《操作系统》的实验代码。
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#define _GNU_SOURCE
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <stdint.h>
#include <limits.h>
#include <dirent.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <errno.h>
#include <assert.h>
typedef int bool;
#define __error(msg, quit, ...) \
do { \
fprintf(stderr, #msg ": function %s - line %d: ", __FUNCTION__, __LINE__); \
if (errno != 0) { \
fprintf(stderr, "[error] %s: ", strerror(errno)); \
} \
fprintf(stderr, "\n\t"), fprintf(stderr, __VA_ARGS__); \
errno = 0; \
if (quit) { \
exit(-1); \
} \
} while (0)
#define warn(...) __error(warn, 0, __VA_ARGS__)
#define bug(...) __error(bug, 1, __VA_ARGS__)
#define static_assert(x) \
switch (x) {case 0: case (x): ; }
/* 2^31 + 2^29 - 2^25 + 2^22 - 2^19 - 2^16 + 1 */
#define GOLDEN_RATIO_PRIME_32 0x9e370001UL
#define HASH_SHIFT 10
#define HASH_LIST_SIZE (1 << HASH_SHIFT)
static inline uint32_t
__hash32(uint32_t val, unsigned int bits) {
uint32_t hash = val * GOLDEN_RATIO_PRIME_32;
return (hash >> (32 - bits));
}
static uint32_t
hash32(uint32_t val) {
return __hash32(val, HASH_SHIFT);
}
static uint32_t
hash64(uint64_t val) {
return __hash32((uint32_t)val, HASH_SHIFT);
}
void *
safe_malloc(size_t size) {
void *ret;
if ((ret = malloc(size)) == NULL) {
bug("malloc %lu bytes failed.\n", (long unsigned)size);
}
return ret;
}
char *
safe_strdup(const char *str) {
char *ret;
if ((ret = strdup(str)) == NULL) {
bug("strdup failed: %s\n", str);
}
return ret;
}
struct stat *
safe_stat(const char *filename) {
static struct stat __stat;
if (stat(filename, &__stat) != 0) {
bug("stat %s failed.\n", filename);
}
return &__stat;
}
struct stat *
safe_fstat(int fd) {
static struct stat __stat;
if (fstat(fd, &__stat) != 0) {
bug("fstat %d failed.\n", fd);
}
return &__stat;
}
struct stat *
safe_lstat(const char *name) {
static struct stat __stat;
if (lstat(name, &__stat) != 0) {
bug("lstat '%s' failed.\n", name);
}
return &__stat;
}
void
safe_fchdir(int fd) {
if (fchdir(fd) != 0) {
bug("fchdir failed %d.\n", fd);
}
}
#define SFS_MAGIC 0x2f8dbe2a
#define SFS_NDIRECT 12
#define SFS_BLKSIZE 4096 // 4K
#define SFS_MAX_NBLKS (1024UL * 512) // 4K * 512K
#define SFS_MAX_INFO_LEN 31
#define SFS_MAX_FNAME_LEN 255
#define SFS_MAX_FILE_SIZE (1024UL * 1024 * 128) // 128M
#define SFS_BLKBITS (SFS_BLKSIZE * CHAR_BIT)
#define SFS_TYPE_FILE 1
#define SFS_TYPE_DIR 2
#define SFS_TYPE_LINK 3
#define SFS_BLKN_SUPER 0
#define SFS_BLKN_ROOT 1
#define SFS_BLKN_FREEMAP 2
struct cache_block {
uint32_t ino;
struct cache_block *hash_next;
void *cache;
};
struct cache_inode {
struct inode {
uint32_t size;
uint16_t type;
uint16_t nlinks;
uint32_t blocks;
uint32_t direct[SFS_NDIRECT];
uint32_t indirect;
uint32_t db_indirect;
} inode;
ino_t real;
uint32_t ino;
uint32_t nblks;
struct cache_block *l1, *l2;
struct cache_inode *hash_next;
};
struct sfs_fs {
struct {
uint32_t magic;
uint32_t blocks;
uint32_t unused_blocks;
char info[SFS_MAX_INFO_LEN + 1];
} super;
struct subpath {
struct subpath *next, *prev;
