Default mount options from superblock for ext2/3 filesystems

This patch adds support for default mount options to be stored in the
superblock, so they don't have to be specified on the mount command line
(or in /etc/fstab).  While I was in the code, I also cleaned up the
handling of how mount options are processed in the ext2 and ext3
filesystems.

Most mount options are now processed *after* the superblock has been
read in.  This allows for a much cleaner handling of those default mount
option parameters that were already stored in the superblock: the
resuid, resgid, and s_errors fields were handled using some fairly gross
special cases.  Now the only mount option which is processed first is
the sb option, which specifies the location of the superblock.  This
allows the handling of all of the default mount parameters to be much
more cleanly and more generally handled.

This does change the behaviour from earlier kernels, in that if the sb
mount option is specified, it must be specified *first*.  However, this
option is rarely used, and if it is, it generally is specified first, so
this seems to be a reasonable restriction.

fs/ext2/super.c

@@ -52,16 +52,12 @@ void ext2_error (struct super_block * sb, const char * function,
 	va_start (args, fmt);
 	vsprintf (error_buf, fmt, args);
 	va_end (args);
-	if (test_opt (sb, ERRORS_PANIC) ||
-	    (le16_to_cpu(sbi->s_es->s_errors) == EXT2_ERRORS_PANIC &&
-	     !test_opt (sb, ERRORS_CONT) && !test_opt (sb, ERRORS_RO)))
+	if (test_opt (sb, ERRORS_PANIC))
 		panic ("EXT2-fs panic (device %s): %s: %s\n",
 		       sb->s_id, function, error_buf);
 	printk (KERN_CRIT "EXT2-fs error (device %s): %s: %s\n",
 		sb->s_id, function, error_buf);
-	if (test_opt (sb, ERRORS_RO) ||
-	    (le16_to_cpu(sbi->s_es->s_errors) == EXT2_ERRORS_RO &&
-	     !test_opt (sb, ERRORS_CONT) && !test_opt (sb, ERRORS_PANIC))) {
+	if (test_opt (sb, ERRORS_RO)) {
 		printk ("Remounting filesystem read-only\n");
 		sb->s_flags |= MS_RDONLY;
 	}
@@ -216,12 +212,61 @@ static struct export_operations ext2_export_ops = {
 	.get_parent = ext2_get_parent,
 };
 
