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Re: [PATCH] nbd: Fix regression with multiple meta contexts

From: Laurent Vivier
Subject: Re: [PATCH] nbd: Fix regression with multiple meta contexts
Date: Wed, 12 Feb 2020 13:13:17 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.3.1

Le 12/02/2020 à 13:10, Eric Blake a écrit :
> On 2/12/20 3:24 AM, Laurent Vivier wrote:
>> Le 06/02/2020 à 18:38, Eric Blake a écrit :
>>> Detected by a hang in the libnbd testsuite.  If a client requests
>>> multiple meta contexts (both base:allocation and qemu:dirty-bitmap:x)
>>> at the same time, our attempt to silence a false-positive warning
>>> about a potential uninitialized variable introduced botched logic: we
>>> were short-circuiting the second context, and never sending the
>>> NBD_REPLY_FLAG_DONE.  Combining two 'if' into one 'if/else' in
>>> bdf200a55 was wrong (I'm a bit embarrassed that such a change was my
>>> initial suggestion after the v1 patch, then I did not review the v2
>>> patch that actually got committed). Revert that, and instead silence
>>> the false positive warning by replacing 'return ret' with 'return 0'
>>> (the value it always has at that point in the code, even though it
>>> eluded the deduction abilities of the robot that reported the false
>>> positive).
>>> Fixes: bdf200a5535
>>> Signed-off-by: Eric Blake <address@hidden>
>>> ---
>>> It's never fun when a regression is caused by a patch taken through
>>> qemu-trivial, proving that the patch was not trivial after all.
>> Do you want this one be merged using the trivial branch?
> Up to you; I'm also fine taking it through my NBD tree as I have a few
> other NBD patches landing soon.

For the moment, I have only one patch in my queue so I think you can
take it.


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