Re: [Qemu-stable] [PATCH 2/4] nbd: Limit nbdflags to 16 bits

[Paolo Bonzini]

On 21/07/2016 21:34, Eric Blake wrote:
> Furthermore, upstream NBD has never passed the global flags to
> the kernel via ioctl(NBD_SET_FLAGS) (the ioctl was first
> introduced in NBD 2.9.22; then a latent bug in NBD 3.1 actually
> tried to OR the global flags with the transmission flags, with
> the disaster that the addition of NBD_FLAG_NO_ZEROES in 3.9
> caused all earlier NBD 3.x clients to treat every export as
> read-only; NBD 3.10 and later intentionally clip things to 16
> bits to pass only transmission flags).  Qemu should follow suit,
> since the current two global flags (NBD_FLAG_FIXED_NEWSTYLE
> and NBD_FLAG_NO_ZEROES) have no impact on the kernel's behavior
> during transmission.

Should squash this in too:

diff --git a/nbd/server.c b/nbd/server.c
index 80fbb4d..6fa2f9c 100644
--- a/nbd/server.c
+++ b/nbd/server.c
@@ -575,7 +575,7 @@ static coroutine_fn int nbd_negotiate(NBDClientNewData 
*data)
 
     oldStyle = client->exp != NULL && !client->tlscreds;
     if (oldStyle) {
-        TRACE("advertising size %" PRIu64 " and flags %x",
+        TRACE("advertising size %" PRIu64 " and flags %" PRIx16,
               client->exp->size, client->exp->nbdflags | myflags);
         stq_be_p(buf + 8, NBD_CLIENT_MAGIC);
         stq_be_p(buf + 16, client->exp->size);
@@ -605,7 +605,7 @@ static coroutine_fn int nbd_negotiate(NBDClientNewData 
*data)
             goto fail;
         }
 
-        TRACE("advertising size %" PRIu64 " and flags %x",
+        TRACE("advertising size %" PRIu64 " and flags %" PRIx16,
               client->exp->size, client->exp->nbdflags | myflags);
         stq_be_p(buf + 18, client->exp->size);
         stw_be_p(buf + 26, client->exp->nbdflags | myflags);