char *subname;
} __sp_nil, *sp_root, *sp_end;
int imgfd;
uint32_t ninos, next_ino;
struct cache_inode *root;
struct cache_inode *inodes[HASH_LIST_SIZE];
struct cache_block *blocks[HASH_LIST_SIZE];
};
struct sfs_entry {
uint32_t ino;
char name[SFS_MAX_FNAME_LEN + 1];
};
static uint32_t
sfs_alloc_ino(struct sfs_fs *sfs) {
if (sfs->next_ino < sfs->ninos) {
sfs->super.unused_blocks --;
return sfs->next_ino ++;
}
bug("out of disk space.\n");
}
static struct cache_block *
alloc_cache_block(struct sfs_fs *sfs, uint32_t ino) {
struct cache_block *cb = safe_malloc(sizeof(struct cache_block));
cb->ino = (ino != 0) ? ino : sfs_alloc_ino(sfs);
cb->cache = memset(safe_malloc(SFS_BLKSIZE), 0, SFS_BLKSIZE);
struct cache_block **head = sfs->blocks + hash32(ino);
cb->hash_next = *head, *head = cb;
return cb;
}
struct cache_block *
search_cache_block(struct sfs_fs *sfs, uint32_t ino) {
struct cache_block *cb = sfs->blocks[hash32(ino)];
while (cb != NULL && cb->ino != ino) {
cb = cb->hash_next;
}
return cb;
}
static struct cache_inode *
alloc_cache_inode(struct sfs_fs *sfs, ino_t real, uint32_t ino, uint16_t type) {
struct cache_inode *ci = safe_malloc(sizeof(struct cache_inode));
ci->ino = (ino != 0) ? ino : sfs_alloc_ino(sfs);
ci->real = real, ci->nblks = 0, ci->l1 = ci->l2 = NULL;
struct inode *inode = &(ci->inode);
memset(inode, 0, sizeof(struct inode));
inode->type = type;
struct cache_inode **head = sfs->inodes + hash64(real);
ci->hash_next = *head, *head = ci;
return ci;
}
struct cache_inode *
search_cache_inode(struct sfs_fs *sfs, ino_t real) {
struct cache_inode *ci = sfs->inodes[hash64(real)];
while (ci != NULL && ci->real != real) {
ci = ci->hash_next;
}
return ci;
}
struct sfs_fs *
create_sfs(int imgfd) {
uint32_t ninos, next_ino;
struct stat *stat = safe_fstat(imgfd);
if ((ninos = stat->st_size / SFS_BLKSIZE) > SFS_MAX_NBLKS) {
ninos = SFS_MAX_NBLKS;
warn("img file is too big (%llu bytes, only use %u blocks).\n",
(unsigned long long)stat->st_size, ninos);
}
if ((next_ino = SFS_BLKN_FREEMAP + (ninos + SFS_BLKBITS - 1) / SFS_BLKBITS) >= ninos) {
bug("img file is too small (%llu bytes, %u blocks, bitmap use at least %u blocks).\n",
(unsigned long long)stat->st_size, ninos, next_ino - 2);
}
struct sfs_fs *sfs = safe_malloc(sizeof(struct sfs_fs));
sfs->super.magic = SFS_MAGIC;
sfs->super.blocks = ninos, sfs->super.unused_blocks = ninos - next_ino;
snprintf(sfs->super.info, SFS_MAX_INFO_LEN, "simple file system");
sfs->ninos = ninos, sfs->next_ino = next_ino, sfs->imgfd = imgfd;
sfs->sp_root = sfs->sp_end = &(sfs->__sp_nil);
sfs->sp_end->prev = sfs->sp_end->next = NULL;
int i;
for (i = 0; i < HASH_LIST_SIZE; i ++) {
sfs->inodes[i] = NULL;
sfs->blocks[i] = NULL;
}
sfs->root = alloc_cache_inode(sfs, 0, SFS_BLKN_ROOT, SFS_TYPE_DIR);
return sfs;
}
static void
subpath_push(struct sfs_fs *sfs, const char *subname) {
struct subpath *subpath = safe_malloc(sizeof(struct subpath));
subpath->subname = safe_strdup(subname);
sfs->sp_end->next = subpath;
subpath->prev = sfs->sp_end;
