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busybox/util-linux/mkfs_ext2.c
Denys Vlasenko 9c2708ebf9 mkfs_ext2: code shrink 
function                                             old     new   delta
div_roundup                                            -      15     +15
mkfs_ext2_main                                      1980    1933     -47

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2009-10-17 23:27:29 +02:00

486 lines
16 KiB
C
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/* vi: set sw=4 ts=4: */
/*
* mkfs_ext2: utility to create EXT2 filesystem
* inspired by genext2fs
*
* Busybox'ed (2009) by Vladimir Dronnikov <dronnikov@gmail.com>
*
* Licensed under GPLv2, see file LICENSE in this tarball for details.
*/
#include "libbb.h"
#include <linux/fs.h>
#include <linux/ext2_fs.h>
#include "volume_id/volume_id_internal.h"
#define ENABLE_FEATURE_MKFS_EXT2_RESERVED_GDT 0
#define ENABLE_FEATURE_MKFS_EXT2_DIR_INDEX 1
// from e2fsprogs
#define s_reserved_gdt_blocks s_padding1
#define s_mkfs_time s_reserved[0]
#define s_flags s_reserved[22]
#define EXT2_HASH_HALF_MD4 1
#define EXT2_FLAGS_SIGNED_HASH 0x0001
// whiteout: for writable overlays
//#define LINUX_S_IFWHT 0160000
//#define EXT2_FEATURE_INCOMPAT_WHITEOUT 0x0020
// storage helper
void BUG_unsupported_field_size(void);
#define STORE_LE(field, value) \
do { \
if (sizeof(field) == 4) \
field = cpu_to_le32(value); \
else if (sizeof(field) == 2) \
field = cpu_to_le16(value); \
else if (sizeof(field) == 1) \
field = (value); \
else \
BUG_unsupported_field_size(); \
} while (0)
// All fields are little-endian
struct ext2_dir {
uint32_t inode1;
uint16_t rec_len1;
uint8_t name_len1;
uint8_t file_type1;
char name1[4];
uint32_t inode2;
uint16_t rec_len2;
uint8_t name_len2;
uint8_t file_type2;
char name2[4];
uint32_t inode3;
uint16_t rec_len3;
uint8_t name_len3;
uint8_t file_type3;
char name3[12];
};
static unsigned int_log2(unsigned arg)
{
unsigned r = 0;
while ((arg >>= 1) != 0)
r++;
return r;
}
// taken from mkfs_minix.c. libbb candidate?
static unsigned div_roundup(uint32_t size, uint32_t n)
{
return (size + n-1) / n;
}
static void allocate(uint8_t *bitmap, uint32_t blocksize, uint32_t start, uint32_t end)
{
uint32_t i;
memset(bitmap, 0, blocksize);
i = start/8;
memset(bitmap, 0xFF, i);
bitmap[i] = 0xFF >> (8-(start&7));
//bb_info_msg("ALLOC: [%u][%u][%u]: [%u]:=[%x]", blocksize, start, end, blocksize - end/8 - 1, (uint8_t)(0xFF << (8-(end&7))));
i = end/8;
bitmap[blocksize - i - 1] = 0xFF << (8-(end&7));
memset(bitmap + blocksize - i, 0xFF, i); // N.B. no overflow here!
}
#if 0
// TODO: get rid of FPU
static bool is_power_of(uint32_t x, uint16_t n)
{
// return (!(x % n) && is_power_of(x / n, n));
double z = logf(x)/logf(n);
return (z == (int)z);
}
static uint32_t has_super(uint32_t x)
{
return (0 == x || 1 == x || is_power_of(x, 3) || is_power_of(x, 5) || is_power_of(x, 7));
}
#else
static uint32_t has_super(uint32_t x)
{
static const uint32_t supers[] = {
0, 1, 3, 5, 7, 9, 25, 27, 49, 81, 125, 243, 343, 625, 729,
2187, 2401, 3125, 6561, 15625, 16807, 19683, 59049, 78125,
117649, 177147, 390625, 531441, 823543, 1594323, 1953125,
4782969, 5764801, 9765625, 14348907, 40353607, 43046721,
48828125, 129140163, 244140625, 282475249, 387420489,
1162261467, 1220703125, 1977326743, 3486784401/* >2^31 */,
};
const uint32_t *sp = supers + ARRAY_SIZE(supers)-1;
while (1) {
if (x == *sp)
return 1;
if (0 == *sp)
return 0;
sp--;
}
}
#endif
/* Standard mke2fs 1.41.9:
* Usage: mke2fs [-c|-l filename] [-b block-size] [-f fragment-size]
* [-i bytes-per-inode] [-I inode-size] [-J journal-options]
* [-G meta group size] [-N number-of-inodes]
* [-m reserved-blocks-percentage] [-o creator-os]
* [-g blocks-per-group] [-L volume-label] [-M last-mounted-directory]
* [-O feature[,...]] [-r fs-revision] [-E extended-option[,...]]
