tdb: fix tdb_check() on read-only TDBs to actually work.

But make sure we can still do tdb_check() inside a transaction (weird,
but we previously allowed it).

diff --git a/ccan/tdb/check.c b/ccan/tdb/check.c
index c5469e9998122dc57eefcdb90ddb747cb99d684d..a9a9ece0da37c01eb87c0dbf3e4ac6ee05250d07 100644 (file)
--- a/ccan/tdb/check.c
+++ b/ccan/tdb/check.c
@@ -327,9 +327,17 @@ int tdb_check(struct tdb_context *tdb,
        struct tdb_record rec;
        bool found_recovery = false;
        tdb_len_t dead;
-
-       if (tdb_lockall_read(tdb) == -1)
-               return -1;
+       bool locked;
+
+       /* Read-only databases use no locking at all: it's best-effort.
+        * We may have a write lock already, so skip that case too. */
+       if (tdb->read_only || tdb->allrecord_lock.count != 0) {
+               locked = false;
+       } else {
+               if (tdb_lockall_read(tdb) == -1)
+                       return -1;
+               locked = true;
+       }
 
        /* Make sure we know true size of the underlying file. */
        tdb->methods->tdb_oob(tdb, tdb->map_size + 1, 1);
@@ -444,12 +452,16 @@ int tdb_check(struct tdb_context *tdb,
        }
 
        free(hashes);
-       tdb_unlockall_read(tdb);
+       if (locked) {
+               tdb_unlockall_read(tdb);
+       }
        return 0;
 
 free:
        free(hashes);
 unlock:
-       tdb_unlockall_read(tdb);
+       if (locked) {
+               tdb_unlockall_read(tdb);
+       }
        return -1;
 }

diff --git a/ccan/tdb/test/run-readonly-check.c b/ccan/tdb/test/run-readonly-check.c
new file mode 100644 (file)
index 0000000..87cdd64
--- /dev/null
+++ b/ccan/tdb/test/run-readonly-check.c
@@ -0,0 +1,53 @@
+/* We should be able to tdb_check a O_RDONLY tdb, and we were previously allowed
+ * to tdb_check() inside a transaction (though that's paranoia!). */
+#define _XOPEN_SOURCE 500
+#include <ccan/tdb/tdb.h>
+#include <ccan/tdb/io.c>
+#include <ccan/tdb/tdb.c>
+#include <ccan/tdb/lock.c>
+#include <ccan/tdb/freelist.c>
+#include <ccan/tdb/traverse.c>
+#include <ccan/tdb/transaction.c>
+#include <ccan/tdb/error.c>
+#include <ccan/tdb/open.c>
+#include <ccan/tdb/check.c>
+#include <ccan/tap/tap.h>
+#include <stdlib.h>
+#include <err.h>
+#include "logging.h"
+
+int main(int argc, char *argv[])
+{
+       struct tdb_context *tdb;
+       TDB_DATA key, data;
+
+       plan_tests(11);
+       tdb = tdb_open_ex("run-readonly-check.tdb", 1024,
+                         TDB_DEFAULT,
+                         O_CREAT|O_TRUNC|O_RDWR, 0600, &taplogctx, NULL);
+
+       ok1(tdb);
+       key.dsize = strlen("hi");
+       key.dptr = (void *)"hi";
+       data.dsize = strlen("world");
+       data.dptr = (void *)"world";
+
+       ok1(tdb_store(tdb, key, data, TDB_INSERT) == 0);
+       ok1(tdb_check(tdb, NULL, NULL) == 0);
+
+       /* We are also allowed to do a check inside a transaction. */
+       ok1(tdb_transaction_start(tdb) == 0);
+       ok1(tdb_check(tdb, NULL, NULL) == 0);
+       ok1(tdb_close(tdb) == 0);
+
+       tdb = tdb_open_ex("run-readonly-check.tdb", 1024,
+                         TDB_DEFAULT, O_RDONLY, 0, &taplogctx, NULL);
+
+       ok1(tdb);
+       ok1(tdb_store(tdb, key, data, TDB_MODIFY) == -1);
+       ok1(tdb_error(tdb) == TDB_ERR_RDONLY);
+       ok1(tdb_check(tdb, NULL, NULL) == 0);
+       ok1(tdb_close(tdb) == 0);
+
+       return exit_status();
+}