ISO SR is confused by unreadable files

[ydirson]

When a file is created on an ISO SR with no read access, the file is discovered by SR scan and a VDI is created, but on attempts to use it the user faces a non-obvious diagnostic, as shown below. Let the SR just warn and skip it instead would likely be a better behavior?

• commands like a xe vm-start for a VM with that ISO inserted fail with Error code: SR_BACKEND_FAILURE_1200 Error parameters: , No such Tapdisk(minor=1)
• we can see in SMlog:

May 21 11:30:25 xcpng83-bzkcpvhy SM: [6322] ['/usr/sbin/tap-ctl', 'attach', '-p', '6335', '-m', '1']
May 21 11:30:25 xcpng83-bzkcpvhy SM: [6322]  = 0
May 21 11:30:25 xcpng83-bzkcpvhy SM: [6322] ['/usr/sbin/tap-ctl', 'open', '-p', '6335', '-m', '1', '-a', 'aio:/var/run/sr-mount/364d8fbc-f587-52e6-8499-382c4d3bdbc8/tmpdi2m5lzx.iso', '-R']
May 21 11:30:25 xcpng83-bzkcpvhy SM: [6322]  = 13
May 21 11:30:25 xcpng83-bzkcpvhy SM: [6322] ['/usr/sbin/tap-ctl', 'close', '-p', '6335', '-m', '1', '-t', '120']
May 21 11:30:25 xcpng83-bzkcpvhy SM: [6322]  = 0
May 21 11:30:25 xcpng83-bzkcpvhy SM: [6322] ['/usr/sbin/tap-ctl', 'detach', '-p', '6335', '-m', '1']
May 21 11:30:25 xcpng83-bzkcpvhy SM: [6322]  = 0
May 21 11:30:25 xcpng83-bzkcpvhy SM: [6322] ['/usr/sbin/tap-ctl', 'free', '-m', '1']
May 21 11:30:25 xcpng83-bzkcpvhy SM: [6322]  = 0
May 21 11:30:25 xcpng83-bzkcpvhy SM: [6322] ***** generic exception: vdi_attach: EXCEPTION <class 'blktap2.TapdiskNotRunning'>, No such Tapdisk(minor=1)
May 21 11:30:25 xcpng83-bzkcpvhy SM: [6322]   File "/opt/xensource/sm/SRCommand.py", line 111, in run
May 21 11:30:25 xcpng83-bzkcpvhy SM: [6322]     return self._run_locked(sr)
May 21 11:30:25 xcpng83-bzkcpvhy SM: [6322]   File "/opt/xensource/sm/SRCommand.py", line 161, in _run_locked
May 21 11:30:25 xcpng83-bzkcpvhy SM: [6322]     rv = self._run(sr, target)
May 21 11:30:25 xcpng83-bzkcpvhy SM: [6322]   File "/opt/xensource/sm/SRCommand.py", line 253, in _run
May 21 11:30:25 xcpng83-bzkcpvhy SM: [6322]     writable, caching_params=caching_params)
May 21 11:30:25 xcpng83-bzkcpvhy SM: [6322]   File "/opt/xensource/sm/blktap2.py", line 1567, in attach
May 21 11:30:25 xcpng83-bzkcpvhy SM: [6322]     {"rdonly": not writable})
May 21 11:30:25 xcpng83-bzkcpvhy SM: [6322]   File "/opt/xensource/sm/blktap2.py", line 1730, in _activate
May 21 11:30:25 xcpng83-bzkcpvhy SM: [6322]     self._get_pool_config(sr_uuid).get("mem-pool-size"))
May 21 11:30:25 xcpng83-bzkcpvhy SM: [6322]   File "/opt/xensource/sm/blktap2.py", line 1351, in _tap_activate
May 21 11:30:25 xcpng83-bzkcpvhy SM: [6322]     options)
May 21 11:30:25 xcpng83-bzkcpvhy SM: [6322]   File "/opt/xensource/sm/blktap2.py", line 842, in launch_on_tap
May 21 11:30:25 xcpng83-bzkcpvhy SM: [6322]     tapdisk = cls.__from_blktap(blktap)
May 21 11:30:25 xcpng83-bzkcpvhy SM: [6322]   File "/opt/xensource/sm/blktap2.py", line 737, in __from_blktap
