X-Git-Url: http://git.ozlabs.org/?p=ccan;a=blobdiff_plain;f=ccan%2Ftdb%2Ftransaction.c;h=ded3fa836fc721a07932c54a6f741b89c8329066;hp=e8b0e6856110a401d89a93c9e1336bb6acb5190f;hb=e9989ef0758b3b660abf444d014c5b51a3a7c1b4;hpb=03d4aa56b8bd381db449b36befa6928594cea994 diff --git a/ccan/tdb/transaction.c b/ccan/tdb/transaction.c index e8b0e685..ded3fa83 100644 --- a/ccan/tdb/transaction.c +++ b/ccan/tdb/transaction.c @@ -76,7 +76,7 @@ to reduce this to 3 or even 2 with some more work. - check for a valid recovery record on open of the tdb, while the - global lock is held. Automatically recover from the transaction + open lock is held. Automatically recover from the transaction recovery area if needed, then continue with the open as usual. This allows for smooth crash recovery with no administrator intervention. @@ -86,12 +86,20 @@ fsync/msync calls are made. - if TDB_ALLOW_NESTING is passed to flags in tdb open, or added using - tdb_add_flags() transaction is enabled. - The default is that transaction nesting is not allowed and an attempt - to create a nested transaction will fail with TDB_ERR_NESTING. + tdb_add_flags() transaction nesting is enabled. + It resets the TDB_DISALLOW_NESTING flag, as both cannot be used together. + The default is that transaction nesting is allowed. + Note: this default may change in future versions of tdb. Beware. when transactions are nested a transaction successfully completed with tdb_transaction_commit() can be silently unrolled later. + + - if TDB_DISALLOW_NESTING is passed to flags in tdb open, or added using + tdb_add_flags() transaction nesting is disabled. + It resets the TDB_ALLOW_NESTING flag, as both cannot be used together. + An attempt create a nested transaction will fail with TDB_ERR_NESTING. + The default is that transaction nesting is allowed. + Note: this default may change in future versions of tdb. */ @@ -407,6 +415,9 @@ static int transaction_brlock(struct tdb_context *tdb, int rw_type, tdb_off_t offset, size_t len, enum tdb_lock_flags flags) { + /* FIXME: We actually grab the open lock during a transaction. */ + if (offset == OPEN_LOCK) + return tdb_brlock(tdb, rw_type, offset, len, flags); return 0; } @@ -483,33 +494,18 @@ int _tdb_transaction_cancel(struct tdb_context *tdb, int ltype) if (tdb->transaction->magic_offset) { const struct tdb_methods *methods = tdb->transaction->io_methods; - uint32_t zero = 0; + uint32_t invalid = TDB_RECOVERY_INVALID_MAGIC; /* remove the recovery marker */ - if (methods->tdb_write(tdb, tdb->transaction->magic_offset, &zero, 4) == -1 || + if (methods->tdb_write(tdb, tdb->transaction->magic_offset, &invalid, 4) == -1 || transaction_sync(tdb, tdb->transaction->magic_offset, 4) == -1) { TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_cancel: failed to remove recovery magic\n")); ret = -1; } } - /* remove any global lock created during the transaction */ - if (tdb->global_lock.count != 0) { - tdb_brunlock(tdb, tdb->global_lock.ltype, - FREELIST_TOP, 4*tdb->header.hash_size); - tdb->global_lock.count = 0; - } - - /* remove any locks created during the transaction */ - if (tdb->num_locks != 0) { - for (i=0;inum_lockrecs;i++) { - tdb_brunlock(tdb, tdb->lockrecs[i].ltype, - FREELIST_TOP+4*tdb->lockrecs[i].list, 1); - } - tdb->num_locks = 0; - tdb->num_lockrecs = 0; - SAFE_FREE(tdb->lockrecs); - } + /* This also removes the OPEN_LOCK, if we have it. */ + tdb_release_extra_locks(tdb); /* restore the normal io methods */ tdb->methods = tdb->transaction->io_methods; @@ -548,7 +544,7 @@ int tdb_transaction_start(struct tdb_context *tdb) return 0; } - if (tdb->num_locks != 0 || tdb->global_lock.count) { + if (tdb_have_extra_locks(tdb)) { /* the caller must not have any locks when starting a transaction as otherwise we'll be screwed by lack of nested locks in posix */ @@ -789,7 +785,7 @@ static int transaction_setup_recovery(struct tdb_context *tdb, rec = (struct tdb_record *)data; memset(rec, 0, sizeof(*rec)); - rec->magic = 0; + rec->magic = TDB_RECOVERY_INVALID_MAGIC; rec->data_len = recovery_size; rec->rec_len = recovery_max_size; rec->key_len = old_map_size; @@ -928,7 +924,7 @@ static int _tdb_transaction_prepare_commit(struct tdb_context *tdb) /* if there are any locks pending then the caller has not nested their locks properly, so fail the transaction */ - if (tdb->num_locks || tdb->global_lock.count) { + if (tdb_have_extra_locks(tdb)) { tdb->ecode = TDB_ERR_LOCK; TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_prepare_commit: locks pending on commit\n")); _tdb_transaction_cancel(tdb, F_RDLCK); @@ -943,11 +939,10 @@ static int _tdb_transaction_prepare_commit(struct tdb_context *tdb) return -1; } - /* get the global lock - this prevents new users attaching to the database + /* get the open lock - this prevents new users attaching to the database during the commit */ - if (tdb_brlock(tdb, F_WRLCK, GLOBAL_LOCK, 1, TDB_LOCK_WAIT) == -1) { - TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_prepare_commit: failed to get global lock\n")); - tdb->ecode = TDB_ERR_LOCK; + if (tdb_nest_lock(tdb, OPEN_LOCK, F_WRLCK, TDB_LOCK_WAIT) == -1) { + TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_prepare_commit: failed to get open lock\n")); _tdb_transaction_cancel(tdb, F_WRLCK); return -1; } @@ -956,7 +951,6 @@ static int _tdb_transaction_prepare_commit(struct tdb_context *tdb) /* write the recovery data to the end of the file */ if (transaction_setup_recovery(tdb, &tdb->transaction->magic_offset) == -1) { TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_prepare_commit: failed to setup recovery data\n")); - tdb_brunlock(tdb, F_WRLCK, GLOBAL_LOCK, 1); _tdb_transaction_cancel(tdb, F_WRLCK); return -1; } @@ -971,7 +965,6 @@ static int _tdb_transaction_prepare_commit(struct tdb_context *tdb) tdb->transaction->old_map_size) == -1) { tdb->ecode = TDB_ERR_IO; TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_prepare_commit: expansion failed\n")); - tdb_brunlock(tdb, F_WRLCK, GLOBAL_LOCK, 1); _tdb_transaction_cancel(tdb, F_WRLCK); return -1; } @@ -979,7 +972,7 @@ static int _tdb_transaction_prepare_commit(struct tdb_context *tdb) methods->tdb_oob(tdb, tdb->map_size + 1, 1); } - /* Keep the global lock until the actual commit */ + /* Keep the open lock until the actual commit */ return 0; } @@ -1061,7 +1054,6 @@ int tdb_transaction_commit(struct tdb_context *tdb) tdb_transaction_recover(tdb); _tdb_transaction_cancel(tdb, F_WRLCK); - tdb_brunlock(tdb, F_WRLCK, GLOBAL_LOCK, 1); TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_commit: write failed\n")); return -1; @@ -1077,8 +1069,6 @@ int tdb_transaction_commit(struct tdb_context *tdb) return -1; } - tdb_brunlock(tdb, F_WRLCK, GLOBAL_LOCK, 1); - /* TODO: maybe write to some dummy hdr field, or write to magic offset without mmap, before the last sync, instead of the @@ -1110,7 +1100,7 @@ int tdb_transaction_commit(struct tdb_context *tdb) /* recover from an aborted transaction. Must be called with exclusive - database write access already established (including the global + database write access already established (including the open lock to prevent new processes attaching) */ int tdb_transaction_recover(struct tdb_context *tdb)