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cyrusdb_skiplist.c
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cyrusdb_skiplist.c
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/* cyrusdb_skiplist.c -- cyrusdb skiplist implementation
*
* Copyright (c) 1994-2008 Carnegie Mellon University. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* 3. The name "Carnegie Mellon University" must not be used to
* endorse or promote products derived from this software without
* prior written permission. For permission or any legal
* details, please contact
* Carnegie Mellon University
* Center for Technology Transfer and Enterprise Creation
* 4615 Forbes Avenue
* Suite 302
* Pittsburgh, PA 15213
* (412) 268-7393, fax: (412) 268-7395
* innovation@andrew.cmu.edu
*
* 4. Redistributions of any form whatsoever must retain the following
* acknowledgment:
* "This product includes software developed by Computing Services
* at Carnegie Mellon University (http://www.cmu.edu/computing/)."
*
* CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
* THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
* AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
* FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
* AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
* OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
/* xxx check retry_xxx for failure */
/* xxx all offsets should be uint32_ts i think */
#include <config.h>
#include <stdlib.h>
#include <string.h>
#include <limits.h>
#include <errno.h>
#include <syslog.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#include <netinet/in.h>
#include "assert.h"
#include "bsearch.h"
#include "cyrusdb.h"
#include "libcyr_cfg.h"
#include "cyr_lock.h"
#include "map.h"
#include "retry.h"
#include "util.h"
#include "xmalloc.h"
#include "xunlink.h"
#define PROB (0.5)
/*
*
* disk format; all numbers in network byte order
*
* there's the data file, consisting of the
* multiple records of "key", "data", and "skip pointers", where skip
* pointers are the record number of the data pointer.
*
* on startup, recovery is performed. the last known good data file
* is taken and the intent log is replayed on it. the index file is
* regenerated from scratch.
*
* during operation checkpoints will compress the data. the data file
* is locked. then a checkpoint rewrites the data file in order,
* removing any unused records. this is written and fsync'd to
* dfile.NEW and stored for use during recovery.
*/
/*
header "skiplist file\0\0\0"
version (4 bytes)
version_minor (4 bytes)
maxlevel (4 bytes)
curlevel (4 bytes)
listsize (4 bytes)
in active items
log start (4 bytes)
offset where log records start, used mainly to tell when to compress
last recovery (4 bytes)
seconds since unix epoch
1 or more skipnodes, one of:
record type (4 bytes) [DUMMY, INORDER, ADD]
key size (4 bytes)
key string (bit string, rounded to up to 4 byte multiples w/ 0s)
data size (4 bytes)
data string (bit string, rounded to up to 4 byte multiples w/ 0s)
skip pointers (4 bytes each)
least to most
padding (4 bytes, must be -1)
record type (4 bytes) [DELETE]
record ptr (4 bytes; record to be deleted)
record type (4 bytes) [COMMIT]
record type is either
DUMMY (first node is of this type)
INORDER
ADD
DELETE
COMMIT (commit the previous records)
*/
enum {
INORDER = 1,
ADD = 2,
DELETE = 4,
COMMIT = 255,
DUMMY = 257
};
enum {
UNLOCKED = 0,
READLOCKED = 1,
WRITELOCKED = 2,
};
struct txn {
int syncfd;
/* logstart is where we start changes from on commit, where we truncate
to on abort */
unsigned logstart;
unsigned logend; /* where to write to continue this txn */
};
struct dbengine {
/* file data */
char *fname;
int fd;
const char *map_base;
size_t map_len; /* mapped size */
size_t map_size; /* actual size */
ino_t map_ino;
/* header info */
uint32_t version;
uint32_t version_minor;
uint32_t maxlevel;
uint32_t curlevel;
uint32_t listsize;
uint32_t logstart; /* where the log starts from last chkpnt */
time_t last_recovery;
/* tracking info */
int lock_status;
