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mdb.c
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#include <sys/types.h>
#include <sys/stat.h>
#include <sys/queue.h>
#include <sys/param.h>
#include <sys/uio.h>
#include <sys/mman.h>
#ifdef HAVE_SYS_FILE_H
#include <sys/file.h>
#endif
#include <sys/ipc.h>
#include <sys/shm.h>
#include <assert.h>
#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
#include <pthread.h>
#include "mdb.h"
#define DEBUG
#ifdef DEBUG
# define DPRINTF(...) do { fprintf(stderr, "%s:%d: ", __func__, __LINE__); \
fprintf(stderr, __VA_ARGS__); \
fprintf(stderr, "\n"); } while(0)
#else
# define DPRINTF(...)
#endif
#define PAGESIZE 4096
#define MDB_MINKEYS 4
#define MDB_MAGIC 0xBEEFC0DE
#define MDB_VERSION 1
#define MAXKEYSIZE 255
#define P_INVALID (~0L)
#define F_ISSET(w, f) (((w) & (f)) == (f))
typedef ulong pgno_t;
typedef uint16_t indx_t;
#define DEFAULT_READERS 126
#define DEFAULT_MAPSIZE 1048576
/* Lock descriptor stuff */
#define RXBODY \
ulong mr_txnid; \
pid_t mr_pid; \
pthread_t mr_tid
typedef struct MDB_rxbody {
RXBODY;
} MDB_rxbody;
#ifndef CACHELINE
#define CACHELINE 64 /* most CPUs. Itanium uses 128 */
#endif
typedef struct MDB_reader {
RXBODY;
/* cache line alignment */
char pad[CACHELINE-sizeof(MDB_rxbody)];
} MDB_reader;
#define TXBODY \
uint32_t mt_magic; \
uint32_t mt_version; \
pthread_mutex_t mt_mutex; \
ulong mt_txnid; \
uint32_t mt_numreaders
typedef struct MDB_txbody {
TXBODY;
} MDB_txbody;
typedef struct MDB_txninfo {
TXBODY;
char pad[CACHELINE-sizeof(MDB_txbody)];
pthread_mutex_t mt_wmutex;
char pad2[CACHELINE-sizeof(pthread_mutex_t)];
MDB_reader mt_readers[1];
} MDB_txninfo;
/* Common header for all page types. Overflow pages
* occupy a number of contiguous pages with no
* headers on any page after the first.
*/
typedef struct MDB_page { /* represents a page of storage */
pgno_t mp_pgno; /* page number */
#define P_BRANCH 0x01 /* branch page */
#define P_LEAF 0x02 /* leaf page */
#define P_OVERFLOW 0x04 /* overflow page */
#define P_META 0x08 /* meta page */
#define P_HEAD 0x10 /* header page */
#define P_DIRTY 0x20 /* dirty page */
uint32_t mp_flags;
#define mp_lower mp_pb.pb.pb_lower
#define mp_upper mp_pb.pb.pb_upper
#define mp_pages mp_pb.pb_pages
union page_bounds {
struct {
indx_t pb_lower; /* lower bound of free space */
indx_t pb_upper; /* upper bound of free space */
} pb;
uint32_t pb_pages; /* number of overflow pages */
} mp_pb;
indx_t mp_ptrs[1]; /* dynamic size */
} MDB_page;
#define PAGEHDRSZ offsetof(MDB_page, mp_ptrs)
#define NUMKEYS(p) (((p)->mp_lower - PAGEHDRSZ) >> 1)
#define SIZELEFT(p) (indx_t)((p)->mp_upper - (p)->mp_lower)
#define PAGEFILL(env, p) (1000 * ((env)->me_head.mh_psize - PAGEHDRSZ - SIZELEFT(p)) / \
((env)->me_head.mh_psize - PAGEHDRSZ))
#define IS_LEAF(p) F_ISSET((p)->mp_flags, P_LEAF)
#define IS_BRANCH(p) F_ISSET((p)->mp_flags, P_BRANCH)
#define IS_OVERFLOW(p) F_ISSET((p)->mp_flags, P_OVERFLOW)
