Expose ZFS dataset case sensitivity setting via sb_opts

Makes the case sensitivity setting visible on Linux in /proc/mounts.

Reviewed-by: Ryan Moeller <ryan@iXsystems.com>
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Signed-off-by: Ameer Hamza <ahamza@ixsystems.com>
Closes #13607

include/sys/mntent.h

@@ -108,5 +108,8 @@
 #define	MNTOPT_NOACL	"noacl"		/* likewise */
 #define	MNTOPT_POSIXACL	"posixacl"	/* likewise */
 #define	MNTOPT_MNTPOINT	"mntpoint"	/* mount point hint */
+#define	MNTOPT_CASESENSITIVE	"casesensitive"		/* case sensitivity */
+#define	MNTOPT_CASEINSENSITIVE	"caseinsensitive"	/* case insensitivity */
+#define	MNTOPT_CASEMIXED	"casemixed"		/* case mixed */
 
 #endif	/* _SYS_MNTENT_H */

lib/libzfs/os/linux/libzfs_mount_os.c

@@ -84,6 +84,13 @@ static const option_map_t option_map[] = {
 	{ MNTOPT_ACL,		MS_POSIXACL,	ZS_COMMENT	},
 	{ MNTOPT_NOACL,		MS_COMMENT,	ZS_COMMENT	},
 	{ MNTOPT_POSIXACL,	MS_POSIXACL,	ZS_COMMENT	},
+	/*
+	 * Case sensitive options are just listed here to silently
+	 * ignore the error if passed with zfs mount command.
+	 */
+	{ MNTOPT_CASESENSITIVE,		MS_COMMENT,	ZS_COMMENT	},
+	{ MNTOPT_CASEINSENSITIVE,	MS_COMMENT,	ZS_COMMENT	},
+	{ MNTOPT_CASEMIXED,		MS_COMMENT,	ZS_COMMENT	},
 #ifdef MS_NOATIME
 	{ MNTOPT_NOATIME,	MS_NOATIME,	ZS_COMMENT	},
 	{ MNTOPT_ATIME,		MS_COMMENT,	ZS_COMMENT	},

module/os/linux/zfs/zpl_super.c

@@ -233,6 +233,18 @@ __zpl_show_options(struct seq_file *seq, zfsvfs_t *zfsvfs)
 	}
 #endif /* CONFIG_FS_POSIX_ACL */
 
+	switch (zfsvfs->z_case) {
+	case ZFS_CASE_SENSITIVE:
+		seq_puts(seq, ",casesensitive");
+		break;
+	case ZFS_CASE_INSENSITIVE:
+		seq_puts(seq, ",caseinsensitive");
+		break;
+	default:
+		seq_puts(seq, ",casemixed");
+		break;
+	}
+
 	return (0);
 }