ceph: extract entity name from device id

Previously, the "name" in the new device syntax "<name>@<fsid>.<fsname>"
was ignored because (presumably) tests were done using mount.ceph which
also passed the entity name using "-o name=foo". If mounting is done
without the mount.ceph helper, the new device id syntax fails to set
the name properly.

Cc: stable@vger.kernel.org
Link: https://tracker.ceph.com/issues/68516
Signed-off-by: Patrick Donnelly <pdonnell@redhat.com>
Reviewed-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

fs/ceph/super.c

@@ -285,7 +285,9 @@ static int ceph_parse_new_source(const char *dev_name, const char *dev_name_end,
 	size_t len;
 	struct ceph_fsid fsid;
 	struct ceph_parse_opts_ctx *pctx = fc->fs_private;
+	struct ceph_options *opts = pctx->copts;
 	struct ceph_mount_options *fsopt = pctx->opts;
+	const char *name_start = dev_name;
 	char *fsid_start, *fs_name_start;
 
 	if (*dev_name_end != '=') {
@@ -296,8 +298,14 @@ static int ceph_parse_new_source(const char *dev_name, const char *dev_name_end,
 	fsid_start = strchr(dev_name, '@');
 	if (!fsid_start)
 		return invalfc(fc, "missing cluster fsid");
-	++fsid_start; /* start of cluster fsid */
+	len = fsid_start - name_start;
+	kfree(opts->name);
+	opts->name = kstrndup(name_start, len, GFP_KERNEL);
+	if (!opts->name)
+		return -ENOMEM;
+	dout("using %s entity name", opts->name);
 
+	++fsid_start; /* start of cluster fsid */
 	fs_name_start = strchr(fsid_start, '.');
 	if (!fs_name_start)
 		return invalfc(fc, "missing file system name");