netexport: Move struct netexport into a .h file and refcnt it

[rmacklem]

Summary

This patch moves "struct netexport" into a separate
netexport.h file and refcounts the structure, plus adds
a few fields that will be used in a future NFS server
commit.

malloc()/free() is replaced by vfs_netexport_alloc()
and vfs_netexport_free().

Test Plan

Tested with a NFS patch that uses the new fields
and does acquire a refcount on the structure so
that it will not be free'd prematurely.

[kib]

sys/kern/vfs_export.c

687

Should be refcount_init()

[rmacklem]

Use refcount_init() as suggested by kib@.

[markj]

sys/kern/vfs_export.c

61

Why not group it with the other sys/* includes?

351–353

Is this line resetting the netexport structure? It will clobber the refcount and mutex.

[rmacklem]

sys/kern/vfs_export.c

61

Because it won't compile.. netexport needs
the radix_node structure defined.

351–353

Ouch!! Good catch. I'll fix this for the next version of
the patch.

[rmacklem]

Fix the memset() so that it only zeros out
part of the structure, as spotted by markj@.

[kib]

sys/kern/vfs_export.c

61

I would add a short comment on this line to explain the ordering requirement.