int is_open;
int open_flags;
struct txn *current_txn;
struct timeval starttime;
/* comparator function to use for sorting */
int (*compar) (const char *s1, int l1, const char *s2, int l2);
};
struct db_list {
struct dbengine *db;
struct db_list *next;
int refcount;
};
static time_t global_recovery = 0;
static struct db_list *open_db = NULL;
/* Perform an FSYNC/FDATASYNC if we are *not* operating in UNSAFE mode */
#define DO_FSYNC (!libcyrus_config_getswitch(CYRUSOPT_SKIPLIST_UNSAFE))
enum {
be_paranoid = 0,
use_osync = 0
};
static void getsyncfd(struct dbengine *db, struct txn *t)
{
if (!use_osync) {
t->syncfd = db->fd;
} else if (t->syncfd == -1) {
t->syncfd = open(db->fname, O_RDWR | O_DSYNC, 0666);
assert(t->syncfd != -1); /* xxx do better error recovery */
}
}
static void closesyncfd(struct dbengine *db __attribute__((unused)),
struct txn *t)
{
/* if we're using fsync, then we don't want to close the file */
if (use_osync && (t->syncfd != -1)) {
close(t->syncfd);
}
t->syncfd = -1;
}
static int myinit(const char *dbdir, int myflags)
{
char sfile[1024];
int fd = -1, r = 0;
uint32_t net32_time = 0;
snprintf(sfile, sizeof(sfile), "%s/skipstamp", dbdir);
if (myflags & CYRUSDB_RECOVER) {
struct stat sbuf;
char cleanfile[1024];
/* n.b. nothing in cyrus creates this file, but presumably some
* init.d or systemd script does
*/
snprintf(cleanfile, sizeof(cleanfile), "%s/skipcleanshutdown", dbdir);
/* if we had a clean shutdown, we don't need to run recovery on
* everything, unless we've never previously run it */
if (stat(cleanfile, &sbuf) == 0) {
xunlink(cleanfile);
if (stat(sfile, &sbuf) == 0) {
syslog(LOG_NOTICE, "skiplist: clean shutdown detected,"
" starting normally");
goto normal;
}
}
syslog(LOG_NOTICE, "skiplist: clean shutdown file missing, updating recovery stamp");
/* set the recovery timestamp; all databases earlier than this
time need recovery run when opened */
global_recovery = time(NULL);
fd = open(sfile, O_RDWR | O_CREAT, 0644);
if (fd == -1) r = -1;
if (r != -1) r = ftruncate(fd, 0);
net32_time = htonl(global_recovery);
if (r != -1) r = retry_write(fd, &net32_time, 4);
xclose(fd);
if (r == -1) {
xsyslog(LOG_ERR, "DBERROR: write failed",
"filename=<%s>", sfile);
xclose(fd);
return CYRUSDB_IOERROR;
}
} else {
normal:
/* read the global recovery timestamp */
errno = 0;
r = fd = open(sfile, O_RDONLY, 0644);
if (r == -1 && errno == ENOENT) {
/* tell the admin what they need to do! */
xsyslog(LOG_INFO, "skipstamp is missing, have you run `ctl_cyrusdb -r`?",
"filename=<%s>", sfile);
}
if (r != -1) r = retry_read(fd, &net32_time, 4);
if (r == -1) {
xsyslog(LOG_ERR, "DBERROR: skipstamp unreadable, assuming the worst",
"filename=<%s>", sfile);
/* "assuming the worst" means recovery will run for every skiplist
* database every time it's opened, because we can't determine that
* it doesn't need it.
*/
global_recovery = 0;
} else {
global_recovery = ntohl(net32_time);
}
xclose(fd);
errno = 0;
}
srand(time(NULL) * getpid());
open_db = NULL;
return 0;
}
enum {
SKIPLIST_VERSION = 1,
SKIPLIST_VERSION_MINOR = 2,
SKIPLIST_MAXLEVEL = 20,
SKIPLIST_MINREWRITE = 16834 /* don't rewrite logs smaller than this */
};
#define HEADER_MAGIC ("\241\002\213\015skiplist file\0\0\0")
#define HEADER_MAGIC_SIZE (20)
/* offsets of header files */
enum {
OFFSET_HEADER = 0,
OFFSET_VERSION = 20,
OFFSET_VERSION_MINOR = 24,
OFFSET_MAXLEVEL = 28,
OFFSET_CURLEVEL = 32,
OFFSET_LISTSIZE = 36,
OFFSET_LOGSTART = 40,
OFFSET_LASTRECOVERY = 44
};
enum {
HEADER_SIZE = OFFSET_LASTRECOVERY + 4
};
static int mycommit(struct dbengine *db, struct txn *tid);
static int myabort(struct dbengine *db, struct txn *tid);
static int mycheckpoint(struct dbengine *db);
static int myconsistent(struct dbengine *db, struct txn *tid, int locked);
static int recovery(struct dbengine *db, int flags);
enum {
/* Force recovery regardless of timestamp on database */
RECOVERY_FORCE = 1,
/* Caller already has a write lock on the database. In the case
* of successful recovery, the database will still be locked on return.
