tdb2: allow nesting of read locks on top of write locks.

[ccan] / ccan / tdb2 / lock.c

diff --git a/ccan/tdb2/lock.c b/ccan/tdb2/lock.c
index 10d1e18a512b6d0f0964e8eda80fb33b5914dd54..60ed46379aa7b6960d51e5778c907945614b7c0f 100644 (file)
--- a/ccan/tdb2/lock.c
+++ b/ccan/tdb2/lock.c
@@ -257,7 +257,7 @@ static int tdb_nest_lock(struct tdb_context *tdb, tdb_off_t offset, int ltype,
 {
        struct tdb_lock_type *new_lck;
 
-       if (offset >= TDB_HASH_LOCK_START + TDB_HASH_LOCK_RANGE + tdb->map_size / 8) {
+       if (offset > TDB_HASH_LOCK_START + TDB_HASH_LOCK_RANGE + tdb->map_size / 8) {
                tdb->ecode = TDB_ERR_LOCK;
                tdb->log(tdb, TDB_DEBUG_FATAL, tdb->log_priv,
                         "tdb_nest_lock: invalid offset %llu ltype=%d\n",
@@ -270,10 +270,14 @@ static int tdb_nest_lock(struct tdb_context *tdb, tdb_off_t offset, int ltype,
 
        new_lck = find_nestlock(tdb, offset);
        if (new_lck) {
-               /*
-                * Just increment the in-memory struct, posix locks
-                * don't stack.
-                */
+               if (new_lck->ltype == F_RDLCK && ltype == F_WRLCK) {
+                       tdb->ecode = TDB_ERR_LOCK;
+                       tdb->log(tdb, TDB_DEBUG_FATAL, tdb->log_priv,
+                                "tdb_nest_lock: offset %llu has read lock\n",
+                                (long long)offset);
+                       return -1;
+               }
+               /* Just increment the struct, posix locks don't stack. */
                new_lck->count++;
                return 0;
        }
@@ -454,7 +458,8 @@ int tdb_allrecord_lock(struct tdb_context *tdb, int ltype,
                return -1;
        }
 
-       if (tdb->allrecord_lock.count && tdb->allrecord_lock.ltype == ltype) {
+       if (tdb->allrecord_lock.count
+           && (ltype == F_RDLCK || tdb->allrecord_lock.ltype == F_WRLCK)) {
                tdb->allrecord_lock.count++;
                return 0;
        }