UBI: add ioctl for is_mapped operation

This patch adds ioctl to check if an LEB is mapped or not (as a
debugging option so far).

[Re-named ioctl to make it look the same as the other one and made
 some minor stylistic changes. Artem Bityutskiy.]
Signed-off-by: Corentin Chary <corentincj@iksaif.net>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>

drivers/mtd/ubi/cdev.c

@@ -546,6 +546,20 @@ static int vol_cdev_ioctl(struct inode *inode, struct file *file,
 		err = ubi_leb_unmap(desc, lnum);
 		break;
 	}
+
+	/* Check if logical eraseblock is mapped command */
+	case UBI_IOCEBISMAP:
+	{
+		int32_t lnum;
+
+		err = get_user(lnum, (__user int32_t *)argp);
+		if (err) {
+			err = -EFAULT;
+			break;
+		}
+		err = ubi_is_mapped(desc, lnum);
+		break;
+	}
 #endif
 
 	default:

include/mtd/ubi-user.h

@@ -137,6 +137,8 @@
 #define UBI_IOCEBMAP _IOW(UBI_VOL_IOC_MAGIC, 3, struct ubi_map_req)
 /* Unmap an eraseblock, used for debugging, disabled by default */
 #define UBI_IOCEBUNMAP _IOW(UBI_VOL_IOC_MAGIC, 4, int32_t)
+/* Check if an eraseblock is mapped, used for debugging, disabled by default */
+#define UBI_IOCEBISMAP _IOR(UBI_VOL_IOC_MAGIC, 5, int32_t)
 
 /* Maximum MTD device name length supported by UBI */
 #define MAX_UBI_MTD_NAME_LEN 127