*
* If the recovery fails, then the database will be unlocked an an
* error will be returned */
RECOVERY_CALLER_LOCKED = 2
};
/* file looks like:
struct header {
...
}
struct dummy {
uint32_t t = htonl(DUMMY);
uint32_t ks = 0;
uint32_t ds = 0;
uint32_t forward[db->maxlevel];
uint32_t pad = -1;
} */
#define DUMMY_OFFSET(db) (HEADER_SIZE)
#define DUMMY_PTR(db) ((db)->map_base + HEADER_SIZE)
#define DUMMY_SIZE(db) (4 * (3 + db->maxlevel + 1))
/* bump to the next multiple of 4 bytes */
#define ROUNDUP(num) (((num) + 3) & 0xFFFFFFFC)
#define TYPE(ptr) (ntohl(*((uint32_t *)(ptr))))
#define KEY(ptr) ((ptr) + 8)
#define KEYLEN(ptr) (ntohl(*((uint32_t *)((ptr) + 4))))
#define DATA(ptr) ((ptr) + 8 + ROUNDUP(KEYLEN(ptr)) + 4)
#define DATALEN(ptr) (ntohl(*((uint32_t *)((ptr) + 8 + ROUNDUP(KEYLEN(ptr))))))
#define FIRSTPTR(ptr) ((ptr) + 8 + ROUNDUP(KEYLEN(ptr)) + 4 + ROUNDUP(DATALEN(ptr)))
/* return a pointer to the pointer */
#define PTR(ptr, x) (FIRSTPTR(ptr) + 4 * (x))
/* FORWARD(ptr, x)
* given a pointer to the start of the record, return the offset
* corresponding to the xth pointer
*/
#define FORWARD(ptr, x) (ntohl(*((uint32_t *)(FIRSTPTR(ptr) + 4 * (x)))))
static int is_safe(struct dbengine *db, const char *ptr)
{
if (ptr < db->map_base)
return 0;
if (ptr > db->map_base + db->map_size)
return 0;
return 1;
}
static unsigned LEVEL_safe(struct dbengine *db, const char *ptr)
{
const uint32_t *p, *q;
assert(TYPE(ptr) == DUMMY || TYPE(ptr) == INORDER || TYPE(ptr) == ADD);
if (!is_safe(db, ptr + 12))
return 0;
if (!is_safe(db, ptr + 12 + KEYLEN(ptr)))
return 0;
p = q = (uint32_t *) FIRSTPTR(ptr);
if (!is_safe(db, (const char *)p))
return 0;
while (*p != (uint32_t)-1) {
p++;
if (!is_safe(db, (const char *)p))
return 0;
}
return p - q;
}
/* how big is this record? */
static unsigned RECSIZE_safe(struct dbengine *db, const char *ptr)
{
int ret = 0;
int level;
switch (TYPE(ptr)) {
case DUMMY:
case INORDER:
case ADD:
level = LEVEL_safe(db, ptr);
if (!level) {
xsyslog(LOG_ERR, "IOERROR: skiplist RECSIZE not safe",
"filename=<%s> offset=<" OFF_T_FMT ">",
db->fname, ptr - db->map_base);
return 0;
}
ret += 4; /* tag */
ret += 4; /* keylen */
ret += ROUNDUP(KEYLEN(ptr)); /* key */
ret += 4; /* datalen */
ret += ROUNDUP(DATALEN(ptr)); /* data */
ret += 4 * level; /* pointers */
ret += 4; /* padding */
break;
case DELETE:
if (!is_safe(db, ptr+8)) {
xsyslog(LOG_ERR, "IOERROR: skiplist RECSIZE not safe",
"filename=<%s> offset=<" OFF_T_FMT ">",
db->fname, ptr - db->map_base);
return 0;
}
ret += 8;
break;
case COMMIT:
if (!is_safe(db, ptr+4)) {
xsyslog(LOG_ERR, "IOERROR: skiplist RECSIZE not safe",
"filename=<%s> offset=<" OFF_T_FMT ">",
db->fname, ptr - db->map_base);
return 0;
}
ret += 4;
break;
}
return ret;
}
/* Determine if it is safe to append to this skiplist database.
