Nicholas A. Bellinger, on 09/15/2009 12:49 AM wrote:
On Mon, 2009-09-14 at 22:50 +0400, Vladislav Bolkhovitin wrote:
Nicholas A. Bellinger, on 09/12/2009 05:55 AM wrote:
Greetings all,
This is my humble request for review and inclusion of
Target_Core_Mod/ConfigFS v3.2 from lio-core-2.6.git code into mainline
v2.6.32. With TCM v3.2, the two major SPC-4 SCSI target mode fabric
features that have now been completed: Persistent Reservation APTPL and
implict/explict ALUA are the first all optional SPC4 defined feature
implementation of PR and ALUA in the Linux OSS target theatre using an
upstream user-driven virtual filesystem directory hierarchy structure
based on configfs that can be configured in realtime in combination with
interpreted userspace code.
Both of these new features are now being used to provide Persistent Reservations
across target power loss and asymmetric multipath I/O to both Linux and non-Linux
clients. There is also an optional ALUA transition delay logic that has been
included to futher debug and improve existing upstream client side Linux kernel code
using TCM v3.2. These patches have been diffed against v2.6.31, and tested on x86
32-bit HVM, x86_64 KVM, and powerpc.
There is cleanup work continuing to make the TCM code to use dprintk(),
and some include cleanups, and other minor fixes. The code has also
been run through checkpatch again since the posting in April, and all
errors have been removed, with the exception of one ConfigFS macro
define triggering a checkpatch false positive.
As with the posting of the TCM v3.0 code earlier in April, I have
decided to break up the submissions into the generic target_core_mod
piece (this patch series) and then a seperate one that will be appearing
in the next days for v3.2 of the LIO-Target iSCSI fabric module.
More Information about Target_Core_Mod/ConfigFS, and PR and ALUA:
http://www.linux-iscsi.org/index.php/Target_Core_Mod/ConfigFS
http://www.linux-iscsi.org/index.php/Persistent_Reservations
http://www.linux-iscsi.org/index.php/ALUA
The complete v3.x TCM CLI operations set can be found here:
http://www.linux-iscsi.org/index.php/Lio-utils#v3.1_TCM_CLI_operations
Instructions and examples for getting setup:
http://linux-iscsi.org/builds/docs/LIO-3.0-Users_Reference_Manual.pdf
http://www.linux-iscsi.org/index.php/Howto#Start_target_core_mod
Some questions among many I have:
1. Where and how TCM is better over the existing mainline target
framework STGT to justify such a move as adding a new piece of code
doing the same job?
I think from reading my original email and the list of patches it is
quite obvious to the people involved what are the major pieces of
functionality available in TCM v3.2 that people actually *want* and
*care* about that is not available in the existing STGT framework.
Probably, I'm not sufficiently smart, but benefits of "TCM v3.2" aren't
obvious for me at all. Could you list them point by point?
Especially interesting, why the above mentioned features can't be added
in the STGT instead of creating something a whole new?
2. On the linux-iscsi.org main page (BTW, the comparison on that page
isn't fully correct about STGT and SCST) you claim that TCM is a generic
target engine. But how can you prove (and test) that if there are no
hardware target drivers for TCM?
I am not sure why you think you need hardware target drivers to prove
that a target engine is generic..? Why don't you look at the TCM v3.2
code (like everyone else is doing) and see for yourself..?
I looked there many times. Hardware target drivers fundamentally
different from software drivers, because they need to do some processing
on IRQ level. You can't test the corresponding target's framework
branches and prove they provide sufficient functionality using a driver,
which doesn't need such functionality.
Also patch 7 implements MIBs through procfs. Procfs is for long time
forbidden for adding anything like that, so you can't push it in the
mainline.
There are other subsystems (Linux/Net and SCTP for example) that use
procfs for read-only MIBs statistics, so TCM actually having an
implementation of SCSI MIBs available (no other target projects have
SCSI MIBs btw) under procfs is hardly a show-stopper considering the
*entire* control path for TCM v3.2 is using upstream configfs code
anyways.
Addition of new non-process related entries in /proc is fully forbidden
and it doesn't matter if those entries used on "control path" or in
corner cases.
Vlad
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