Re: [Qemu-devel] [Nbd] [PATCH 2/2] Correct definition of NBD_CMD_FLAG_FUA

[Alex Bligh]

On 1 Apr 2016, at 08:59, Wouter Verhelst <address@hidden> wrote:

> On Thu, Mar 31, 2016 at 07:15:32PM +0100, Alex Bligh wrote:
>> NBD_CMD_FLAG_FUA is defined as 1<<0 in the documentation, but
>> 1<<16 in nbd.h. It is not used anywhere within the code.
> 
> Yes it is:
> 
> address@hidden:~/code/c/nbd$ grep -rl CMD_FLAG_FUA *
> doc/proto.md
> make-integrityhuge.c
> nbd.h
> nbd-server.c
> nbd-trdump.c
> tests/run/nbd-tester-client.c
> address@hidden:~/code/c/nbd$ 
> 
> I don't mind bringing the code in sync with what the documentation says,
> but it should not change behaviour ;-)

Sorry - I think I must have done 'git grep' in the wrong directory
or something. Ignore this patch and I'll redo it.

I think probably the easiest fix is (beware, manually generated
untested patch) as follows, which at least shows the reason for the
discrepancy.

diff --git a/nbd.h b/nbd.h
index f2a32dd..53b6ca1 100644
--- a/nbd.h
+++ b/nbd.h
@@ -38,7 +38,9 @@ enum {
};

#define NBD_CMD_MASK_COMMAND 0x0000ffff
-#define NBD_CMD_FLAG_FUA (1<<16)
+#define NBD_CMD_SHIFT (16)
+#define NBD_CMD_FLAG_FUA ((1 << 0) << NBD_CMD_SHIFT)

/* values for flags field */
#define NBD_FLAG_HAS_FLAGS      (1 << 0)        /* Flags are there */

-- 
Alex Bligh