romfs: do not use mtd->get_unmapped_area directly

Remove direct usage of mtd->get_unmapped_area. Instead, just call
'mtd_get_unmapped_area()' which will return -EOPNOTSUPP if the function
is not implemented, and then test for this code.

We also translate -EOPNOTSUPP to -ENOSYS because this return code is
probably part of the kernel ABI which we do not want to break.

Cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

fs/romfs/mmap-nommu.c

@@ -28,9 +28,10 @@ static unsigned long romfs_get_unmapped_area(struct file *file,
 	struct inode *inode = file->f_mapping->host;
 	struct mtd_info *mtd = inode->i_sb->s_mtd;
 	unsigned long isize, offset, maxpages, lpages;
+	int ret;
 
 	if (!mtd)
-		goto cant_map_directly;
+		return (unsigned long) -ENOSYS;
 
 	/* the mapping mustn't extend beyond the EOF */
 	lpages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
@@ -41,8 +42,6 @@ static unsigned long romfs_get_unmapped_area(struct file *file,
 	if ((pgoff >= maxpages) || (maxpages - pgoff < lpages))
 		return (unsigned long) -EINVAL;
 
-	/* we need to call down to the MTD layer to do the actual mapping */
-	if (mtd->get_unmapped_area) {
 	if (addr != 0)
 		return (unsigned long) -EINVAL;
 
@@ -53,11 +52,10 @@ static unsigned long romfs_get_unmapped_area(struct file *file,
 	if (offset > mtd->size - len)
 		return (unsigned long) -EINVAL;
 
-		return mtd_get_unmapped_area(mtd, len, offset, flags);
-	}
-
-cant_map_directly:
-	return (unsigned long) -ENOSYS;
+	ret = mtd_get_unmapped_area(mtd, len, offset, flags);
+	if (ret == -EOPNOTSUPP)
+		ret = -ENOSYS;
+	return (unsigned long) ret;
 }
 
 /*