minix/servers/ext2/super.c

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/* This file manages the super block structure.
*
* The entry points into this file are
* get_super: search the 'superblock' table for a device
* read_super: read a superblock
*
* Created (MFS based):
* February 2010 (Evgeniy Ivanov)
*/
#include "fs.h"
#include <string.h>
#include <stdlib.h>
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#include <assert.h>
#include <minix/com.h>
#include <minix/u64.h>
#include <minix/bdev.h>
#include "buf.h"
#include "inode.h"
#include "super.h"
#include "const.h"
FORWARD _PROTOTYPE( off_t ext2_max_size, (int block_size) );
FORWARD _PROTOTYPE( u32_t ext2_count_dirs, (struct super_block *sp) );
FORWARD _PROTOTYPE( void super_copy, (register struct super_block *dest,
register struct super_block *source));
FORWARD _PROTOTYPE( void copy_group_descriptors,
(register struct group_desc *dest_array,
register struct group_desc *source_array,
unsigned int ngroups));
PRIVATE off_t super_block_offset;
/*===========================================================================*
* get_super *
*===========================================================================*/
PUBLIC struct super_block *get_super(
dev_t dev /* device number whose super_block is sought */
)
{
if (dev == NO_DEV)
panic("request for super_block of NO_DEV");
if (superblock->s_dev != dev)
panic("wrong superblock", (int) dev);
return(superblock);
}
/*===========================================================================*
* get_block_size *
*===========================================================================*/
PUBLIC unsigned int get_block_size(dev_t dev)
{
if (dev == NO_DEV)
panic("request for block size of NO_DEV");
return(fs_block_size);
}
PRIVATE struct group_desc *ondisk_group_descs;
/*===========================================================================*
* read_super *
*===========================================================================*/
PUBLIC int read_super(sp)
register struct super_block *sp; /* pointer to a superblock */
{
/* Read a superblock. */
dev_t dev;
int r;
/* group descriptors, sp->s_group_desc points to this. */
static struct group_desc *group_descs;
char *buf;
block_t gd_size; /* group descriptors table size in blocks */
int gdt_position;
dev = sp->s_dev; /* save device (will be overwritten by copy) */
if (dev == NO_DEV)
panic("request for super_block of NO_DEV");
if (opt.block_with_super == 0) {
super_block_offset = SUPER_BLOCK_BYTES;
} else {
/* The block number here uses 1k units */
super_block_offset = opt.block_with_super * 1024;
}
STATICINIT(ondisk_superblock, 1);
if (!sp || !ondisk_superblock)
panic("can't allocate memory for super_block buffers");
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assert(_MIN_BLOCK_SIZE <= sizeof(*ondisk_superblock));
r = bdev_read(dev, cvu64(super_block_offset), (char*) ondisk_superblock,
_MIN_BLOCK_SIZE, BDEV_NOFLAGS);
if (r != _MIN_BLOCK_SIZE)
return(EINVAL);
super_copy(sp, ondisk_superblock);
sp->s_dev = NO_DEV; /* restore later */
if (sp->s_magic != SUPER_MAGIC)
return(EINVAL);
sp->s_block_size = 1024*(1<<sp->s_log_block_size);
if (sp->s_block_size < _MIN_BLOCK_SIZE
|| sp->s_block_size >_MAX_BLOCK_SIZE) {
return(EINVAL);
printf("data block size is too large\n");
}
if ((sp->s_block_size % 512) != 0)
return(EINVAL);
if (SUPER_SIZE_D > sp->s_block_size)
return(EINVAL);
/* Variable added for convinience (i_blocks counts 512-byte blocks). */
sp->s_sectors_in_block = sp->s_block_size / 512;
/* TODO: this code is for revision 1 (but bw compatible with 0)
* inode must be power of 2 and smaller, than block size.
