** Description changed:

+ == SRU Justification ==
+ 
+ When running the Ubuntu nbd autotest regression test we trip a hang
+ and then a little later a panic message.  There are two upstream
+ fixes required as this is actually two issues in one. One fix is to 
+ not to shutdown the sock when IRQs are disable and a second to fix is
+ to race in the nbd ioctl.
+ 
+ == Fix ==
+ 
+ Upstream commits:
+ 
+ 23272a6754b81ff6503e09c743bb4ceeeab39997
+   nbd: Remove signal usage
+ 
+ 1f7b5cf1be4351e60cf8ae7aab976503dd73c5f8
+   nbd: Timeouts are not user requested disconnects
+ 
+ 0e4f0f6f63d3416a9e529d99febfe98545427b81
+   nbd: Cleanup reset of nbd and bdev after a disconnect
+ 
+ c261189862c6f65117eb3b1748622a08ef49c262
+   nbd: don't shutdown sock with irq's disabled
+ 
+ 97240963eb308d8d21a89c0459822f7ea98463b4
+   nbd: fix race in ioctl
+ 
+ The first 3 patches are prerequisites required for the latter two fixes to 
apply and work correctly.  Most of these backports are minor patch wiggles
+ required because later patches have been applied to the driver in earlier 
fixes to this driver.
+    
+ 
+ == Regression Potential ==
+ 
+ These fixes just touch nbd, so the regression potential is just limited
+ to this. Secondly, we are pulling in upstream fixes that exist in Bionic
+ and Cosmic kernels, so these are tried and tested fixes.
+ 
+ == Test Case ==
+ 
+   1. Deploy a node with 4.4 Xenial
+   2. Run the ubuntu_nbd_smoke_test
+ 
+ Without the fix, we get hang/crashes.  With the fix one can run this test
+ multiple times without any issues at all.
+ 
+ 
+ ----
+ 
  This issue can be reproduced on AMD64 KVM //bare-metal node, s390x zKVM
  node
  
  The test itself will pass, but the system will hang after a few second.
  
  Steps:
    1. Deploy a node with 4.4 Xenial
    2. Run the ubuntu_nbd_smoke_test
  
  If you have access to the console, you will see that this system
  actually bumped into a kernel panic:
  
   Unable to handle kernel pointer dereference in virtual kernel address space
   failing address: 000003ff802c1000 TEID: 000003ff802c1803
   Fault in home space mode while using kernel ASCE.
   Log here (s390x KVM): https://pastebin.ubuntu.com/p/dNmtvbGjmz/
  
  ProblemType: Bug
  DistroRelease: Ubuntu 16.04
  Package: linux-image-4.4.0-136-generic 4.4.0-136.162
  ProcVersionSignature: Ubuntu 4.4.0-136.162-generic 4.4.144
  Uname: Linux 4.4.0-136-generic s390x
  NonfreeKernelModules: zfs zunicode zcommon znvpair zavl
  AlsaDevices: Error: command ['ls', '-l', '/dev/snd/'] failed with exit code 
2: ls: cannot access '/dev/snd/': No such file or directory
  AplayDevices: Error: [Errno 2] No such file or directory: 'aplay'
  ApportVersion: 2.20.1-0ubuntu2.18
  Architecture: s390x
  ArecordDevices: Error: [Errno 2] No such file or directory: 'arecord'
  CRDA: Error: command ['iw', 'reg', 'get'] failed with exit code 1: nl80211 
not found.
  Date: Thu Sep 20 03:46:00 2018
  HibernationDevice: RESUME=UUID=ca468a9c-9563-442c-85c6-6055e800a66e
  IwConfig: Error: [Errno 2] No such file or directory: 'iwconfig'
  Lspci:
  
  Lsusb: Error: command ['lsusb'] failed with exit code 1:
  PciMultimedia:
  
  ProcFB: Error: [Errno 2] No such file or directory: '/proc/fb'
  ProcKernelCmdLine: root=UUID=b65b756a-ba4e-4c53-aa32-0db2bdb50bb3 
crashkernel=196M
  RelatedPackageVersions:
   linux-restricted-modules-4.4.0-136-generic N/A
   linux-backports-modules-4.4.0-136-generic  N/A
   linux-firmware                             1.157.20
  RfKill: Error: [Errno 2] No such file or directory: 'rfkill'
  SourcePackage: linux
  UpgradeStatus: No upgrade log present (probably fresh install)

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https://bugs.launchpad.net/bugs/1793464

Title:
  Kernel panic after the ubuntu_nbd_smoke_test on Xenial kernel

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