LDLM Resource Descriptor
^^^^^^^^^^^^^^^^^^^^^^^^
[[struct-ldlm-resource-desc]]

The resource descriptor identifies the individual resource that is
being locked, along with what sort of thing it is.

----
struct ldlm_resource_desc {
        ldlm_type_t lr_type;
        __u32 lr_padding;       /* also fix lustre_swab_ldlm_resource_desc */
        struct ldlm_res_id lr_name;
};
----

The 'lr_type' field identifies one of the four types of lock that
might be placed on a resource. A "plain" lock type just locks a
particular resource. An "extent" lock type only locks a contiguous
sequence of byte offsets within a regular file. An "flock" lock type
represents an application layer advisory lock from the 'flock()'
system call. While Lustre manages "flock" types locks on behalf of the
application, they do not affect Lustre operation.  An "ibits" lock
type allows fine grained locking of different parts of a single
resource. A single lock request or cancellation may operate on one or
more lock bits, or individual lock bits may be granted on the same
resource separately.  See also <<ldlm-wire-policy-data-t>>.  A lock
descriptor may also have no type at all, in which case the 'lr_type'
field is 0, meaning "no lock".

The 'lr_name' field identifies (by name) the resource(s) that are the
objects of the locking operation. See the discussion of
<<struct-ldlm-res-id>>.

----
typedef enum {
        LDLM_PLAIN     = 10,
        LDLM_EXTENT    = 11,
        LDLM_FLOCK     = 12,
        LDLM_IBITS     = 13,
} ldlm_type_t;
----