9p: Implement TGETLOCK

Synopsis

    size[4] TGetlock tag[2] fid[4] getlock[n]
    size[4] RGetlock tag[2] getlock[n]

Description

TGetlock is used to test for the existence of byte range posix locks on a file
identified by given fid. The reply contains getlock structure. If the lock could
be placed it returns F_UNLCK in type field of getlock structure.  Otherwise it
returns the details of the conflicting locks in the getlock structure

    getlock structure:
      type[1] - Type of lock: F_RDLCK, F_WRLCK
      start[8] - Starting offset for lock
      length[8] - Number of bytes to check for the lock
             If length is 0, check for lock in all bytes starting at the location
            'start' through to the end of file
      pid[4] - PID of the process that wants to take lock/owns the task
               in case of reply
      client[4] - Client id of the system that owns the process which
                  has the conflicting lock

Signed-off-by: M. Mohan Kumar <mohan@in.ibm.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Venkateswararao Jujjuri <jvrao@linux.vnet.ibm.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>

include/net/9p/9p.h

@@ -167,6 +167,8 @@ enum p9_msg_t {
 	P9_RFSYNC,
 	P9_TLOCK = 52,
 	P9_RLOCK,
+	P9_TGETLOCK = 54,
+	P9_RGETLOCK,
 	P9_TLINK = 70,
 	P9_RLINK,
 	P9_TMKDIR = 72,
@@ -492,6 +494,22 @@ struct p9_flock {
 	char *client_id;
 };
 
+/* struct p9_getlock: getlock structure
+ * @type - type of lock
+ * @start - starting offset of the lock
+ * @length - number of bytes
+ * @proc_id - process id which wants to take lock
+ * @client_id - client id
+ */
+
+struct p9_getlock {
+	u8 type;
+	u64 start;
+	u64 length;
+	u32 proc_id;
+	char *client_id;
+};
+
 /* Structures for Protocol Operations */
 struct p9_tstatfs {
 	u32 fid;

include/net/9p/client.h

@@ -250,6 +250,7 @@ int p9_client_mknod_dotl(struct p9_fid *oldfid, char *name, int mode,
 int p9_client_mkdir_dotl(struct p9_fid *fid, char *name, int mode,
 				gid_t gid, struct p9_qid *);
 int p9_client_lock_dotl(struct p9_fid *fid, struct p9_flock *flock, u8 *status);
+int p9_client_getlock_dotl(struct p9_fid *fid, struct p9_getlock *fl);
 struct p9_req_t *p9_tag_lookup(struct p9_client *, u16);
 void p9_client_cb(struct p9_client *c, struct p9_req_t *req);