[Patch 02/18] include/linux/logfs.h

Jörn Engel
2007-08-08T16:18:50Z

--- /dev/null 2007-08-05 21:14:35.622844160 +0200
+++ linux-2.6.21logfs/include/linux/logfs.h 2007-08-08 02:57:37.000000000 +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 <joern@logfs.org>
+ *
+ * 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_MAGIC 0xb21f205ac97e8168ull
+#define LOGFS_MAGIC_U32 0xc97e8168u
+
+/*
+ * 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 of the inode file).
+ * Data blocks reside on level 0, 1x indirect block on level 1, etc.
+ * Inodes reside on level 6, indirect blocks for the inode file on levels 7-11.
+ * This effort is necessary to guarantee garbage collection to always make
+ * progress.
+ *
+ * LOGFS_MAX_INDIRECT is the maximal indirection through indirect blocks,
+ * LOGFS_MAX_LEVELS is one more for the actual data level of a file. It is
+ * the maximal number of levels for one file.
+ * LOGFS_NO_AREAS is twice that, as the inode file and regular files are
+ * effectively stacked on top of each other.
+ */
+#define LOGFS_MAX_INDIRECT (5)
+#define LOGFS_MAX_LEVELS (LOGFS_MAX_INDIRECT + 1)
+#define LOGFS_NO_AREAS (2 * LOGFS_MAX_LEVELS)
+
+/* Maximum size of filenames */
+#define LOGFS_MAX_NAMELEN (255)
+
+/* Number of segments in the primary journal. */
+#define LOGFS_JOURNAL_SEGS (4)
+
+
+/*
+ * LOGFS_HEADERSIZE is the size of a single header in the object store,
+ * LOGFS_MAX_OBJECTSIZE the size of the largest possible object, including
+ * its header,
+ * LOGFS_SEGMENT_RESERVE is the amount of space reserved for each segment for
+ * its segment header and the padded space at the end when no further objects
+ * fit.
+ */
+#define LOGFS_HEADERSIZE (0x1c)
+#define LOGFS_SEGMENT_HEADERSIZE (0x18)
+#define LOGFS_MAX_OBJECTSIZE (LOGFS_HEADERSIZE + LOGFS_BLOCKSIZE)
+#define LOGFS_SEGMENT_RESERVE (LOGFS_HEADERSIZE + LOGFS_MAX_OBJECTSIZE - 1)
+
+
+/**
+ * struct logfs_disk_super - on-medium superblock
+ *
+ * @ds_magic: magic number, must equal LOGFS_MAGIC
+ * @ds_crc: crc32 of structure starting with the next field
+ * @ds_ifile_levels: maximum number of levels for ifile
+ * @ds_iblock_levels: maximum number of levels for regular files
+ * @ds_data_levels: number of seperate levels for data
+ * @pad0: reserved, must be 0
+ * @ds_feature_incompat: incompatible filesystem features
+ * @ds_feature_ro_compat: read-only compatible filesystem features
+ * @ds_feature_compat: compatible filesystem features
+ * @ds_flags: flags
+ * @ds_segment_shift: log2 of segment size
+ * @ds_block_shift: log2 of block size
+ * @ds_write_shift: log2 of write size
+ * @pad1: reserved, must be 0
+ * @ds_journal_seg: segments used by primary journal
+ * @ds_root_reserve: bytes reserved for the superuser
+ * @pad2: reserved, must be 0
+ *
+ * Contains only read-only fields. Read-write fields like the amount of used
+ * space is tracked in the dynamic superblock, which is stored in the journal.
+ */
+struct logfs_disk_super {
+ __be64 ds_magic;
+ __be32 ds_crc;
+ __u8 ds_ifile_levels;
+ __u8 ds_iblock_levels;
+ __u8 ds_data_levels;
+ __u8 pad0;
+
+ __be64 ds_feature_incompat;
+ __be64 ds_feature_ro_compat;
+
+ __be64 ds_feature_compat;
+ __be64 ds_flags;
+
+ __be64 ds_filesystem_size;
+ __u8 ds_segment_shift;
+ __u8 ds_block_shift;
+ __u8 ds_write_shift;
+ __u8 pad1[5];
+
+ __be64 ds_journal_seg[LOGFS_JOURNAL_SEGS];
+
+ __be64 ds_root_reserve;
+
+ __be64 pad2[19];
+}__attribute__((packed));
+
+
+/*
+ * Inode flags. High bits should never be written to the medium. Used either
+ * to catch obviously corrupt data (all 0xff) or for flags that are used
+ * in-memory only.