typedef struct MDB_head { /* header page content */
uint32_t mh_magic;
uint32_t mh_version;
uint32_t mh_flags;
uint32_t mh_psize; /* page size */
void *mh_address; /* address for fixed mapping */
size_t mh_mapsize; /* size of mmap region */
} MDB_head;
typedef struct MDB_meta { /* meta (footer) page content */
MDB_stat mm_stat;
pgno_t mm_root; /* page number of root page */
pgno_t mm_last_pg; /* last used page in file */
ulong mm_txnid; /* txnid that committed this page */
} MDB_meta;
typedef struct MDB_dhead { /* a dirty page */
SIMPLEQ_ENTRY(MDB_dpage) md_next; /* queue of dirty pages */
MDB_page *md_parent;
int md_pi; /* parent index */
int md_num;
} MDB_dhead;
typedef struct MDB_dpage {
MDB_dhead h;
MDB_page p;
} MDB_dpage;
SIMPLEQ_HEAD(dirty_queue, MDB_dpage);
typedef struct MDB_pageparent {
MDB_page *mp_page;
MDB_page *mp_parent;
int mp_pi;
} MDB_pageparent;
static MDB_dpage *mdb_newpage(MDB_txn *txn, MDB_page *parent, int parent_idx, int num);
static int mdb_touch(MDB_txn *txn, MDB_pageparent *mp);
typedef struct MDB_ppage { /* ordered list of pages */
SLIST_ENTRY(MDB_ppage) mp_entry;
MDB_page *mp_page;
unsigned int mp_ki; /* cursor index on page */
} MDB_ppage;
SLIST_HEAD(page_stack, MDB_ppage);
#define CURSOR_EMPTY(c) SLIST_EMPTY(&(c)->mc_stack)
#define CURSOR_TOP(c) SLIST_FIRST(&(c)->mc_stack)
#define CURSOR_POP(c) SLIST_REMOVE_HEAD(&(c)->mc_stack, mp_entry)
#define CURSOR_PUSH(c,p) SLIST_INSERT_HEAD(&(c)->mc_stack, p, mp_entry)
struct MDB_cursor {
MDB_db *mc_db;
MDB_txn *mc_txn;
struct page_stack mc_stack; /* stack of parent pages */
short mc_initialized; /* 1 if initialized */
short mc_eof; /* 1 if end is reached */
};
#define METAHASHLEN offsetof(MDB_meta, mm_hash)
#define METADATA(p) ((void *)((char *)p + PAGEHDRSZ))
typedef struct MDB_node {
#define mn_pgno mn_p.np_pgno
#define mn_dsize mn_p.np_dsize
union {
pgno_t np_pgno; /* child page number */
uint32_t np_dsize; /* leaf data size */
} mn_p;
unsigned int mn_flags:4;
unsigned int mn_ksize:12; /* key size */
#define F_BIGDATA 0x01 /* data put on overflow page */
char mn_data[1];
} MDB_node;
struct MDB_txn {
pgno_t mt_root; /* current / new root page */
pgno_t mt_next_pgno; /* next unallocated page */
pgno_t mt_first_pgno;
ulong mt_txnid;
MDB_env *mt_env;
union {
struct dirty_queue *dirty_queue; /* modified pages */
MDB_reader *reader;
} mt_u;
#define MDB_TXN_RDONLY 0x01 /* read-only transaction */
#define MDB_TXN_ERROR 0x02 /* an error has occurred */
unsigned int mt_flags;
};
/* Must be same as MDB_db, minus md_root/md_stat */
typedef struct MDB_db0 {
unsigned int md_flags;
MDB_cmp_func *md_cmp; /* user compare function */
MDB_rel_func *md_rel; /* user relocate function */
MDB_db *md_parent; /* parent tree */
MDB_env *md_env;
} MDB_db0;
struct MDB_db {
unsigned int md_flags;
MDB_cmp_func *md_cmp; /* user compare function */
MDB_rel_func *md_rel; /* user relocate function */
MDB_db *md_parent; /* parent tree */
