Ext2/3 forward compatibility: inode size

This patch allows filesystems with expanded inodes to be mounted.
(compatibility feature flags will be used to control whether or not the
filesystem should be mounted in case the new inode fields will result in
compatibility issues).  This allows for future compatibility with newer
versions of ext2fs.

fs/ext2/ext2.h

@@ -10,6 +10,7 @@ struct ext2_inode_info {
 	__u32	i_faddr;
 	__u8	i_frag_no;
 	__u8	i_frag_size;
+	__u16	i_state;
 	__u32	i_file_acl;
 	__u32	i_dir_acl;
 	__u32	i_dtime;
@@ -23,6 +24,12 @@ struct ext2_inode_info {
 	struct inode	vfs_inode;
 };
 
+/*
+ * Inode dynamic state flags
+ */
+#define EXT2_STATE_NEW			0x00000001 /* inode is newly created */
+
+
 /*
  * Function prototypes
  */

fs/ext2/ialloc.c

@@ -386,6 +386,7 @@ struct inode * ext2_new_inode(struct inode * dir, int mode)
 	ei->i_prealloc_block = 0;
 	ei->i_prealloc_count = 0;
 	ei->i_dir_start_lookup = 0;
+	ei->i_state = EXT2_STATE_NEW;
 	if (ei->i_flags & EXT2_SYNC_FL)
 		inode->i_flags |= S_SYNC;
 	if (ei->i_flags & EXT2_DIRSYNC_FL)

fs/ext2/inode.c

@@ -1012,6 +1012,7 @@ void ext2_read_inode (struct inode * inode)
 		ei->i_dir_acl = le32_to_cpu(raw_inode->i_dir_acl);
 	ei->i_dtime = 0;
 	inode->i_generation = le32_to_cpu(raw_inode->i_generation);
+	ei->i_state = 0;
 	ei->i_next_alloc_block = 0;
 	ei->i_next_alloc_goal = 0;
 	ei->i_prealloc_count = 0;
@@ -1076,6 +1077,11 @@ static int ext2_update_inode(struct inode * inode, int do_sync)
 	if (IS_ERR(raw_inode))
  		return -EIO;
 
+	/* For fields not not tracking in the in-memory inode,
+	 * initialise them to zero for new inodes. */
+	if (ei->i_state & EXT2_STATE_NEW)
+		memset(raw_inode, 0, EXT2_SB(sb)->s_inode_size);
+
 	if (ino == EXT2_ACL_IDX_INO || ino == EXT2_ACL_DATA_INO) {
 		ext2_error (sb, "ext2_write_inode", "bad inode number: %lu",
 			    (unsigned long) ino);
@@ -1152,6 +1158,7 @@ static int ext2_update_inode(struct inode * inode, int do_sync)
 			err = -EIO;
 		}
 	}
+	ei->i_state &= ~EXT2_STATE_NEW;
 	brelse (bh);
 	return err;
 }

fs/ext2/super.c

@@ -630,7 +630,9 @@ static int ext2_fill_super(struct super_block *sb, void *data, int silent)
 	} else {
 		sbi->s_inode_size = le16_to_cpu(es->s_inode_size);
 		sbi->s_first_ino = le32_to_cpu(es->s_first_ino);
-		if (sbi->s_inode_size != EXT2_GOOD_OLD_INODE_SIZE) {
+		if ((sbi->s_inode_size < EXT2_GOOD_OLD_INODE_SIZE) ||
+		    (sbi->s_inode_size & (sbi->s_inode_size - 1)) ||
+		    (sbi->s_inode_size > blocksize)) {
 			printk ("EXT2-fs: unsupported inode size: %d\n",
 				sbi->s_inode_size);
 			goto failed_mount;

fs/ext3/inode.c

@@ -2325,6 +2325,11 @@ static int ext3_do_update_inode(handle_t *handle,
 		if (err)
 			goto out_brelse;
 	}
+	/* For fields not not tracking in the in-memory inode,
+	 * initialise them to zero for new inodes. */
+	if (ei->i_state & EXT3_STATE_NEW)
+		memset(raw_inode, 0, EXT3_SB(inode->i_sb)->s_inode_size);
+
 	raw_inode->i_mode = cpu_to_le16(inode->i_mode);
 	if(!(test_opt(inode->i_sb, NO_UID32))) {
 		raw_inode->i_uid_low = cpu_to_le16(low_16_bits(inode->i_uid));
@@ -2362,15 +2367,6 @@ static int ext3_do_update_inode(handle_t *handle,
 	raw_inode->i_faddr = cpu_to_le32(ei->i_faddr);
 	raw_inode->i_frag = ei->i_frag_no;
 	raw_inode->i_fsize = ei->i_frag_size;
-#else
-	/* If we are not tracking these fields in the in-memory inode,
-	 * then preserve them on disk, but still initialise them to zero
-	 * for new inodes. */
-	if (ei->i_state & EXT3_STATE_NEW) {
-		raw_inode->i_faddr = 0;
-		raw_inode->i_frag = 0;
-		raw_inode->i_fsize = 0;
-	}
 #endif
 	raw_inode->i_file_acl = cpu_to_le32(ei->i_file_acl);
 	if (!S_ISREG(inode->i_mode)) {

fs/ext3/super.c

@@ -1109,7 +1109,9 @@ static int ext3_fill_super (struct super_block *sb, void *data, int silent)
 	} else {
 		sbi->s_inode_size = le16_to_cpu(es->s_inode_size);
 		sbi->s_first_ino = le32_to_cpu(es->s_first_ino);
-		if (sbi->s_inode_size != EXT3_GOOD_OLD_INODE_SIZE) {
+		if ((sbi->s_inode_size < EXT3_GOOD_OLD_INODE_SIZE) ||
+		    (sbi->s_inode_size & (sbi->s_inode_size - 1)) ||
+		    (sbi->s_inode_size > blocksize)) {
 			printk (KERN_ERR
 				"EXT3-fs: unsupported inode size: %d\n",
 				sbi->s_inode_size);