On Sat, 10 Jun 2000, Alexander Viro wrote:
> > - although not documented, you need to do kern_mount() before trying
> Yup.
> > normal mounts of a FS_SINGLE; perhaps kern_mount()/kern_umount()
> > should be called automatically in
> > register_filesystem()/unregister_filesystem()?
>
> I don't think so. They are different operations and I'm not too happy
> about mixing them together. Matter of taste, but...
In get_sb_single() you wrote:
sb = fs_type->kern_mnt->mnt_sb;
if (!sb)
BUG();
and it is kern_mount() that initialises type->kern_mnt. So, if one forgot
to kern_mount a FS_SINGLE filesystem prior to letting userspace try to
mount(2) it, then it is not the BUG() that we hit but an oops of this
kind:
Code; c013c6b1 <get_sb_single+59/98> <=====
0: 8b 58 1c mov 0x1c(%eax),%ebx <=====
(0x1c being offset of mnt_sb in vfsmount)
i.e. maybe we should really have in get_sb_single():
if (!fs_type->kern_mnt || !(sb = fs_type->kern_mnt->mnt_sb))
BUG();
I.e. if one forgot to kern_mount then fs_type->kern_mnt will be probably
left at NULL so one is more likely to follow a NULL pointer via ->kern_mnt
rather that follow somewhere valid and then find NULL via ->mnt_sb?
Richard, how is it that you actually hit the BUG() above?
Regards,
Tigran
