pseudofs: make dup name an error instead of panic

[kib]

Summary

There are enough cases where the duplicate name is caused by dubious
hardware configuration.  Stopping the whole system instead of failing a
driver, or even a diagnostic subsystem in a driver, is more
user-friendly.

[markj]

sys/fs/pseudofs/pseudofs.c

136–137

pfs_fileno_alloc() assumes that pn->pn_parent is set in some cases. It might be sufficient to temporarily assign pn->pn_parent, then clear it below if there is a conflict.

[kib]

Assign pn_parent for the time of allocating proto-ino.

[des]

sys/fs/pseudofs/pseudofs.c

147

269

indentation looks suspect

[kib]

sys/fs/pseudofs/pseudofs.c

269

Why? Can you provide specifics?

[kib]

s/EINVAL/EEXIST/
Print the parent name as well.

[markj]

sys/fs/pseudofs/pseudofs.c

144

[kib]

Make comment the full sentence.