* [-T fs-type] [-U UUID] [-jnqvFSV] device [blocks-count]
*/
// N.B. not commented below options are taken and silently ignored
enum {
OPT_c = 1 << 0,
OPT_l = 1 << 1,
OPT_b = 1 << 2, // block size, in bytes
OPT_f = 1 << 3,
OPT_i = 1 << 4, // bytes per inode
OPT_I = 1 << 5,
OPT_J = 1 << 6,
OPT_G = 1 << 7,
OPT_N = 1 << 8,
OPT_m = 1 << 9, // percentage of blocks reserved for superuser
OPT_o = 1 << 10,
OPT_g = 1 << 11,
OPT_L = 1 << 12, // label
OPT_M = 1 << 13,
OPT_O = 1 << 14,
OPT_r = 1 << 15,
OPT_E = 1 << 16,
OPT_T = 1 << 17,
OPT_U = 1 << 18,
OPT_j = 1 << 19,
OPT_n = 1 << 20,
OPT_q = 1 << 21,
OPT_v = 1 << 22,
OPT_F = 1 << 23,
OPT_S = 1 << 24,
//OPT_V = 1 << 25, // -V version. bbox applets don't support that
};
#define fd 3 /* predefined output descriptor */
static void PUT(uint64_t off, void *buf, uint32_t size)
{
if (!(option_mask32 & OPT_n)) {
xlseek(fd, off, SEEK_SET);
xwrite(fd, buf, size);
}
}
int mkfs_ext2_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int mkfs_ext2_main(int argc UNUSED_PARAM, char **argv)
{
unsigned i, pos, n;
unsigned bs, blocksize;
unsigned nreserved = 5;
uint32_t nblocks;
uint32_t ngroups;
unsigned bytes_per_inode;
uint32_t nblocks_per_group;
uint32_t first_data_block;
uint32_t ninodes;
uint32_t ninodes_per_group;
uint32_t gdtsz, rgdtsz, itsz;
time_t timestamp;
unsigned opts;
const char *label;
struct stat st;
struct ext2_super_block *sb; // superblock
struct ext2_group_desc *gd; // group descriptors
struct ext2_inode *inode;
struct ext2_dir *dir;
uint8_t *buf;
bs = EXT2_MIN_BLOCK_SIZE;
opt_complementary = "-1:b+:m+:i+";
opts = getopt32(argv, "cl:b:f:i:I:J:G:N:m:o:g:L:M:O:r:E:T:U:jnqvFS",
NULL, &bs, NULL, &bytes_per_inode, NULL, NULL, NULL, NULL,
&nreserved, NULL, NULL, &label, NULL, NULL, NULL, NULL, NULL, NULL);
argv += optind; // argv[0] -- device
// block size minimax, block size is a multiple of minimum
blocksize = bs;
if (blocksize < EXT2_MIN_BLOCK_SIZE
|| blocksize > EXT2_MAX_BLOCK_SIZE
|| (blocksize & (blocksize - 1)) // not power of 2
) {
bb_error_msg_and_die("-%c is bad", 'b');
}
// reserved blocks count
if (nreserved > 50)
bb_error_msg_and_die("-%c is bad", 'm');
// check the device is a block device
xstat(argv[0], &st);
if (!S_ISBLK(st.st_mode) && !(opts & OPT_F))
bb_error_msg_and_die("not a block device");
// check if it is mounted
// N.B. what if we format a file? find_mount_point will return false negative since
// it is loop block device which mounted!
if (find_mount_point(argv[0], 0))
bb_error_msg_and_die("can't format mounted filesystem");
// TODO: 5?/5 WE MUST NOT DEPEND ON WHETHER DEVICE IS /dev/zero 'ed OR NOT
// TODO: 3/5 refuse if mounted
// TODO: 4/5 compat options
// TODO: 1/5 sanity checks
// TODO: 0/5 more verbose error messages
// TODO: 0/5 info printing
// TODO: 2/5 bigendianness! Spot where it comes to play! sb->, gd->
// TODO: 2/5 reserved GDT: how to mark but not allocate?
