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Diffstat (limited to '')
| -rw-r--r-- | lib/tdb/common/lock.c | 1033 |
1 files changed, 1033 insertions, 0 deletions
diff --git a/lib/tdb/common/lock.c b/lib/tdb/common/lock.c new file mode 100644 index 0000000..c4e276f --- /dev/null +++ b/lib/tdb/common/lock.c @@ -0,0 +1,1033 @@ + /* + 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" + +_PUBLIC_ 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; + int cmd; + +#ifdef USE_TDB_MUTEX_LOCKING + { + int ret; + if (tdb_mutex_lock(tdb, rw, off, len, waitflag, &ret)) { + return ret; + } + } +#endif + + fl.l_type = rw; + fl.l_whence = SEEK_SET; + fl.l_start = off; + fl.l_len = len; + fl.l_pid = 0; + + cmd = waitflag ? F_SETLKW : F_SETLK; + + return fcntl(tdb->fd, cmd, &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 + +#ifdef USE_TDB_MUTEX_LOCKING + { + int ret; + if (tdb_mutex_unlock(tdb, rw, off, len, &ret)) { + return ret; + } + } +#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); +} + +/* + * Calculate the lock offset for a list + * + * list -1 is the freelist, otherwise a hash chain. + * + * Note that we consistently (but without real reason) lock hash chains at an + * offset that is 4 bytes below the real offset of the corresponding list head + * in the db. + * + * This is the memory layout of the hashchain array: + * + * FREELIST_TOP + 0 = freelist + * FREELIST_TOP + 4 = hashtable list 0 + * FREELIST_TOP + 8 = hashtable list 1 + * ... + * + * Otoh lock_offset computes: + * + * freelist = FREELIST_TOP - 4 + * list 0 = FREELIST_TOP + 0 + * list 1 = FREELIST_TOP + 4 + * ... + * + * Unfortunately we can't change this calculation in order to align the locking + * offset with the memory layout, as that would make the locking incompatible + * between different tdb versions. + */ +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 "len" 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; + } + + 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 %u rw_type=%d flags=%d len=%zu\n", + tdb->fd, offset, rw_type, flags, 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 %u rw_type=%u len=%zu\n", + tdb->fd, offset, rw_type, len)); + } + return ret; +} + +/* + * Do a tdb_brlock in a loop. 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. + */ + +static int tdb_brlock_retry(struct tdb_context *tdb, + int rw_type, tdb_off_t offset, size_t len, + enum tdb_lock_flags flags) +{ + int count = 1000; + + while (count--) { + struct timeval tv; + int ret; + + ret = tdb_brlock(tdb, rw_type, offset, len, flags); + if (ret == 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); + } + return -1; +} + +/* + upgrade a read lock to a write lock. +*/ +int tdb_allrecord_upgrade(struct tdb_context *tdb) +{ + int ret; + + 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)); + tdb->ecode = TDB_ERR_LOCK; + return -1; + } + + if (tdb->allrecord_lock.off != 1) { + TDB_LOG((tdb, TDB_DEBUG_ERROR, + "tdb_allrecord_upgrade failed: already upgraded?\n")); + tdb->ecode = TDB_ERR_LOCK; + return -1; + } + + if (tdb_have_mutexes(tdb)) { + ret = tdb_mutex_allrecord_upgrade(tdb); + if (ret == -1) { + goto fail; + } + ret = tdb_brlock_retry(tdb, F_WRLCK, lock_offset(tdb->hash_size), + 0, TDB_LOCK_WAIT|TDB_LOCK_PROBE); + if (ret == -1) { + tdb_mutex_allrecord_downgrade(tdb); + } + } else { + ret = tdb_brlock_retry(tdb, F_WRLCK, FREELIST_TOP, 0, + TDB_LOCK_WAIT|TDB_LOCK_PROBE); + } + + if (ret == 0) { + tdb->allrecord_lock.ltype = F_WRLCK; + tdb->allrecord_lock.off = 0; + return 0; + } +fail: + 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) +{ + 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->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) { + if ((new_lck->ltype == F_RDLCK) && (ltype == F_WRLCK)) { + if (!tdb_have_mutexes(tdb)) { + int