pstore: Implement show_options

Implement the show_options superblock op for pstore as part of a bid to get
rid of s_options and generic_show_options() to make it easier to implement
a context-based mount where the mount options can be passed individually
over a file descriptor.
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Kees Cook <keescook@chromium.org>
cc: Anton Vorontsov <anton@enomsg.org>
cc: Colin Cross <ccross@android.com>
cc: Tony Luck <tony.luck@intel.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/pstore/inode.c

@@ -283,6 +283,16 @@ static void parse_options(char *options)
 	}
 }
 
+/*
+ * Display the mount options in /proc/mounts.
+ */
+static int pstore_show_options(struct seq_file *m, struct dentry *root)
+{
+	if (kmsg_bytes != PSTORE_DEFAULT_KMSG_BYTES)
+		seq_printf(m, ",kmsg_bytes=%lu", kmsg_bytes);
+	return 0;
+}
+
 static int pstore_remount(struct super_block *sb, int *flags, char *data)
 {
 	sync_filesystem(sb);
@@ -296,7 +306,7 @@ static const struct super_operations pstore_ops = {
 	.drop_inode	= generic_delete_inode,
 	.evict_inode	= pstore_evict_inode,
 	.remount_fs	= pstore_remount,
-	.show_options	= generic_show_options,
+	.show_options	= pstore_show_options,
 };
 
 static struct super_block *pstore_sb;
@@ -448,8 +458,6 @@ static int pstore_fill_super(struct super_block *sb, void *data, int silent)
 {
 	struct inode *inode;
 
-	save_mount_options(sb, data);
-
 	pstore_sb = sb;
 
 	sb->s_maxbytes		= MAX_LFS_FILESIZE;

fs/pstore/internal.h

@@ -5,6 +5,9 @@
 #include <linux/time.h>
 #include <linux/pstore.h>
 
+#define PSTORE_DEFAULT_KMSG_BYTES 10240
+extern unsigned long kmsg_bytes;
+
 #ifdef CONFIG_PSTORE_FTRACE
 extern void pstore_register_ftrace(void);
 extern void pstore_unregister_ftrace(void);

fs/pstore/platform.c

@@ -99,7 +99,7 @@ static char *big_oops_buf;
 static size_t big_oops_buf_sz;
 
 /* How much of the console log to snapshot */
-static unsigned long kmsg_bytes = 10240;
+unsigned long kmsg_bytes = PSTORE_DEFAULT_KMSG_BYTES;
 
 void pstore_set_kmsg_bytes(int bytes)
 {