+static unsigned long get_sb_block(void **data)
+{
+	unsigned long 	sb_block;
+	char 		*options = (char *) *data;
+
+	if (!options || strncmp(options, "sb=", 3) != 0)
+		return 1;	/* Default location */
+	options += 3;
+	sb_block = simple_strtoul(options, &options, 0);
+	if (*options && *options != ',') {
+		printk("EXT2-fs: Invalid sb specification: %s\n",
+		       (char *) *data);
+		return 1;
+	}
+	if (*options == ',')
+		options++;
+	*data = (void *) options;
+	return sb_block;
+}
+
+static int want_value(char *value, char *option)
+{
+	if (!value || !*value) {
+		printk(KERN_NOTICE "EXT2-fs: the %s option needs an argument\n",
+		       option);
+		return -1;
+	}
+	return 0;
+}
+
+static int want_null_value(char *value, char *option)
+{
+	if (*value) {
+		printk(KERN_NOTICE "EXT2-fs: Invalid %s argument: %s\n",
+		       option, value);
+		return -1;
+	}
+	return 0;
+}
+
+static int want_numeric(char *value, char *option, unsigned long *number)
+{
+	if (want_value(value, option))
+		return -1;
+	*number = simple_strtoul(value, &value, 0);
+	if (want_null_value(value, option))
+		return -1;
+	return 0;
+}
+
 /*
  * This function has been shamelessly adapted from the msdos fs
  */
-static int parse_options (char * options, unsigned long * sb_block,
-			  unsigned short *resuid, unsigned short * resgid,
-			  unsigned long * mount_options)
+static int parse_options (char * options,
+			  struct ext2_sb_info *sbi)
 {
 	char * this_char;
 	char * value;
@@ -234,22 +279,22 @@ static int parse_options (char * options, unsigned long * sb_block,
 		if ((value = strchr (this_char, '=')) != NULL)
 			*value++ = 0;
 		if (!strcmp (this_char, "bsddf"))
-			clear_opt (*mount_options, MINIX_DF);
+			clear_opt (sbi->s_mount_opt, MINIX_DF);
 		else if (!strcmp (this_char, "nouid32")) {
-			set_opt (*mount_options, NO_UID32);
+			set_opt (sbi->s_mount_opt, NO_UID32);
 		}
 		else if (!strcmp (this_char, "check")) {
 			if (!value || !*value || !strcmp (value, "none"))
-				clear_opt (*mount_options, CHECK);
+				clear_opt (sbi->s_mount_opt, CHECK);
 			else
 #ifdef CONFIG_EXT2_CHECK
-				set_opt (*mount_options, CHECK);
+				set_opt (sbi->s_mount_opt, CHECK);
 #else
 				printk("EXT2 Check option not supported\n");
 #endif
 		}
 		else if (!strcmp (this_char, "debug"))
-			set_opt (*mount_options, DEBUG);
+			set_opt (sbi->s_mount_opt, DEBUG);
 		else if (!strcmp (this_char, "errors")) {
 			if (!value || !*value) {
 				printk ("EXT2-fs: the errors option requires "
@@ -257,19 +302,19 @@ static int parse_options (char * options, unsigned long * sb_block,
 				return 0;
 			}
 			if (!strcmp (value, "continue")) {
-				clear_opt (*mount_options, ERRORS_RO);
-				clear_opt (*mount_options, ERRORS_PANIC);
-				set_opt (*mount_options, ERRORS_CONT);
+				clear_opt (sbi->s_mount_opt, ERRORS_RO);
+				clear_opt (sbi->s_mount_opt, ERRORS_PANIC);
+				set_opt (sbi->s_mount_opt, ERRORS_CONT);
 			}
 			else if (!strcmp (value, "remount-ro")) {
-				clear_opt (*mount_options, ERRORS_CONT);
-				clear_opt (*mount_options, ERRORS_PANIC);
-				set_opt (*mount_options, ERRORS_RO);
+				clear_opt (sbi->s_mount_opt, ERRORS_CONT);
+				clear_opt (sbi->s_mount_opt, ERRORS_PANIC);
+				set_opt (sbi->s_mount_opt, ERRORS_RO);
 			}
 			else if (!strcmp (value, "panic")) {
-				clear_opt (*mount_options, ERRORS_CONT);
-				clear_opt (*mount_options, ERRORS_RO);
-				set_opt (*mount_options, ERRORS_PANIC);
+				clear_opt (sbi->s_mount_opt, ERRORS_CONT);
+				clear_opt (sbi->s_mount_opt, ERRORS_RO);
+				set_opt (sbi->s_mount_opt, ERRORS_PANIC);
 			}
 			else {
 				printk ("EXT2-fs: Invalid errors option: %s\n",
@@ -279,52 +324,25 @@ static int parse_options (char * options, unsigned long * sb_block,
 		}
 		else if (!strcmp (this_char, "grpid") ||
 			 !strcmp (this_char, "bsdgroups"))
-			set_opt (*mount_options, GRPID);
+			set_opt (sbi->s_mount_opt, GRPID);
 		else if (!strcmp (this_char, "minixdf"))
-			set_opt (*mount_options, MINIX_DF);
+			set_opt (sbi->s_mount_opt, MINIX_DF);
 		else if (!strcmp (this_char, "nocheck"))
-			clear_opt (*mount_options, CHECK);
+			clear_opt (sbi->s_mount_opt, CHECK);
 		else if (!strcmp (this_char, "nogrpid") ||
 			 !strcmp (this_char, "sysvgroups"))
-			clear_opt (*mount_options, GRPID);
+			clear_opt (sbi->s_mount_opt, GRPID);
 		else if (!strcmp (this_char, "resgid")) {
-			if (!value || !*value) {
-				printk ("EXT2-fs: the resgid option requires "
-					"an argument\n");
+			unsigned long v;
+			if (want_numeric(value, "resgid", &v))
 				return 0;
-			}
-			*resgid = simple_strtoul (value, &value, 0);
-			if (*value) {
-				printk ("EXT2-fs: Invalid resgid option: %s\n",
-					value);
-				return 0;
-			}
+			sbi->s_resgid = v;
 		}
 		else if (!strcmp (this_char, "resuid")) {
-			if (!value || !*value) {
-				printk ("EXT2-fs: the resuid option requires "
-					"an argument");
-				return 0;
-			}
-			*resuid = simple_strtoul (value, &value, 0);
-			if (*value) {
-				printk ("EXT2-fs: Invalid resuid option: %s\n",
-					value);
-				return 0;
-			}
-		}
-		else if (!strcmp (this_char, "sb")) {
-			if (!value || !*value) {
-				printk ("EXT2-fs: the sb option requires "
-					"an argument");
-				return 0;
-			}
-			*sb_block = simple_strtoul (value, &value, 0);
-			if (*value) {
-				printk ("EXT2-fs: Invalid sb option: %s\n",
-					value);
+			unsigned long v;
+			if (want_numeric(value, "resuid", &v))
 				return 0;
-			}
+			sbi->s_resuid = v;
 		}
 		/* Silently ignore the quota options */
 		else if (!strcmp (this_char, "grpquota")
@@ -464,10 +482,9 @@ static int ext2_fill_super(struct super_block *sb, void *data, int silent)
 	struct ext2_sb_info * sbi;
 	struct ext2_super_block * es;
 	unsigned long sb_block = 1;
-	unsigned short resuid = EXT2_DEF_RESUID;
-	unsigned short resgid = EXT2_DEF_RESGID;
-	unsigned long logic_sb_block = 1;
+	unsigned long logic_sb_block = get_sb_block(&data);
 	unsigned long offset = 0;
+	unsigned long def_mount_opts;
 	int blocksize = BLOCK_SIZE;
 	int db_count;
 	int i, j;
@@ -485,12 +502,6 @@ static int ext2_fill_super(struct super_block *sb, void *data, int silent)
 	 * This is important for devices that have a hardware
 	 * sectorsize that is larger than the default.
 	 */
-
-	sbi->s_mount_opt = 0;
-	if (!parse_options ((char *) data, &sb_block, &resuid, &resgid,
-	    &sbi->s_mount_opt))
-		goto failed_sbi;
-
 	blocksize = sb_min_blocksize(sb, BLOCK_SIZE);
 	if (!blocksize) {
 		printk ("EXT2-fs: unable to set blocksize\n");
@@ -498,9 +509,8 @@ static int ext2_fill_super(struct super_block *sb, void *data, int silent)
 	}
 