* e.g. does it end in 4 bytes of -1 followed by a commit record?
* *or* does it end with 'DELETE' + 4 bytes + a commit record?
* *or* is this the beginning of the log, in which case we only need
* the padding from the last INORDER (or DUMMY) record
*/
static int SAFE_TO_APPEND(struct dbengine *db)
{
/* check it's a multiple of 4 */
if (db->map_size % 4) return 1;
/* is it the beginning of the log? */
if (db->map_size == db->logstart) {
if (*((uint32_t *)(db->map_base + db->map_size - 4)) != htonl(-1)) {
return 1;
}
}
/* in the middle of the log somewhere */
else {
if (*((uint32_t *)(db->map_base + db->map_size - 4)) != htonl(COMMIT)) {
return 1;
}
/* if it's not an end of a record or a delete */
if (!((*((uint32_t *)(db->map_base + db->map_size - 8)) == htonl(-1)) ||
(*((uint32_t *)(db->map_base + db->map_size -12)) == htonl(DELETE)))) {
return 1;
}
}
return 0;
}
static int newtxn(struct dbengine *db, struct txn **tidptr)
{
struct txn *tid;
/* is this file safe to append to?
*
* If it isn't, we need to run recovery. */
if (SAFE_TO_APPEND(db)) {
int r = recovery(db, RECOVERY_FORCE | RECOVERY_CALLER_LOCKED);
if (r) return r;
}
/* create the transaction */
tid = xmalloc(sizeof(struct txn));
tid->syncfd = -1;
tid->logstart = db->map_size;
/* assert(t->logstart != -1);*/
tid->logend = tid->logstart;
db->current_txn = tid;
/* pass it back out */
*tidptr = tid;
return 0;
}
static unsigned PADDING_safe(struct dbengine *db, const char *ptr)
{
unsigned size = RECSIZE_safe(db, ptr);
if (!size) return 0;
return ntohl(*((uint32_t *)((ptr) + size - 4)));
}
/* given an open, mapped db, read in the header information */
static int read_header(struct dbengine *db)
{
const char *dptr;
assert(db && db->map_len && db->fname && db->map_base
&& db->is_open && db->lock_status);
if (db->map_len < HEADER_SIZE) {
syslog(LOG_ERR,
"skiplist: file not large enough for header: %s", db->fname);
}
if (memcmp(db->map_base, HEADER_MAGIC, HEADER_MAGIC_SIZE)) {
syslog(LOG_ERR, "skiplist: invalid magic header: %s", db->fname);
return CYRUSDB_IOERROR;
}
db->version = ntohl(*((uint32_t *)(db->map_base + OFFSET_VERSION)));
db->version_minor =
ntohl(*((uint32_t *)(db->map_base + OFFSET_VERSION_MINOR)));
if (db->version != SKIPLIST_VERSION) {
syslog(LOG_ERR, "skiplist: version mismatch: %s has version %d.%d",
db->fname, db->version, db->version_minor);
return CYRUSDB_IOERROR;
}
db->maxlevel = ntohl(*((uint32_t *)(db->map_base + OFFSET_MAXLEVEL)));
if (db->maxlevel > SKIPLIST_MAXLEVEL) {
syslog(LOG_ERR,
"skiplist %s: MAXLEVEL %d in database beyond maximum %d",
db->fname, db->maxlevel, SKIPLIST_MAXLEVEL);
return CYRUSDB_IOERROR;
}
db->curlevel = ntohl(*((uint32_t *)(db->map_base + OFFSET_CURLEVEL)));
if (db->curlevel > db->maxlevel) {
syslog(LOG_ERR,
"skiplist %s: CURLEVEL %d in database beyond maximum %d",
db->fname, db->curlevel, db->maxlevel);
return CYRUSDB_IOERROR;
}
db->listsize = ntohl(*((uint32_t *)(db->map_base + OFFSET_LISTSIZE)));
db->logstart = ntohl(*((uint32_t *)(db->map_base + OFFSET_LOGSTART)));
db->last_recovery =
ntohl(*((uint32_t *)(db->map_base + OFFSET_LASTRECOVERY)));
/* verify dummy node */