MDB_env *md_env;
MDB_stat md_stat;
pgno_t md_root; /* page number of root page */
};
struct MDB_env {
int me_fd;
key_t me_shmkey;
uint32_t me_flags;
int me_maxreaders;
int me_metatoggle;
char *me_path;
char *me_map;
MDB_txninfo *me_txns;
MDB_head me_head;
MDB_db0 me_db; /* first DB, overlaps with meta */
MDB_meta me_meta;
MDB_txn *me_txn; /* current write transaction */
size_t me_mapsize;
off_t me_size; /* current file size */
pthread_key_t me_txkey; /* thread-key for readers */
};
#define NODESIZE offsetof(MDB_node, mn_data)
#define INDXSIZE(k) (NODESIZE + ((k) == NULL ? 0 : (k)->mv_size))
#define LEAFSIZE(k, d) (NODESIZE + (k)->mv_size + (d)->mv_size)
#define NODEPTR(p, i) ((MDB_node *)((char *)(p) + (p)->mp_ptrs[i]))
#define NODEKEY(node) (void *)((node)->mn_data)
#define NODEDATA(node) (void *)((char *)(node)->mn_data + (node)->mn_ksize)
#define NODEPGNO(node) ((node)->mn_pgno)
#define NODEDSZ(node) ((node)->mn_dsize)
#define MDB_COMMIT_PAGES 64 /* max number of pages to write in one commit */
#define MDB_MAXCACHE_DEF 1024 /* max number of pages to keep in cache */
static int mdb_search_page_root(MDB_db *db,
MDB_val *key,
MDB_cursor *cursor, int modify,
MDB_pageparent *mpp);
static int mdb_search_page(MDB_db *db,
MDB_txn *txn, MDB_val *key,
MDB_cursor *cursor, int modify,
MDB_pageparent *mpp);
static int mdbenv_write_header(MDB_env *env);
static int mdbenv_read_header(MDB_env *env);
static int mdb_check_meta_page(MDB_page *p);
static int mdbenv_read_meta(MDB_env *env);
static int mdbenv_write_meta(MDB_txn *txn);
static MDB_page *mdbenv_get_page(MDB_env *env, pgno_t pgno);
static MDB_node *mdb_search_node(MDB_db *db, MDB_page *mp,
MDB_val *key, int *exactp, unsigned int *kip);
static int mdb_add_node(MDB_db *bt, MDB_page *mp,
indx_t indx, MDB_val *key, MDB_val *data,
pgno_t pgno, uint8_t flags);
static void mdb_del_node(MDB_db *bt, MDB_page *mp,
indx_t indx);
static int mdb_read_data(MDB_db *bt, MDB_page *mp,
MDB_node *leaf, MDB_val *data);
static int mdb_rebalance(MDB_db *bt, MDB_pageparent *mp);
static int mdb_update_key(MDB_db *bt, MDB_page *mp,
indx_t indx, MDB_val *key);
static int mdb_move_node(MDB_db *bt,
MDB_pageparent *src, indx_t srcindx,
MDB_pageparent *dst, indx_t dstindx);
static int mdb_merge(MDB_db *bt, MDB_pageparent *src,
MDB_pageparent *dst);
static int mdb_split(MDB_db *bt, MDB_page **mpp,
unsigned int *newindxp, MDB_val *newkey,
MDB_val *newdata, pgno_t newpgno);
static MDB_dpage *mdbenv_new_page(MDB_env *env, uint32_t flags, int num);
static void cursor_pop_page(MDB_cursor *cursor);
static MDB_ppage *cursor_push_page(MDB_cursor *cursor,
MDB_page *mp);
static int mdb_set_key(MDB_db *bt, MDB_page *mp,
MDB_node *node, MDB_val *key);
static int mdb_sibling(MDB_cursor *cursor, int move_right);
static int mdb_cursor_next(MDB_cursor *cursor,
MDB_val *key, MDB_val *data);
static int mdb_cursor_set(MDB_cursor *cursor,
MDB_val *key, MDB_val *data, int *exactp);