 	/*
-	 * If the superblock doesn't start on a sector boundary,
-	 * calculate the offset.  FIXME(eric) this doesn't make sense
-	 * that we would have to do this.
+	 * If the superblock doesn't start on a hardware sector boundary,
+	 * calculate the offset.  
 	 */
 	if (blocksize != BLOCK_SIZE) {
 		logic_sb_block = (sb_block*BLOCK_SIZE) / blocksize;
@@ -524,6 +534,27 @@ static int ext2_fill_super(struct super_block *sb, void *data, int silent)
 				sb->s_id);
 		goto failed_mount;
 	}
+
+	/* Set defaults before we parse the mount options */
+	def_mount_opts = le32_to_cpu(es->s_default_mount_opts);
+	if (def_mount_opts & EXT2_DEFM_DEBUG)
+		set_opt(sbi->s_mount_opt, DEBUG);
+	if (def_mount_opts & EXT2_DEFM_BSDGROUPS)
+		set_opt(sbi->s_mount_opt, GRPID);
+	if (def_mount_opts & EXT2_DEFM_UID16)
+		set_opt(sbi->s_mount_opt, NO_UID32);
+	
+	if (le16_to_cpu(sbi->s_es->s_errors) == EXT2_ERRORS_PANIC)
+		set_opt(sbi->s_mount_opt, ERRORS_PANIC);
+	else if (le16_to_cpu(sbi->s_es->s_errors) == EXT2_ERRORS_RO)
+		set_opt(sbi->s_mount_opt, ERRORS_RO);
+
+	sbi->s_resuid = le16_to_cpu(es->s_def_resuid);
+	sbi->s_resgid = le16_to_cpu(es->s_def_resgid);
+	
+	if (!parse_options ((char *) data, sbi))
+		goto failed_mount;
+
 	if (le32_to_cpu(es->s_rev_level) == EXT2_GOOD_OLD_REV &&
 	    (EXT2_HAS_COMPAT_FEATURE(sb, ~0U) ||
 	     EXT2_HAS_RO_COMPAT_FEATURE(sb, ~0U) ||
@@ -605,14 +636,6 @@ static int ext2_fill_super(struct super_block *sb, void *data, int silent)
 	sbi->s_desc_per_block = sb->s_blocksize /
 					 sizeof (struct ext2_group_desc);
 	sbi->s_sbh = bh;
-	if (resuid != EXT2_DEF_RESUID)
-		sbi->s_resuid = resuid;
-	else
-		sbi->s_resuid = le16_to_cpu(es->s_def_resuid);
-	if (resgid != EXT2_DEF_RESGID)
-		sbi->s_resgid = resgid;
-	else
-		sbi->s_resgid = le16_to_cpu(es->s_def_resgid);
 	sbi->s_mount_state = le16_to_cpu(es->s_state);
 	sbi->s_addr_per_block_bits =
 		log2 (EXT2_ADDR_PER_BLOCK(sb));
@@ -767,22 +790,13 @@ static int ext2_remount (struct super_block * sb, int * flags, char * data)
 {
 	struct ext2_sb_info * sbi = EXT2_SB(sb);
 	struct ext2_super_block * es;
-	unsigned short resuid = sbi->s_resuid;
-	unsigned short resgid = sbi->s_resgid;
-	unsigned long new_mount_opt;
-	unsigned long tmp;
 
