cifs: export supported mount options via new mount_params /proc file

Can aid in making mount problems easier to diagnose
Signed-off-by: Aurelien Aptel <aaptel@suse.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/cifs/cifs_debug.c

@@ -17,6 +17,7 @@
 #include "cifsproto.h"
 #include "cifs_debug.h"
 #include "cifsfs.h"
+#include "fs_context.h"
 #ifdef CONFIG_CIFS_DFS_UPCALL
 #include "dfs_cache.h"
 #endif
@@ -696,6 +697,7 @@ static const struct proc_ops cifs_lookup_cache_proc_ops;
 static const struct proc_ops traceSMB_proc_ops;
 static const struct proc_ops cifs_security_flags_proc_ops;
 static const struct proc_ops cifs_linux_ext_proc_ops;
+static const struct proc_ops cifs_mount_params_proc_ops;
 
 void
 cifs_proc_init(void)
@@ -720,6 +722,8 @@ cifs_proc_init(void)
 	proc_create("LookupCacheEnabled", 0644, proc_fs_cifs,
 		    &cifs_lookup_cache_proc_ops);
 
+	proc_create("mount_params", 0444, proc_fs_cifs, &cifs_mount_params_proc_ops);
+
 #ifdef CONFIG_CIFS_DFS_UPCALL
 	proc_create("dfscache", 0644, proc_fs_cifs, &dfscache_proc_ops);
 #endif
@@ -758,6 +762,7 @@ cifs_proc_clean(void)
 	remove_proc_entry("SecurityFlags", proc_fs_cifs);
 	remove_proc_entry("LinuxExtensionsEnabled", proc_fs_cifs);
 	remove_proc_entry("LookupCacheEnabled", proc_fs_cifs);
+	remove_proc_entry("mount_params", proc_fs_cifs);
 
 #ifdef CONFIG_CIFS_DFS_UPCALL
 	remove_proc_entry("dfscache", proc_fs_cifs);
@@ -1017,6 +1022,51 @@ static const struct proc_ops cifs_security_flags_proc_ops = {
 	.proc_release	= single_release,
 	.proc_write	= cifs_security_flags_proc_write,
 };
+
+/* To make it easier to debug, can help to show mount params */
+static int cifs_mount_params_proc_show(struct seq_file *m, void *v)
+{
+	const struct fs_parameter_spec *p;
+	const char *type;
+
+	for (p = smb3_fs_parameters; p->name; p++) {
+		/* cannot use switch with pointers... */
+		if (!p->type) {
+			if (p->flags == fs_param_neg_with_no)
+				type = "noflag";
+			else
+				type = "flag";
+		} else if (p->type == fs_param_is_bool)
+			type = "bool";
+		else if (p->type == fs_param_is_u32)
+			type = "u32";
+		else if (p->type == fs_param_is_u64)
+			type = "u64";
+		else if (p->type == fs_param_is_string)
+			type = "string";
+		else
+			type = "unknown";
+
+		seq_printf(m, "%s:%s\n", p->name, type);
+	}
+
+	return 0;
+}
+
+static int cifs_mount_params_proc_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, cifs_mount_params_proc_show, NULL);
+}
+
+static const struct proc_ops cifs_mount_params_proc_ops = {
+	.proc_open	= cifs_mount_params_proc_open,
+	.proc_read	= seq_read,
+	.proc_lseek	= seq_lseek,
+	.proc_release	= single_release,
+	/* No need for write for now */
+	/* .proc_write	= cifs_mount_params_proc_write, */
+};
+
 #else
 inline void cifs_proc_init(void)
 {