*/
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if ((EXT2_INODE_SIZE(sp) & (EXT2_INODE_SIZE(sp) - 1)) != 0
|| EXT2_INODE_SIZE(sp) > sp->s_block_size) {
printf("superblock->s_inode_size is incorrect...\n");
return(EINVAL);
}
sp->s_blocksize_bits = sp->s_log_block_size + 10;
sp->s_max_size = ext2_max_size(sp->s_block_size);
sp->s_inodes_per_block = sp->s_block_size / EXT2_INODE_SIZE(sp);
if (sp->s_inodes_per_block == 0 || sp->s_inodes_per_group == 0) {
printf("either inodes_per_block or inodes_per_group count is 0\n");
return(EINVAL);
}
sp->s_itb_per_group = sp->s_inodes_per_group / sp->s_inodes_per_block;
sp->s_desc_per_block = sp->s_block_size / sizeof(struct group_desc);
sp->s_groups_count = ((sp->s_blocks_count - sp->s_first_data_block - 1)
/ sp->s_blocks_per_group) + 1;
/* ceil(groups_count/desc_per_block) */
sp->s_gdb_count = (sp->s_groups_count + sp->s_desc_per_block - 1)
/ sp->s_desc_per_block;
gd_size = sp->s_gdb_count * sp->s_block_size;
buf = 0;
STATICINIT(buf, gd_size);
group_descs = (struct group_desc *) buf;
buf = 0;
STATICINIT(buf, gd_size);
ondisk_group_descs = (struct group_desc *) buf;
if (!group_descs || !ondisk_group_descs)
panic("can't allocate memory for gdt buffer");
/* s_first_data_block (block number, where superblock is stored)
* is 1 for 1Kb blocks and 0 for larger blocks.
* For fs with 1024-byte blocks first 1024 bytes (block0) used by MBR,
* and block1 stores superblock. When block size is larger, block0 stores
* both MBR and superblock, but gdt lives in next block anyway.
* If sb=N was specified, then gdt is stored in N+1 block, the block number
* here uses 1k units.
*
*/
if (opt.block_with_super == 0) {
gdt_position = (sp->s_first_data_block + 1) * sp->s_block_size;
} else {
gdt_position = (opt.block_with_super + 1) * 1024;
}
r = bdev_read(dev, cvu64(gdt_position), (char*) ondisk_group_descs,
gd_size, BDEV_NOFLAGS);
if (r != gd_size) {
printf("Can not read group descriptors\n");
return(EINVAL);
}
/* TODO: check descriptors we just read */
copy_group_descriptors(group_descs, ondisk_group_descs, sp->s_groups_count);
sp->s_group_desc = group_descs;
/* Make a few basic checks to see if super block looks reasonable. */
if (sp->s_inodes_count < 1 || sp->s_blocks_count < 1) {
printf("not enough inodes or data blocks, \n");
return(EINVAL);
}
sp->s_dirs_counter = ext2_count_dirs(sp);
/* Start block search from this block.
* We skip superblock (1 block), group descriptors blocks (sp->s_gdb_count)
* block and inode bitmaps (2 blocks) and inode table.
*/
sp->s_bsearch = sp->s_first_data_block + 1 + sp->s_gdb_count + 2
+ sp->s_itb_per_group;
sp->s_igsearch = 0;
sp->s_dev = dev; /* restore device number */
return(OK);
}
/*===========================================================================*
* write_super *
*===========================================================================*/
PUBLIC void write_super(sp)
struct super_block *sp; /* pointer to a superblock */
{
/* Write a superblock and gdt. */
int r;
block_t gd_size; /* group descriptors table size in blocks */
int gdt_position;
if (sp->s_rd_only)
panic("can't write superblock on read-only filesys.");
if (sp->s_dev == NO_DEV)
panic("request to write super_block, but NO_DEV");
super_copy(ondisk_superblock, sp);
r = bdev_write(sp->s_dev, cvu64(super_block_offset), (char *) sp,
SUPER_SIZE_D, BDEV_NOFLAGS);
if (r != SUPER_SIZE_D)
printf("ext2: Warning, failed to write superblock to the disk!\n");
if (group_descriptors_dirty == DIRTY) {
/* Locate the appropriate super_block. */
gd_size = sp->s_gdb_count * sp->s_block_size;
if (opt.block_with_super == 0) {
gdt_position = (sp->s_first_data_block + 1) * sp->s_block_size;
} else {
gdt_position = (opt.block_with_super + 1) * 1024;
}
copy_group_descriptors(ondisk_group_descs, sp->s_group_desc,
sp->s_groups_count);
r = bdev_write(sp->s_dev, cvu64(gdt_position),
(char*) ondisk_group_descs, gd_size, BDEV_NOFLAGS);
if (r != gd_size) {
printf("Can not write group descriptors\n");
}
group_descriptors_dirty = CLEAN;
}
}
/*===========================================================================*
* get_group_desc *
*===========================================================================*/
struct group_desc* get_group_desc(unsigned int bnum)
{
if (bnum >= superblock->s_groups_count) {
printf("ext2, get_group_desc: wrong bnum (%d) requested\n", bnum);
return NULL;
}
return &superblock->s_group_desc[bnum];
}
PRIVATE u32_t ext2_count_dirs(struct super_block *sp)
{
u32_t count = 0;
int i;
for (i = 0; i < sp->s_groups_count; i++) {
struct group_desc *desc = get_group_desc(i);
if (!desc)
continue; /* TODO: fail? */
count += desc->used_dirs_count;
}
return count;
}
/*===========================================================================*
* ext2_max_size *
*===========================================================================*/
/* There are several things, which affect max filesize:
* - inode.i_blocks (512-byte blocks) is limited to (2^32 - 1).
