fiemap_extent
#define FIEMAP_MAX_EXTENTS (UINT_MAX / sizeof(struct fiemap_extent))
struct fiemap_extent __user *dest = fi->fi_extents_start;
struct fiemap_extent extent;
struct fiemap_extent __user *dest = fieinfo->fi_extents_start;
#define FIEMAP_MAX_EXTENTS (UINT_MAX / sizeof(struct fiemap_extent))
struct fiemap_extent __user *fi_extents_start;
struct fiemap_extent fm_extents[];