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Re: [Nbd] 3.12 BUG() on ext4, kernel crash on nbd-client when nbd server rebooting

On Tue, Nov 19, 2013 at 2:19 PM, Wouter Verhelst <w@...112...> wrote:

Op 19-11-13 02:43, Paul Clements schreef:
> On Monday, November 18, 2013, Wouter Verhelst wrote:
>     Op 18-11-13 23:17, Paul Clements schreef:
>     [...]
>     > Right, some rearrangement of the ioctls would be required too...we'd
>     > probably want alternate versions of SET_SOCK and DO_IT that are
>     > re-entrant (right now those will error on an already-configured
>     device,
>     > and they're doing some setup and teardown that is unneeded in the
>     > reconnect case).
>     Since all this is a significant departure of the current API, I suppose
>     it would be good if there would be a way for the client to detect what
>     the currently-running kernel supports, without having to resort to
>     things like calling 'uname -r' (or equivalent in C code) or extensive
>     error handling based on "that ioctl isn't supported, so let's fall back
>     to previous API versions."
> Anything specific that would make it easier from your perspective?  One
> thought is to have SET_FLAGS fail when an unknown flag is passed. Or
> say a get_capabilities() type call?

A get_capabilities() would be most useful, yes. 

Anything besides supported flags that the client needs to know? Or are we really maybe just talking about a GET_FLAGS ioctl or other (possibly sysfs) advertisement of flags?

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