static int mdb_cursor_first(MDB_cursor *cursor,
MDB_val *key, MDB_val *data);
static size_t mdb_leaf_size(MDB_db *bt, MDB_val *key,
MDB_val *data);
static size_t mdb_branch_size(MDB_db *bt, MDB_val *key);
static pgno_t mdbenv_compact_tree(MDB_env *env, pgno_t pgno,
MDB_env *envc);
static int memncmp(const void *s1, size_t n1,
const void *s2, size_t n2);
static int memnrcmp(const void *s1, size_t n1,
const void *s2, size_t n2);
static int
memncmp(const void *s1, size_t n1, const void *s2, size_t n2)
{
if (n1 < n2) {
if (memcmp(s1, s2, n1) == 0)
return -1;
}
else if (n1 > n2) {
if (memcmp(s1, s2, n2) == 0)
return 1;
}
return memcmp(s1, s2, n1);
}
static int
memnrcmp(const void *s1, size_t n1, const void *s2, size_t n2)
{
const unsigned char *p1;
const unsigned char *p2;
if (n1 == 0)
return n2 == 0 ? 0 : -1;
if (n2 == 0)
return n1 == 0 ? 0 : 1;
p1 = (const unsigned char *)s1 + n1 - 1;
p2 = (const unsigned char *)s2 + n2 - 1;
while (*p1 == *p2) {
if (p1 == s1)
return (p2 == s2) ? 0 : -1;
if (p2 == s2)
return (p1 == p2) ? 0 : 1;
p1--;
p2--;
}
return *p1 - *p2;
}
int
mdb_cmp(MDB_db *db, const MDB_val *a, const MDB_val *b)
{
return db->md_cmp(a, b);
}
static int
_mdb_cmp(MDB_db *db, const MDB_val *key1, const MDB_val *key2)
{
if (F_ISSET(db->md_flags, MDB_REVERSEKEY))
return memnrcmp(key1->mv_data, key1->mv_size, key2->mv_data, key2->mv_size);
else
return memncmp((char *)key1->mv_data, key1->mv_size, key2->mv_data, key2->mv_size);
}
/* Allocate new page(s) for writing */
static MDB_dpage *
mdb_newpage(MDB_txn *txn, MDB_page *parent, int parent_idx, int num)
{
MDB_dpage *dp;
if ((dp = malloc(txn->mt_env->me_head.mh_psize * num + sizeof(MDB_dhead))) == NULL)
return NULL;
dp->h.md_num = num;
dp->h.md_parent = parent;
dp->h.md_pi = parent_idx;
SIMPLEQ_INSERT_TAIL(txn->mt_u.dirty_queue, dp, h.md_next);
dp->p.mp_pgno = txn->mt_next_pgno;
txn->mt_next_pgno += num;
return dp;
}
/* Touch a page: make it dirty and re-insert into tree with updated pgno.
*/
static int
mdb_touch(MDB_txn *txn, MDB_pageparent *pp)
{
int rc;
MDB_page *mp = pp->mp_page;
pgno_t pgno;
assert(txn != NULL);
assert(pp != NULL);
if (!F_ISSET(mp->mp_flags, P_DIRTY)) {
MDB_dpage *dp;
DPRINTF("touching page %lu -> %lu", mp->mp_pgno, txn->mt_next_pgno);
if ((dp = mdb_newpage(txn, pp->mp_parent, pp->mp_pi, 1)) == NULL)
return ENOMEM;
pgno = dp->p.mp_pgno;
bcopy(mp, &dp->p, txn->mt_env->me_head.mh_psize);
mp = &dp->p;
mp->mp_pgno = pgno;
mp->mp_flags |= P_DIRTY;
/* Update the page number to new touched page. */
if (pp->mp_parent != NULL)
NODEPGNO(NODEPTR(pp->mp_parent, pp->mp_pi)) = mp->mp_pgno;
pp->mp_page = mp;
}
return 0;
}
int
mdbenv_sync(MDB_env *env)
{
int rc = 0;
if (!F_ISSET(env->me_flags, MDB_NOSYNC)) {
if (fsync(env->me_fd))
rc = errno;
}
return rc;
}
int
mdb_txn_begin(MDB_env *env, int rdonly, MDB_txn **ret)
{
MDB_txn *txn;
int rc;
if ((txn = calloc(1, sizeof(*txn))) == NULL) {
DPRINTF("calloc: %s", strerror(errno));
return ENOMEM;
