linux/drivers/target
bstroesser@ts.fujitsu.com 6c3796d130 scsi: target: tcmu: add read length support
Generally target core and TCMUser seem to work fine for tape devices and
media changers.  But there is at least one situation where TCMUser is not
able to support sequential access device emulation correctly.

The situation is when an initiator sends a SCSI READ CDB with a length that
is greater than the length of the tape block to read. We can distinguish
two subcases:

A) The initiator sent the READ CDB with the SILI bit being set.

   In this case the sequential access device has to transfer the data from
   the tape block (only the length of the tape block) and transmit a good
   status.  The current interface between TCMUser and the userspace does
   not support reduction of the read data size by the userspace program.

   The patch below fixes this subcase by allowing the userspace program to
   specify a reduced data size in read direction.

B) The initiator sent the READ CDB with the SILI bit not being set.

   In this case the sequential access device has to transfer the data from
   the tape block as in A), but additionally has to transmit CHECK
   CONDITION with the ILI bit set and NO SENSE in the sensebytes. The
   information field in the sensebytes must contain the residual count.

   With the below patch a user space program can specify the real read data
   length and appropriate sensebytes.  TCMUser then uses the se_cmd flag
   SCF_TREAT_READ_AS_NORMAL, to force target core to transmit the real data
   size and the sensebytes.  Note: the flag SCF_TREAT_READ_AS_NORMAL is
   introduced by Lee Duncan's patch "[PATCH v4] target: transport should
   handle st FM/EOM/ILI reads" from Tue, 15 May 2018 18:25:24 -0700.

Signed-off-by: Bodo Stroesser <bstroesser@ts.fujitsu.com>
Acked-by: Mike Christie <mchristi@redhat.com>
Reviewed-by: Lee Duncan <lduncan@suse.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
2018-06-18 21:02:52 -04:00
..
iscsi for-4.17/block-20180402 2018-04-05 14:27:02 -07:00
loopback target/tcm_loop: Use blk_queue_flag_set() 2018-03-08 14:13:48 -07:00
sbp sbp-target: Delete an error message for a failed memory allocation in three functions 2018-01-12 15:07:21 -08:00
tcm_fc License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
Kconfig target: Use sgl_alloc_order() and sgl_free() 2018-01-06 09:18:00 -07:00
Makefile License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
target_core_alua.c target: fix ALUA state file path truncation 2017-11-04 15:00:30 -07:00
target_core_alua.h Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/nab/target-pending 2017-11-24 19:19:20 -10:00
target_core_configfs.c scsi: target: prefer dbroot of /etc/target over /var/target 2018-04-19 00:47:02 -04:00
target_core_device.c target: fix destroy device in target_configure_device 2018-01-18 01:21:11 -08:00
target_core_fabric_configfs.c target: Move a declaration of a global variable into a header file 2017-11-04 15:15:30 -07:00
target_core_fabric_lib.c target-core: don't use "const char*" for a buffer that is written to 2018-01-12 15:07:09 -08:00
target_core_file.c scsi: target: target/file: Add support of direct and async I/O 2018-05-14 22:40:08 -04:00
target_core_file.h scsi: target: target/file: Add support of direct and async I/O 2018-05-14 22:40:08 -04:00
target_core_hba.c
target_core_iblock.c target: convert to bioset_init()/mempool_init() 2018-05-30 15:33:32 -06:00
target_core_iblock.h target: convert to bioset_init()/mempool_init() 2018-05-30 15:33:32 -06:00
target_core_internal.h scsi: target: prefer dbroot of /etc/target over /var/target 2018-04-19 00:47:02 -04:00
target_core_pr.c target-core: don't use "const char*" for a buffer that is written to 2018-01-12 15:07:09 -08:00
target_core_pr.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
target_core_pscsi.c SCSI misc on 20180610 2018-06-10 13:01:12 -07:00
target_core_pscsi.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
target_core_rd.c target: break up free_device callback 2017-07-06 23:11:37 -07:00
target_core_rd.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
target_core_sbc.c target: don't call an unmap callback if a range length is zero 2018-01-12 15:07:28 -08:00
target_core_spc.c target: Fix cmd size for PR-OUT in passthrough_parse_cdb 2017-07-09 20:58:49 -07:00
target_core_stat.c target: make config_item_type const 2017-10-19 16:15:17 +02:00
target_core_tmr.c target: Avoid early CMD_T_PRE_EXECUTE failures during ABORT_TASK 2017-11-07 19:50:24 -08:00
target_core_tpg.c target: Fix node_acl demo-mode + uncached dynamic shutdown regression 2017-08-09 20:55:19 -07:00
target_core_transport.c treewide: Use array_size() in vzalloc() 2018-06-12 16:19:22 -07:00
target_core_ua.c
target_core_ua.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
target_core_user.c scsi: target: tcmu: add read length support 2018-06-18 21:02:52 -04:00
target_core_xcopy.c xcopy: loop over devices using idr helper 2017-07-06 23:11:40 -07:00
target_core_xcopy.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00