// TODO: 0/5 dir_index?
// fill the superblock
sb = xzalloc(blocksize);
sb->s_rev_level = 1; // revision 1 filesystem
sb->s_magic = EXT2_SUPER_MAGIC;
sb->s_inode_size = sizeof(*inode);
sb->s_first_ino = EXT2_GOOD_OLD_FIRST_INO;
sb->s_log_block_size = sb->s_log_frag_size = int_log2(blocksize >> EXT2_MIN_BLOCK_LOG_SIZE);
// first 1024 bytes of the device are for boot record. If block size is 1024 bytes, then
// the first block available for data is 1, otherwise 0
first_data_block = sb->s_first_data_block = (EXT2_MIN_BLOCK_SIZE == blocksize);
// block and inode bitmaps occupy no more than one block, so maximum number of blocks is
// number of bits in one block, i.e. 8*blocksize
nblocks_per_group = sb->s_blocks_per_group = sb->s_frags_per_group = sb->s_inodes_per_group = 8*blocksize;
timestamp = time(NULL);
sb->s_mkfs_time = sb->s_wtime = sb->s_lastcheck = timestamp;
sb->s_state = 1;
sb->s_creator_os = EXT2_OS_LINUX;
sb->s_max_mnt_count = EXT2_DFL_MAX_MNT_COUNT;
sb->s_checkinterval = 24*60*60 * 180; // 180 days
sb->s_errors = EXT2_ERRORS_DEFAULT;
sb->s_feature_compat = EXT2_FEATURE_COMPAT_SUPP
| (EXT2_FEATURE_COMPAT_RESIZE_INO * ENABLE_FEATURE_MKFS_EXT2_RESERVED_GDT)
| (EXT2_FEATURE_COMPAT_DIR_INDEX * ENABLE_FEATURE_MKFS_EXT2_DIR_INDEX)
;
// e2fsprogs-1.41.9 doesn't like EXT2_FEATURE_INCOMPAT_WHITEOUT
sb->s_feature_incompat = EXT2_FEATURE_INCOMPAT_FILETYPE;// | EXT2_FEATURE_INCOMPAT_WHITEOUT;
sb->s_feature_ro_compat = EXT2_FEATURE_RO_COMPAT_SPARSE_SUPER;
sb->s_flags = EXT2_FLAGS_SIGNED_HASH * ENABLE_FEATURE_MKFS_EXT2_DIR_INDEX;
generate_uuid(sb->s_uuid);
#if ENABLE_FEATURE_MKFS_EXT2_DIR_INDEX
sb->s_def_hash_version = EXT2_HASH_HALF_MD4;
generate_uuid((uint8_t *)sb->s_hash_seed);
#endif
/*
* From e2fsprogs: add "jitter" to the superblock's check interval so that we
* don't check all the filesystems at the same time. We use a
* kludgy hack of using the UUID to derive a random jitter value.
*/
for (i = 0, n = 0; i < sizeof(sb->s_uuid); i++)
n += sb->s_uuid[i];
sb->s_max_mnt_count += n % EXT2_DFL_MAX_MNT_COUNT;
// open the device, get number of blocks
xmove_fd(xopen3(argv[0], O_WRONLY | O_CREAT, 0666), fd);
if (argv[1]) {
nblocks = xatou(argv[1]);
} else {
nblocks = ((uoff_t)xlseek(fd, 0, SEEK_END)) / blocksize;
xlseek(fd, 0, SEEK_SET);
}
sb->s_blocks_count = nblocks;
// nblocks is the total number of blocks in the filesystem
if (nblocks < 8)
bb_error_msg_and_die("nblocks");
// reserve blocks for superuser
sb->s_r_blocks_count = ((uint64_t) nblocks * nreserved) / 100;
// N.B. a block group can have no more than nblocks_per_group blocks
ngroups = div_roundup(nblocks - first_data_block, nblocks_per_group);
if (0 == ngroups)
bb_error_msg_and_die("ngroups");
gdtsz = div_roundup(ngroups, EXT2_DESC_PER_BLOCK(sb));
/*
* From e2fsprogs: Calculate the number of GDT blocks to reserve for online
* filesystem growth.
* The absolute maximum number of GDT blocks we can reserve is determined by
* the number of block pointers that can fit into a single block.
*/
/* We set it at 1024x the current filesystem size, or
* the upper block count limit (2^32), whichever is lower.
