smbd: Introduce static_share_mode_record

The next commit will introduce share_mode_do_locked(), which allocates
a share mode record on the stack. We have to expect nested
get_share_mode_lock() calls from within share_mode_do_locked() for
which we need to share a db_record.

Signed-off-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Ralph Boehme <slow@samba.org>

diff --git a/source3/locking/share_mode_lock.c b/source3/locking/share_mode_lock.c
index 1244c21ebba1ca431ddfa9b9250214534ddf6b9f..f80b9845d163274d6585352d1f5c9210f2d7adb8 100644 (file)
--- a/source3/locking/share_mode_lock.c
+++ b/source3/locking/share_mode_lock.c
@@ -430,6 +430,14 @@ fail:
 static struct share_mode_data *static_share_mode_data = NULL;
 static size_t static_share_mode_data_refcount = 0;
 
+/*
+ * db_record for the above. With dbwrap_do_locked we can get a
+ * db_record on the stack, which we can't TALLOC_FREE but which we
+ * need to share with a nested get_share_mode_lock call.
+ */
+static struct db_record *static_share_mode_record = NULL;
+static bool static_share_mode_record_talloced = false;
+
 /*******************************************************************
  Either fetch a share mode from the database, or allocate a fresh
  one if the record doesn't exist.
@@ -483,7 +491,6 @@ struct share_mode_lock *get_share_mode_lock(
        const struct timespec *old_write_time)
 {
        TDB_DATA key = locking_key(&id);
-       struct db_record *rec = NULL;
        struct share_mode_lock *lck = NULL;
        NTSTATUS status;
 
@@ -504,28 +511,32 @@ struct share_mode_lock *get_share_mode_lock(
 
        SMB_ASSERT(static_share_mode_data_refcount == 0);
 
-       rec = dbwrap_fetch_locked(lock_db, lock_db, key);
-       if (rec == NULL) {
-               DEBUG(3, ("Could not lock share entry\n"));
-               goto fail;
-       }
-
-       status = get_static_share_mode_data(
-               rec, id, servicepath, smb_fname, old_write_time);
-       if (!NT_STATUS_IS_OK(status)) {
-               DBG_WARNING("get_static_share_mode_data failed: %s\n",
-                           nt_errstr(status));
-               TALLOC_FREE(rec);
-               goto fail;
+       if (static_share_mode_record == NULL) {
+               static_share_mode_record = dbwrap_fetch_locked(
+                       lock_db, lock_db, key);
+               if (static_share_mode_record == NULL) {
+                       DEBUG(3, ("Could not lock share entry\n"));
+                       goto fail;
+               }
+               static_share_mode_record_talloced = true;
+
+               status = get_static_share_mode_data(
+                       static_share_mode_record,
+                       id,
+                       servicepath,
+                       smb_fname,
+                       old_write_time);
+               if (!NT_STATUS_IS_OK(status)) {
+                       DBG_WARNING("get_static_share_mode_data failed: %s\n",
+                                   nt_errstr(status));
+                       TALLOC_FREE(static_share_mode_record);
+                       goto fail;
+               }
+       } else {
+               /* This panic will go away in the next commit */
+               smb_panic("static_share_mode_record != NULL\n");
        }
 
-       /*
-        * This is unnecessary, in share_mode_lock_destructor we
-        * explicitly TALLOC_FREE lck->data->rec. Leave it here as
-        * it's cleaner in the talloc report.
-        */
-       talloc_reparent(lock_db, static_share_mode_data, rec);
-
 done:
        static_share_mode_data_refcount += 1;
        lck->data = static_share_mode_data;
@@ -560,7 +571,12 @@ static int share_mode_lock_destructor(struct share_mode_lock *lck)
         * Drop the locking.tdb lock before moving the share_mode_data
         * to memcache
         */
-       TALLOC_FREE(static_share_mode_data->record);
+       SMB_ASSERT(static_share_mode_data->record == static_share_mode_record);
+       static_share_mode_data->record = NULL;
+
+       if (static_share_mode_record_talloced) {
+               TALLOC_FREE(static_share_mode_record);
+       }
 
        if (static_share_mode_data->num_share_modes != 0) {
                /*