/* 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 3 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, see <http://www.gnu.org/licenses/>. */ #include "tdb_private.h" void tdb_setalarm_sigptr(struct tdb_context *tdb, volatile sig_atomic_t *ptr) { tdb->interrupt_sig_ptr = ptr; } static int fcntl_lock(struct tdb_context *tdb, int rw, off_t off, off_t len, bool waitflag) { struct flock fl; fl.l_type = rw; fl.l_whence = SEEK_SET; fl.l_start = off; fl.l_len = len; fl.l_pid = 0; if (waitflag) return fcntl(tdb->fd, F_SETLKW, &fl); else return fcntl(tdb->fd, F_SETLK, &fl); } static int fcntl_unlock(struct tdb_context *tdb, int rw, off_t off, off_t len) { struct flock fl; #if 0 /* Check they matched up locks and unlocks correctly. */ char line[80]; FILE *locks; bool found = false; locks = fopen("/proc/locks", "r"); while (fgets(line, 80, locks)) { char *p; int type, start, l; /* eg. 1: FLOCK ADVISORY WRITE 2440 08:01:2180826 0 EOF */ p = strchr(line, ':') + 1; if (strncmp(p, " POSIX ADVISORY ", strlen(" POSIX ADVISORY "))) continue; p += strlen(" FLOCK ADVISORY "); if (strncmp(p, "READ ", strlen("READ ")) == 0) type = F_RDLCK; else if (strncmp(p, "WRITE ", strlen("WRITE ")) == 0) type = F_WRLCK; else abort(); p += 6; if (atoi(p) != getpid()) continue; p = strchr(strchr(p, ' ') + 1, ' ') + 1; start = atoi(p); p = strchr(p, ' ') + 1; if (strncmp(p, "EOF", 3) == 0) l = 0; else l = atoi(p) - start + 1; if (off == start) { if (len != l) { fprintf(stderr, "Len %u should be %u: %s", (int)len, l, line); abort(); } if (type != rw) { fprintf(stderr, "Type %s wrong: %s", rw == F_RDLCK ? "READ" : "WRITE", line); abort(); } found = true; break; } } if (!found) { fprintf(stderr, "Unlock on %u@%u not found!\n", (int)off, (int)len); abort(); } fclose(locks); #endif fl.l_type = F_UNLCK; fl.l_whence = SEEK_SET; fl.l_start = off; fl.l_len = len; fl.l_pid = 0; return fcntl(tdb->fd, F_SETLKW, &fl); } /* list -1 is the alloc list, otherwise a hash chain. */ static tdb_off_t lock_offset(int list) { return FREELIST_TOP + 4*list; } /* 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(). note that a len of zero means lock to end of file */ int tdb_brlock(struct tdb_context *tdb, int rw_type, tdb_off_t offset, size_t len, enum tdb_lock_flags flags) { int ret; if (tdb->flags & TDB_NOLOCK) { return 0; } if (flags & TDB_LOCK_MARK_ONLY) { return 0; } if ((rw_type == F_WRLCK) && (tdb->read_only || tdb->traverse_read)) { tdb->ecode = TDB_ERR_RDONLY; return -1; } /* Sanity check */ if (tdb->transaction && offset >= lock_offset(-1) && len != 0) { tdb->ecode = TDB_ERR_RDONLY; TDB_LOG((tdb, TDB_DEBUG_TRACE, "tdb_brlock attempted in transaction at offset %d rw_type=%d flags=%d len=%d\n", offset, rw_type, flags, (int)len)); return -1; } do { ret = fcntl_lock(tdb, rw_type, offset, len, flags & TDB_LOCK_WAIT); /* Check for a sigalarm break. */ if (ret == -1 && errno == EINTR && tdb->interrupt_sig_ptr && *tdb->interrupt_sig_ptr) { break; } } while (ret == -1 && errno == EINTR); if (ret == -1) { tdb->ecode = TDB_ERR_LOCK; /* Generic lock error. errno set by fcntl. * EAGAIN is an expected return from non-blocking * locks. */ if (!