*/
#if ENABLE_FEATURE_MKFS_EXT2_RESERVED_GDT
rgdtsz = 0xFFFFFFFF; // maximum block number
if (nblocks < rgdtsz / 1024)
rgdtsz = nblocks * 1024;
rgdtsz = div_roundup(rgdtsz - first_data_block, nblocks_per_group);
rgdtsz = div_roundup(rgdtsz, EXT2_DESC_PER_BLOCK(sb)) - gdtsz;
if (rgdtsz > EXT2_ADDR_PER_BLOCK(sb))
rgdtsz = EXT2_ADDR_PER_BLOCK(sb);
sb->s_reserved_gdt_blocks = rgdtsz;
//bb_info_msg("RSRVD[%u]", n);
#else
rgdtsz = 0;
#endif
// ninodes is the total number of inodes (files) in the file system
if (!(opts & OPT_i)) {
bytes_per_inode = 16384;
if (nblocks < 512*1024)
bytes_per_inode = 4096;
if (nblocks < 3*1024)
bytes_per_inode = 8192;
}
ninodes = nblocks / (bytes_per_inode / blocksize);
if (ninodes < EXT2_GOOD_OLD_FIRST_INO+1)
ninodes = EXT2_GOOD_OLD_FIRST_INO+1;
ninodes_per_group = div_roundup(ninodes, ngroups);
if (ninodes_per_group < 16)
ninodes_per_group = 16; // minimum number because the first 10 are reserved
// N.B. a block group can have no more than 8*blocksize = sb->s_inodes_per_group inodes
if (ninodes_per_group > sb->s_inodes_per_group)
ninodes_per_group = sb->s_inodes_per_group;
// adjust inodes per group so they completely fill the inode table blocks in the descriptor
ninodes_per_group = ((div_roundup(ninodes_per_group * EXT2_INODE_SIZE(sb), blocksize) * blocksize) / EXT2_INODE_SIZE(sb));
// make sure the number of inodes per group is a multiple of 8
ninodes_per_group &= ~7;
sb->s_inodes_per_group = ninodes_per_group;// = div_roundup(ninodes_per_group * sb->s_inode_size, blocksize);
// total ninodes
ninodes = sb->s_inodes_count = ninodes_per_group * ngroups;
itsz = ninodes_per_group * sb->s_inode_size / blocksize;
sb->s_free_inodes_count = sb->s_inodes_count - EXT2_GOOD_OLD_FIRST_INO;
// write the label, if any
if (opts & OPT_L)
safe_strncpy((char *)sb->s_volume_name, label, sizeof(sb->s_volume_name));
// fill group descriptors
gd = xzalloc((gdtsz + rgdtsz) * blocksize);
sb->s_free_blocks_count = 0;
for (i = 0, pos = first_data_block, n = nblocks;
i < ngroups;
i++, pos += nblocks_per_group, n -= nblocks_per_group
) {
uint32_t overhead = pos + (has_super(i) ? (1/*sb*/ + gdtsz + rgdtsz) : 0);
gd[i].bg_block_bitmap = overhead + 0;
gd[i].bg_inode_bitmap = overhead + 1;
gd[i].bg_inode_table = overhead + 2;
overhead = overhead - pos + 1/*bbmp*/ + 1/*ibmp*/ + itsz;
gd[i].bg_free_inodes_count = ninodes_per_group;
// N.B. both root and lost+found dirs are within the first block group, thus +2
//gd[i].bg_used_dirs_count = 0;
if (0 == i) {
overhead += 2;
gd[i].bg_used_dirs_count = 2;
gd[i].bg_free_inodes_count -= EXT2_GOOD_OLD_FIRST_INO;
}
// N.B. the following is pure heuristics!
