From 9934c8c04561413609d2bc38c6b9f268cba774a4 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Fri, 8 May 2009 11:54:16 +0900 Subject: 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 Cc: Rusty Russell Cc: James Bottomley Cc: Mike Miller Cc: unsik Kim Cc: Paul Clements Cc: Tim Waugh Cc: Geert Uytterhoeven Cc: David S. Miller Cc: Laurent Vivier Cc: Jeff Garzik Cc: Jeremy Fitzhardinge Cc: Grant Likely Cc: Adrian McMenamin Cc: Stephen Rothwell Cc: Bartlomiej Zolnierkiewicz Cc: Borislav Petkov Cc: Sergei Shtylyov Cc: Alex Dubov Cc: Pierre Ossman Cc: David Woodhouse Cc: Markus Lidel Cc: Stefan Weinhuber Cc: Martin Schwidefsky Cc: Pete Zaitcev Cc: FUJITA Tomonori Signed-off-by: Jens Axboe --- drivers/scsi/scsi_lib.c | 10 +++++----- drivers/scsi/scsi_transport_sas.c | 4 +--- 2 files changed, 6 insertions(+), 8 deletions(-) (limited to 'drivers/scsi') diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c index ee308f6f7982..b12750f82169 100644 --- a/drivers/scsi/scsi_lib.c +++ b/drivers/scsi/scsi_lib.c @@ -1207,7 +1207,7 @@ int scsi_prep_return(struct request_queue *q, struct request *req, int ret) break; case BLKPREP_DEFER: /* - * If we defer, the elv_next_request() returns NULL, but the + * If we defer, the blk_peek_request() returns NULL, but the * queue must be restarted, so we plug here if no returning * command will automatically do that. */ @@ -1385,7 +1385,7 @@ static void scsi_kill_request(struct request *req, struct request_queue *q) struct scsi_target *starget = scsi_target(sdev); struct Scsi_Host *shost = sdev->host; - blkdev_dequeue_request(req); + blk_start_request(req); if (unlikely(cmd == NULL)) { printk(KERN_CRIT "impossible request in %s.\n", @@ -1477,7 +1477,7 @@ static void scsi_request_fn(struct request_queue *q) if (!sdev) { printk("scsi: killing requests for dead queue\n"); - while ((req = elv_next_request(q)) != NULL) + while ((req = blk_peek_request(q)) != NULL) scsi_kill_request(req, q); return; } @@ -1498,7 +1498,7 @@ static void scsi_request_fn(struct request_queue *q) * that the request is fully prepared even if we cannot * accept it. */ - req = elv_next_request(q); + req = blk_peek_request(q); if (!req || !scsi_dev_queue_ready(q, sdev)) break; @@ -1514,7 +1514,7 @@ static void scsi_request_fn(struct request_queue *q) * Remove the request from the request list. */ if (!(blk_queue_tagged(q) && !blk_queue_start_tag(q, req))) - blkdev_dequeue_request(req); + blk_start_request(req); sdev->device_busy++; spin_unlock(q->queue_lock); diff --git a/drivers/scsi/scsi_transport_sas.c b/drivers/scsi/scsi_transport_sas.c index 50988cbf7b2d..d606452297cf 100644 --- a/drivers/scsi/scsi_transport_sas.c +++ b/drivers/scsi/scsi_transport_sas.c @@ -163,12 +163,10 @@ static void sas_smp_request(struct request_queue *q, struct Scsi_Host *shost, int (*handler)(struct Scsi_Host *, struct sas_rphy *, struct request *); while (!blk_queue_plugged(q)) { - req = elv_next_request(q); + req = blk_fetch_request(q); if (!req) break; - blkdev_dequeue_request(req); - spin_unlock_irq(q->queue_lock); handler = to_sas_internal(shost->transportt)->f->smp_handler; -- cgit v1.2.3