[PATCH 1/3] ceph: new device mount syntax

[Venky Shankar <vshankar@redhat.com>]

Old mount device syntax (source) has the following problems:

- mounts to the same cluster but with different fsnames
  and/or creds have identical device string which can
  confuse xfstests.

- Userspace mount helper tool resolves monitor addresses
  and fill in mon addrs automatically, but that means the
  device shown in /proc/mounts is different than what was
  used for mounting.

New device syntax is as follows:

  cephuser@mycephfs2=/path

Note, there is no "monitor address" in the device string.
That gets passed in as mount option. This keeps the device
string same when monitor addresses change (on remounts).

Also note that the userspace mount helper tool is backward
compatible. I.e., the mount helper will fallback to using
old syntax after trying to mount with the new syntax.

Signed-off-by: Venky Shankar <vshankar@redhat.com>
---
 fs/ceph/super.c | 69 +++++++++++++++++++++++++++++++++----------------
 fs/ceph/super.h |  1 +
 2 files changed, 48 insertions(+), 22 deletions(-)

diff --git a/fs/ceph/super.c b/fs/ceph/super.c
index 9b1b7f4cfdd4..e273eabb0397 100644
--- a/fs/ceph/super.c
+++ b/fs/ceph/super.c
@@ -142,9 +142,9 @@ enum {
 	Opt_congestion_kb,
 	/* int args above */
 	Opt_snapdirname,
-	Opt_mds_namespace,
 	Opt_recover_session,
 	Opt_source,
+	Opt_mon_addr,
 	/* string args above */
 	Opt_dirstat,
 	Opt_rbytes,
@@ -184,7 +184,6 @@ static const struct fs_parameter_spec ceph_mount_parameters[] = {
 	fsparam_flag_no	("fsc",				Opt_fscache), // fsc|nofsc
 	fsparam_string	("fsc",				Opt_fscache), // fsc=...
 	fsparam_flag_no ("ino32",			Opt_ino32),
-	fsparam_string	("mds_namespace",		Opt_mds_namespace),
 	fsparam_flag_no ("poolperm",			Opt_poolperm),
 	fsparam_flag_no ("quotadf",			Opt_quotadf),
 	fsparam_u32	("rasize",			Opt_rasize),
@@ -196,6 +195,7 @@ static const struct fs_parameter_spec ceph_mount_parameters[] = {
 	fsparam_u32	("rsize",			Opt_rsize),
 	fsparam_string	("snapdirname",			Opt_snapdirname),
 	fsparam_string	("source",			Opt_source),
+	fsparam_string	("mon_addr",			Opt_mon_addr),
 	fsparam_u32	("wsize",			Opt_wsize),
 	fsparam_flag_no	("wsync",			Opt_wsync),
 	{}
@@ -227,12 +227,12 @@ static void canonicalize_path(char *path)
 }
 
 /*
- * Parse the source parameter.  Distinguish the server list from the path.
+ * Parse the source parameter.  Distinguish the device spec from the path.
  *
  * The source will look like:
- *     <server_spec>[,<server_spec>...]:[<path>]
+ *     <device_spec>=/<path>
  * where
- *     <server_spec> is <ip>[:<port>]
+ *     <device_spec> is name@fsname
  *     <path> is optional, but if present must begin with '/'
  */
 static int ceph_parse_source(struct fs_parameter *param, struct fs_context *fc)
@@ -240,12 +240,17 @@ static int ceph_parse_source(struct fs_parameter *param, struct fs_context *fc)
 	struct ceph_parse_opts_ctx *pctx = fc->fs_private;
 	struct ceph_mount_options *fsopt = pctx->opts;
 	char *dev_name = param->string, *dev_name_end;
-	int ret;
+	char *fs_name_start;
 
 	dout("%s '%s'\n", __func__, dev_name);
 	if (!dev_name || !*dev_name)
 		return invalfc(fc, "Empty source");
 
+	fs_name_start = strchr(dev_name, '@');
+	if (!fs_name_start)
+		return invalfc(fc, "Missing file system name");
+	++fs_name_start; /* start of file system name */
+
 	dev_name_end = strchr(dev_name, '/');
 	if (dev_name_end) {
 		/*
@@ -262,24 +267,42 @@ static int ceph_parse_source(struct fs_parameter *param, struct fs_context *fc)
 		dev_name_end = dev_name + strlen(dev_name);
 	}
 