// Likely to cope with 1024-byte blocks, when first block is for boot sectors
if (ngroups-1 == i) {
overhead += first_data_block;
}
gd[i].bg_free_blocks_count = (n < nblocks_per_group ? n : nblocks_per_group) - overhead;
sb->s_free_blocks_count += gd[i].bg_free_blocks_count;
}
STORE_LE(sb->s_free_blocks_count, sb->s_free_blocks_count);
// dump filesystem skeleton structures
buf = xmalloc(blocksize);
for (i = 0, pos = first_data_block; i < ngroups; i++, pos += nblocks_per_group) {
uint32_t overhead = has_super(i) ? (1/*sb*/ + gdtsz + rgdtsz) : 0;
uint32_t start;// = has_super(i) ? (1/*sb*/ + gdtsz + rgdtsz) : 0;
uint32_t end;
// dump superblock and group descriptors and their backups
if (overhead) { // N.B. in fact, we want (has_super(i)) condition, but it is equal to (overhead != 0) and is cheaper
//bb_info_msg("SUPER@[%d]", pos);
// N.B. 1024 byte blocks are special
PUT(blocksize * pos + ((0 == i && 0 == first_data_block) ? 1024 : 0), sb, blocksize);
PUT(blocksize * pos + blocksize, gd, (gdtsz + rgdtsz) * blocksize);
}
start = overhead + 1/*bbmp*/ + 1/*ibmp*/ + itsz;
if (i == 0)
start += 2; // for / and /lost+found
end = nblocks_per_group - (start + gd[i].bg_free_blocks_count);
// mark preallocated blocks as allocated
allocate(buf, blocksize, start, end);
// dump block bitmap
PUT((pos + overhead) * blocksize, buf, blocksize);
// mark preallocated inodes as allocated
allocate(buf, blocksize,
ninodes_per_group - gd[i].bg_free_inodes_count,
8*blocksize - ninodes_per_group
);
// dump inode bitmap
PUT((pos + overhead + 1) * blocksize, buf, blocksize);
}
// zero boot sectors
memset(buf, 0, blocksize);
PUT(0, buf, 1024); // N.B. 1024 <= blocksize
// zero inode tables
for (i = 0; i < ngroups; ++i)
for (n = 0; n < itsz; ++n)
PUT((gd[i].bg_inode_table + n) * blocksize, buf, blocksize);
// prepare directory inode
inode = (struct ext2_inode *)buf;
STORE_LE(inode->i_mode, S_IFDIR | S_IRWXU | S_IRGRP | S_IROTH | S_IXGRP | S_IXOTH);
inode->i_mtime = inode->i_atime = timestamp;
STORE_LE(inode->i_ctime, timestamp);
STORE_LE(inode->i_size, blocksize);
// N.B. inode->i_blocks stores the number of 512 byte data blocks. Why on Earth?!
STORE_LE(inode->i_blocks, blocksize / 512);
// dump root dir inode
STORE_LE(inode->i_links_count, 3); // "/.", "/..", "/lost+found/.." point to this inode
STORE_LE(inode->i_block[0], gd[0].bg_inode_table + itsz);
PUT(gd[0].bg_inode_table * blocksize + (EXT2_ROOT_INO-1) * sizeof(*inode), buf, sizeof(*inode));
// dump lost+found dir inode
STORE_LE(inode->i_links_count, 2); // both "/lost+found" and "/lost+found/." point to this inode
STORE_LE(inode->i_block[0], inode->i_block[0]+1); // use next block //= gd[0].bg_inode_table + itsz + 1;
PUT(gd[0].bg_inode_table * blocksize + (EXT2_GOOD_OLD_FIRST_INO-1) * sizeof(*inode), buf, sizeof(*inode));
// dump directories
memset(buf, 0, blocksize);
dir = (struct ext2_dir *)buf;
// dump lost+found dir block
STORE_LE(dir->inode1, EXT2_GOOD_OLD_FIRST_INO);
STORE_LE(dir->rec_len1, 12);
STORE_LE(dir->name_len1, 1);
STORE_LE(dir->file_type1, EXT2_FT_DIR);
dir->name1[0] = '.';
STORE_LE(dir->inode2, EXT2_ROOT_INO);
STORE_LE(dir->rec_len2, blocksize - 12);
STORE_LE(dir->name_len2, 2);
STORE_LE(dir->file_type2, EXT2_FT_DIR);
dir->name2[0] = '.'; dir->name2[1] = '.';
PUT((gd[0].bg_inode_table + itsz + 1) * blocksize, buf, blocksize);
// dump root dir block
STORE_LE(dir->inode1, EXT2_ROOT_INO);
STORE_LE(dir->rec_len2, 12);
STORE_LE(dir->inode3, EXT2_GOOD_OLD_FIRST_INO);
STORE_LE(dir->rec_len3, blocksize - 12 - 12);
STORE_LE(dir->name_len3, 10);
STORE_LE(dir->file_type3, EXT2_FT_DIR);
strcpy(dir->name3, "lost+found");
PUT((gd[0].bg_inode_table + itsz + 0) * blocksize, buf, blocksize);
// cleanup
if (ENABLE_FEATURE_CLEAN_UP) {
free(buf);
free(gd);
free(sb);
close(fd);
}
return EXIT_SUCCESS;
}
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