Commit c2e4cd57 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Jens Axboe
Browse files

block: lift setting the readahead size into the block layer 



Drivers shouldn't really mess with the readahead size, as that is a VM
concept.  Instead set it based on the optimal I/O size by lifting the
algorithm from the md driver when registering the disk.  Also set
bdi->io_pages there as well by applying the same scheme based on
max_sectors.  To ensure the limits work well for stacking drivers a
new helper is added to update the readahead limits from the block
limits, which is also called from disk_stack_limits.

Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarJohannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: default avatarJan Kara <jack@suse.cz>
Reviewed-by: default avatarMike Snitzer <snitzer@redhat.com>
Reviewed-by: default avatarMartin K. Petersen <martin.petersen@oracle.com>
Acked-by: default avatarColy Li <colyli@suse.de>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 16ef5101

block/blk-settings.c

+16 −2
Original line number Diff line number Diff line
@@ -372,6 +372,19 @@ void blk_queue_alignment_offset(struct request_queue *q, unsigned int offset) 
}

EXPORT_SYMBOL(blk_queue_alignment_offset);



void blk_queue_update_readahead(struct request_queue *q)

{

	/*

	 * For read-ahead of large files to be effective, we need to read ahead

	 * at least twice the optimal I/O size.

	 */

	q->backing_dev_info->ra_pages =

		max(queue_io_opt(q) * 2 / PAGE_SIZE, VM_READAHEAD_PAGES);

	q->backing_dev_info->io_pages =

		queue_max_sectors(q) >> (PAGE_SHIFT - 9);

}

EXPORT_SYMBOL_GPL(blk_queue_update_readahead);



/**

 * blk_limits_io_min - set minimum request size for a device

 * @limits: the queue limits
@@ -450,6 +463,8 @@ EXPORT_SYMBOL(blk_limits_io_opt); 
void blk_queue_io_opt(struct request_queue *q, unsigned int opt)

{

	blk_limits_io_opt(&q->limits, opt);

	q->backing_dev_info->ra_pages =

		max(queue_io_opt(q) * 2 / PAGE_SIZE, VM_READAHEAD_PAGES);

}

EXPORT_SYMBOL(blk_queue_io_opt);
@@ -631,8 +646,7 @@ void disk_stack_limits(struct gendisk *disk, struct block_device *bdev, 
		       top, bottom);

	}



	t->backing_dev_info->io_pages =

		t->limits.max_sectors >> (PAGE_SHIFT - 9);

	blk_queue_update_readahead(disk->queue);

}

EXPORT_SYMBOL(disk_stack_limits);

block/blk-sysfs.c

+2 −0
Original line number Diff line number Diff line
@@ -854,6 +854,8 @@ int blk_register_queue(struct gendisk *disk) 
		percpu_ref_switch_to_percpu(&q->q_usage_counter);

	}



	blk_queue_update_readahead(q);



	ret = blk_trace_init_sysfs(dev);

	if (ret)

		return ret;

drivers/block/aoe/aoeblk.c

+0 −1
Original line number Diff line number Diff line
@@ -406,7 +406,6 @@ aoeblk_gdalloc(void *vp) 
	WARN_ON(d->gd);

	WARN_ON(d->flags & DEVFL_UP);

	blk_queue_max_hw_sectors(q, BLK_DEF_MAX_SECTORS);

	q->backing_dev_info->ra_pages = SZ_2M / PAGE_SIZE;

	blk_queue_io_opt(q, SZ_2M);

	d->bufpool = mp;

	d->blkq = gd->queue = q;

drivers/block/drbd/drbd_nl.c

+1 −9
Original line number Diff line number Diff line
@@ -1362,15 +1362,7 @@ static void drbd_setup_queue_param(struct drbd_device *device, struct drbd_backi 


	if (b) {

		blk_stack_limits(&q->limits, &b->limits, 0);



		if (q->backing_dev_info->ra_pages !=

		    b->backing_dev_info->ra_pages) {

			drbd_info(device, "Adjusting my ra_pages to backing device's (%lu -> %lu)\n",

				 q->backing_dev_info->ra_pages,

				 b->backing_dev_info->ra_pages);

			q->backing_dev_info->ra_pages =

						b->backing_dev_info->ra_pages;

		}

		blk_queue_update_readahead(q);

	}

	fixup_discard_if_not_supported(q);

	fixup_write_zeroes(device, q);

drivers/md/bcache/super.c

+0 −3
Original line number Diff line number Diff line
@@ -1427,9 +1427,6 @@ static int cached_dev_init(struct cached_dev *dc, unsigned int block_size) 
	if (ret)

		return ret;



	dc->disk.disk->queue->backing_dev_info->ra_pages =

		max(dc->disk.disk->queue->backing_dev_info->ra_pages,

		    q->backing_dev_info->ra_pages);

	blk_queue_io_opt(dc->disk.disk->queue,

		max(queue_io_opt(dc->disk.disk->queue), queue_io_opt(q)));

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