Messages in this thread | | | Date | Tue, 10 Feb 2009 13:35:37 -0800 | From | Andrew Morton <> | Subject | Re: [PATCH 1/1] NBD: fix I/O hang on disconnected nbds |
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On Mon, 09 Feb 2009 13:21:51 -0500 Paul Clements <paul.clements@steeleye.com> wrote:
> This patch fixes a problem that causes I/O to a disconnected > (or partially initialized) nbd device to hang indefinitely. To reproduce: > > # ioctl NBD_SET_SIZE_BLOCKS /dev/nbd23 514048 > # dd if=/dev/nbd23 of=/dev/null bs=4096 count=1 > > ...hangs... > > This can also occur when an nbd device loses its nbd-client/server > connection. Although we clear the queue of any outstanding I/Os after > the client/server connection fails, any additional I/Os that get queued > later will hang. > > This bug may also be the problem reported in this bug report: > http://bugzilla.kernel.org/show_bug.cgi?id=12277 > > Testing would need to be performed to determine if the two issues are > the same. > > This problem was introduced by the new request handling thread code > ("NBD: allow nbd to be used locally", 3/2008), which entered into > mainline around 2.6.25.
Seems that the patch applies to 2.6.26, but not to 2.6.25.
> > The fix, which is fairly simple, is to restore the check for lo->sock > being NULL in do_nbd_request. This causes I/O to an uninitialized nbd to > immediately fail with an I/O error, as it did prior to the introduction > of this bug.
I marked this as needing backporting into 2.6.26.x, 2.6.27.x and 2.6.28.x. OK?
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