Re: [PATCH 4/4] target: Add a user-passthrough backstore

2014-09-22 Thread Nicholas A. Bellinger
On Fri, 2014-09-19 at 16:51 -0700, Alex Elsayed wrote: Nicholas A. Bellinger wrote: On Fri, 2014-09-19 at 14:43 -0700, Alex Elsayed wrote: Nicholas A. Bellinger wrote: snip So the idea of allowing the in-kernel CDB emulation to run after user-space has returned unsupported opcode

Re: [PATCH 4/4] target: Add a user-passthrough backstore

2014-09-22 Thread Nicholas A. Bellinger
On Fri, 2014-09-19 at 17:35 -0700, Andy Grover wrote: On 09/19/2014 04:51 PM, Alex Elsayed wrote: Not sure I follow.. How does the proposed passthrough mode prevent someone from emulating OSDs, media changers, optical disks or anything else in userspace with TCMU..? The main thing

Re: [PATCH 4/4] target: Add a user-passthrough backstore

2014-09-22 Thread Andy Grover
On 09/22/2014 01:58 PM, Nicholas A. Bellinger wrote: So I'd still like to start for an initial merge with the two different modes mentioned earlier. The pure-passthrough mode where everything is handled by user-space, and an I/O passthrough mode where only SCF_SCSI_DATA_CDB is passed along to

Re: [PATCH 4/4] target: Add a user-passthrough backstore

2014-09-22 Thread Nicholas A. Bellinger
On Mon, 2014-09-22 at 14:00 -0700, Andy Grover wrote: On 09/22/2014 01:58 PM, Nicholas A. Bellinger wrote: So I'd still like to start for an initial merge with the two different modes mentioned earlier. The pure-passthrough mode where everything is handled by user-space, and an I/O

Re: [PATCH 4/4] target: Add a user-passthrough backstore

2014-09-19 Thread Nicholas A. Bellinger
Hi Andy, A few comments are inline below. On Mon, 2014-09-15 at 16:12 -0700, Andy Grover wrote: Add a LIO storage engine that presents commands to userspace for execution. This would allow more complex backstores to be implemented out-of-kernel, and also make experimentation a-la FUSE (but at

Re: [PATCH 4/4] target: Add a user-passthrough backstore

2014-09-19 Thread Alex Elsayed
Nicholas A. Bellinger wrote: snip So the idea of allowing the in-kernel CDB emulation to run after user-space has returned unsupported opcode is problematic for a couple of different reasons. First, if the correct feature bits in standard INQUIRY + EVPD INQUIRY, etc are not populated by

Re: [PATCH 4/4] target: Add a user-passthrough backstore

2014-09-19 Thread Nicholas A. Bellinger
On Fri, 2014-09-19 at 14:43 -0700, Alex Elsayed wrote: Nicholas A. Bellinger wrote: snip So the idea of allowing the in-kernel CDB emulation to run after user-space has returned unsupported opcode is problematic for a couple of different reasons. First, if the correct feature bits

Re: [PATCH 4/4] target: Add a user-passthrough backstore

2014-09-19 Thread Alex Elsayed
Nicholas A. Bellinger wrote: On Fri, 2014-09-19 at 14:43 -0700, Alex Elsayed wrote: Nicholas A. Bellinger wrote: snip So the idea of allowing the in-kernel CDB emulation to run after user-space has returned unsupported opcode is problematic for a couple of different reasons.

Re: [PATCH 4/4] target: Add a user-passthrough backstore

2014-09-19 Thread Andy Grover
On 09/19/2014 04:51 PM, Alex Elsayed wrote: Not sure I follow.. How does the proposed passthrough mode prevent someone from emulating OSDs, media changers, optical disks or anything else in userspace with TCMU..? The main thing that the above comments highlight is why attempting to combine

[PATCH 4/4] target: Add a user-passthrough backstore

2014-09-15 Thread Andy Grover
Add a LIO storage engine that presents commands to userspace for execution. This would allow more complex backstores to be implemented out-of-kernel, and also make experimentation a-la FUSE (but at the SCSI level -- SUSE?) possible. It uses a mmap()able UIO device per LUN to share a command ring