- remove the support of variable-sized filehandle from compat version of
syscalls. (strictly speaking, it breaks abi. i don't think it's a problem
because this feature is short-lived and there are no affected in-tree
filesystems.)
- unify vfs_copyinfh_alloc and vfs_copyinfh_alloc_size.
- vfs_copyinfh_alloc_size: check fhsize strictly.
- reduce code duplication between compat and current syscalls.
While touching all vptofh/fhtovp functions, get rid of VFS_MAXFIDSIZ,
version the getfh(2) syscall and explicitly pass the size available in
the filehandle from userland.
Discussed on tech-kern, with lots of help from yamt (thanks!).
- use vmspace rather than proc or lwp where appropriate.
the latter is more natural to specify an address space.
(and less likely to be abused for random purposes.)
- fix a swdmover race.