* - number of addressed direct, single, double and triple indirect blocks.
* Number of addressed blocks depends on block_size only, thus unlike in
* linux (ext2_max_size) we do not make calculations, but use constants
* for different block sizes. Calculations (gcc code) are commented.
* Note: linux ext2_max_size makes calculated based on shifting, not
* arithmetics.
* (!!!)Note: constants hardly tight to EXT2_NDIR_BLOCKS, but I doubt its value
* will be changed someday. So if it's changed, then just recalculate constatns.
* Anyway this function is safe for any change.
* Note: there is also limitation from VFS (to LONG_MAX, i.e. 2GB).
*/
PRIVATE off_t ext2_max_size(int block_size)
{
/* 12 is EXT2_NDIR_BLOCKS used in calculations. */
if (EXT2_NDIR_BLOCKS != 12)
panic("ext2_max_size needs modification!");
switch(block_size) {
case 1024: return LONG_MAX; /* actually 17247252480 */
case 2048: return LONG_MAX; /* 275415851008 */
case 4096: return LONG_MAX; /* 2194719883264 */
default: {
ext2_debug("ext2_max_size: Unsupported block_size! \
Assuming bs is 1024 bytes\n");
return 67383296L;
}
}
#if 0
long addr_in_block = block_size/4; /* 4 bytes per addr */
long sectors_in_block = block_size/512;
long long meta_blocks; /* single, double and triple indirect blocks */
unsigned long long out_range_s; /* max blocks addressed by inode */
unsigned long long max_bytes;
unsigned long long upper_limit;
/* 1 indirect block, 1 + addr_in_block dindirect and 1 + addr_in_block +
* + addr_in_block*addr_in_block triple indirect blocks */
meta_blocks = 2*addr_in_block + addr_in_block*addr_in_block + 3;
out_range_s = EXT2_NDIR_BLOCKS + addr_in_block + addr_in_block * addr_in_block
+ addr_in_block * addr_in_block * addr_in_block;
max_bytes = out_range_s * block_size;
upper_limit = (1LL << 32) - 1; /* max 512-byte blocks by i_blocks */
upper_limit /= sectors_in_block; /* total block_size blocks */
upper_limit -= meta_blocks; /* total data blocks */
upper_limit *= (long long)block_size; /* max size in bytes */
if (max_bytes > upper_limit)
max_bytes = upper_limit;
/* Limit s_max_size to LONG_MAX */
if (max_bytes > LONG_MAX)
max_bytes = LONG_MAX;
return max_bytes;
#endif
}
/*===========================================================================*
* super_copy *
*===========================================================================*/
PRIVATE void super_copy(
register struct super_block *dest,
register struct super_block *source
)
/* Note: we don't convert stuff, used in ext3. */
{
/* Copy super_block to the in-core table, swapping bytes if need be. */
if (le_CPU) {
/* Just use memcpy */
memcpy(dest, source, SUPER_SIZE_D);
return;
}
dest->s_inodes_count = conv4(le_CPU, source->s_inodes_count);
dest->s_blocks_count = conv4(le_CPU, source->s_blocks_count);
dest->s_r_blocks_count = conv4(le_CPU, source->s_r_blocks_count);
dest->s_free_blocks_count = conv4(le_CPU, source->s_free_blocks_count);
dest->s_free_inodes_count = conv4(le_CPU, source->s_free_inodes_count);
dest->s_first_data_block = conv4(le_CPU, source->s_first_data_block);
dest->s_log_block_size = conv4(le_CPU, source->s_log_block_size);
