a9d0ffbd0d
The next commit will make mode_t 32-bits, ino_t 64-bits, nlink_t 32-bits, and off_t 64-bits. However, in the protocol there is no room for that. When analyzing the usage of these data types we can see that of mode_t we currently use 15 bits and that future flags (if copied from NetBSD) are only of importance to VFS and not to the actual file system on disk. Therefore we can get away with keeping the protocol version of mode_t (pmode_t) 16 bits. At this point it is unlikely that MINIX will support file systems that can hold more than 2^32 files. Keeping the protocol version of ino_t (pino_t) 32-bits and exposing it as 64-bits to the rest of the system is fine. uid_t and gid_t are already 32-bits, but in behind the scenes they're 16-bits. This is sufficient since we don't support uid/gids larger than 2^16-1. off_t will become 64-bits, but the protocol had room reserved for that since it was revised years ago. So to make the difference clear between what the protocol supports and what is exposed to the system, we define protocol version of these data types. Change-Id: Ifb883aafb222142e69d6dcc3049a47170b78b3ee
84 lines
3.6 KiB
C
84 lines
3.6 KiB
C
#ifndef __MFS_SUPER_H__
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#define __MFS_SUPER_H__
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/* Super block table. The root file system and every mounted file system
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* has an entry here. The entry holds information about the sizes of the bit
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* maps and inodes. The s_ninodes field gives the number of inodes available
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* for files and directories, including the root directory. Inode 0 is
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* on the disk, but not used. Thus s_ninodes = 4 means that 5 bits will be
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* used in the bit map, bit 0, which is always 1 and not used, and bits 1-4
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* for files and directories. The disk layout is:
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*
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* Item # blocks
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* boot block 1
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* super block 1 (offset 1kB)
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* inode map s_imap_blocks
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* zone map s_zmap_blocks
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* inodes (s_ninodes + 'inodes per block' - 1)/'inodes per block'
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* unused whatever is needed to fill out the current zone
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* data zones (s_zones - s_firstdatazone) << s_log_zone_size
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*
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* A super_block slot is free if s_dev == NO_DEV.
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*/
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EXTERN struct super_block {
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pino_t s_ninodes; /* # usable inodes on the minor device */
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zone1_t s_nzones; /* total device size, including bit maps etc */
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short s_imap_blocks; /* # of blocks used by inode bit map */
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short s_zmap_blocks; /* # of blocks used by zone bit map */
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zone1_t s_firstdatazone_old; /* number of first data zone (small) */
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short s_log_zone_size; /* log2 of blocks/zone */
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unsigned short s_flags; /* FS state flags */
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off_t s_max_size; /* maximum file size on this device */
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zone_t s_zones; /* number of zones (replaces s_nzones in V2) */
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short s_magic; /* magic number to recognize super-blocks */
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/* The following items are valid on disk only for V3 and above */
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/* The block size in bytes. Minimum MIN_BLOCK SIZE. SECTOR_SIZE
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* multiple. If V1 or V2 filesystem, this should be
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* initialised to STATIC_BLOCK_SIZE.
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*/
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short s_pad2; /* try to avoid compiler-dependent padding */
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unsigned short s_block_size; /* block size in bytes. */
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char s_disk_version; /* filesystem format sub-version */
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/* The following items are only used when the super_block is in memory.
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* If this ever changes, i.e. more fields after s_disk_version has to go to
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* disk, update LAST_ONDISK_FIELD in super.c as that controls which part of the
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* struct is copied to and from disk.
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*/
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/*struct inode *s_isup;*/ /* inode for root dir of mounted file sys */
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/*struct inode *s_imount;*/ /* inode mounted on */
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unsigned s_inodes_per_block; /* precalculated from magic number */
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zone_t s_firstdatazone; /* number of first data zone (big) */
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dev_t s_dev; /* whose super block is this? */
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int s_rd_only; /* set to 1 iff file sys mounted read only */
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int s_native; /* set to 1 iff not byte swapped file system */
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int s_version; /* file system version, zero means bad magic */
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int s_ndzones; /* # direct zones in an inode */
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int s_nindirs; /* # indirect zones per indirect block */
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bit_t s_isearch; /* inodes below this bit number are in use */
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bit_t s_zsearch; /* all zones below this bit number are in use*/
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char s_is_root;
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} superblock;
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#define IMAP 0 /* operating on the inode bit map */
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#define ZMAP 1 /* operating on the zone bit map */
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/* s_flags contents; undefined flags are guaranteed to be zero on disk
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* (not counting future versions of mfs setting them!)
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*/
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#define MFSFLAG_CLEAN (1L << 0) /* 0: dirty; 1: FS was unmounted cleanly */
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/* Future compatability (or at least, graceful failure):
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* if any of these bits are on, and the MFS or fsck
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* implementation doesn't understand them, do not mount/fsck
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* the FS.
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*/
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#define MFSFLAG_MANDATORY_MASK 0xff00
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#endif
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