-	dev_name_end--;		/* back up to ':' separator */
-	if (dev_name_end < dev_name || *dev_name_end != ':')
-		return invalfc(fc, "No path or : separator in source");
+	dev_name_end--;		/* back up to '=' separator */
+	if (dev_name_end < dev_name || *dev_name_end != '=')
+		return invalfc(fc, "No path or = separator in source");
 
 	dout("device name '%.*s'\n", (int)(dev_name_end - dev_name), dev_name);
-	if (fsopt->server_path)
-		dout("server path '%s'\n", fsopt->server_path);
 
-	ret = ceph_parse_mon_ips(param->string, dev_name_end - dev_name,
-				 pctx->copts, fc->log.log);
-	if (ret)
-		return ret;
+	fsopt->mds_namespace = kstrndup(fs_name_start,
+					dev_name_end - fs_name_start, GFP_KERNEL);
+	dout("file system (mds namespace) '%s'\n", fsopt->mds_namespace);
 
+	if (fsopt->server_path)
+		dout("server path '%s'\n", fsopt->server_path);
 	fc->source = param->string;
 	param->string = NULL;
 	return 0;
 }
 
+static int ceph_parse_mon_addr(struct fs_parameter *param,
+			       struct fs_context *fc)
+{
+	int r;
+	struct ceph_parse_opts_ctx *pctx = fc->fs_private;
+	struct ceph_mount_options *fsopt = pctx->opts;
+
+	kfree(fsopt->mon_addr);
+	fsopt->mon_addr = kstrdup(param->string, GFP_KERNEL);
+	if (!fsopt->mon_addr)
+		return -ENOMEM;
+
+	strreplace(param->string, '/', ',');
+	r = ceph_parse_mon_ips(param->string, strlen(param->string),
+			       pctx->copts, fc->log.log);
+	param->string = NULL;
+	return r;
+}
+
 static int ceph_parse_mount_param(struct fs_context *fc,
 				  struct fs_parameter *param)
 {
@@ -304,11 +327,6 @@ static int ceph_parse_mount_param(struct fs_context *fc,
 		fsopt->snapdir_name = param->string;
 		param->string = NULL;
 		break;
-	case Opt_mds_namespace:
-		kfree(fsopt->mds_namespace);
-		fsopt->mds_namespace = param->string;
-		param->string = NULL;
-		break;
 	case Opt_recover_session:
 		mode = result.uint_32;
 		if (mode == ceph_recover_session_no)
@@ -322,6 +340,8 @@ static int ceph_parse_mount_param(struct fs_context *fc,
 		if (fc->source)
 			return invalfc(fc, "Multiple sources specified");
 		return ceph_parse_source(param, fc);
+	case Opt_mon_addr:
+		return ceph_parse_mon_addr(param, fc);
 	case Opt_wsize:
 		if (result.uint_32 < PAGE_SIZE ||
 		    result.uint_32 > CEPH_MAX_WRITE_SIZE)
@@ -473,6 +493,7 @@ static void destroy_mount_options(struct ceph_mount_options *args)
 	kfree(args->mds_namespace);
 	kfree(args->server_path);
 	kfree(args->fscache_uniq);
+	kfree(args->mon_addr);
 	kfree(args);
 }
 
@@ -516,6 +537,10 @@ static int compare_mount_options(struct ceph_mount_options *new_fsopt,
 	if (ret)
 		return ret;
 
+	ret = strcmp_null(fsopt1->mon_addr, fsopt2->mon_addr);
+	if (ret)
+		return ret;
+
 	return ceph_compare_options(new_opt, fsc->client);
 }
 
@@ -571,8 +596,8 @@ static int ceph_show_options(struct seq_file *m, struct dentry *root)
 	if ((fsopt->flags & CEPH_MOUNT_OPT_NOCOPYFROM) == 0)
 		seq_puts(m, ",copyfrom");
 
-	if (fsopt->mds_namespace)
-		seq_show_option(m, "mds_namespace", fsopt->mds_namespace);
+	if (fsopt->mon_addr)
+		seq_printf(m, ",mon_addr=%s", fsopt->mon_addr);
 
 	if (fsopt->flags & CEPH_MOUNT_OPT_CLEANRECOVER)
 		seq_show_option(m, "recover_session", "clean");
diff --git a/fs/ceph/super.h b/fs/ceph/super.h
index db80d89556b1..ead73dfb8804 100644
--- a/fs/ceph/super.h
+++ b/fs/ceph/super.h
@@ -97,6 +97,7 @@ struct ceph_mount_options {
 	char *mds_namespace;  /* default NULL */
 	char *server_path;    /* default NULL (means "/") */
 	char *fscache_uniq;   /* default NULL */
+	char *mon_addr;
 };
 
 struct ceph_fs_client {
-- 
2.27.0