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authorTejun Heo <tj@kernel.org>2009-05-07 22:54:16 -0400
committerJens Axboe <jens.axboe@oracle.com>2009-05-11 03:52:18 -0400
commit9934c8c04561413609d2bc38c6b9f268cba774a4 (patch)
tree30dd8f7be54f9b2e03094de9cd03b6a9ee2909cd /include/linux/blkdev.h
parent2343046826a8ca426b07601d9593ee046c298b68 (diff)
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>
Diffstat (limited to 'include/linux/blkdev.h')
-rw-r--r--include/linux/blkdev.h9
1 files changed, 7 insertions, 2 deletions
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index c75580345700..6e59d3b92ff2 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -818,8 +818,6 @@ static inline void blk_run_address_space(struct address_space *mapping)
818 blk_run_backing_dev(mapping->backing_dev_info, NULL); 818 blk_run_backing_dev(mapping->backing_dev_info, NULL);
819} 819}
820 820
821extern void blkdev_dequeue_request(struct request *req);
822
823/* 821/*
824 * blk_rq_pos() : the current sector 822 * blk_rq_pos() : the current sector
825 * blk_rq_bytes() : bytes left in the entire request 823 * blk_rq_bytes() : bytes left in the entire request
@@ -853,6 +851,13 @@ static inline unsigned int blk_rq_cur_sectors(const struct request *rq)
853} 851}
854 852
855/* 853/*
854 * Request issue related functions.
855 */
856extern struct request *blk_peek_request(struct request_queue *q);
857extern void blk_start_request(struct request *rq);
858extern struct request *blk_fetch_request(struct request_queue *q);
859
860/*
856 * Request completion related functions. 861 * Request completion related functions.
857 * 862 *
858 * blk_update_request() completes given number of bytes and updates 863 * blk_update_request() completes given number of bytes and updates