(flags & TDB_LOCK_PROBE) && errno != EAGAIN) { TDB_LOG((tdb, TDB_DEBUG_TRACE,"tdb_brlock failed (fd=%d) at offset %d rw_type=%d flags=%d len=%d\n", tdb->fd, offset, rw_type, flags, (int)len)); } return -1; } return 0; } int tdb_brunlock(struct tdb_context *tdb, int rw_type, tdb_off_t offset, size_t len) { int ret; if (tdb->flags & TDB_NOLOCK) { return 0; } do { ret = fcntl_unlock(tdb, rw_type, offset, len); } while (ret == -1 && errno == EINTR); if (ret == -1) { TDB_LOG((tdb, TDB_DEBUG_TRACE,"tdb_brunlock failed (fd=%d) at offset %d rw_type=%d len=%d\n", tdb->fd, offset, rw_type, (int)len)); } return ret; } /* upgrade a read lock to a write lock. This needs to be handled in a special way as some OSes (such as solaris) have too conservative deadlock detection and claim a deadlock when progress can be made. For those OSes we may loop for a while. */ int tdb_allrecord_upgrade(struct tdb_context *tdb) { int count = 1000; if (tdb->allrecord_lock.count != 1) { TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_allrecord_upgrade failed: count %u too high\n", tdb->allrecord_lock.count)); return -1; } if (tdb->allrecord_lock.off != 1) { TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_allrecord_upgrade failed: already upgraded?\n")); return -1; } while (count--) { struct timeval tv; if (tdb_brlock(tdb, F_WRLCK, FREELIST_TOP, 0, TDB_LOCK_WAIT|TDB_LOCK_PROBE) == 0) { tdb->allrecord_lock.ltype = F_WRLCK; tdb->allrecord_lock.off = 0; return 0; } if (errno != EDEADLK) { break; } /* sleep for as short a time as we can - more portable than usleep() */ tv.tv_sec = 0; tv.tv_usec = 1; select(0, NULL, NULL, NULL, &tv); } TDB_LOG((tdb, TDB_DEBUG_TRACE,"tdb_allrecord_upgrade failed\n")); return -1; } static struct tdb_lock_type *find_nestlock(struct tdb_context *tdb, tdb_off_t offset) { unsigned int i; for (i=0; i<tdb->num_lockrecs; i++) { if (tdb->lockrecs[i].off == offset) { return &tdb->lockrecs[i]; } } return NULL; } /* lock an offset in the database. */ int tdb_nest_lock(struct tdb_context *tdb, uint32_t offset, int ltype, enum tdb_lock_flags flags) { struct tdb_lock_type *new_lck; if (offset >= lock_offset(tdb->header.hash_size)) { tdb->ecode = TDB_ERR_LOCK; TDB_LOG((tdb, TDB_DEBUG_ERROR,"tdb_lock: invalid offset %u for ltype=%d\n", offset, ltype)); return -1; } if (tdb->flags & TDB_NOLOCK) return 0; new_lck = find_nestlock(tdb, offset); if (new_lck) { /* * Just increment the in-memory struct, posix locks * don't stack. */ new_lck->count++; return 0; } new_lck = (struct tdb_lock_type *)realloc( tdb->lockrecs, sizeof(*tdb->lockrecs) * (tdb->num_lockrecs+1)); if (new_lck == NULL) { errno = ENOMEM; return -1; } tdb->lockrecs = new_lck; /* Since fcntl locks don't nest, we do a lock for the first one, and simply bump the count for future ones */ if (tdb_brlock(tdb, ltype, offset, 1, flags)) { return -1; } tdb->lockrecs[tdb->num_lockrecs].off = offset; tdb->lockrecs[tdb->num_lockrecs].count = 1; tdb->lockrecs[tdb->num_lockrecs].ltype = ltype; tdb->num_lockrecs++; return 0; } static int tdb_lock_and_recover(struct tdb_context *tdb) { int ret; /* We need to match locking order in transaction commit. */ if (tdb_brlock(tdb, F_WRLCK, FREELIST_TOP, 0, TDB_LOCK_WAIT)) { return -1; } if (tdb_brlock(tdb, F_WRLCK, OPEN_LOCK, 1, TDB_LOCK_WAIT)) { tdb_brunlock(tdb, F_WRLCK, FREELIST_TOP, 0); return -1; } ret = tdb_transaction_recover(tdb); tdb_brunlock(tdb, F_WRLCK, OPEN_LOCK, 1); tdb_brunlock(tdb, F_WRLCK, FREELIST_TOP, 0); return ret; } static bool have_data_locks(const struct tdb_context *tdb) { unsigned int i; for (i = 0; i < tdb->num_lockrecs; i++) { if (tdb->lockrecs[i].off >= lock_offset(-1)) return true; } return false; } static int tdb_lock_list(struct tdb_context *tdb, int list, int ltype, enum tdb_lock_flags waitflag) { int ret; bool check = false; /* a allrecord lock allows us to avoid per chain locks */ if (tdb->allrecord_lock.count && (ltype == tdb->allrecord_lock.ltype || ltype == F_RDLCK)) { return 0; } if (tdb->allrecord_lock.count) { tdb->ecode = TDB_ERR_LOCK; ret = -1; } else { /* Only check when we grab first data lock. */ check = !have_data_locks(tdb); ret = tdb_nest_lock(tdb, lock_offset(list), ltype, waitflag); if (ret == 0 && check && tdb_needs_recovery(tdb)) { tdb_nest_unlock(tdb, lock_offset(list), ltype, false); if (tdb_lock_and_recover(tdb) == -1) { return -1; } return tdb_lock_list(tdb, list, ltype, waitflag); } } return ret; } /* lock a list in the database. list -1 is the alloc list */ int tdb_lock(struct tdb_context *tdb, int list, int ltype) { int ret; ret = tdb_lock_list(tdb, list, ltype, TDB_LOCK_WAIT); if (ret) { TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_lock failed on list %d " "ltype=%d (%s)\n", list, ltype, strerror(errno))); } return ret; } /* lock a list in the database. list -1 is the alloc list. non-blocking lock */ int tdb_lock_nonblock(struct tdb_context *tdb, int list, int ltype) { return tdb_lock_list(tdb, list, ltype, TDB_LOCK_NOWAIT); } int tdb_nest_unlock(struct tdb_context *tdb, uint32_t offset, int ltype, bool mark_lock) { int ret = -1; struct tdb_lock_type *lck; if (tdb->flags & TDB_NOLOCK) return 0; /* Sanity checks */ if (offset >= lock_offset(tdb->header.hash_size)) { TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_unlock: offset %u invalid (%d)\n", offset, tdb->header.hash_size)); return ret; } lck = find_nestlock(tdb, offset); if ((lck == NULL) || (lck->count == 0)) { TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_unlock: count is 0\n")); return -1; } if (lck->count > 1) { lck->count--; return 0; } /* * This lock has count==1 left, so we need to unlock it in the * kernel. We don't bother with decrementing the in-memory array * element, we're about to overwrite it with the last array element * anyway. */ if (mark_lock) { ret = 0; } else { ret = tdb_brunlock(tdb, ltype, offset, 1); } /* * Shrink the array by overwriting the element just unlocked with the * last array element. */ *lck = tdb->lockrecs[--tdb->num_lockrecs]; /* * We don't bother with realloc when the array shrinks, but if we have * a completely idle tdb we should get rid of the locked array. */ if (tdb->num_lockrecs == 0) { SAFE_FREE(tdb->lockrecs); } if (ret) TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_unlock: An error occurred unlocking!\n")); return ret; } int tdb_unlock(struct tdb_context *tdb, int list, int ltype) { /* a global lock allows us to avoid per chain locks */ if (tdb->allrecord_lock.count && (ltype == tdb->allrecord_lock.ltype || ltype == F_RDLCK)) { return 0; } if (tdb->allrecord_lock.count) { tdb->ecode = TDB_ERR_LOCK; return -1; } return tdb_nest_unlock(tdb, lock_offset(list), ltype, false); } /* get the transaction lock */ int tdb_transaction_lock(struct tdb_context *tdb, int ltype, enum tdb_lock_flags lockflags) { return tdb_nest_lock(tdb, TRANSACTION_LOCK, ltype, lockflags); } /* release the transaction lock */ int tdb_transaction_unlock(struct tdb_context *tdb, int ltype) { return tdb_nest_unlock(tdb, TRANSACTION_LOCK, ltype, false); } /* lock/unlock entire database. It can only be upgradable if you have some * other way of guaranteeing exclusivity (ie. transaction write lock). */ int tdb_allrecord_lock(struct tdb_context *tdb, int ltype, enum tdb_lock_flags flags, bool upgradable) { /* There are no locks on read-only dbs */ if (tdb->read_only || tdb->traverse_read) { tdb->ecode = TDB_ERR_LOCK; return -1; } if (tdb->allrecord_lock.count && tdb->allrecord_lock.ltype == ltype) { tdb->allrecord_lock.count++; return 0; } if (tdb->allrecord_lock.count) { /* a global