}
if (rdonly) {
txn->mt_flags |= MDB_TXN_RDONLY;
} else {
txn->mt_u.dirty_queue = calloc(1, sizeof(*txn->mt_u.dirty_queue));
if (txn->mt_u.dirty_queue == NULL) {
free(txn);
return ENOMEM;
}
SIMPLEQ_INIT(txn->mt_u.dirty_queue);
pthread_mutex_lock(&env->me_txns->mt_wmutex);
env->me_txns->mt_txnid++;
}
txn->mt_txnid = env->me_txns->mt_txnid;
if (rdonly) {
MDB_reader *r = pthread_getspecific(env->me_txkey);
if (!r) {
int i;
pthread_mutex_lock(&env->me_txns->mt_mutex);
for (i=0; i<env->me_maxreaders; i++) {
if (env->me_txns->mt_readers[i].mr_pid == 0) {
env->me_txns->mt_readers[i].mr_pid = getpid();
env->me_txns->mt_readers[i].mr_tid = pthread_self();
pthread_setspecific(env->me_txkey, &env->me_txns->mt_readers[i]);
if (i >= env->me_txns->mt_numreaders)
env->me_txns->mt_numreaders = i+1;
break;
}
}
pthread_mutex_unlock(&env->me_txns->mt_mutex);
if (i == env->me_maxreaders) {
return ENOSPC;
}
}
r->mr_txnid = txn->mt_txnid;
txn->mt_u.reader = r;
} else {
env->me_txn = txn;
}
txn->mt_env = env;
if ((rc = mdbenv_read_meta(env)) != MDB_SUCCESS) {
mdb_txn_abort(txn);
return rc;
}
txn->mt_next_pgno = env->me_meta.mm_last_pg+1;
txn->mt_first_pgno = txn->mt_next_pgno;
txn->mt_root = env->me_meta.mm_root;
DPRINTF("begin transaction %lu on mdbenv %p, root page %lu", txn->mt_txnid, env, txn->mt_root);
*ret = txn;
return MDB_SUCCESS;
}
void
mdb_txn_abort(MDB_txn *txn)
{
MDB_dpage *dp;
MDB_env *env;
if (txn == NULL)
return;
env = txn->mt_env;
DPRINTF("abort transaction %lu on mdbenv %p, root page %lu", txn->mt_txnid, env, txn->mt_root);
if (F_ISSET(txn->mt_flags, MDB_TXN_RDONLY)) {
txn->mt_u.reader->mr_txnid = 0;
} else {
/* Discard all dirty pages.
*/
while (!SIMPLEQ_EMPTY(txn->mt_u.dirty_queue)) {
dp = SIMPLEQ_FIRST(txn->mt_u.dirty_queue);
SIMPLEQ_REMOVE_HEAD(txn->mt_u.dirty_queue, h.md_next);
free(dp);
}
#if 0
DPRINTF("releasing write lock on txn %p", txn);
txn->bt->txn = NULL;
if (flock(txn->bt->fd, LOCK_UN) != 0) {
DPRINTF("failed to unlock fd %d: %s",
txn->bt->fd, strerror(errno));
}
#endif
free(txn->mt_u.dirty_queue);
env->me_txn = NULL;
pthread_mutex_unlock(&env->me_txns->mt_wmutex);
}
free(txn);
}
int
mdb_txn_commit(MDB_txn *txn)
{
int n, done;
ssize_t rc;
off_t size;
MDB_dpage *dp;
MDB_env *env;
pgno_t next;
struct iovec iov[MDB_COMMIT_PAGES];
assert(txn != NULL);
assert(txn->mt_env != NULL);
env = txn->mt_env;
if (F_ISSET(txn->mt_flags, MDB_TXN_RDONLY)) {
DPRINTF("attempt to commit read-only transaction");
mdb_txn_abort(txn);
return EPERM;
}
if (txn != env->me_txn) {
DPRINTF("attempt to commit unknown transaction");
mdb_txn_abort(txn);
return EINVAL;
}
if (F_ISSET(txn->mt_flags, MDB_TXN_ERROR)) {
DPRINTF("error flag is set, can't commit");
mdb_txn_abort(txn);
return EINVAL;
}
if (SIMPLEQ_EMPTY(txn->mt_u.dirty_queue))
goto done;
DPRINTF("committing transaction %lu on mdbenv %p, root page %lu",
txn->mt_txnid, env, txn->mt_root);
/* Commit up to MDB_COMMIT_PAGES dirty pages to disk until done.
