X-Git-Url: http://git.ozlabs.org/?p=ccan;a=blobdiff_plain;f=ccan%2Ftdb%2Flock.c;h=dfcac7a540adc30482dcd86e0c299b36bfb52e0b;hp=2a681efc9963afa9e2e3db7b7122f7e7beb3c65e;hb=448b9194f76a138eef05047b1aaa5d211f72e97f;hpb=f4ed21278307cb2af87f811c3f509d11a4221d2f diff --git a/ccan/tdb/lock.c b/ccan/tdb/lock.c index 2a681efc..dfcac7a5 100644 --- a/ccan/tdb/lock.c +++ b/ccan/tdb/lock.c @@ -119,6 +119,12 @@ static int fcntl_unlock(struct tdb_context *tdb, int rw, off_t off, off_t len) 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. @@ -234,12 +240,6 @@ int tdb_allrecord_upgrade(struct tdb_context *tdb) return -1; } -/* list -1 is the alloc list, otherwise a hash chain. */ -static tdb_off_t lock_offset(int list) -{ - return FREELIST_TOP + 4*list; -} - static struct tdb_lock_type *find_nestlock(struct tdb_context *tdb, tdb_off_t offset) { @@ -289,7 +289,7 @@ int tdb_nest_lock(struct tdb_context *tdb, uint32_t offset, int ltype, /* Since fcntl locks don't nest, we do a lock for the first one, and simply bump the count for future ones */ - if (tdb->methods->brlock(tdb, ltype, offset, 1, flags)) { + if (tdb_brlock(tdb, ltype, offset, 1, flags)) { return -1; } @@ -301,10 +301,44 @@ int tdb_nest_lock(struct tdb_context *tdb, uint32_t offset, int ltype, 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) +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 && @@ -316,9 +350,28 @@ int tdb_lock(struct tdb_context *tdb, int list, int ltype) tdb->ecode = TDB_ERR_LOCK; ret = -1; } else { - ret = tdb_nest_lock(tdb, lock_offset(list), ltype, - TDB_LOCK_WAIT); + /* 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))); @@ -329,18 +382,7 @@ int tdb_lock(struct tdb_context *tdb, int list, int ltype) /* 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) { - /* 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; - return -1; - } - - return tdb_nest_lock(tdb, lock_offset(list), ltype, TDB_LOCK_NOWAIT); + return tdb_lock_list(tdb, list, ltype, TDB_LOCK_NOWAIT); } @@ -380,7 +422,7 @@ int tdb_nest_unlock(struct tdb_context *tdb, uint32_t offset, int ltype, if (mark_lock) { ret = 0; } else { - ret = tdb->methods->brunlock(tdb, ltype, offset, 1); + ret = tdb_brunlock(tdb, ltype, offset, 1); } /* @@ -435,11 +477,9 @@ 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) +/* 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) { @@ -469,11 +509,73 @@ int tdb_allrecord_lock(struct tdb_context *tdb, int ltype, tdb->ecode = TDB_ERR_LOCK; return -1; } + return 1; +} - if (tdb->methods->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))); - } +/* 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) +{ + 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. + * 3) 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_chainlock_gradual(tdb, ltype, flags, FREELIST_TOP, + tdb->header.hash_size * 4) == -1) { + return -1; + } + + /* Grab individual record locks. */ + if (tdb_brlock(tdb, ltype, lock_offset(tdb->header.hash_size), 0, + flags) == -1) { + tdb_brunlock(tdb, ltype, FREELIST_TOP, + tdb->header.hash_size * 4); return -1; } @@ -483,6 +585,21 @@ int tdb_allrecord_lock(struct tdb_context *tdb, int ltype, 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; } @@ -514,8 +631,7 @@ int tdb_allrecord_unlock(struct tdb_context *tdb, int ltype, bool mark_lock) return 0; } - if (!mark_lock && - tdb->methods->brunlock(tdb, ltype, FREELIST_TOP, 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; } @@ -648,7 +764,7 @@ int tdb_lock_record(struct tdb_context *tdb, tdb_off_t off) if (tdb->allrecord_lock.count) { return 0; } - return off ? tdb->methods->brlock(tdb, F_RDLCK, off, 1, TDB_LOCK_WAIT) : 0; + return off ? tdb_brlock(tdb, F_RDLCK, off, 1, TDB_LOCK_WAIT) : 0; } /* @@ -668,7 +784,7 @@ int tdb_write_lock_record(struct tdb_context *tdb, tdb_off_t off) } return -1; } - return tdb->methods->brlock(tdb, F_WRLCK, off, 1, TDB_LOCK_NOWAIT|TDB_LOCK_PROBE); + 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) @@ -676,7 +792,7 @@ int tdb_write_unlock_record(struct tdb_context *tdb, tdb_off_t off) if (tdb->allrecord_lock.count) { return 0; } - return tdb->methods->brunlock(tdb, F_WRLCK, off, 1); + return tdb_brunlock(tdb, F_WRLCK, off, 1); } /* fcntl locks don't stack: avoid unlocking someone else's */ @@ -694,7 +810,7 @@ int tdb_unlock_record(struct tdb_context *tdb, tdb_off_t off) for (i = &tdb->travlocks; i; i = i->next) if (i->off == off) count++; - return (count == 1 ? tdb->methods->brunlock(tdb, F_RDLCK, off, 1) : 0); + return (count == 1 ? tdb_brunlock(tdb, F_RDLCK, off, 1) : 0); } bool tdb_have_extra_locks(struct tdb_context *tdb)