From: Paul Clements Date: Wed, 11 Feb 2009 21:04:45 +0000 (-0800) Subject: nbd: fix I/O hang on disconnected nbds X-Git-Tag: v2.6.29-rc5~8 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=4d48a542b42747c36a5937447d9c3de7c897ea50;p=pandora-kernel.git nbd: fix I/O hang on disconnected nbds Fix 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. 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. Signed-off-by: Paul Clements Reported-by: Jon Nelson Acked-by: Pavel Machek Cc: [2.6.26.x, 2.6.27.x, 2.6.28.x] Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Reading git-diff-tree failed