*/
next = 0;
do {
n = 0;
done = 1;
size = 0;
SIMPLEQ_FOREACH(dp, txn->mt_u.dirty_queue, h.md_next) {
if (dp->p.mp_pgno != next) {
lseek(env->me_fd, dp->p.mp_pgno * env->me_head.mh_psize, SEEK_SET);
next = dp->p.mp_pgno;
if (n)
break;
}
DPRINTF("committing page %lu", dp->p.mp_pgno);
iov[n].iov_len = env->me_head.mh_psize * dp->h.md_num;
iov[n].iov_base = &dp->p;
size += iov[n].iov_len;
next = dp->p.mp_pgno + dp->h.md_num;
/* clear dirty flag */
dp->p.mp_flags &= ~P_DIRTY;
if (++n >= MDB_COMMIT_PAGES) {
done = 0;
break;
}
}
if (n == 0)
break;
DPRINTF("committing %u dirty pages", n);
rc = writev(env->me_fd, iov, n);
if (rc != size) {
n = errno;
if (rc > 0)
DPRINTF("short write, filesystem full?");
else
DPRINTF("writev: %s", strerror(errno));
mdb_txn_abort(txn);
return n;
}
/* Drop the dirty pages.
*/
while (!SIMPLEQ_EMPTY(txn->mt_u.dirty_queue)) {
dp = SIMPLEQ_FIRST(txn->mt_u.dirty_queue);
SIMPLEQ_REMOVE_HEAD(txn->mt_u.dirty_queue, h.md_next);
free(dp);
if (--n == 0)
break;
}
} while (!done);
if ((n = mdbenv_sync(env)) != 0 ||
(n = mdbenv_write_meta(txn)) != MDB_SUCCESS ||
(n = mdbenv_sync(env)) != 0) {
mdb_txn_abort(txn);
return n;
}
env->me_txn = NULL;
pthread_mutex_unlock(&env->me_txns->mt_wmutex);
free(txn->mt_u.dirty_queue);
free(txn);
txn = NULL;
done:
mdb_txn_abort(txn);
return MDB_SUCCESS;
}
static int
mdbenv_write_header(MDB_env *env)
{
struct stat sb;
MDB_head *h;
MDB_page *p;
ssize_t rc;
unsigned int psize;
DPRINTF("writing header page");
assert(env != NULL);
psize = sysconf(_SC_PAGE_SIZE);
if ((p = calloc(1, psize)) == NULL)
return ENOMEM;
p->mp_flags = P_HEAD;
env->me_head.mh_psize = psize;
env->me_head.mh_flags = env->me_flags & 0xffff;
h = METADATA(p);
bcopy(&env->me_head, h, sizeof(*h));
rc = write(env->me_fd, p, env->me_head.mh_psize);
free(p);
if (rc != (ssize_t)env->me_head.mh_psize) {
int err = errno;
if (rc > 0)
DPRINTF("short write, filesystem full?");
return err;
}
return MDB_SUCCESS;
}
static int
mdbenv_read_header(MDB_env *env)
{
char page[PAGESIZE];
MDB_page *p;
MDB_head *h;
int rc;
assert(env != NULL);
/* We don't know the page size yet, so use a minimum value.
