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Re: [Qemu-devel] [PATCH v3 06/12] nbd-server: Clear "can_read" when "dev

From: Max Reitz
Subject: Re: [Qemu-devel] [PATCH v3 06/12] nbd-server: Clear "can_read" when "device io" blocker is set
Date: Mon, 18 May 2015 20:35:32 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.6.0

On 15.05.2015 08:04, Fam Zheng wrote:
So that NBD export cannot submit IO during bdrv_drain_all().

Signed-off-by: Fam Zheng <address@hidden>
  nbd.c | 18 ++++++++++++++++++
  1 file changed, 18 insertions(+)

But can_read is not cleared until nbd_update_can_read() is called, which is only in nbd_request_get(), nbd_request_put(), and nbd_co_receive_request(), which are all called from nbd_trip() - so the one request which clears can_read will most probably be itself processed.

Maybe we should call nbd_update_can_read() in nbd_op_blocker_changed(), for all clients of the export? Or just once somewhere at the beginning of processing a request, and if io_blocked is set, just yield...


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