lock of a different type exists */ tdb->ecode = TDB_ERR_LOCK; return -1; } if (tdb_have_extra_locks(tdb)) { /* can't combine global and chain locks */ tdb->ecode = TDB_ERR_LOCK; return -1; } if (upgradable && ltype != F_RDLCK) { /* tdb error: you can't upgrade a write lock! */ tdb->ecode = TDB_ERR_LOCK; return -1; } if (tdb_brlock(tdb, ltype, FREELIST_TOP, 0, flags)) { if (flags & TDB_LOCK_WAIT) { TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_lockall failed (%s)\n", strerror(errno))); } return -1; } tdb->allrecord_lock.count = 1; /* If it's upgradable, it's actually exclusive so we can treat * it as a write lock. */ tdb->allrecord_lock.ltype = upgradable ? F_WRLCK : ltype; tdb->allrecord_lock.off = upgradable; if (tdb_needs_recovery(tdb)) { bool mark = flags & TDB_LOCK_MARK_ONLY; tdb_allrecord_unlock(tdb, ltype, mark); if (mark) { tdb->ecode = TDB_ERR_LOCK; TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_lockall_mark cannot do recovery\n")); return -1; } if (tdb_lock_and_recover(tdb) == -1) { return -1; } return tdb_allrecord_lock(tdb, ltype, flags, upgradable); } return 0; } /* unlock entire db */ int tdb_allrecord_unlock(struct tdb_context *tdb, int ltype, bool mark_lock) { /* There are no locks on read-only dbs */ if (tdb->read_only || tdb->traverse_read) { tdb->ecode = TDB_ERR_LOCK; return -1; } if (tdb->allrecord_lock.count == 0) { tdb->ecode = TDB_ERR_LOCK; return -1; } /* Upgradable locks are marked as write locks. */ if (tdb->allrecord_lock.ltype != ltype && (!tdb->allrecord_lock.off || ltype != F_RDLCK)) { tdb->ecode = TDB_ERR_LOCK; return -1; } if (tdb->allrecord_lock.count > 1) { tdb->allrecord_lock.count--; return 0; } if (!mark_lock && tdb_brunlock(tdb, ltype, FREELIST_TOP, 0)) { TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_unlockall failed (%s)\n", strerror(errno))); return -1; } tdb->allrecord_lock.count = 0; tdb->allrecord_lock.ltype = 0; return 0; } /* lock entire database with write lock */ int tdb_lockall(struct tdb_context *tdb) { tdb_trace(tdb, "tdb_lockall"); return tdb_allrecord_lock(tdb, F_WRLCK, TDB_LOCK_WAIT, false); } /* lock entire database with write lock - mark only */ int tdb_lockall_mark(struct tdb_context *tdb) { tdb_trace(tdb, "tdb_lockall_mark"); return tdb_allrecord_lock(tdb, F_WRLCK, TDB_LOCK_MARK_ONLY, false); } /* unlock entire database with write lock - unmark only */ int tdb_lockall_unmark(struct tdb_context *tdb) { tdb_trace(tdb, "tdb_lockall_unmark"); return tdb_allrecord_unlock(tdb, F_WRLCK, true); } /* lock entire database with write lock - nonblocking varient */ int tdb_lockall_nonblock(struct tdb_context *tdb) { int ret = tdb_allrecord_lock(tdb, F_WRLCK, TDB_LOCK_NOWAIT, false); tdb_trace_ret(tdb, "tdb_lockall_nonblock", ret); return ret; } /* unlock entire database with write lock */ int tdb_unlockall(struct tdb_context *tdb) { tdb_trace(tdb, "tdb_unlockall"); return tdb_allrecord_unlock(tdb, F_WRLCK, false); } /* lock entire database with read lock */ int tdb_lockall_read(struct tdb_context *tdb) { tdb_trace(tdb, "tdb_lockall_read"); return tdb_allrecord_lock(tdb, F_RDLCK, TDB_LOCK_WAIT, false); } /* lock entire database with read lock - nonblock varient */ int tdb_lockall_read_nonblock(struct tdb_context *tdb) { int ret = tdb_allrecord_lock(tdb, F_RDLCK, TDB_LOCK_NOWAIT, false); tdb_trace_ret(tdb, "tdb_lockall_read_nonblock", ret); return ret; } /* unlock entire database with read lock */ int tdb_unlockall_read(struct tdb_context *tdb) { tdb_trace(tdb, "tdb_unlockall_read"); return tdb_allrecord_unlock(tdb, F_RDLCK, false); } /* 