eea9343411
This patch will make mode_t 16-bits->32-bits, off_t 32-bits->64-bits,
ino_t 32-bits->64-bits, and nlink_t 16-bits->32-bits. As uid_t and
gid_t were already 32-bits we can drop the big_{mode,off,ino,uid,
gid,nlink}_t types from struct stat. This has huge consequences:
. lseek now has to accept a 64-bit argument and returns a 64-bit
result. Therefore we need a new lseek and return proper results
based on the used version (i.e., translate).
. some fcntl functions take and return a struct flock which holds 2
off_t fields. Like lseek, we need to distinguish between old and
new versions.
. getdents uses struct dirent which has among other fields an ino_t
and off_t field. Consequently we need a new getdents system call
and have to translate when we encounter an old call.
. truncate and ftruncate also take off_t arguments and therefore
require a new version.
To add insult to injury VFS itself uses getdents. This has as
consequence that we have 2^3 combinations of version for getdents; old
and new version of libc (new system calls), new and old version of VFS
(when booting an old image), old and new version of an FS. We can
distinguish between these cases as follows; libc will use new system
call numbers that have not yet been in use. When using a new number,
VFS knows libc is new, otherwise it's an old libc. Vice versa, libc
first tries the new number and if that fails due to ENOSYS (unknown
system call number) it knows it's dealing with an old VFS. Finally,
since we now have VFS-FS protocol versioning and by bumping the version
to 1, VFS knows an FS is old when it reports version 0 and an FS knows
VFS is old when VFS reports it's using version 0.
0 = old version, 1 = new version
libc | VFS | FS | approach
----------------------------
0 | 0 | 0 | Nothing to do
----------------------------
0 | 0 | 1 | VFS reports protocol version 0, FS falls back
| to using the old getdents function
----------------------------
0 | 1 | 0 | VFS reports protocol version 1, FS version 0.
| libc requires old getdents so there is nothing
| to do. VFS itself needs new getdents and will
| translate.
----------------------------
0 | 1 | 1 | VFS reports protocol version 1, FS version 1.
| VFS intercepts getdents results and translates
| them on the fly before returning results to libc
----------------------------
1 | 0 | 0 | libc first tries new system call number and
| then fall back to the old number. libc first
| translates the results to the new getdents before
| returning.
----------------------------
1 | 0 | 1 | VFS reports protocol version 0, so FS uses fall
| back. libc translates.
----------------------------
1 | 1 | 0 | VFS reports protocol version 1, FS version 0. VFS
| will intercept all results and translate on the
| fly.
----------------------------
1 | 1 | 1 | Nothing to do.
As VFS can distinguish between old and new system calls of (f)truncate,
lseek, and fcntl, it will translate the arguments and results if
necessary. Likewise libc falls back to using the old calls and
translating the results to the new version if necessary.
Change-Id: Id5bc819e6ef90f317dbddb21020e0a65028225ce
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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u32_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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i32_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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