dptr = DUMMY_PTR(db);
if (TYPE(dptr) != DUMMY) {
xsyslog(LOG_ERR, "DBERROR: first node not type DUMMY",
"filename=<%s>", db->fname);
return CYRUSDB_IOERROR;
}
if (KEYLEN(dptr) != 0) {
xsyslog(LOG_ERR, "DBERROR: DUMMY has non-zero KEYLEN",
"filename=<%s>", db->fname);
return CYRUSDB_IOERROR;
}
if (DATALEN(dptr) != 0) {
xsyslog(LOG_ERR, "DBERROR: DUMMY has non-zero DATALEN",
"filename=<%s>", db->fname);
return CYRUSDB_IOERROR;
}
if (LEVEL_safe(db, dptr) != db->maxlevel) {
xsyslog(LOG_ERR, "DBERROR: DUMMY level != maxlevel",
"filename=<%s> level=<%d> maxlevel=<%d>",
db->fname, LEVEL_safe(db, dptr), db->maxlevel);
return CYRUSDB_IOERROR;
}
return 0;
}
/* given an open, mapped db, locked db,
write the header information */
static int write_header(struct dbengine *db)
{
char buf[HEADER_SIZE];
assert (db->lock_status == WRITELOCKED);
memcpy(buf + 0, HEADER_MAGIC, HEADER_MAGIC_SIZE);
*((uint32_t *)(buf + OFFSET_VERSION)) = htonl(db->version);
*((uint32_t *)(buf + OFFSET_VERSION_MINOR)) = htonl(db->version_minor);
*((uint32_t *)(buf + OFFSET_MAXLEVEL)) = htonl(db->maxlevel);
*((uint32_t *)(buf + OFFSET_CURLEVEL)) = htonl(db->curlevel);
*((uint32_t *)(buf + OFFSET_LISTSIZE)) = htonl(db->listsize);
*((uint32_t *)(buf + OFFSET_LOGSTART)) = htonl(db->logstart);
*((uint32_t *)(buf + OFFSET_LASTRECOVERY)) = htonl(db->last_recovery);
/* write it out */
lseek(db->fd, 0, SEEK_SET);
if (retry_write(db->fd, buf, HEADER_SIZE) != HEADER_SIZE) {
xsyslog(LOG_ERR, "DBERROR: writing skiplist header failed",
"filename=<%s>", db->fname);
return CYRUSDB_IOERROR;
}
return 0;
}
/* make sure our mmap() is big enough */
static int update_lock(struct dbengine *db, struct txn *txn)
{
/* txn->logend is the current size of the file */
assert (db->is_open && db->lock_status == WRITELOCKED);
map_refresh(db->fd, 0, &db->map_base, &db->map_len, txn->logend,
db->fname, 0);
db->map_size = txn->logend;
return 0;
}
static int write_lock(struct dbengine *db, const char *altname)
{
struct stat sbuf;
const char *lockfailaction;
const char *fname = altname ? altname : db->fname;
assert(db->lock_status == UNLOCKED);
if (lock_reopen(db->fd, fname, &sbuf, &lockfailaction) < 0) {
xsyslog(LOG_ERR, "IOERROR: lock_reopen failed",
"action=<%s> filename=<%s>",
lockfailaction, fname);
return CYRUSDB_IOERROR;
}
if (db->map_ino != sbuf.st_ino) {
map_free(&db->map_base, &db->map_len);
}
db->map_size = sbuf.st_size;
db->map_ino = sbuf.st_ino;
db->lock_status = WRITELOCKED;
gettimeofday(&db->starttime, 0);
map_refresh(db->fd, 0, &db->map_base, &db->map_len, sbuf.st_size,
fname, 0);
if (db->is_open) {
/* reread header */
read_header(db);
}
/* printf("%d: write lock: %d\n", getpid(), db->map_ino); */
return 0;
}
static int read_lock(struct dbengine *db)
{
struct stat sbuf, sbuffile;
int newfd = -1;
assert(db->lock_status == UNLOCKED);
for (;;) {
if (lock_shared(db->fd, db->fname) < 0) {
xsyslog(LOG_ERR, "IOERROR: lock_shared failed",
"filename=<%s>", db->fname);
return CYRUSDB_IOERROR;
}
if (fstat(db->fd, &sbuf) == -1) {
xsyslog(LOG_ERR, "IOERROR: fstat failed",
"filename=<%s>", db->fname);
lock_unlock(db->fd, db->fname);
return CYRUSDB_IOERROR;
}
