• Tejun Heo's avatar
    block: implement and enforce request peek/start/fetch · 9934c8c0
    Tejun Heo authored
    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: default avatarTejun 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: default avatarJens Axboe <jens.axboe@oracle.com>
    9934c8c0
blk-tag.c 9.79 KB