New: LIO ignores XCOPY source and destination descriptor IDs

https://bugzilla.kernel.org/show_bug.cgi?id=191381

            Bug ID: 191381
           Summary: LIO ignores XCOPY source and destination descriptor
                    IDs
           Product: IO/Storage
           Version: 2.5
    Kernel Version: 4.9.0
          Hardware: All
                OS: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: SCSI
          Assignee: [email protected]
          Reporter: [email protected]
        Regression: No

The EXTENDED COPY SCSI command (XCOPY) is used extensively by VMware ESX initiators, to offload to the iSCSI target, the process of copying data between a source and destination LU region.
XCOPY is also supported by other initiators, such as ddpt
(http://sg.danny.cz/sg/ddpt.html), libiscsi, etc.

The XCOPY specification in SPC-4 (revision 37) states that the XCOPY source and destination device(s) should be derived from the copy source and copy destination descriptor (CSCD) IDs in the XCOPY segment descriptor. The CSCD IDs are generally (for block -> block copies), indexes into the corresponding CSCD list, i.e.

=================================
XCOPY Header
=================================
CSCD List
- entry 0
+ LU ID
- entry 2
+ LU ID
=================================
Segment Descriptor List
- segment 0
+ src CSCD ID = (CSCD entry 0)
+ dest CSCD ID = (CSCD entry 1)
+ len
+ src lba
+ dest lba
=================================

Currently LIO completely ignores the src and dest CSCD IDs in the Segment Descriptor List, and instead assumes that the first entry in the CSCD list corresponds to the source, and the second to the destination.

This assumption appears to stand true for XCOPY requests from ESXi initiators. However, deviation from the spec may break other initiators - it causes a number of libiscsi tests to fail.

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https://bugzilla.kernel.org/show_bug.cgi?id=191381

--- Comment #1 from David Disseldorp <[email protected]> --- I've pushed a reproducer to:
https://github.com/ddiss/libiscsi/commit/ae159e147ddf7192ff41e2375c073a10d6c90fb6

Usage is:
examples/iscsi-dd --xcopy --src iscsi://192.168.155.101:3260/<iqn>/<src_lun> --dst iscsi://192.168.155.101:3260/<iqn>/<dst_lun>

iscsi-dd has been modified to issue XCOPY requests with the CSCD List order modified such that the destination (specified via segment descriptor ID) appears before the source.

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https://bugzilla.kernel.org/show_bug.cgi?id=191381

David Disseldorp <[email protected]> changed:

What |Removed |Added
----------------------------------------------------------------------------

             Status|NEW                         |RESOLVED
         Resolution|---                         |CODE_FIX

--- Comment #2 from David Disseldorp <[email protected]> --- LIO XCOPY fixes merged to Linus' tree:
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/log/?id=87156518da94a696f2b27ab8945d531af2f1d339&showmsg=1

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