Re: [Qemu-devel] [PATCH 00/12] nbd improvements

[Paolo Bonzini]

On 09/09/2011 11:00 AM, Kevin Wolf wrote:
> There is anonther patch enabling AIO for NBD on the list [1], by
> Nicholas Thomas (CCed), that lacked review so far. Can you guys please
> review each others approach and then converge on a solution? I guess
> Paolo's patches 1-7 can be applied in any case, probably causing minor
> conflicts, but for the rest we need to decide which one to pick.

Stefan also pointed me to Nicholas's patches yesterday.  I would go with 
mine, if only because his work predates coroutines (at least the older 
versions) and are much more complex.

On the other hand, Nicholas's work includes timeout and reconnect.  I'm 
not sure how complicated it is to include it in my series, but probably 
not much.  With coroutines, preserving the list of outstanding I/O 
requests is done implicitly by the CoMutex, so you basically have to 
check errno for ECONNRESET and similar errors, reconnect, and retry 
issuing the current request only.

Timeout can be done with a QEMUTimer that shuts down the socket 
(shutdown(2) I mean).  This triggers an EPIPE when writing, or a 
zero-sized read when reading.  The timeout can be set every time the 
coroutine is (re)entered, and reset before exiting nbd_co_readv/writev.

What do you think?

Paolo