--- /dev/null 2007-08-05 21:14:35.622844160 +0200
+++ linux-2.6.21logfs/include/linux/logfs.h 2007-08-08 02:57:37.0
+0200
@@ -0,0 +1,500 @@
+/*
+ * fs/logfs/logfs.h
+ *
+ * As should be obvious for Linux kernel code, license is GPLv2
+ *
+ * Copyright (c) 2005-2007 Joern Engel [EMAIL PROTECTED]
+ *
+ * Public header for logfs.
+ */
+#ifndef linux_logfs_h
+#define linux_logfs_h
+
+
+/*
+ * Throughout the logfs code, we're constantly dealing with blocks at
+ * various positions or offsets. To remove confusion, we stricly
+ * distinguish between a position - the logical position within a
+ * file and an offset - the physical location within the device.
+ *
+ * Any usage of the term offset for a logical location or position for
+ * a physical one is a bug and should get fixed.
+ */
+
+/*
+ * Block are allocated in one of several segments depending on their
+ * level. The following levels are used:
+ * 0 - regular data block
+ * 1 - i1 indirect blocks
+ * 2 - i2 indirect blocks
+ * 3 - i3 indirect blocks
+ * 4 - i4 indirect blocks
+ * 5 - i5 indirect blocks
+ * 6 - ifile data blocks
+ * 7 - ifile i1 indirect blocks
+ * 8 - ifile i2 indirect blocks
+ * 9 - ifile i3 indirect blocks
+ * 10 - ifile i4 indirect blocks
+ * 11 - ifile i5 indirect blocks
+ * Potential levels to be used in the future:
+ * 12 - gc recycled blocks, long-lived data
+ * 13 - replacement blocks, short-lived data
+ *
+ * Levels 1-11 are necessary for robust gc operations and help seperate
+ * short-lived metadata from longer-lived file data. In the future,
+ * file data should get seperated into several segments based on simple
+ * heuristics. Old data recycled during gc operation is expected to be
+ * long-lived. New data is of uncertain life expectancy. New data
+ * used to replace older blocks in existing files is expected to be
+ * short-lived.
+ */
+
+
+/* Magic numbers. 64bit for superblock, 32bit for statfs f_type */
+#define LOGFS_MAGIC0xb21f205ac97e8168ull
+#define LOGFS_MAGIC_U320xc97e8168u
+
+/*
+ * Various blocksize related macros. Blocksize is currently fixed at 4KiB.
+ * Sooner or later that should become configurable and the macros replaced
+ * by something superblock-dependent. Pointers in indirect blocks are and
+ * will remain 64bit.
+ *
+ * LOGFS_BLOCKSIZE - self-explaining
+ * LOGFS_BLOCK_FACTOR - number of pointers per indirect block
+ * LOGFS_BLOCK_BITS- log2 of LOGFS_BLOCK_FACTOR, used for shifts
+ */
+#define LOGFS_BLOCKSIZE(4096ull)
+#define LOGFS_BLOCK_FACTOR (LOGFS_BLOCKSIZE / sizeof(u64))
+#define LOGFS_BLOCK_BITS (9)
+
+/*
+ * Number of blocks at various levels of indirection. Each inode originally
+ * had 9 block pointers. Later the inode size was doubled and there are now
+ * 9+16 pointers - the notation is just historical.
+ *
+ * I0_BLOCKS is the number of direct block pointer in each inode. The
+ * remaining five pointers are for indirect pointers, up to 5x indirect.
+ * Only 3x is tested and supported at the moment. 5x would allow for truly
+ * humongous files if the need ever arises.
+ * I1_BLOCKS is the number of blocks behind a 1x indirect block,
+ * I2_BLOCKS is the number of blocks behind a 2x indirect block, not counting
+ * the 1x indirect blocks. etc.
+ */
+#define I0_BLOCKS (4+16)
+#define I1_BLOCKS LOGFS_BLOCK_FACTOR
+#define I2_BLOCKS (LOGFS_BLOCK_FACTOR * I1_BLOCKS)
+#define I3_BLOCKS (LOGFS_BLOCK_FACTOR * I2_BLOCKS)
+#define I4_BLOCKS (LOGFS_BLOCK_FACTOR * I3_BLOCKS)
+#define I5_BLOCKS (LOGFS_BLOCK_FACTOR * I4_BLOCKS)
+
+/* The indices in the block array where the Nx indirect block pointers reside
*/
+#define I1_INDEX (4+16)
+#define I2_INDEX (5+16)
+#define I3_INDEX (6+16)
+#define I4_INDEX (7+16)
+#define I5_INDEX (8+16)
+
+/* The total number of block pointers in each inode */
+#define LOGFS_EMBEDDED_FIELDS (9+16)
+
+/*
+ * Sizes at which files require another level of indirection. Files smaller
+ * than LOGFS_EMBEDDED_SIZE can be completely stored in the inode itself,
+ * similar like ext2 fast symlinks.
+ *
+ * Data at a position smaller than LOGFS_I0_SIZE is accessed through the
+ * direct pointers, else through the 1x indirect pointer and so forth.
+ */
+#define LOGFS_EMBEDDED_SIZE(LOGFS_EMBEDDED_FIELDS * sizeof(u64))
+#define LOGFS_I0_SIZE (I0_BLOCKS * LOGFS_BLOCKSIZE)
+#define LOGFS_I1_SIZE (I1_BLOCKS * LOGFS_BLOCKSIZE)
+#define LOGFS_I2_SIZE (I2_BLOCKS * LOGFS_BLOCKSIZE)
+#define LOGFS_I3_SIZE (I3_BLOCKS * LOGFS_BLOCKSIZE)
+#define LOGFS_I4_SIZE (I4_BLOCKS * LOGFS_BLOCKSIZE)
+#define LOGFS_I5_SIZE (I5_BLOCKS * LOGFS_BLOCKSIZE)
+
+/*
+ * LogFS needs to seperate data into levels. Each level is defined as the
+ * maximal possible distance from the master inode (inode