+ *
+ * LOGFS_IF_VALID Inode is valid, must be 1 (catch all 0x00 case)
+ * LOGFS_IF_EMBEDDED Inode is a fast inode (data embedded in pointers)
+ * LOGFS_IF_ZOMBIE Inode has been deleted
+ * LOGFS_IF_STILLBORN -ENOSPC happened when creating inode
+ * LOGFS_IF_INVALID Inode is invalid, must be 0 (catch all 0xff case)
+ */
+#define LOGFS_IF_VALID 0x00000001
+#define LOGFS_IF_EMBEDDED 0x00000002
+#define LOGFS_IF_COMPRESSED 0x00000004 /* == FS_COMPR_FL */
+#define LOGFS_IF_ZOMBIE 0x20000000
+#define LOGFS_IF_STILLBORN 0x40000000
+#define LOGFS_IF_INVALID 0x80000000
+
+
+/* Flags available to chattr */
+#define LOGFS_FL_USER_VISIBLE ( LOGFS_IF_COMPRESSED )
+#define LOGFS_FL_USER_MODIFIABLE ( LOGFS_IF_COMPRESSED )
+/* Flags inherited from parent directory on file/directory creation */
+#define LOGFS_FL_INHERITED ( LOGFS_IF_COMPRESSED )
+
+
+/**
+ * struct logfs_disk_inode - on-medium inode
+ *
+ * @di_mode: file mode
+ * @di_pad: reserved, must be 0
+ * @di_flags: inode flags, see above
+ * @di_uid: user id
+ * @di_gid: group id
+ * @di_ctime: change time
+ * @di_mtime: modify time
+ * @di_refcount: reference count (aka nlink or link count)
+ * @di_generation: inode generation, for nfs
+ * @di_used_bytes: number of bytes used
+ * @di_size: file size
+ * @di_data: data pointers
+ */
+struct logfs_disk_inode {
+ __be16 di_mode;
+ __u8 di_height;
+ __u8 di_pad;
+ __be32 di_flags;
+ __be32 di_uid;
+ __be32 di_gid;
+
+ __be64 di_ctime;
+ __be64 di_mtime;
+
+ __be32 di_refcount;
+ __be32 di_generation;
+ __be64 di_used_bytes;
+
+ __be64 di_size;
+ __be64 di_data[LOGFS_EMBEDDED_FIELDS];
+}__attribute__((packed));
+
+
+/**
+ * struct logfs_disk_dentry - on-medium dentry structure
+ *
+ * @ino: inode number
+ * @namelen: length of file name
+ * @type: file type, identical to bits 12..15 of mode
+ * @name: file name
+ */
+struct logfs_disk_dentry {
+ __be64 ino;
+ __be16 namelen;
+ __u8 type;
+ __u8 name[LOGFS_MAX_NAMELEN];
+}__attribute__((packed));
+
+
+#define OBJ_TOP_JOURNAL 1 /* segment header for master journal */
+#define OBJ_JOURNAL 2 /* segment header for journal */
+#define OBJ_OSTORE 3 /* segment header for ostore */
+#define OBJ_BLOCK 4 /* data block */
+#define OBJ_INODE 5 /* inode */
+#define OBJ_DENTRY 6 /* dentry */
+
+
+/**
+ * struct logfs_object_header - per-object header in the ostore
+ *
+ * @crc: crc32 of header, excluding data_crc
+ * @len: length of data
+ * @type: object type, see above
+ * @compr: compression type
+ * @ino: inode number the object belongs to
+ * @pos: file position the object belongs to
+ * @data_crc: crc32 of payload
+ */
+struct logfs_object_header {
+ __be32 crc;
+ __be16 len;
+ __u8 type;
+ __u8 compr;
+ __be64 ino;
+ __be64 pos;
+ __be32 data_crc;
+}__attribute__((packed));
+
+
+/**
+ * struct logfs_segment_header - per-segment header in the ostore
+ *
+ * @crc: crc32 of header (there is no data)
+ * @pad: unused, must be 0
+ * @type: object type, see above
+ * @level: GC level for all objects in this segment
+ * @segno: segment number
+ * @ec: erase count for this segment
+ * @gec: global erase count at time of writing
+ */
+struct logfs_segment_header {
+ __be32 crc;
+ __be16 pad;
+ __u8 type;
+ __u8 level;
+ __be32 segno;
+ __be32 ec;
+ __be64 gec;
+}__attribute__((packed));
+
+
+/**
+ * struct logfs_journal_header - header for journal entries (JEs)
+ *
+ * @h_crc: crc32 of journal entry
+ * @h_len: length of compressed journal entry
+ * @h_datalen: length of uncompressed data
+ * @h_type: JE type
+ * @h_version: unnormalized version of journal entry
+ * @h_compr: compression type
+ * @h_pad: reserved
+ */
+struct logfs_journal_header {
+ __be32 h_crc;
+ __be16 h_len;
+ __be16 h_datalen;
+ __be16 h_type;
+ __be16 h_version;
+ __u8 h_compr;
+ __u8 h_pad[3];
+}__attribute__((packed));
+
+
+/**
+ * struct logfs_je_dynsb - dynamic superblock
+ *
+ * @ds_gec: global erase count
+ * @ds_sweeper: current position of GC "sweeper"
+ * @ds_rename_dir: source directory ino (see dir.c documentation)
+ * @ds_rename_pos: position of source dd (see dir.c documentation)
+ * @ds_victim_ino: victims of incomplete dir operation (see dir.c)
+ * @ds_used_bytes: number of used bytes
+ */
+struct logfs_je_dynsb {
+ __be64 ds_gec;
+ __be64 ds_sweeper;
+
+ __be64 ds_rename_dir;
+ __be64 ds_rename_pos;
+
+ __be64 ds_victim_ino;
+ __be64 ds_used_bytes;
+};
+
+
+/**
+ * struct logfs_je_anchor - anchor of filesystem tree, aka master inode
+ *
+ * @da_size: size of inode file
+ * @da_last_ino: last created inode
+ * @da_used_bytes: number of bytes used
+ * @da_data: data pointers
+ */
+struct logfs_je_anchor {
+ __be64 da_size;
+ __be64 da_last_ino;
+
+ __be64 da_used_bytes;
+ __be64 da_data[LOGFS_EMBEDDED_FIELDS];
+}__attribute__((packed));
+
+
+/**
+ * struct logfs_je_spillout - spillout entry (from 1st to 2nd journal)
+ *
+ * @so_segment: segments used for 2nd journal
+ *
+ * Length of the array is given by h_len field in the header.