ret; + /* + * Upgrade the underlying fcntl + * lock. Mutexes don't do readlocks, + * so this only applies to fcntl + * locking. + */ + ret = tdb_brlock(tdb, ltype, offset, 1, flags); + if (ret != 0) { + return ret; + } + } + new_lck->ltype = F_WRLCK; + } + /* + * Just increment the in-memory struct, posix locks + * don't stack. + */ + new_lck->count++; + return 0; + } + + if (tdb->num_lockrecs == tdb->lockrecs_array_length) { + 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_array_length = tdb->num_lockrecs+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; + } + + new_lck = &tdb->lockrecs[tdb->num_lockrecs]; + + new_lck->off = offset; + new_lck->count = 1; + new_lck->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) +{ + int i; + + for (i = 0; i < tdb->num_lockrecs; i++) { + if (tdb->lockrecs[i].off >= lock_offset(-1)) + return true; + } + return false; +} + +/* + * A allrecord lock allows us to avoid per chain locks. Check if the allrecord + * lock is strong enough. + */ +static int tdb_lock_covered_by_allrecord_lock(struct tdb_context *tdb, + int ltype) +{ + if (ltype == F_RDLCK) { + /* + * The allrecord_lock is equal (F_RDLCK) or stronger + * (F_WRLCK). Pass. + */ + return 0; + } + + if (tdb->allrecord_lock.ltype == F_RDLCK) { + /* + * We ask for ltype==F_WRLCK, but the allrecord_lock + * is too weak. We can't upgrade here, so fail. + */ + tdb->ecode = TDB_ERR_LOCK; + return -1; + } + + /* + * Asking for F_WRLCK, allrecord is F_WRLCK as well. Pass. + */ + return 0; +} + +static int tdb_lock_list(struct tdb_context *tdb, int list, int ltype, + enum tdb_lock_flags waitflag) +{ + int ret; + bool check = false; + + if (tdb->allrecord_lock.count) { + return tdb_lock_covered_by_allrecord_lock(tdb, ltype); + } + + /* + * Check for recoveries: Someone might have kill -9'ed a process + * during a commit. + */ + 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 */ +_PUBLIC_ int tdb_lock_nonblock(struct tdb_context *tdb, int list, int ltype); +_PUBLIC_ 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->hash_size)) { + TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_unlock: offset %u invalid (%d)\n", offset, tdb->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 (ret) + TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_unlock: An error occurred unlocking!\n")); + return ret; +} + +_PUBLIC_ int tdb_unlock(struct tdb_context *tdb, int list, int ltype); +_PUBLIC_ 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) { + return tdb_lock_covered_by_allrecord_lock(tdb, ltype); + } + + 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); +} + +/* Returns 0 if all done, -1 if error, 1 if ok. */ +static int tdb_allrecord_check(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 == (uint32_t)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; + } + return 1; +} + +/* We only need to lock individual bytes, but Linux merges consecutive locks + * so we lock in contiguous ranges. */ +static int tdb_chainlock_gradual(struct tdb_context *tdb, + int ltype, enum tdb_lock_flags flags, + size_t off, size_t len) +{ + int ret; + enum tdb_lock_flags nb_flags = (flags & ~TDB_LOCK_WAIT); + + if (len <= 4) { + /* Single record. Just do blocking lock. */ + return tdb_brlock(tdb, ltype, off, len, flags); + } + + /* First we try non-blocking. */ + ret = tdb_brlock(tdb, ltype, off, len, nb_flags); + if (ret == 0) { + return 0; + } + + /* Try locking first half, then second. */ + ret = tdb_chainlock_gradual(tdb, ltype, flags, off, len / 2); + if (ret == -1) + return -1; + + ret = tdb_chainlock_gradual(tdb, ltype, flags, + off + len / 2, len - len / 2); + if (ret == -1) { + tdb_brunlock(tdb, ltype, off, len / 2); + return -1; + } + return 0; +} + +/* lock/unlock entire database. It can only be upgradable if you have some + * other way