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


From: Paolo Bonzini
Subject: Re: [Qemu-devel] [PATCH 2/4] nbd: Limit nbdflags to 16 bits
Date: Mon, 1 Aug 2016 11:17:42 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.1.1


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);



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