 	/*
 	 * Allow the "check" option to be passed as a remount option.
 	 */
-	new_mount_opt = sbi->s_mount_opt;
-	if (!parse_options (data, &tmp, &resuid, &resgid,
-			    &new_mount_opt))
+	if (!parse_options (data, sbi))
 		return -EINVAL;
 
-	sbi->s_mount_opt = new_mount_opt;
-	sbi->s_resuid = resuid;
-	sbi->s_resgid = resgid;
 	es = sbi->s_es;
 	if ((*flags & MS_RDONLY) == (sb->s_flags & MS_RDONLY))
 		return 0;

include/linux/ext2_fs.h

@@ -410,7 +410,19 @@ struct ext2_super_block {
 	__u8	s_prealloc_blocks;	/* Nr of blocks to try to preallocate*/
 	__u8	s_prealloc_dir_blocks;	/* Nr to preallocate for dirs */
 	__u16	s_padding1;
-	__u32	s_reserved[204];	/* Padding to the end of the block */
+	/*
+	 * Journaling support valid if EXT3_FEATURE_COMPAT_HAS_JOURNAL set.
+	 */
+	__u8	s_journal_uuid[16];	/* uuid of journal superblock */
+	__u32	s_journal_inum;		/* inode number of journal file */
+	__u32	s_journal_dev;		/* device number of journal file */
+	__u32	s_last_orphan;		/* start of list of inodes to delete */
+	__u32	s_hash_seed[4];		/* HTREE hash seed */
+	__u8	s_def_hash_version;	/* Default hash version to use */
+	__u8	s_reserved_char_pad;
+	__u16	s_reserved_word_pad;
+	__u32	s_default_mount_opts;
+	__u32	s_reserved[191];	/* Padding to the end of the block */
 };
 
 /*
@@ -489,6 +501,20 @@ struct ext2_super_block {
 #define	EXT2_DEF_RESUID		0
 #define	EXT2_DEF_RESGID		0
 
+/*
+ * Default mount options
+ */
+#define EXT2_DEFM_DEBUG		0x0001
+#define EXT2_DEFM_BSDGROUPS	0x0002
+#define EXT2_DEFM_XATTR_USER	0x0004
+#define EXT2_DEFM_ACL		0x0008
+#define EXT2_DEFM_UID16		0x0010
+    /* Not used by ext2, but reserved for use by ext3 */
+#define EXT3_DEFM_JMODE		0x0060 
+#define EXT3_DEFM_JMODE_DATA	0x0020
+#define EXT3_DEFM_JMODE_ORDERED	0x0040
+#define EXT3_DEFM_JMODE_WBACK	0x0060
+
 /*
  * Structure of a directory entry
  */

include/linux/ext3_fs.h

@@ -449,7 +449,8 @@ struct ext3_super_block {
 	__u8	s_def_hash_version;	/* Default hash version to use */
 	__u8	s_reserved_char_pad;
 	__u16	s_reserved_word_pad;
-	__u32	s_reserved[192];	/* Padding to the end of the block */
+	__u32	s_default_mount_opts;
+	__u32	s_reserved[191];	/* Padding to the end of the block */
 };
 
 #ifdef __KERNEL__
@@ -542,6 +543,19 @@ static inline struct ext3_inode_info *EXT3_I(struct inode *inode)
 #define	EXT3_DEF_RESUID		0
 #define	EXT3_DEF_RESGID		0
 
+/*
+ * Default mount options
+ */
+#define EXT3_DEFM_DEBUG		0x0001
+#define EXT3_DEFM_BSDGROUPS	0x0002
+#define EXT3_DEFM_XATTR_USER	0x0004
+#define EXT3_DEFM_ACL		0x0008
+#define EXT3_DEFM_UID16		0x0010
+#define EXT3_DEFM_JMODE		0x0060
+#define EXT3_DEFM_JMODE_DATA	0x0020
+#define EXT3_DEFM_JMODE_ORDERED	0x0040
+#define EXT3_DEFM_JMODE_WBACK	0x0060
+
 /*
  * Structure of a directory entry
  */