of guaranteeing exclusivity (ie. transaction write lock). + * We do the locking gradually to avoid being starved by smaller locks. */ +int tdb_allrecord_lock(struct tdb_context *tdb, int ltype, + enum tdb_lock_flags flags, bool upgradable) +{ + int ret; + + switch (tdb_allrecord_check(tdb, ltype, flags, upgradable)) { + case -1: + return -1; + case 0: + return 0; + } + + /* We cover two kinds of locks: + * 1) Normal chain locks. Taken for almost all operations. + * 2) Individual records locks. Taken after normal or free + * chain locks. + * + * It is (1) which cause the starvation problem, so we're only + * gradual for that. */ + + if (tdb_have_mutexes(tdb)) { + ret = tdb_mutex_allrecord_lock(tdb, ltype, flags); + } else { + ret = tdb_chainlock_gradual(tdb, ltype, flags, FREELIST_TOP, + tdb->hash_size * 4); + } + + if (ret == -1) { + return -1; + } + + /* Grab individual record locks. */ + if (tdb_brlock(tdb, ltype, lock_offset(tdb->hash_size), 0, + flags) == -1) { + if (tdb_have_mutexes(tdb)) { + tdb_mutex_allrecord_unlock(tdb); + } else { + tdb_brunlock(tdb, ltype, FREELIST_TOP, + tdb->hash_size * 4); + } + 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 != (uint32_t)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) { + int ret; + + if (tdb_have_mutexes(tdb)) { + ret = tdb_mutex_allrecord_unlock(tdb); + if (ret == 0) { + ret = tdb_brunlock(tdb, ltype, + lock_offset(tdb->hash_size), + 0); + } + } else { + ret = tdb_brunlock(tdb, ltype, FREELIST_TOP, 0); + } + + if (ret != 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 */ +_PUBLIC_ 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 */ +_PUBLIC_ 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 */ +_PUBLIC_ 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 */ +_PUBLIC_ 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 */ +_PUBLIC_ 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 */ +_PUBLIC_ 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 */ +_PUBLIC_ 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 */ +_PUBLIC_ 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 */ +_PUBLIC_ 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 */ +_PUBLIC_ 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! */ +_PUBLIC_ 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! */ +_PUBLIC_ 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); +} + +_PUBLIC_ 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); +} + +_PUBLIC_ 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; +} + +_PUBLIC_ 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); +} + +_PUBLIC_ int tdb_chainlock_read_nonblock(struct tdb_context *tdb, TDB_DATA key) +{ + int ret = tdb_lock_nonblock(tdb, BUCKET(tdb->hash_fn(&key)), F_RDLCK); + tdb_trace_1rec_ret(tdb, "tdb_chainlock_read_nonblock", key, ret); + return ret; +} + +/* 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; + if (tdb == NULL) { + return -1; + } + 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) +{ + int i; + unsigned int active = 0; + + if (tdb->allrecord_lock.count != 0) { + tdb_allrecord_unlock(tdb, tdb->allrecord_lock.ltype, false); + 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; +} + +/* Following functions are added specifically to support CTDB. */ + +/* Don't do actual fcntl locking, just mark tdb locked */ +_PUBLIC_ int tdb_transaction_write_lock_mark(struct tdb_context *tdb); +_PUBLIC_ int tdb_transaction_write_lock_mark(struct tdb_context *tdb) +{ + return tdb_transaction_lock(tdb, F_WRLCK, TDB_LOCK_MARK_ONLY); +} + +/* Don't do actual fcntl unlocking, just mark tdb unlocked */ +_PUBLIC_ int tdb_transaction_write_lock_unmark(struct tdb_context *tdb); +_PUBLIC_ int tdb_transaction_write_lock_unmark(struct tdb_context *tdb) +{ + return tdb_nest_unlock(tdb, TRANSACTION_LOCK, F_WRLCK, true); +} |