+ */
+struct logfs_je_spillout {
+ __be64 so_segment[0];
+}__attribute__((packed));
+
+
+/**
+ * struct logfs_je_journal_ec - erase counts for all journal segments
+ *
+ * @ec: erase count
+ *
+ * Length of the array is given by h_len field in the header.
+ */
+struct logfs_je_journal_ec {
+ __be32 ec[0];
+}__attribute__((packed));
+
+
+/**
+ * struct logfs_je_areas - management information for current areas
+ *
+ * @used_bytes: number of bytes already used
+ * @segno: segment number of area
+ *
+ * "Areas" are segments currently being used for writing. There is one area
+ * per GC level. Each erea also has a write buffer that is stored in the
+ * journal, in entries 0x10..0x1f.
+ */
+struct logfs_je_areas {
+ __be32 used_bytes[16];
+ __be32 segno[16];
+};
+
+
+enum {
+ COMPR_NONE = 0,
+ COMPR_ZLIB = 1,
+};
+
+
+/*
+ * Journal entries come in groups of 16. First group contains unique
+ * entries, next groups contain one entry per level
+ *
+ * JE_FIRST - smallest possible journal entry number
+ *
+ * JEG_BASE - base group, containing unique entries
+ * JE_COMMIT - commit entry, validates all previous entries
+ * JE_ABORT - abort entry, invalidates all previous non-committed entries
+ * JE_DYNSB - dynamic superblock, anything that ought to be in the
+ * superblock but cannot because it is read-write data
+ * JE_ANCHOR - anchor aka master inode aka inode file's inode
+ * JE_ERASECOUNT erasecounts for all journal segments
+ * JE_SPILLOUT - unused
+ * JE_BADSEGMENTS bad segments
+ * JE_AREAS - area description sans wbuf
+ * JE_FREESEGS - free segments that can get deleted immediatly
+ * JE_LOWSEGS - segments with low population, good candidates for GC
+ * JE_OLDSEGS - segments with low erasecount, may need to get moved
+ *
+ * JEG_WBUF - wbuf group, one entry per area
+ *
+ * JE_LAST - largest possible journal entry number
+ */
+enum {
+ JE_FIRST = 0x01,
+
+ JEG_BASE = 0x00,
+ JE_COMMIT = 0x01,
+ JE_ABORT = 0x02,
+ JE_DYNSB = 0x03,
+ JE_ANCHOR = 0x04,
+ JE_ERASECOUNT = 0x05,
+ JE_SPILLOUT = 0x06,
+ JE_BADSEGMENTS = 0x08,
+ JE_AREAS = 0x09,
+ JE_FREESEGS = 0x0a,
+ JE_LOWSEGS = 0x0b,
+ JE_OLDSEGS = 0x0c,
+
+ JEG_WBUF = 0x10,
+
+ JE_LAST = 0x1f,
+};
+
+
+ /* 0 reserved for gc markers */
+#define LOGFS_INO_MASTER 1 /* inode file */
+#define LOGFS_INO_ROOT 2 /* root directory */
+#define LOGFS_INO_ATIME 4 /* atime for all inodes */
+#define LOGFS_INO_BAD_BLOCKS 5 /* bad blocks */
+#define LOGFS_INO_OBSOLETE 6 /* obsolete block count */
+#define LOGFS_INO_ERASE_COUNT 7 /* erase count */
+#define LOGFS_RESERVED_INOS 16
+
+#endif