dest->s_log_frag_size = conv4(le_CPU, source->s_log_frag_size);
dest->s_blocks_per_group = conv4(le_CPU, source->s_blocks_per_group);
dest->s_frags_per_group = conv4(le_CPU, source->s_frags_per_group);
dest->s_inodes_per_group = conv4(le_CPU, source->s_inodes_per_group);
dest->s_mtime = conv4(le_CPU, source->s_mtime);
dest->s_wtime = conv4(le_CPU, source->s_wtime);
dest->s_mnt_count = conv2(le_CPU, source->s_mnt_count);
dest->s_max_mnt_count = conv2(le_CPU, source->s_max_mnt_count);
dest->s_magic = conv2(le_CPU, source->s_magic);
dest->s_state = conv2(le_CPU, source->s_state);
dest->s_errors = conv2(le_CPU, source->s_errors);
dest->s_minor_rev_level = conv2(le_CPU, source->s_minor_rev_level);
dest->s_lastcheck = conv4(le_CPU, source->s_lastcheck);
dest->s_checkinterval = conv4(le_CPU, source->s_checkinterval);
dest->s_creator_os = conv4(le_CPU, source->s_creator_os);
dest->s_rev_level = conv4(le_CPU, source->s_rev_level);
dest->s_def_resuid = conv2(le_CPU, source->s_def_resuid);
dest->s_def_resgid = conv2(le_CPU, source->s_def_resgid);
dest->s_first_ino = conv4(le_CPU, source->s_first_ino);
dest->s_inode_size = conv2(le_CPU, source->s_inode_size);
dest->s_block_group_nr = conv2(le_CPU, source->s_block_group_nr);
dest->s_feature_compat = conv4(le_CPU, source->s_feature_compat);
dest->s_feature_incompat = conv4(le_CPU, source->s_feature_incompat);
dest->s_feature_ro_compat = conv4(le_CPU, source->s_feature_ro_compat);
memcpy(dest->s_uuid, source->s_uuid, sizeof(dest->s_uuid));
memcpy(dest->s_volume_name, source->s_volume_name,
sizeof(dest->s_volume_name));
memcpy(dest->s_last_mounted, source->s_last_mounted,
sizeof(dest->s_last_mounted));
dest->s_algorithm_usage_bitmap =
conv4(le_CPU, source->s_algorithm_usage_bitmap);
dest->s_prealloc_blocks = source->s_prealloc_blocks;
dest->s_prealloc_dir_blocks = source->s_prealloc_dir_blocks;
dest->s_padding1 = conv2(le_CPU, source->s_padding1);
}
/*===========================================================================*
* gd_copy *
*===========================================================================*/
PRIVATE void gd_copy(
register struct group_desc *dest,
register struct group_desc *source
)
{
/* Copy super_block to the in-core table, swapping bytes if need be. */
if (le_CPU) {
/* Just use memcpy */
memcpy(dest, source, sizeof(struct group_desc));
return;
}
dest->block_bitmap = conv4(le_CPU, source->block_bitmap);
dest->inode_bitmap = conv4(le_CPU, source->inode_bitmap);
dest->inode_table = conv4(le_CPU, source->inode_table);
dest->free_blocks_count = conv2(le_CPU, source->free_blocks_count);
dest->free_inodes_count = conv2(le_CPU, source->free_inodes_count);
dest->used_dirs_count = conv2(le_CPU, source->used_dirs_count);
}
/*===========================================================================*
* copy_group_descriptors *
*===========================================================================*/
PRIVATE void copy_group_descriptors(
register struct group_desc *dest_array,
register struct group_desc *source_array,
unsigned int ngroups
)
{
int i;
for (i = 0; i < ngroups; i++)
gd_copy(&dest_array[i], &source_array[i]);
}