May 21 11:30:25 xcpng83-bzkcpvhy SM: [6322]     tapdisk = cls.from_minor(minor=blktap.minor)
May 21 11:30:25 xcpng83-bzkcpvhy SM: [6322]   File "/opt/xensource/sm/blktap2.py", line 733, in from_minor
May 21 11:30:25 xcpng83-bzkcpvhy SM: [6322]     return cls.get(minor=minor)
May 21 11:30:25 xcpng83-bzkcpvhy SM: [6322]   File "/opt/xensource/sm/blktap2.py", line 723, in get
May 21 11:30:25 xcpng83-bzkcpvhy SM: [6322]     raise TapdiskNotRunning( ** attrs)
May 21 11:30:25 xcpng83-bzkcpvhy SM: [6322]
May 21 11:30:25 xcpng83-bzkcpvhy SM: [6322] ***** ISO: EXCEPTION <class 'blktap2.TapdiskNotRunning'>, No such Tapdisk(minor=1)
May 21 11:30:25 xcpng83-bzkcpvhy SM: [6322]   File "/opt/xensource/sm/SRCommand.py", line 385, in run
May 21 11:30:25 xcpng83-bzkcpvhy SM: [6322]     ret = cmd.run(sr)
May 21 11:30:25 xcpng83-bzkcpvhy SM: [6322]   File "/opt/xensource/sm/SRCommand.py", line 111, in run
May 21 11:30:25 xcpng83-bzkcpvhy SM: [6322]     return self._run_locked(sr)
May 21 11:30:25 xcpng83-bzkcpvhy SM: [6322]   File "/opt/xensource/sm/SRCommand.py", line 161, in _run_locked
May 21 11:30:25 xcpng83-bzkcpvhy SM: [6322]     rv = self._run(sr, target)
May 21 11:30:25 xcpng83-bzkcpvhy SM: [6322]   File "/opt/xensource/sm/SRCommand.py", line 253, in _run
May 21 11:30:25 xcpng83-bzkcpvhy SM: [6322]     writable, caching_params=caching_params)
May 21 11:30:25 xcpng83-bzkcpvhy SM: [6322]   File "/opt/xensource/sm/blktap2.py", line 1567, in attach
May 21 11:30:25 xcpng83-bzkcpvhy SM: [6322]     {"rdonly": not writable})
May 21 11:30:25 xcpng83-bzkcpvhy SM: [6322]   File "/opt/xensource/sm/blktap2.py", line 1730, in _activate
May 21 11:30:25 xcpng83-bzkcpvhy SM: [6322]     self._get_pool_config(sr_uuid).get("mem-pool-size"))
May 21 11:30:25 xcpng83-bzkcpvhy SM: [6322]   File "/opt/xensource/sm/blktap2.py", line 1351, in _tap_activate
May 21 11:30:25 xcpng83-bzkcpvhy SM: [6322]     options)
May 21 11:30:25 xcpng83-bzkcpvhy SM: [6322]   File "/opt/xensource/sm/blktap2.py", line 842, in launch_on_tap
May 21 11:30:25 xcpng83-bzkcpvhy SM: [6322]     tapdisk = cls.__from_blktap(blktap)
May 21 11:30:25 xcpng83-bzkcpvhy SM: [6322]   File "/opt/xensource/sm/blktap2.py", line 737, in __from_blktap
May 21 11:30:25 xcpng83-bzkcpvhy SM: [6322]     tapdisk = cls.from_minor(minor=blktap.minor)
May 21 11:30:25 xcpng83-bzkcpvhy SM: [6322]   File "/opt/xensource/sm/blktap2.py", line 733, in from_minor
May 21 11:30:25 xcpng83-bzkcpvhy SM: [6322]     return cls.get(minor=minor)
May 21 11:30:25 xcpng83-bzkcpvhy SM: [6322]   File "/opt/xensource/sm/blktap2.py", line 723, in get
May 21 11:30:25 xcpng83-bzkcpvhy SM: [6322]     raise TapdiskNotRunning( ** attrs)
May 21 11:30:25 xcpng83-bzkcpvhy SM: [6322]

• only daemon.log then can give the hint to the user (assuming the user can make the link between -13 and EPERM):

tapdisk[6335]: Unable to open [/var/run/sr-mount/364d8fbc-f587-52e6-8499-382c4d3bdbc8/tmpdi2m5lzx.iso] (-13)!