tcm: Add TPE=1 / UNMAP emulation + passthrough support

From: Nicholas Bellinger <[email protected]>

Greetings all,

This series adds generic TPE=1 / UNMAP support into TCM Core and TCM/IBLOCK + TCM/FILEIO subsystem plugin code code to issue blkdev_issue_discard() for struct block_device that support QUEUE_FLAG_DISCARD. Using TPE=1 / UNMAP is also supported with direct struct request passthrough using TCM/pSCSI and everything required for this to function is included in patch #1.

Patch #1 also includes the addition of the SBC-3 Block Limits VPD (0xb0) page and adds the following UNMAP related knobs returned into configfs attributes in /sys/kernel/config/target/core/$HBA/$DEV/attrib, the new ones include:

*) optimal_sectors (currently set to our ->max_sectors) *) max_unmap_block_desc_count (set to 0 by default) *) max_unmap_lba_count (set to 0 by default) *) unmap_granularity (set to 0 by default)
*) unmap_granularity_alignment (set to 0 by default)

Patch #2 includes the necessary changes to IBLOCK to detect QUEUE_FLAG_DISCARD and call transport_generic_unmap() for each UNMAP op.

Patch #3 includes the necessary changes to FILEIO w/ a valid S_ISBLK() to detect QUEUE_FLAG_DISCARD and call transport_generic_unmap() for each UNMAP op. This is the one item I am unsure about, eg: using iget() + iput() to locate struct block_device for blk_issue_discard()..? hch..?

So far these patches have been tested with scsi_debug LUNs w/ TPE=1 with both IBLOCK and FILEIO TPE=1 emulation modes, along with TCM/pSCSI passthrough mode on v2.6.36-rc4 HVM. Here is what Block Limits VPD output looks like via TCM_Loop:

target# sg_inq --page=0xb0 /dev/sdh
VPD INQUIRY: Block limits page (SBC)
Maximum compare and write length: 0 blocks Optimal transfer length granularity: 1 blocks Maximum transfer length: 1024 blocks
Optimal transfer length: 1024 blocks
Maximum prefetch, xdread, xdwrite transfer length: 0 blocks Maximum unmap LBA count: 0
Maximum unmap block descriptor count: 0
Optimal unmap granularity: 0
Unmap granularity alignment valid: 0
Unmap granularity alignment: 0

and with sg_unmap:

	target# sg_unmap -v --lba=78 --num=4 --verbose /dev/sdh
	open /dev/sdh with flags=0x802
	    unmap cdb: 42 00 00 00 00 00 00 00 18 00 
	    unmap parameter list:
	        00 16 00 10 00 00 00 00  00 00 00 00 00 00 00 4e    
	        00 00 00 04 00 00 00 00                         

Comments are welcome!

Nicholas Bellinger (3):
tcm: Add Thin Provisioning / UNMAP emulation and Block Limits VPD
page
tcm/iblock: Add UNMAP / Block DISCARD support tcm/fileio: Add UNMAP / Block DISCARD support

 drivers/target/target_core_configfs.c  |   24 +++++
 drivers/target/target_core_device.c    |   90 +++++++++++++++++++
 drivers/target/target_core_file.c      |   53 +++++++++++-
 drivers/target/target_core_iblock.c    |   19 ++++-
 drivers/target/target_core_transport.c |  152 ++++++++++++++++++++++++++++++++
 include/target/target_core_base.h      |    9 ++-
 include/target/target_core_device.h    |    6 ++
 include/target/target_core_transport.h |   11 +++
 8 files changed, 361 insertions(+), 3 deletions(-)