Make xenstored use tdb, transactions can soft-fail (EAGAIN)

Transactions no longer take root dir, no longer lock & block: commit can fail spuriously with EAGAIN, not ETIMEDOUT.
Speeds up transactions by over 1000 times, should be NFS safe.
New program: xs_tdb_dump to dump raw TDB contents.
Don't do failure testing: we are no longer robust against all ENOMEM 8(
Introduce "struct node" which contains perms, children and data.
Make struct xs_permissions unpadded, so we can write to tdb w/o valgrind complaints.
Gently modify TDB to use talloc, not do alloc on tdb_delete.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

1 files changed, 2 insertions, 3 deletions

diff --git a/tools/xenstore/xs.c b/tools/xenstore/xs.c
index 7036774f09..a842a6e39c 100644
--- a/tools/xenstore/xs.c
+++ b/tools/xenstore/xs.c
@@ -497,13 +497,12 @@ bool xs_unwatch(struct xs_handle *h, const char *path, const char *token)
 
 /* Start a transaction: changes by others will not be seen during this
  * transaction, and changes will not be visible to others until end.
- * Transaction only applies to the given subtree.
  * You can only have one transaction at any time.
  * Returns false on failure.
  */
-bool xs_transaction_start(struct xs_handle *h, const char *subtree)
+bool xs_transaction_start(struct xs_handle *h)
 {
-	return xs_bool(xs_single(h, XS_TRANSACTION_START, subtree, NULL));
+	return xs_bool(xs_single(h, XS_TRANSACTION_START, "", NULL));
 }
 
 /* End a transaction.