tarfs: 'struct tarfs_fid': Switch 'gen' to 'u_int', avoid packing

[olce]

Summary

As the 'gen' field in 'struct tarfs_node' (and then 'struct tarfs_fid')
is filled with arc4random() which returns an unsigned int, change its
type in both structures. This allows reordering fields in 'struct
tarfs_fid' to reduce its size, finally avoiding the use of '__packed' to
ensure it fits into 'struct fid'.

[rmacklem]

sys/fs/tarfs/tarfs.h

78

arc4random() is listed as returning uint32_t,
so why not change it to that type?
(This makes it crystal clear it is 32bits.)

166

Ditto above.

[olce]

unsigned int => uint32_t as suggested.

[olce]

sys/fs/tarfs/tarfs.h

78

I initially wanted to put uint32_t for this exact reason, but then I surveyed tarfs code and saw there were no occurrences of uint32_t (consistency of style). Also, as this is a purely internal structure, I thought that being explicit with its size wasn't that much required here.

Either way is fine with me (just saying in case someone insists in keeping unsigned int).

166

This case is a bit different, as struct tarfs_fid is meant to be an encoding, so the need to change it is more compelling. There's perhaps still the style consistency issue.

[des]

sys/fs/tarfs/tarfs.h

165

this isn't needed if the struct isn't packed.