
 	/*
@@ -304,7 +306,8 @@ struct ubi_wl_entry;
  * @vtbl_size: size of the volume table in bytes
  * @vtbl: in-RAM volume table copy
  * @volumes_mutex: protects on-flash volume table and serializes volume
- *                 changes, like creation, deletion, update, re-size and re-name
+ *                 changes, like creation, deletion, update, re-size,
+ *                 re-name and set property
  *
  * @max_ec: current highest erase counter value
  * @mean_ec: current mean erase counter value