if (stat(db->fname, &sbuffile) == -1) {
xsyslog(LOG_ERR, "IOERROR: stat failed",
"filename=<%s>", db->fname);
lock_unlock(db->fd, db->fname);
return CYRUSDB_IOERROR;
}
if (sbuf.st_ino == sbuffile.st_ino) break;
newfd = open(db->fname, O_RDWR, 0644);
if (newfd == -1) {
xsyslog(LOG_ERR, "IOERROR: open failed",
"filename=<%s>", db->fname);
lock_unlock(db->fd, db->fname);
return CYRUSDB_IOERROR;
}
dup2(newfd, db->fd);
close(newfd);
}
if (db->map_ino != sbuf.st_ino) {
map_free(&db->map_base, &db->map_len);
}
db->map_size = sbuf.st_size;
db->map_ino = sbuf.st_ino;
db->lock_status = READLOCKED;
gettimeofday(&db->starttime, 0);
/* printf("%d: read lock: %d\n", getpid(), db->map_ino); */
map_refresh(db->fd, 0, &db->map_base, &db->map_len, sbuf.st_size,
db->fname, 0);
if (db->is_open) {
/* reread header */
read_header(db);
}
return 0;
}
static int unlock(struct dbengine *db)
{
struct timeval endtime;
double timediff;
if (db->lock_status == UNLOCKED) {
syslog(LOG_NOTICE, "skiplist: unlock while not locked");
}
if (lock_unlock(db->fd, db->fname) < 0) {
xsyslog(LOG_ERR, "IOERROR: lock_unlock failed",
"filename=<%s>", db->fname);
return CYRUSDB_IOERROR;
}
db->lock_status = UNLOCKED;
gettimeofday(&endtime, 0);
timediff = timesub(&db->starttime, &endtime);
if (timediff > 1.0) {
syslog(LOG_NOTICE, "skiplist: longlock %s for %0.1f seconds",
db->fname, timediff);
}
/* printf("%d: unlock: %d\n", getpid(), db->map_ino); */
return 0;
}
static int lock_or_refresh(struct dbengine *db, struct txn **tidptr)
{
int r;
assert(db);
if (!tidptr) {
/* just grab a readlock */
r = read_lock(db);
if (r) return r;
/* start tracking the lock time */
gettimeofday(&db->starttime, 0);
return 0;
}
if (*tidptr) {
/* check that the DB agrees that we're in this transaction */
assert(db->current_txn == *tidptr);
/* just update the active transaction */
return update_lock(db, *tidptr);
}
/* check that the DB isn't in a transaction */
assert(db->current_txn == NULL);
/* grab a r/w lock */
r = write_lock(db, NULL);
if (r) return r;
/* start the transaction */
r = newtxn(db, tidptr);
if (r) return r;
/* start tracking the lock time */
gettimeofday(&db->starttime, 0);
return 0;
}
static int dispose_db(struct dbengine *db)
{
if (!db) return 0;
if (db->lock_status) {
syslog(LOG_ERR, "skiplist: closed while still locked");
unlock(db);
}
if (db->fname) {
free(db->fname);
}
if (db->map_base) {
map_free(&db->map_base, &db->map_len);
}
if (db->fd != -1) {
close(db->fd);
}
free(db);
return 0;
}
/* NOTE: this function compares with the SIGNED CHAR value of
* the individual characters. This is a pretty bogus sort order,
* but for backwards compatibility reasons we're stuck with it
* for skiplist files at least */
static int compare_signed(const char *s1, int l1, const char *s2, int l2)
{
int min = l1 < l2 ? l1 : l2;
int cmp = 0;
while (min-- > 0 && (cmp = *s1 - *s2) == 0) {
s1++;
s2++;
}
if (min >= 0) return cmp;
if (l1 > l2) return 1;
if (l2 > l1) return -1;
return 0;
}
static int mylock(struct dbengine *db, struct txn **mytid, int flags __attribute__((unused)))
{
return lock_or_refresh(db, mytid);
}
