linux/block
Tejun Heo 9934c8c045 block: implement and enforce request peek/start/fetch
Till now block layer allowed two separate modes of request execution.
A request is always acquired from the request queue via
elv_next_request().  After that, drivers are free to either dequeue it
or process it without dequeueing.  Dequeue allows elv_next_request()
to return the next request so that multiple requests can be in flight.

Executing requests without dequeueing has its merits mostly in
allowing drivers for simpler devices which can't do sg to deal with
segments only without considering request boundary.  However, the
benefit this brings is dubious and declining while the cost of the API
ambiguity is increasing.  Segment based drivers are usually for very
old or limited devices and as converting to dequeueing model isn't
difficult, it doesn't justify the API overhead it puts on block layer
and its more modern users.

Previous patches converted all block low level drivers to dequeueing
model.  This patch completes the API transition by...

* renaming elv_next_request() to blk_peek_request()

* renaming blkdev_dequeue_request() to blk_start_request()

* adding blk_fetch_request() which is combination of peek and start

* disallowing completion of queued (not started) requests

* applying new API to all LLDs

Renamings are for consistency and to break out of tree code so that
it's apparent that out of tree drivers need updating.

[ Impact: block request issue API cleanup, no functional change ]

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Mike Miller <mike.miller@hp.com>
Cc: unsik Kim <donari75@gmail.com>
Cc: Paul Clements <paul.clements@steeleye.com>
Cc: Tim Waugh <tim@cyberelk.net>
Cc: Geert Uytterhoeven <Geert.Uytterhoeven@sonycom.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Laurent Vivier <Laurent@lvivier.info>
Cc: Jeff Garzik <jgarzik@pobox.com>
Cc: Jeremy Fitzhardinge <jeremy@xensource.com>
Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: Adrian McMenamin <adrian@mcmen.demon.co.uk>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Cc: Borislav Petkov <petkovbb@googlemail.com>
Cc: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Cc: Alex Dubov <oakad@yahoo.com>
Cc: Pierre Ossman <drzeus@drzeus.cx>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Markus Lidel <Markus.Lidel@shadowconnect.com>
Cc: Stefan Weinhuber <wein@de.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Pete Zaitcev <zaitcev@redhat.com>
Cc: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-05-11 09:52:18 +02:00
..
as-iosched.c block: convert to pos and nr_sectors accessors 2009-05-11 09:50:54 +02:00
blk-barrier.c block: implement and enforce request peek/start/fetch 2009-05-11 09:52:18 +02:00
blk-core.c block: implement and enforce request peek/start/fetch 2009-05-11 09:52:18 +02:00
blk-exec.c block: don't set REQ_NOMERGE unnecessarily 2009-04-28 07:37:33 +02:00
blk-integrity.c block: Allow empty integrity profile 2009-01-30 12:34:36 +01:00
blk-ioc.c cfq-iosched: fix RCU race in the cfq io_context destructor handling 2008-05-07 09:28:57 +02:00
blk-map.c block: hide request sector and data_len 2009-05-11 09:50:55 +02:00
blk-merge.c block: hide request sector and data_len 2009-05-11 09:50:55 +02:00
blk-settings.c block: fix queue bounce limit setting 2009-04-22 08:35:09 +02:00
blk-softirq.c generic-ipi: remove CSD_FLAG_WAIT 2009-02-25 14:13:44 +01:00
blk-sysfs.c block: simplify I/O stat accounting 2009-04-24 08:54:21 +02:00
blk-tag.c block: implement and enforce request peek/start/fetch 2009-05-11 09:52:18 +02:00
blk-timeout.c block: clean up misc stuff after block layer timeout conversion 2009-04-28 07:37:34 +02:00
blk.h block: implement and enforce request peek/start/fetch 2009-05-11 09:52:18 +02:00
bsg.c block: add rq->resid_len 2009-05-11 09:50:53 +02:00
cfq-iosched.c block: drop request->hard_* and *nr_sectors 2009-05-11 09:50:54 +02:00
cmd-filter.c [SCSI] Make scsi.h independent of the rest of the scsi includes 2009-03-12 12:58:13 -05:00
compat_ioctl.c block: don't take lock on changing ra_pages 2008-12-29 08:28:43 +01:00
deadline-iosched.c block: convert to pos and nr_sectors accessors 2009-05-11 09:50:54 +02:00
elevator.c block: convert to pos and nr_sectors accessors 2009-05-11 09:50:54 +02:00
genhd.c block: include empty disks in /proc/diskstats 2009-04-22 08:35:10 +02:00
ioctl.c block: Remove code handling bio_alloc failure with __GFP_WAIT 2009-04-15 12:10:12 +02:00
Kconfig block: enable by default support for large devices and files on 32-bit archs 2009-04-28 07:37:33 +02:00
Kconfig.iosched update I/O sched Kconfig help texts - CFQ is now default, not AS. 2007-02-17 20:08:22 +01:00
Makefile tracing/blktrace: move the tracing file to kernel/trace 2009-02-09 10:51:02 +01:00
noop-iosched.c block: get rid of elevator_t typedef 2008-12-29 08:29:50 +01:00
scsi_ioctl.c block: add rq->resid_len 2009-05-11 09:50:53 +02:00