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: Christoph Hellwig <hch@lst.de>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Mike Snitzer <snitzer@redhat.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Acked-by: Coly Li <colyli@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index 5edc307..ef27570 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -1925,8 +1925,7 @@ void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,
}
#endif
- /* Allow reads to exceed readahead limits */
- q->backing_dev_info->io_pages = limits->max_sectors >> (PAGE_SHIFT - 9);
+ blk_queue_update_readahead(q);
}
unsigned int dm_table_get_num_targets(struct dm_table *t)