*/
if ((rc = pread(env->me_fd, page, PAGESIZE, 0)) == 0) {
return ENOENT;
} else if (rc != PAGESIZE) {
if (rc > 0)
errno = EINVAL;
DPRINTF("read: %s", strerror(errno));
return errno;
}
p = (MDB_page *)page;
if (!F_ISSET(p->mp_flags, P_HEAD)) {
DPRINTF("page %lu not a header page", p->mp_pgno);
return EINVAL;
}
h = METADATA(p);
if (h->mh_magic != MDB_MAGIC) {
DPRINTF("header has invalid magic");
return EINVAL;
}
if (h->mh_version != MDB_VERSION) {
DPRINTF("database is version %u, expected version %u",
h->mh_version, MDB_VERSION);
return EINVAL;
}
bcopy(h, &env->me_head, sizeof(*h));
return 0;
}
static int
mdbenv_init_meta(MDB_env *env)
{
MDB_page *p, *q;
MDB_meta *meta;
int rc;
p = calloc(2, env->me_head.mh_psize);
p->mp_pgno = 1;
p->mp_flags = P_META;
meta = METADATA(p);
meta->mm_root = P_INVALID;
meta->mm_last_pg = 2;
q = (MDB_page *)((char *)p + env->me_head.mh_psize);
q->mp_pgno = 2;
q->mp_flags = P_META;
meta = METADATA(q);
meta->mm_root = P_INVALID;
meta->mm_last_pg = 2;
rc = write(env->me_fd, p, env->me_head.mh_psize * 2);
free(p);
return (rc == env->me_head.mh_psize * 2) ? MDB_SUCCESS : errno;
}
static int
mdbenv_write_meta(MDB_txn *txn)
{
MDB_env *env;
MDB_meta meta;
off_t off;
int rc;
assert(txn != NULL);
assert(txn->mt_env != NULL);
DPRINTF("writing meta page for root page %lu", txn->mt_root);
env = txn->mt_env;
bcopy(&env->me_meta, &meta, sizeof(meta));
meta.mm_root = txn->mt_root;
meta.mm_last_pg = txn->mt_next_pgno - 1;
meta.mm_txnid = txn->mt_txnid;
off = env->me_head.mh_psize;
if (!env->me_metatoggle)
off *= 2;
off += PAGEHDRSZ;
lseek(env->me_fd, off, SEEK_SET);
rc = write(env->me_fd, &meta, sizeof(meta));
if (rc != sizeof(meta)) {
DPRINTF("write failed, disk error?");
return errno;
}
return MDB_SUCCESS;
}
/* Returns true if page p is a valid meta page, false otherwise.
*/
static int
mdb_check_meta_page(MDB_page *p)
{
if (!F_ISSET(p->mp_flags, P_META)) {
DPRINTF("page %lu not a meta page", p->mp_pgno);
return EINVAL;
}
return 0;
}
static int
mdbenv_read_meta(MDB_env *env)
{
MDB_page *mp0, *mp1;
MDB_meta *meta[2];
int toggle = 0, rc;
assert(env != NULL);
if ((mp0 = mdbenv_get_page(env, 1)) == NULL ||
(mp1 = mdbenv_get_page(env, 2)) == NULL)
return EIO;
rc = mdb_check_meta_page(mp0);
if (rc) return rc;
rc = mdb_check_meta_page(mp1);
if (rc) return rc;
meta[0] = METADATA(mp0);
meta[1] = METADATA(mp1);
if (meta[0]->mm_txnid < meta[1]->mm_txnid)
toggle = 1;
if (meta[toggle]->mm_txnid > env->me_meta.mm_txnid) {
bcopy(meta[toggle], &env->me_meta, sizeof(env->me_meta));
env->me_metatoggle = toggle;
}
DPRINTF("Using meta page %d", toggle);
return MDB_SUCCESS;
}
int
mdbenv_create(MDB_env **env)
{
MDB_env *e;
e = calloc(1, sizeof(*e));
if (!e) return ENOMEM;
e->me_head.mh_magic = MDB_MAGIC;
e->me_head.mh_version = MDB_VERSION;
e->me_head.mh_mapsize = DEFAULT_MAPSIZE;
e->me_maxreaders = DEFAULT_READERS;