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) { int ret = tdb_lock(tdb, BUCKET(tdb->hash_fn(&key)), F_WRLCK); tdb_trace_1rec(tdb, "tdb_chainlock", key); return ret; } /* lock/unlock one hash chain, non-blocking. This is meant to be used to reduce contention - it cannot guarantee how many records will be locked */ int tdb_chainlock_nonblock(struct tdb_context *tdb, TDB_DATA key) { int ret = tdb_lock_nonblock(tdb, BUCKET(tdb->hash_fn(&key)), F_WRLCK); tdb_trace_1rec_ret(tdb, "tdb_chainlock_nonblock", key, ret); return ret; } /* mark a chain as locked without actually locking it. Warning! use with great caution! */ int tdb_chainlock_mark(struct tdb_context *tdb, TDB_DATA key) { int ret = tdb_nest_lock(tdb, lock_offset(BUCKET(tdb->hash_fn(&key))), F_WRLCK, TDB_LOCK_MARK_ONLY); tdb_trace_1rec(tdb, "tdb_chainlock_mark", key); return ret; } /* unmark a chain as locked without actually locking it. Warning! use with great caution! */ int tdb_chainlock_unmark(struct tdb_context *tdb, TDB_DATA key) { tdb_trace_1rec(tdb, "tdb_chainlock_unmark", key); return tdb_nest_unlock(tdb, lock_offset(BUCKET(tdb->hash_fn(&key))), F_WRLCK, true); } int tdb_chainunlock(struct tdb_context *tdb, TDB_DATA key) { tdb_trace_1rec(tdb, "tdb_chainunlock", key); return tdb_unlock(tdb, BUCKET(tdb->hash_fn(&key)), F_WRLCK); } int tdb_chainlock_read(struct tdb_context *tdb, TDB_DATA key) { int ret; ret = tdb_lock(tdb, BUCKET(tdb->hash_fn(&key)), F_RDLCK); tdb_trace_1rec(tdb, "tdb_chainlock_read", key); return ret; } int tdb_chainunlock_read(struct tdb_context *tdb, TDB_DATA key) { tdb_trace_1rec(tdb, "tdb_chainunlock_read", 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) { if (tdb->allrecord_lock.count) { return 0; } return off ? tdb_brlock(tdb, F_RDLCK, off, 1, TDB_LOCK_WAIT) : 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; if (tdb->allrecord_lock.count) { if (tdb->allrecord_lock.ltype == F_WRLCK) { return 0; } return -1; } return tdb_brlock(tdb, F_WRLCK, off, 1, TDB_LOCK_NOWAIT|TDB_LOCK_PROBE); } int tdb_write_unlock_record(struct tdb_context *tdb, tdb_off_t off) { if (tdb->allrecord_lock.count) { return 0; } return tdb_brunlock(tdb, F_WRLCK, off, 1); } /* 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; uint32_t count = 0; if (tdb->allrecord_lock.count) { return 0; } if (off == 0) return 0; for (i = &tdb->travlocks; i; i = i->next) if (i->off == off) count++; return (count == 1 ? tdb_brunlock(tdb, F_RDLCK, off, 1) : 0); } bool tdb_have_extra_locks(struct tdb_context *tdb) { unsigned int extra = tdb->num_lockrecs; /* A transaction holds the lock for all records. */ if (!tdb->transaction && tdb->allrecord_lock.count) { return true; } /* We always hold the active lock if CLEAR_IF_FIRST. */ if (find_nestlock(tdb, ACTIVE_LOCK)) { extra--; } /* In a transaction, we expect to hold the transaction lock */ if (tdb->transaction && find_nestlock(tdb, TRANSACTION_LOCK)) { extra--; } return extra; } /* The transaction code uses this to remove all locks. */ void tdb_release_transaction_locks(struct tdb_context *tdb) { unsigned int i, active = 0; if (tdb->allrecord_lock.count != 0) { tdb_brunlock(tdb, tdb->allrecord_lock.ltype, FREELIST_TOP, 0); tdb->allrecord_lock.count = 0; } for (i=0;i<tdb->num_lockrecs;i++) { struct tdb_lock_type *lck = &tdb->lockrecs[i]; /* Don't release the active lock! Copy it to first entry. */ if (lck->off == ACTIVE_LOCK) { tdb->lockrecs[active++] = *lck; } else { tdb_brunlock(tdb, lck->ltype, lck->off, 1); } } tdb->num_lockrecs = active; if (tdb->num_lockrecs == 0) { SAFE_FREE(tdb->lockrecs); } }