ext4: Add mount options in superblock

Allow mount options to be stored in the superblock.  Also add default
mount option bits for nobarrier, block_validity, discard, and nodelalloc.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

fs/ext4/ext4.h

@@ -1025,8 +1025,9 @@ struct ext4_super_block {
 	__le32	s_last_error_line;	/* line number where error happened */
 	__le64	s_last_error_block;	/* block involved of last error */
 	__u8	s_last_error_func[32];	/* function where the error happened */
-#define EXT4_S_ERR_END offsetof(struct ext4_super_block, s_reserved)
-	__le32   s_reserved[128];        /* Padding to the end of the block */
+#define EXT4_S_ERR_END offsetof(struct ext4_super_block, s_mount_opts)
+	__u8	s_mount_opts[64];
+	__le32	s_reserved[112];        /* Padding to the end of the block */
 };
 
 #define EXT4_S_ERR_LEN (EXT4_S_ERR_END - EXT4_S_ERR_START)
@@ -1341,6 +1342,10 @@ EXT4_INODE_BIT_FNS(state, state_flags)
 #define EXT4_DEFM_JMODE_DATA	0x0020
 #define EXT4_DEFM_JMODE_ORDERED	0x0040
 #define EXT4_DEFM_JMODE_WBACK	0x0060
+#define EXT4_DEFM_NOBARRIER	0x0100
+#define EXT4_DEFM_BLOCK_VALIDITY 0x0200
+#define EXT4_DEFM_DISCARD	0x0400
+#define EXT4_DEFM_NODELALLOC	0x0800
 
 /*
  * Default journal batch times

fs/ext4/super.c

@@ -1003,10 +1003,10 @@ static int ext4_show_options(struct seq_file *seq, struct vfsmount *vfs)
 		seq_puts(seq, ",journal_checksum");
 	if (test_opt(sb, I_VERSION))
 		seq_puts(seq, ",i_version");
-	if (!test_opt(sb, DELALLOC))
+	if (!test_opt(sb, DELALLOC) &&
+	    !(def_mount_opts & EXT4_DEFM_NODELALLOC))
 		seq_puts(seq, ",nodelalloc");
 
-
 	if (sbi->s_stripe)
 		seq_printf(seq, ",stripe=%lu", sbi->s_stripe);
 	/*
@@ -1030,7 +1030,7 @@ static int ext4_show_options(struct seq_file *seq, struct vfsmount *vfs)
 	if (test_opt(sb, NO_AUTO_DA_ALLOC))
 		seq_puts(seq, ",noauto_da_alloc");
 
-	if (test_opt(sb, DISCARD))
+	if (test_opt(sb, DISCARD) && !(def_mount_opts & EXT4_DEFM_DISCARD))
 		seq_puts(seq, ",discard");
 
 	if (test_opt(sb, NOLOAD))
@@ -1039,6 +1039,10 @@ static int ext4_show_options(struct seq_file *seq, struct vfsmount *vfs)
 	if (test_opt(sb, DIOREAD_NOLOCK))
 		seq_puts(seq, ",dioread_nolock");
 
+	if (test_opt(sb, BLOCK_VALIDITY) &&
+	    !(def_mount_opts & EXT4_DEFM_BLOCK_VALIDITY))
+		seq_puts(seq, ",block_validity");
+
 	ext4_show_quota_options(seq, sb);
 
 	return 0;
@@ -2655,6 +2659,10 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 		set_opt(sbi->s_mount_opt, ERRORS_CONT);
 	else
 		set_opt(sbi->s_mount_opt, ERRORS_RO);
+	if (def_mount_opts & EXT4_DEFM_BLOCK_VALIDITY)
+		set_opt(sbi->s_mount_opt, BLOCK_VALIDITY);
+	if (def_mount_opts & EXT4_DEFM_DISCARD)
+		set_opt(sbi->s_mount_opt, DISCARD);
 
 	sbi->s_resuid = le16_to_cpu(es->s_def_resuid);
 	sbi->s_resgid = le16_to_cpu(es->s_def_resgid);
@@ -2662,15 +2670,23 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 	sbi->s_min_batch_time = EXT4_DEF_MIN_BATCH_TIME;
 	sbi->s_max_batch_time = EXT4_DEF_MAX_BATCH_TIME;
 
-	set_opt(sbi->s_mount_opt, BARRIER);
+	if ((def_mount_opts & EXT4_DEFM_NOBARRIER) == 0)
+		set_opt(sbi->s_mount_opt, BARRIER);
 
 	/*
 	 * enable delayed allocation by default
 	 * Use -o nodelalloc to turn it off
 	 */
-	if (!IS_EXT3_SB(sb))
+	if (!IS_EXT3_SB(sb) &&
+	    ((def_mount_opts & EXT4_DEFM_NODELALLOC) == 0))
 		set_opt(sbi->s_mount_opt, DELALLOC);
 
+	if (!parse_options((char *) sbi->s_es->s_mount_opts, sb,
+			   &journal_devnum, &journal_ioprio, NULL, 0)) {
+		ext4_msg(sb, KERN_WARNING,
+			 "failed to parse options in superblock: %s",
+			 sbi->s_es->s_mount_opts);
+	}
 	if (!parse_options((char *) data, sb, &journal_devnum,
 			   &journal_ioprio, NULL, 0))
 		goto failed_mount;
@@ -3141,7 +3157,8 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 		descr = "out journal";
 
 	ext4_msg(sb, KERN_INFO, "mounted filesystem with%s. "
-		"Opts: %s", descr, orig_data);
+		 "Opts: %s%s%s", descr, sbi->s_es->s_mount_opts,
+		 *sbi->s_es->s_mount_opts ? "; " : "", orig_data);
 
 	init_timer(&sbi->s_err_report);
 	sbi->s_err_report.function = print_daily_error_info;