subpath->next = NULL;
sfs->sp_end = subpath;
}
static void
subpath_pop(struct sfs_fs *sfs) {
assert(sfs->sp_root != sfs->sp_end);
struct subpath *subpath = sfs->sp_end;
sfs->sp_end = sfs->sp_end->prev, sfs->sp_end->next = NULL;
free(subpath->subname), free(subpath);
}
static void
subpath_show(FILE *fout, struct sfs_fs *sfs, const char *name) {
struct subpath *subpath = sfs->sp_root;
fprintf(fout, "current is: /");
while ((subpath = subpath->next) != NULL) {
fprintf(fout, "%s/", subpath->subname);
}
if (name != NULL) {
fprintf(fout, "%s", name);
}
fprintf(fout, "\n");
}
static void
write_block(struct sfs_fs *sfs, void *data, size_t len, uint32_t ino) {
assert(len <= SFS_BLKSIZE && ino < sfs->ninos);
static char buffer[SFS_BLKSIZE];
if (len != SFS_BLKSIZE) {
memset(buffer, 0, sizeof(buffer));
data = memcpy(buffer, data, len);
}
off_t offset = (off_t)ino * SFS_BLKSIZE;
ssize_t ret;
if ((ret = pwrite(sfs->imgfd, data, SFS_BLKSIZE, offset)) != SFS_BLKSIZE) {
bug("write %u block failed: (%d/%d).\n", ino, (int)ret, SFS_BLKSIZE);
}
}
static void
flush_cache_block(struct sfs_fs *sfs, struct cache_block *cb) {
write_block(sfs, cb->cache, SFS_BLKSIZE, cb->ino);
}
static void
flush_cache_inode(struct sfs_fs *sfs, struct cache_inode *ci) {
write_block(sfs, &(ci->inode), sizeof(ci->inode), ci->ino);
}
void
close_sfs(struct sfs_fs *sfs) {
static char buffer[SFS_BLKSIZE];
uint32_t i, j, ino = SFS_BLKN_FREEMAP;
uint32_t ninos = sfs->ninos, next_ino = sfs->next_ino;
for (i = 0; i < ninos; ino ++, i += SFS_BLKBITS) {
memset(buffer, 0, sizeof(buffer));
if (i + SFS_BLKBITS > next_ino) {
uint32_t start = 0, end = SFS_BLKBITS;
if (i < next_ino) {
start = next_ino - i;
}
if (i + SFS_BLKBITS > ninos) {
end = ninos - i;
}
uint32_t *data = (uint32_t *)buffer;
const uint32_t bits = sizeof(bits) * CHAR_BIT;
for (j = start; j < end; j ++) {
data[j / bits] |= (1 << (j % bits));
}
}
write_block(sfs, buffer, sizeof(buffer), ino);
}
write_block(sfs, &(sfs->super), sizeof(sfs->super), SFS_BLKN_SUPER);
for (i = 0; i < HASH_LIST_SIZE; i ++) {
struct cache_block *cb = sfs->blocks[i];
while (cb != NULL) {
flush_cache_block(sfs, cb);
cb = cb->hash_next;
}
struct cache_inode *ci = sfs->inodes[i];
while (ci != NULL) {
flush_cache_inode(sfs, ci);
ci = ci->hash_next;
}
}
}
struct sfs_fs *
open_img(const char *imgname) {
const char *expect = ".img", *ext = imgname + strlen(imgname) - strlen(expect);
if (ext <= imgname || strcmp(ext, expect) != 0) {
bug("invalid .img file name '%s'.\n", imgname);
}
int imgfd;
if ((imgfd = open(imgname, O_WRONLY)) < 0) {
bug("open '%s' failed.\n", imgname);
}
return create_sfs(imgfd);
}
#define open_bug(sfs, name, ...) \
do { \
subpath_show(stderr, sfs, name); \
bug(__VA_ARGS__); \
} while (0)
#define show_fullpath(sfs, name) subpath_show(stderr, sfs, name)
void open_dir(struct sfs_fs *sfs, struct cache_inode *current, struct cache_inode *parent);
void open_file(struct sfs_fs *sfs, struct cache_inode *file, const char *filename, int fd);
void open_link(struct sfs_fs *sfs, struct cache_inode *file, const char *filename);
