ceph: send client metadata to MDS

Implement version 2 of CEPH_MSG_CLIENT_SESSION syntax,
which includes additional client metadata to allow
the MDS to report on clients by user-sensible names
like hostname.

Signed-off-by: John Spray <john.spray@redhat.com>
Reviewed-by: Yan, Zheng <zyan@redhat.com>

diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
index 5edf206..5474feb 100644 (file)
--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -7,6 +7,7 @@
 #include <linux/sched.h>
 #include <linux/debugfs.h>
 #include <linux/seq_file.h>
+#include <linux/utsname.h>
 
 #include "super.h"
 #include "mds_client.h"
@@ -812,6 +813,74 @@ static struct ceph_msg *create_session_msg(u32 op, u64 seq)
        h = msg->front.iov_base;
        h->op = cpu_to_le32(op);
        h->seq = cpu_to_le64(seq);
+
+       return msg;
+}
+
+/*
+ * session message, specialization for CEPH_SESSION_REQUEST_OPEN
+ * to include additional client metadata fields.
+ */
+static struct ceph_msg *create_session_open_msg(struct ceph_mds_client *mdsc, u64 seq)
+{
+       struct ceph_msg *msg;
+       struct ceph_mds_session_head *h;
+       int i = -1;
+       int metadata_bytes = 0;
+       int metadata_key_count = 0;
+       struct ceph_options *opt = mdsc->fsc->client->options;
+       void *p;
+
+       const char* metadata[3][2] = {
+               {"hostname", utsname()->nodename},
+               {"entity_id", opt->name ? opt->name : ""},
+               {NULL, NULL}
+       };
+
+       /* Calculate serialized length of metadata */
+       metadata_bytes = 4;  /* map length */
+       for (i = 0; metadata[i][0] != NULL; ++i) {
+               metadata_bytes += 8 + strlen(metadata[i][0]) +
+                       strlen(metadata[i][1]);
+               metadata_key_count++;
+       }
+
+       /* Allocate the message */
+       msg = ceph_msg_new(CEPH_MSG_CLIENT_SESSION, sizeof(*h) + metadata_bytes,
+                          GFP_NOFS, false);
+       if (!msg) {
+               pr_err("create_session_msg ENOMEM creating msg\n");
+               return NULL;
+       }
+       h = msg->front.iov_base;
+       h->op = cpu_to_le32(CEPH_SESSION_REQUEST_OPEN);
+       h->seq = cpu_to_le64(seq);
+
+       /*
+        * Serialize client metadata into waiting buffer space, using
+        * the format that userspace expects for map<string, string>
+        */
+       msg->hdr.version = 2;  /* ClientSession messages with metadata are v2 */
+
+       /* The write pointer, following the session_head structure */
+       p = msg->front.iov_base + sizeof(*h);
+
+       /* Number of entries in the map */
+       ceph_encode_32(&p, metadata_key_count);
+
+       /* Two length-prefixed strings for each entry in the map */
+       for (i = 0; metadata[i][0] != NULL; ++i) {
+               size_t const key_len = strlen(metadata[i][0]);
+               size_t const val_len = strlen(metadata[i][1]);
+
+               ceph_encode_32(&p, key_len);
+               memcpy(p, metadata[i][0], key_len);
+               p += key_len;
+               ceph_encode_32(&p, val_len);
+               memcpy(p, metadata[i][1], val_len);
+               p += val_len;
+       }
+
        return msg;
 }
 
@@ -835,7 +904,7 @@ static int __open_session(struct ceph_mds_client *mdsc,
        session->s_renew_requested = jiffies;
 
        /* send connect message */
-       msg = create_session_msg(CEPH_SESSION_REQUEST_OPEN, session->s_seq);
+       msg = create_session_open_msg(mdsc, session->s_seq);
        if (!msg)
                return -ENOMEM;
        ceph_con_send(&session->s_con, msg);