[Review] Fixes to the VFS layer

[Francois Tigeot]

Francois Tigeot wrote:
Alex Hornung wrote:
as I said previously on IRC I disagree with this approach to statfs and
hence to your first two patches. You should be using the statfs entry
point and not inspect the statfs structure in the mount point.
For that, you need to simply fix the right thing, which would be the
VOP_STATFS entry of nullfs and make it populate the fields you need as
you expect.
To be honest, I had forgotten about this conversation; I'll try to
replace the direct struct mount accesses by the use of VOP_STATFS.
I'm focusing on the first patch for now, the one which initializes 
mp->mnt_stat.f_mntonname from nullfs_mount()

That the stat field in the mount point is not populated as you would
like it is *not* a bug and doesn't really need fixing, you should be
using the right approach instead, one that is using the API instead of
raw accesses.
Guess where VOP_STATFS takes the values it returns ? From mp->mnt_stat :
http://opengrok.wolfpond.org/source/xref/sys/vfs/nullfs/null_vfsops.c#nullfs_statfs
nullfs_statfs is a very simple function; it only copies existing values.

The initial name of the mount point can only be known from the 
nullfs_mount function; if this patch is not applied, VOP_STATFS will 
never be able to return the correct values.

I'm afraid patch-0008 has to be applied.

--
Francois Tigeot