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/*
Unix SMB/CIFS implementation.
trivial database library
Copyright (C) Andrew Tridgell 1999-2005
Copyright (C) Paul `Rusty' Russell 2000
Copyright (C) Jeremy Allison 2000-2003
** NOTE! The following LGPL license applies to the tdb
** library. This does NOT imply that all of Samba is released
** under the LGPL
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2 of the License, or (at your option) any later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#include "tdb_private.h"
/* a byte range locking function - return 0 on success
this functions locks/unlocks 1 byte at the specified offset.
On error, errno is also set so that errors are passed back properly
through tdb_open(). */
int tdb_brlock(struct tdb_context *tdb, tdb_off_t offset,
int rw_type, int lck_type, int probe)
{
struct flock fl;
int ret;
if (tdb->flags & TDB_NOLOCK)
return 0;
if ((rw_type == F_WRLCK) && (tdb->read_only)) {
errno = EACCES;
return -1;
}
fl.l_type = rw_type;
fl.l_whence = SEEK_SET;
fl.l_start = offset;
fl.l_len = 1;
fl.l_pid = 0;
do {
ret = fcntl(tdb->fd,lck_type,&fl);
} while (ret == -1 && errno == EINTR);
if (ret == -1) {
if (!probe && lck_type != F_SETLK) {
/* Ensure error code is set for log fun to examine. */
tdb->ecode = TDB_ERR_LOCK;
TDB_LOG((tdb, 5,"tdb_brlock failed (fd=%d) at offset %d rw_type=%d lck_type=%d\n",
tdb->fd, offset, rw_type, lck_type));
}
/* Generic lock error. errno set by fcntl.
* EAGAIN is an expected return from non-blocking
* locks. */
if (errno != EAGAIN) {
TDB_LOG((tdb, 5, "tdb_brlock failed (fd=%d) at offset %d rw_type=%d lck_type=%d: %s\n",
tdb->fd, offset, rw_type, lck_type,
strerror(errno)));
}
return TDB_ERRCODE(TDB_ERR_LOCK, -1);
}
return 0;
}
/* lock a list in the database. list -1 is the alloc list */
int tdb_lock(struct tdb_context *tdb, int list, int ltype)
{
if (list < -1 || list >= (int)tdb->header.hash_size) {
TDB_LOG((tdb, 0,"tdb_lock: invalid list %d for ltype=%d\n",
list, ltype));
return -1;
}
if (tdb->flags & TDB_NOLOCK)
return 0;
/* Since fcntl locks don't nest, we do a lock for the first one,
and simply bump the count for future ones */
if (tdb->locked[list+1].count == 0) {
if (tdb_brlock(tdb,FREELIST_TOP+4*list,ltype,F_SETLKW, 0)) {
TDB_LOG((tdb, 0,"tdb_lock failed on list %d ltype=%d (%s)\n",
list, ltype, strerror(errno)));
return -1;
}
tdb->locked[list+1].ltype = ltype;
}
tdb->locked[list+1].count++;
return 0;
}
/* unlock the database: returns void because it's too late for errors. */
/* changed to return int it may be interesting to know there
has been an error --simo */
int tdb_unlock(struct tdb_context *tdb, int list, int ltype)
{
int ret = -1;
if (tdb->flags & TDB_NOLOCK)
return 0;
/* Sanity checks */
if (list < -1 || list >= (int)tdb->header.hash_size) {
TDB_LOG((tdb, 0, "tdb_unlock: list %d invalid (%d)\n", list, tdb->header.hash_size));
return ret;
}
if (tdb->locked[list+1].count==0) {
TDB_LOG((tdb, 0, "tdb_unlock: count is 0\n"));
return ret;
}
if (tdb->locked[list+1].count == 1) {
/* Down to last nested lock: unlock underneath */
ret = tdb_brlock(tdb, FREELIST_TOP+4*list, F_UNLCK, F_SETLKW, 0);
} else {
ret = 0;
}
tdb->locked[list+1].count--;
if (ret)
TDB_LOG((tdb, 0,"tdb_unlock: An error occurred unlocking!\n"));
return ret;
}
/* lock/unlock entire database */
int tdb_lockall(struct tdb_context *tdb)
{
u32 i;
/* There are no locks on read-only dbs */
if (tdb->read_only)
return TDB_ERRCODE(TDB_ERR_LOCK, -1);
for (i = 0; i < tdb->header.hash_size; i++)
if (tdb_lock(tdb, i, F_WRLCK))
break;
/* If error, release locks we have... */
if (i < tdb->header.hash_size) {
u32 j;
for ( j = 0; j < i; j++)
tdb_unlock(tdb, j, F_WRLCK);
return TDB_ERRCODE(TDB_ERR_NOLOCK, -1);
}
return 0;
}
void tdb_unlockall(struct tdb_context *tdb)
{
u32 i;
for (i=0; i < tdb->header.hash_size; i++)
tdb_unlock(tdb, i, F_WRLCK);
}
/* lock/unlock one hash chain. This is meant to be used to reduce
contention - it cannot guarantee how many records will be locked */
int tdb_chainlock(struct tdb_context *tdb, TDB_DATA key)
{
return tdb_lock(tdb, BUCKET(tdb->hash_fn(&key)), F_WRLCK);
}
int tdb_chainunlock(struct tdb_context *tdb, TDB_DATA key)
{
return tdb_unlock(tdb, BUCKET(tdb->hash_fn(&key)), F_WRLCK);
}
int tdb_chainlock_read(struct tdb_context *tdb, TDB_DATA key)
{
return tdb_lock(tdb, BUCKET(tdb->hash_fn(&key)), F_RDLCK);
}
int tdb_chainunlock_read(struct tdb_context *tdb, TDB_DATA key)
{
return tdb_unlock(tdb, BUCKET(tdb->hash_fn(&key)), F_RDLCK);
}
/* record lock stops delete underneath */
int tdb_lock_record(struct tdb_context *tdb, tdb_off_t off)
{
return off ? tdb_brlock(tdb, off, F_RDLCK, F_SETLKW, 0) : 0;
}
/*
Write locks override our own fcntl readlocks, so check it here.
Note this is meant to be F_SETLK, *not* F_SETLKW, as it's not
an error to fail to get the lock here.
*/
int tdb_write_lock_record(struct tdb_context *tdb, tdb_off_t off)
{
struct tdb_traverse_lock *i;
for (i = &tdb->travlocks; i; i = i->next)
if (i->off == off)
return -1;
return tdb_brlock(tdb, off, F_WRLCK, F_SETLK, 1);
}
/*
Note this is meant to be F_SETLK, *not* F_SETLKW, as it's not
an error to fail to get the lock here.
*/
int tdb_write_unlock_record(struct tdb_context *tdb, tdb_off_t off)
{
return tdb_brlock(tdb, off, F_UNLCK, F_SETLK, 0);
}
/* fcntl locks don't stack: avoid unlocking someone else's */
int tdb_unlock_record(struct tdb_context *tdb, tdb_off_t off)
{
struct tdb_traverse_lock *i;
u32 count = 0;
if (off == 0)
return 0;
for (i = &tdb->travlocks; i; i = i->next)
if (i->off == off)
count++;
return (count == 1 ? tdb_brlock(tdb, off, F_UNLCK, F_SETLKW, 0) : 0);
}
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