e->me_db.md_env = e;
*env = e;
return MDB_SUCCESS;
}
int
mdbenv_set_mapsize(MDB_env *env, size_t size)
{
if (env->me_map)
return EINVAL;
env->me_mapsize = env->me_head.mh_mapsize = size;
return MDB_SUCCESS;
}
int
mdbenv_set_maxreaders(MDB_env *env, int readers)
{
env->me_maxreaders = readers;
return MDB_SUCCESS;
}
int
mdbenv_get_maxreaders(MDB_env *env, int *readers)
{
if (!env || !readers)
return EINVAL;
*readers = env->me_maxreaders;
return MDB_SUCCESS;
}
int
mdbenv_open2(MDB_env *env, unsigned int flags)
{
int i, newenv = 0;
env->me_flags = flags;
env->me_meta.mm_root = P_INVALID;
env->me_meta.mm_last_pg = 2;
if ((i = mdbenv_read_header(env)) != 0) {
if (i != ENOENT)
return i;
DPRINTF("new mdbenv");
newenv = 1;
}
if (!env->me_mapsize)
env->me_mapsize = env->me_head.mh_mapsize;
i = MAP_SHARED;
if (env->me_head.mh_address && (flags & MDB_FIXEDMAP))
i |= MAP_FIXED;
env->me_map = mmap(env->me_head.mh_address, env->me_mapsize, PROT_READ, i,
env->me_fd, 0);
if (env->me_map == MAP_FAILED)
return errno;
if (newenv) {
env->me_head.mh_mapsize = env->me_mapsize;
if (flags & MDB_FIXEDMAP)
env->me_head.mh_address = env->me_map;
i = mdbenv_write_header(env);
if (i != MDB_SUCCESS) {
munmap(env->me_map, env->me_mapsize);
return i;
}
i = mdbenv_init_meta(env);
if (i != MDB_SUCCESS) {
munmap(env->me_map, env->me_mapsize);
return i;
}
}
if ((i = mdbenv_read_meta(env)) != 0)
return i;
DPRINTF("opened database version %u, pagesize %u",
env->me_head.mh_version, env->me_head.mh_psize);
DPRINTF("depth: %u", env->me_meta.mm_stat.ms_depth);
DPRINTF("entries: %lu", env->me_meta.mm_stat.ms_entries);
DPRINTF("branch pages: %lu", env->me_meta.mm_stat.ms_branch_pages);
DPRINTF("leaf pages: %lu", env->me_meta.mm_stat.ms_leaf_pages);
DPRINTF("overflow pages: %lu", env->me_meta.mm_stat.ms_overflow_pages);
DPRINTF("root: %lu", env->me_meta.mm_root);
return MDB_SUCCESS;
}
static void
mdbenv_reader_dest(void *ptr)
{
MDB_reader *reader = ptr;
reader->mr_txnid = 0;
reader->mr_pid = 0;
reader->mr_tid = 0;
}
int
mdbenv_open(MDB_env *env, const char *path, unsigned int flags, mode_t mode)
{
int oflags, rc, shmid;
off_t size;
if (F_ISSET(flags, MDB_RDONLY))
oflags = O_RDONLY;
else
oflags = O_RDWR | O_CREAT;
if ((env->me_fd = open(path, oflags, mode)) == -1)
return errno;
env->me_shmkey = ftok(path, 'm');
size = (env->me_maxreaders-1) * sizeof(MDB_reader) + sizeof(MDB_txninfo);
shmid = shmget(env->me_shmkey, size, IPC_CREAT|IPC_EXCL|mode);
if (shmid == -1) {
if (errno == EEXIST) {
shmid = shmget(env->me_shmkey, size, IPC_CREAT|mode);
if (shmid == -1)
return errno;
env->me_txns = shmat(shmid, NULL, 0);
if (env->me_txns->mt_magic != MDB_MAGIC ||
env->me_txns->mt_version != MDB_VERSION) {
DPRINTF("invalid lock region %d", shmid);
shmdt(env->me_txns);
env->me_txns = NULL;
return EIO;
}
} else {
return errno;
}
} else {