#define SFS_BLK_NENTRY (SFS_BLKSIZE / sizeof(uint32_t))
#define SFS_L0_NBLKS SFS_NDIRECT
#define SFS_L1_NBLKS (SFS_BLK_NENTRY + SFS_L0_NBLKS)
#define SFS_L2_NBLKS (SFS_BLK_NENTRY * SFS_BLK_NENTRY + SFS_L1_NBLKS)
#define SFS_LN_NBLKS (SFS_MAX_FILE_SIZE / SFS_BLKSIZE)
static void
update_cache(struct sfs_fs *sfs, struct cache_block **cbp, uint32_t *inop) {
uint32_t ino = *inop;
struct cache_block *cb = *cbp;
if (ino == 0) {
cb = alloc_cache_block(sfs, 0);
ino = cb->ino;
}
else if (cb == NULL || cb->ino != ino) {
cb = search_cache_block(sfs, ino);
assert(cb != NULL && cb->ino == ino);
}
*cbp = cb, *inop = ino;
}
static void
append_block(struct sfs_fs *sfs, struct cache_inode *file, size_t size, uint32_t ino, const char *filename) {
static_assert(SFS_LN_NBLKS <= SFS_L2_NBLKS);
assert(size <= SFS_BLKSIZE);
uint32_t nblks = file->nblks;
struct inode *inode = &(file->inode);
if (nblks >= SFS_LN_NBLKS) {
open_bug(sfs, filename, "file is too big.\n");
}
if (nblks < SFS_L0_NBLKS) {
inode->direct[nblks] = ino;
}
else if (nblks < SFS_L1_NBLKS) {
nblks -= SFS_L0_NBLKS;
update_cache(sfs, &(file->l1), &(inode->indirect));
uint32_t *data = file->l1->cache;
data[nblks] = ino;
}
else if (nblks < SFS_L2_NBLKS) {
nblks -= SFS_L1_NBLKS;
update_cache(sfs, &(file->l2), &(inode->db_indirect));
uint32_t *data2 = file->l2->cache;
update_cache(sfs, &(file->l1), &data2[nblks / SFS_BLK_NENTRY]);
uint32_t *data1 = file->l1->cache;
data1[nblks % SFS_BLK_NENTRY] = ino;
}
file->nblks ++;
inode->size += size;
inode->blocks ++;
}
static void
add_entry(struct sfs_fs *sfs, struct cache_inode *current, struct cache_inode *file, const char *name) {
static struct sfs_entry __entry, *entry = &__entry;
assert(current->inode.type == SFS_TYPE_DIR && strlen(name) <= SFS_MAX_FNAME_LEN);
entry->ino = file->ino, strcpy(entry->name, name);
uint32_t entry_ino = sfs_alloc_ino(sfs);
write_block(sfs, entry, sizeof(entry->name), entry_ino);
append_block(sfs, current, sizeof(entry->name), entry_ino, name);
file->inode.nlinks ++;
}
static void
add_dir(struct sfs_fs *sfs, struct cache_inode *parent, const char *dirname, int curfd, int fd, ino_t real) {
assert(search_cache_inode(sfs, real) == NULL);
struct cache_inode *current = alloc_cache_inode(sfs, real, 0, SFS_TYPE_DIR);
safe_fchdir(fd), subpath_push(sfs, dirname);
open_dir(sfs, current, parent);
safe_fchdir(curfd), subpath_pop(sfs);
add_entry(sfs, parent, current, dirname);
}
static void
add_file(struct sfs_fs *sfs, struct cache_inode *current, const char *filename, int fd, ino_t real) {
struct cache_inode *file;
if ((file = search_cache_inode(sfs, real)) == NULL) {
file = alloc_cache_inode(sfs, real, 0, SFS_TYPE_FILE);
open_file(sfs, file, filename, fd);
}
add_entry(sfs, current, file, filename);
}
static void
add_link(struct sfs_fs *sfs, struct cache_inode *current, const char *filename, ino_t real) {
struct cache_inode *file = alloc_cache_inode(sfs, real, 0, SFS_TYPE_LINK);
open_link(sfs, file, filename);
add_entry(sfs, current, file, filename);