static int myopen(const char *fname, int flags, struct dbengine **ret, struct txn **mytid)
{
struct dbengine *db;
struct db_list *list_ent = open_db;
int r;
while (list_ent && strcmp(list_ent->db->fname, fname)) {
list_ent = list_ent->next;
}
if (list_ent) {
/* we already have this DB open! */
syslog(LOG_NOTICE, "skiplist: %s is already open %d time%s, returning object",
fname, list_ent->refcount, list_ent->refcount == 1 ? "" : "s");
if (list_ent->db->current_txn)
return CYRUSDB_LOCKED;
if (mytid) {
r = lock_or_refresh(list_ent->db, mytid);
if (r) return r;
}
++list_ent->refcount;
*ret = list_ent->db;
return 0;
}
db = (struct dbengine *) xzmalloc(sizeof(struct dbengine));
db->fd = -1;
db->fname = xstrdup(fname);
db->compar = (flags & CYRUSDB_MBOXSORT) ? bsearch_ncompare_mbox : compare_signed;
db->open_flags = (flags & ~CYRUSDB_CREATE);
db->fd = open(fname, O_RDWR, 0644);
if (db->fd == -1 && errno == ENOENT) {
if (!(flags & CYRUSDB_CREATE)) {
dispose_db(db);
return CYRUSDB_NOTFOUND;
}
if (cyrus_mkdir(fname, 0755) == -1) {
dispose_db(db);
return CYRUSDB_IOERROR;
}
db->fd = open(fname, O_RDWR | O_CREAT, 0644);
}
if (db->fd == -1) {
xsyslog(LOG_ERR, "IOERROR: open failed",
"filename=<%s>", fname);
dispose_db(db);
return CYRUSDB_IOERROR;
}
db->curlevel = 0;
db->is_open = 0;
db->lock_status = UNLOCKED;
/* grab a read lock, only reading the header */
r = read_lock(db);
if (r < 0) {
dispose_db(db);
return r;
}
/* if the file is empty, then the header needs to be created first */
if (db->map_size == 0) {
unlock(db);
r = write_lock(db, NULL);
if (r < 0) {
dispose_db(db);
return r;
}
}
/* race condition. Another process may have already got the write
* lock and created the header. Only go ahead if the map_size is
* still zero (read/write_lock updates map_size). */
if (db->map_size == 0) {
/* initialize in memory structure */
db->version = SKIPLIST_VERSION;
db->version_minor = SKIPLIST_VERSION_MINOR;
db->maxlevel = SKIPLIST_MAXLEVEL;
db->curlevel = 1;
db->listsize = 0;
/* where do we start writing new entries? */
db->logstart = DUMMY_OFFSET(db) + DUMMY_SIZE(db);
db->last_recovery = time(NULL);
/* create the header */
r = write_header(db);
if (!r) {
int n;
int dsize = DUMMY_SIZE(db);
uint32_t *buf = (uint32_t *) xzmalloc(dsize);
buf[0] = htonl(DUMMY);
buf[(dsize / 4) - 1] = htonl(-1);
lseek(db->fd, DUMMY_OFFSET(db), SEEK_SET);
n = retry_write(db->fd, (char *) buf, dsize);
if (n != dsize) {
xsyslog(LOG_ERR, "DBERROR: writing dummy node failed",
"filename=<%s>", db->fname);
r = CYRUSDB_IOERROR;
}
free(buf);
}
/* sync the db */
if (!r && DO_FSYNC && (fsync(db->fd) < 0)) {
xsyslog(LOG_ERR, "DBERROR: fsync failed",
"filename=<%s>", db->fname);
r = CYRUSDB_IOERROR;
}
if (r) {
dispose_db(db);
return r;
}
/* map the new file */
db->map_size = db->logstart;
map_refresh(db->fd, 0, &db->map_base, &db->map_len, db->logstart,
db->fname, 0);
}
db->is_open = 1;
r = read_header(db);
if (r) {
dispose_db(db);
return r;
}
/* unlock the db */
unlock(db);
if (!global_recovery || db->last_recovery < global_recovery) {
/* run recovery; we rebooted since the last time recovery
was run */
r = recovery(db, 0);
if (r) {
dispose_db(db);
return r;
}
}
*ret = db;