linux/block
Douglas Gilbert d15156138d block SG_IO: add SG_FLAG_Q_AT_HEAD flag
After the SG_IO ioctl was copied into the block layer and
later into the bsg driver, subtle differences emerged.

One difference is the way injected commands are queued through
the block layer (i.e. this is not SCSI device queueing nor SATA
NCQ). Summarizing:
  - SG_IO on block layer device: blk_exec*(at_head=false)
  - sg device SG_IO: at_head=true
  - bsg device SG_IO: at_head=true

Some time ago Boaz Harrosh introduced a sg v4 flag called
BSG_FLAG_Q_AT_TAIL to override the bsg driver default. A
recent patch titled: "sg: add SG_FLAG_Q_AT_TAIL flag"
allowed the sg driver default to be overridden. This patch
allows a SG_IO ioctl sent to a block layer device to have
its default overridden.

ChangeLog:
    - introduce SG_FLAG_Q_AT_HEAD flag in sg.h to cause
      commands that are injected via a block layer
      device SG_IO ioctl to set at_head=true
    - make comments clearer about queueing in sg.h since the
      header is used both by the sg device and block layer
      device implementations of the SG_IO ioctl.
    - introduce BSG_FLAG_Q_AT_HEAD in bsg.h for compatibility
      (it does nothing) and update comments.

Signed-off-by: Douglas Gilbert <dgilbert@interlog.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: Jens Axboe <axboe@fb.com>
2014-07-01 10:48:05 -06:00
..
partitions block/partitions/efi.c: kerneldoc fixing 2014-07-01 10:40:05 -06:00
bio-integrity.c bio-integrity: add "bip_max_vcnt" into struct bio_integrity_payload 2014-07-01 10:36:47 -06:00
bio.c block: add support for limiting gaps in SG lists 2014-06-24 16:22:24 -06:00
blk-cgroup.c Revert "block: add __init to blkcg_policy_register" 2014-06-22 16:34:11 -06:00
blk-cgroup.h Revert "block: add __init to blkcg_policy_register" 2014-06-22 16:34:11 -06:00
blk-core.c blk-mq: decouble blk-mq freezing from generic bypassing 2014-07-01 10:31:13 -06:00
blk-exec.c block: blk-exec.c: Cleaning up local variable address returnd 2014-06-08 19:51:31 -06:00
blk-flush.c block: remove elv_abort_queue and blk_abort_flushes 2014-06-11 15:31:21 -06:00
blk-integrity.c bio-integrity: Convert to bvec_iter 2013-11-23 22:33:50 -08:00
blk-ioc.c block: Substitute rcu_access_pointer() for rcu_dereference_raw() 2014-02-18 12:21:26 -08:00
blk-iopoll.c Merge branch 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip into next 2014-06-03 12:57:53 -07:00
blk-lib.c block/blk-lib.c: make __blkdev_issue_zeroout static 2014-05-26 17:39:09 -06:00
blk-map.c block: remove struct request buffer member 2014-04-15 14:03:02 -06:00
blk-merge.c block: add support for limiting gaps in SG lists 2014-06-24 16:22:24 -06:00
blk-mq-cpu.c blk-mq: add file comments and update copyright notices 2014-05-28 10:15:41 -06:00
blk-mq-cpumap.c blk-mq: add file comments and update copyright notices 2014-05-28 10:15:41 -06:00
blk-mq-sysfs.c blk-mq: blk_mq_unregister_hctx() can be static 2014-05-30 10:31:13 -06:00
blk-mq-tag.c blk-mq: bitmap tag: fix races in bt_get() function 2014-06-17 22:13:08 -07:00
blk-mq-tag.h blk-mq: bitmap tag: fix races on shared ::wake_index fields 2014-06-17 22:12:35 -07:00
blk-mq.c blk-mq: use percpu_ref for mq usage count 2014-07-01 10:34:38 -06:00
blk-mq.h blk-mq: decouble blk-mq freezing from generic bypassing 2014-07-01 10:31:13 -06:00
blk-settings.c block: ensure that bio_add_page() always accepts a page for an empty bio 2014-06-10 12:53:56 -06:00
blk-softirq.c block: fix regression with block enabled tagging 2014-04-09 21:54:06 -06:00
blk-sysfs.c block, blk-mq: draining can't be skipped even if bypass_depth was non-zero 2014-07-01 10:29:17 -06:00
blk-tag.c block: Reserve only one queue tag for sync IO if only 3 tags are available 2013-06-28 21:32:27 +02:00
blk-throttle.c Merge branch 'for-3.16' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup 2014-06-09 15:03:33 -07:00
blk-timeout.c block: ensure that the timer is always added 2014-05-30 15:41:39 -06:00
blk.h block: remove elv_abort_queue and blk_abort_flushes 2014-06-11 15:31:21 -06:00
bounce.c mm: convert some level-less printks to pr_* 2014-06-06 16:08:18 -07:00
bsg-lib.c bsg: Remove unused function bsg_goose_queue() 2012-12-06 14:33:02 +01:00
bsg.c block: add blk_rq_set_block_pc() 2014-06-06 07:57:37 -06:00
cfq-iosched.c Merge branch 'for-3.16' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup 2014-06-09 15:03:33 -07:00
cmdline-parser.c block: remove unrelated header files and export symbol 2014-01-21 20:18:26 -08:00
compat_ioctl.c block: fix BLKSECTGET ioctl when max_sectors is greater than USHRT_MAX 2014-07-01 10:43:07 -06:00
deadline-iosched.c block: Stop abusing csd.list for fifo_time 2014-02-24 14:46:32 -08:00
elevator.c Revert "block: add __init to elv_register" 2014-06-22 16:34:11 -06:00
genhd.c block: Convert kmalloc_node(...GFP_ZERO...) to kzalloc_node(...) 2013-09-11 13:22:03 -06:00
ioctl.c block: fix BLKSECTGET ioctl when max_sectors is greater than USHRT_MAX 2014-07-01 10:43:07 -06:00
ioprio.c block: move ioprio.c from fs/ to block/ 2014-05-19 11:02:18 -06:00
Kconfig block: change config option name for cmdline partition parsing 2013-09-30 14:31:02 -07:00
Kconfig.iosched blkcg: make CONFIG_BLK_CGROUP bool 2012-03-06 21:27:21 +01:00
Makefile block: move mm/bounce.c to block/ 2014-05-19 20:01:52 -06:00
noop-iosched.c elevator: Fix a race in elevator switching 2013-07-03 13:25:24 +02:00
partition-generic.c Revert "loop: cleanup partitions when detaching loop device" 2013-04-08 10:12:11 +02:00
scsi_ioctl.c block SG_IO: add SG_FLAG_Q_AT_HEAD flag 2014-07-01 10:48:05 -06:00