Replace the magic value ~(u32)0 with a named constant. This value
is used as a synthetic svid when looking up lockowners for DOS
share operations, which have no real process ID associated with
them.

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

In order to convert the NLMv4 server-side XDR functions to use
xdrgen, the internal share helpers need to be decoupled from the
NLMv3-specific struct nlm_args. NLMv4 procedures will use
different argument structures once they are converted.

Refactor nlmsvc_share_file() and nlmsvc_unshare_file() to accept
individual arguments (oh, access, mode) instead of the common
struct nlm_args. This allows both protocol versions to call these
helpers without forcing a common argument structure.

While here, add kdoc comments to both functions and fix a comment
typo in the unshare path.

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

The share.h header defines struct nlm_share and declares the DOS
share management functions used by the NLM server to implement
NLM_SHARE and NLM_UNSHARE operations. These interfaces are used
exclusively within the lockd subsystem. A git grep search confirms
no external code references them.

Relocating this header from include/linux/lockd/ to fs/lockd/
narrows the public API surface of the lockd module. Out-of-tree
code cannot depend on these internal interfaces after this change.
Future refactoring of the share management implementation thus
requires no consideration of external consumers.

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>