}
void
open_dir(struct sfs_fs *sfs, struct cache_inode *current, struct cache_inode *parent) {
DIR *dir;
if ((dir = opendir(".")) == NULL) {
open_bug(sfs, NULL, "opendir failed.\n");
}
add_entry(sfs, current, current, ".");
add_entry(sfs, current, parent, "..");
struct dirent *direntp;
while ((direntp = readdir(dir)) != NULL) {
const char *name = direntp->d_name;
if (strcmp(name, ".") == 0 || strcmp(name, "..") == 0) {
continue ;
}
if (name[0] == '.') {
continue ;
}
if (strlen(name) > SFS_MAX_FNAME_LEN) {
open_bug(sfs, NULL, "file name is too long: %s\n", name);
}
struct stat *stat = safe_lstat(name);
if (S_ISLNK(stat->st_mode)) {
add_link(sfs, current, name, stat->st_ino);
}
else {
int fd;
if ((fd = open(name, O_RDONLY)) < 0) {
open_bug(sfs, NULL, "open failed: %s\n", name);
}
if (S_ISDIR(stat->st_mode)) {
add_dir(sfs, current, name, dirfd(dir), fd, stat->st_ino);
}
else if (S_ISREG(stat->st_mode)) {
add_file(sfs, current, name, fd, stat->st_ino);
}
else {
char mode = '?';
if (S_ISFIFO(stat->st_mode)) mode = 'f';
if (S_ISSOCK(stat->st_mode)) mode = 's';
if (S_ISCHR(stat->st_mode)) mode = 'c';
if (S_ISBLK(stat->st_mode)) mode = 'b';
show_fullpath(sfs, NULL);
warn("unsupported mode %07x (%c): file %s\n", stat->st_mode, mode, name);
}
close(fd);
}
}
closedir(dir);
}
void
open_file(struct sfs_fs *sfs, struct cache_inode *file, const char *filename, int fd) {
static char buffer[SFS_BLKSIZE];
ssize_t ret, last = SFS_BLKSIZE;
while ((ret = read(fd, buffer, sizeof(buffer))) != 0) {
assert(last == SFS_BLKSIZE);
uint32_t ino = sfs_alloc_ino(sfs);
write_block(sfs, buffer, ret, ino);
append_block(sfs, file, ret, ino, filename);
last = ret;
}
if (ret < 0) {
open_bug(sfs, filename, "read file failed.\n");
}
}
void
open_link(struct sfs_fs *sfs, struct cache_inode *file, const char *filename) {
static char buffer[SFS_BLKSIZE];
uint32_t ino = sfs_alloc_ino(sfs);
ssize_t ret = readlink(filename, buffer, sizeof(buffer));
if (ret < 0 || ret == SFS_BLKSIZE) {
open_bug(sfs, filename, "read link failed, %d", (int)ret);
}
write_block(sfs, buffer, ret, ino);
append_block(sfs, file, ret, ino, filename);
}
int
create_img(struct sfs_fs *sfs, const char *home) {
int curfd, homefd;
if ((curfd = open(".", O_RDONLY)) < 0) {
bug("get current fd failed.\n");
}
if ((homefd = open(home, O_RDONLY | O_NOFOLLOW)) < 0) {
bug("open home directory '%s' failed.\n", home);
}
safe_fchdir(homefd);
open_dir(sfs, sfs->root, sfs->root);
safe_fchdir(curfd);
close(curfd), close(homefd);
close_sfs(sfs);
return 0;
}
static void
static_check(void) {
static_assert(sizeof(off_t) == 8);
static_assert(sizeof(ino_t) == 8);
static_assert(SFS_MAX_NBLKS <= 0x80000000UL);
static_assert(SFS_MAX_FILE_SIZE <= 0x80000000UL);
}
int
main(int argc, char **argv) {
static_check();
if (argc != 3) {
bug("usage: <input *.img> <input dirname>\n");
}
const char *imgname = argv[1], *home = argv[2];
if (create_img(open_img(imgname), home) != 0) {
bug("create img failed.\n");
}
printf("create %s (%s) successfully.\n", imgname, home);
return 0;
}