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>

1 files changed, 70 insertions, 1 deletions

diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
index 5edf206354b2..5474feb77743 100644
--- 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);