linux-kernel - [PATCH 0/4] tcm: Add WriteCache + FUA Write support to TCM/FILEIO

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Date:	Thu, 26 Aug 2010 21:32:48 -0700
From:	"Nicholas A. Bellinger" <nab@...ux-iscsi.org>
To:	linux-scsi <linux-scsi@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Cc:	Christoph Hellwig <hch@....de>, Tejun Heo <teheo@...e.de>,
	FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>,
	Mike Christie <michaelc@...wisc.edu>,
	Hannes Reinecke <hare@...e.de>,
	James Bottomley <James.Bottomley@...e.de>,
	Nicholas Bellinger <nab@...ux-iscsi.org>
Subject: [PATCH 0/4] tcm: Add WriteCache + FUA Write support to TCM/FILEIO

From: Nicholas Bellinger <nab@...ux-iscsi.org>

Greetings hch, tejun and Co,

This patch series adds WriteCache + FUA Write emulation support into TCM v4 Core and
ConfigFS generic code at lio-core-2.6.git/lio-4.0.  The series changes the TCM
subsystem plugin API at include/target/target_core_transport.h:struct se_subsystem_api
that allows SYNCHRONIZE_CACHE emulation to be shared amoungst multiple TCM subsystem
plugins (eg: FILEIO, IBLOCK, RAMDISK).  This series includes initial support for
WCE=1 and DPOFUA=1 using the TCM/FILEIO subsystem plugin.

This first patch adds the device attribute infrastructure emulation into
target_core_transport.c and target_core_device.c, and adds four new configfs attributes
that appear in /sys/kernel/config/target/core/fileio_$ID/$DEV/attrib/

The second patch adds SYNCHRONIZE_CACHE and SYNCHRONIZE_CACHE_16 emulation code
capable of LBA + Range (Number of Blocks) context flushing in target_core_transport.c:
transport_generic_synchronize_cache(). This function uses the new struct se_subsystem_api
->do_sync_cache() and ->do_sync_cache_range() function pointers to make the calls out
into TCM subsystem plugin dependent code.

The third patch updates the MODE_SENSE* emulation for TYPE_DISK to change the
Caching Control Page to set WCE=1, and device type specific area for DPOFUA=1
for the FUA Write emulation bit.  And the final patch modifies TCM/FILEIO to use
the new struct se_subsystem_api callers using fs/sync.c:vfs_fsync() and
vfs_fsync_range() from below transport_generic_synchronize_cache()

Here are the remaining item(s) on the TODO:

	*) Support FUA READs..?
	*) Support for DPO aside from FUA WRITE/READ (is this possible..?)
	*) Using kernel level fcntl() to enable/disable O_SYNC using
	   emulate_write_cache configfs attribute (see patch #4)
	*) Add sense data for failed FUA WRITE task case in TCM/FILEIO
	   drivers/target/target_core_file.c:fd_do_task().

Comments are welcome,

Thanks!

Signed-off-by: Nicholas A. Bellinger <nab@...ux-iscsi.org>

Nicholas Bellinger (4):
  tcm: Add WriteCache and FUADPO infrastructure and attributes
  tcm: Add SYNCHRONIZE_CACHE* CDB infrastructure and emulation
  tcm: Add WriteCache and DPOFUA emulation bits to MODE_SENSE
  tcm/fileio: Add WriteCache and Forced Unit Access WRITE emulation

 drivers/target/target_core_configfs.c  |   16 +++
 drivers/target/target_core_device.c    |   84 +++++++++++++++++
 drivers/target/target_core_file.c      |  159 +++++++++++++++++++++++++++++++-
 drivers/target/target_core_transport.c |  156 ++++++++++++++++++++++++++++---
 include/target/target_core_base.h      |    7 ++
 include/target/target_core_device.h    |    4 +
 include/target/target_core_transport.h |   39 ++++++++
 7 files changed, 450 insertions(+), 15 deletions(-)

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