linux/block
Kiyoshi Ueda 336cdb4003 blk_end_request: add new request completion interface (take 4)
This patch adds 2 new interfaces for request completion:
  o blk_end_request()   : called without queue lock
  o __blk_end_request() : called with queue lock held

blk_end_request takes 'error' as an argument instead of 'uptodate',
which current end_that_request_* take.
The meanings of values are below and the value is used when bio is
completed.
    0 : success
  < 0 : error

Some device drivers call some generic functions below between
end_that_request_{first/chunk} and end_that_request_last().
  o add_disk_randomness()
  o blk_queue_end_tag()
  o blkdev_dequeue_request()
These are called in the blk_end_request interfaces as a part of
generic request completion.
So all device drivers become to call above functions.
To decide whether to call blkdev_dequeue_request(), blk_end_request
uses list_empty(&rq->queuelist) (blk_queued_rq() macro is added for it).
So drivers must re-initialize it using list_init() or so before calling
blk_end_request if drivers use it for its specific purpose.
(Currently, there is no driver which completes request without
 re-initializing the queuelist after used it.  So rq->queuelist
 can be used for the purpose above.)

"Normal" drivers can be converted to use blk_end_request()
in a standard way shown below.

 a) end_that_request_{chunk/first}
    spin_lock_irqsave()
    (add_disk_randomness(), blk_queue_end_tag(), blkdev_dequeue_request())
    end_that_request_last()
    spin_unlock_irqrestore()
    => blk_end_request()

 b) spin_lock_irqsave()
    end_that_request_{chunk/first}
    (add_disk_randomness(), blk_queue_end_tag(), blkdev_dequeue_request())
    end_that_request_last()
    spin_unlock_irqrestore()
    => spin_lock_irqsave()
       __blk_end_request()
       spin_unlock_irqsave()

 c) spin_lock_irqsave()
    (add_disk_randomness(), blk_queue_end_tag(), blkdev_dequeue_request())
    end_that_request_last()
    spin_unlock_irqrestore()
    => blk_end_request()   or   spin_lock_irqsave()
                                __blk_end_request()
                                spin_unlock_irqrestore()

Signed-off-by: Kiyoshi Ueda <k-ueda@ct.jp.nec.com>
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-01-28 10:35:53 +01:00
..
as-iosched.c block: let elv_register() return void 2007-12-18 08:29:28 +01:00
blktrace.c blktrace: kill the unneeded initcall 2008-01-11 13:37:01 +01:00
bsg.c [SCSI] libsas, bsg: pass errors through correctly 2008-01-11 18:29:13 -06:00
cfq-iosched.c block: let elv_register() return void 2007-12-18 08:29:28 +01:00
compat_ioctl.c compat_ioctl: fix block device compat ioctl regression 2007-10-29 11:33:06 +01:00
deadline-iosched.c block: let elv_register() return void 2007-12-18 08:29:28 +01:00
elevator.c Kobject: rename kobject_init_ng() to kobject_init() 2008-01-24 20:40:38 -08:00
genhd.c Driver core: convert block from raw kobjects to core devices 2008-01-24 20:40:36 -08:00
ioctl.c compat_ioctl: move common block ioctls to compat_blkdev_ioctl 2007-10-10 09:26:00 +02:00
Kconfig Only enable BLOCK_COMPAT if COMPAT is needed 2007-10-12 17:58:36 -07:00
Kconfig.iosched update I/O sched Kconfig help texts - CFQ is now default, not AS. 2007-02-17 20:08:22 +01:00
ll_rw_blk.c blk_end_request: add new request completion interface (take 4) 2008-01-28 10:35:53 +01:00
Makefile [BLOCK] Only include the compat ioctl code if CONFIG_BLOCK is set 2007-10-12 12:50:41 +02:00
noop-iosched.c block: let elv_register() return void 2007-12-18 08:29:28 +01:00
scsi_ioctl.c block: use jiffies conversion functions in scsi_ioctl.c 2007-12-18 08:29:28 +01:00