From adf54578f8802aba00bf27f0faf2d7f5c51ca056 Mon Sep 17 00:00:00 2001
From: Bahadir Balban <bbalban@b-labs.co.uk>
Date: Fri, 18 Jan 2008 15:20:46 +0000
Subject: [PATCH] Improvising on disk layout of simple unix-like filesystem. 
 modified:   tasks/fs0/include/fs.h 	new file:  
 tasks/fs0/src/simplefs/sfslayout.h

---
 tasks/fs0/include/fs.h             |   1 +
 tasks/fs0/src/simplefs/sfslayout.h | 101 +++++++++++++++++++++++++++++
 2 files changed, 102 insertions(+)
 create mode 100644 tasks/fs0/src/simplefs/sfslayout.h

diff --git a/tasks/fs0/include/fs.h b/tasks/fs0/include/fs.h
index 0bac3c3..c601597 100644
--- a/tasks/fs0/include/fs.h
+++ b/tasks/fs0/include/fs.h
@@ -94,4 +94,5 @@ struct superblock {
 	struct dentry *root_dirent;
 };
 
+
 #endif /* __FS_H__ */
diff --git a/tasks/fs0/src/simplefs/sfslayout.h b/tasks/fs0/src/simplefs/sfslayout.h
new file mode 100644
index 0000000..c5d9f25
--- /dev/null
+++ b/tasks/fs0/src/simplefs/sfslayout.h
@@ -0,0 +1,101 @@
+/*
+ * The disk layout of our simple unix-like filesystem.
+ *
+ * Copyright (C) 2007, 2008 Bahadir Balban
+ */
+
+#ifndef __SFS_LAYOUT_H__
+#define __SFS_LAYOUT_H__
+
+#include <l4lib/types.h>
+
+/*
+ *
+ * Filesystem layout:
+ *
+ * |---------------|
+ * |    Unit 0     |
+ * |---------------|
+ * |    Unit 1     |
+ * |---------------|
+ * |      ...      |
+ * |---------------|
+ * |    Unit n     |
+ * |---------------|
+ *
+ *
+ * Unit layout:
+ *
+ * |---------------|
+ * |  Superblock   |
+ * |---------------|
+ * |  Inode table  |
+ * |---------------|
+ * |  Data blocks  |
+ * |---------------|
+ *
+ * or
+ *
+ * |---------------|
+ * |  Data blocks  |
+ * |---------------|
+ *
+ */
+
+#define SZ_8MB			(0x100000 * 8)
+#define SZ_4KB			0x1000
+#define SZ_4KB_BITS		12
+
+#define UNIT_SIZE		(SZ_8MB)
+#define INODE_TABLE_SIZE	((UNIT_SIZE >> SZ_4KB_BITS) >> 1)
+#define INODE_BITMAP_SZIDX	(INODE_TABLE_SIZE >> 5)
+
+struct sfs_superblock {
+	u32 magic;		/* Filesystem magic number */
+	u32 fssize;		/* Total size of filesystem */
+	u32 szidx;		/* Bitmap index size */
+	u32 unitmap[]		/* Bitmap of all fs units */
+};
+
+struct sfs_inode_table {
+	u32 szidx;
+	u32 inodemap[INODE_BITMAP_SZIDX];
+	struct sfs_inode inode[INODE_TABLE_SIZE];
+};
+
+/*
+ * The purpose of an inode:
+ *
+ * 1) Uniquely identify a file or a directory.
+ * 2) Keep file/directory metadata.
+ * 3) Provide access means to file blocks/directory contents.
+ */
+
+struct sfs_inode_blocks {
+	u32  szidx;		/* Direct array index size */
+	unsigned long indirect;
+	unsigned long indirect2;
+	unsigned long indirect3;
+	unsigned long direct[];
+};
+
+struct sfs_inode {
+	u32 unum;	/* Unit number this inode is in */
+	u32 inum;	/* Inode number */
+	u32 mode;	/* File permissions */
+	u32 owner;	/* File owner */
+	u32 atime;	/* Last access time */
+	u32 mtime;	/* Last content modification */
+	u32 ctime;	/* Last inode modification */
+	u32 size;	/* Size of contents */
+	struct sfs_inode_blocks blocks;
+} __attribute__ ((__packed__));
+
+struct sfs_dentry {
+	u32 inum;	/* Inode number */
+	u32 nlength;	/* Name length */
+	u8  name[];	/* Name string */
+} __attribute__ ((__packed__));
+
+
+#endif /* __SFS_LAYOUT_H__ */