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/block/blk-settings.c b/block/blk-settings.c
index 5ea3de4..4f6eb4b 100644 (file)
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -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);
 

diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 81722cd..869ed21 100644 (file)
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -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;

diff --git a/drivers/block/aoe/aoeblk.c b/drivers/block/aoe/aoeblk.c
index d8cfc23..c34e71b 100644 (file)
--- a/drivers/block/aoe/aoeblk.c
+++ b/drivers/block/aoe/aoeblk.c
@@ -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;

diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
index aaff5bd..54a4930 100644 (file)
--- a/drivers/block/drbd/drbd_nl.c
+++ b/drivers/block/drbd/drbd_nl.c
@@ -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);

diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index 4811300..6bfa771 100644 (file)
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -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)));
 

diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index 5edc307..ef27570 100644 (file)
--- 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)

diff --git a/drivers/md/raid0.c b/drivers/md/raid0.c
index f54a449..aa2d727 100644 (file)
--- a/drivers/md/raid0.c
+++ b/drivers/md/raid0.c
@@ -410,22 +410,6 @@ static int raid0_run(struct mddev *mddev)
                 mdname(mddev),
                 (unsigned long long)mddev->array_sectors);
 
-       if (mddev->queue) {
-               /* calculate the max read-ahead size.
-                * For read-ahead of large files to be effective, we need to
-                * readahead at least twice a whole stripe. i.e. number of devices
-                * multiplied by chunk size times 2.
-                * If an individual device has an ra_pages greater than the
-                * chunk size, then we will not drive that device as hard as it
-                * wants.  We consider this a configuration error: a larger
-                * chunksize should be used in that case.
-                */
-               int stripe = mddev->raid_disks *
-                       (mddev->chunk_sectors << 9) / PAGE_SIZE;
-               if (mddev->queue->backing_dev_info->ra_pages < 2* stripe)
-                       mddev->queue->backing_dev_info->ra_pages = 2* stripe;
-       }
-
        dump_zones(mddev);
 
        ret = md_integrity_register(mddev);

diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 9956a04..5d1bdee 100644 (file)
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -3873,19 +3873,6 @@ static int raid10_run(struct mddev *mddev)
        mddev->resync_max_sectors = size;
        set_bit(MD_FAILFAST_SUPPORTED, &mddev->flags);
 
-       if (mddev->queue) {
-               int stripe = conf->geo.raid_disks *
-                       ((mddev->chunk_sectors << 9) / PAGE_SIZE);
-
-               /* Calculate max read-ahead size.
-                * We need to readahead at least twice a whole stripe....
-                * maybe...
-                */
-               stripe /= conf->geo.near_copies;
-               if (mddev->queue->backing_dev_info->ra_pages < 2 * stripe)
-                       mddev->queue->backing_dev_info->ra_pages = 2 * stripe;
-       }
-
        if (md_integrity_register(mddev))
                goto out_free_conf;
 
@@ -4723,17 +4710,8 @@ static void end_reshape(struct r10conf *conf)
        conf->reshape_safe = MaxSector;
        spin_unlock_irq(&conf->device_lock);
 
-       /* read-ahead size must cover two whole stripes, which is
-        * 2 * (datadisks) * chunksize where 'n' is the number of raid devices
-        */
-       if (conf->mddev->queue) {
-               int stripe = conf->geo.raid_disks *
-                       ((conf->mddev->chunk_sectors << 9) / PAGE_SIZE);
-               stripe /= conf->geo.near_copies;
-               if (conf->mddev->queue->backing_dev_info->ra_pages < 2 * stripe)
-                       conf->mddev->queue->backing_dev_info->ra_pages = 2 * stripe;
+       if (conf->mddev->queue)
                raid10_set_io_opt(conf);
-       }
        conf->fullsync = 0;
 }
 

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 9a7d125..7ace1f7 100644 (file)
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -7522,8 +7522,6 @@ static int raid5_run(struct mddev *mddev)
                int data_disks = conf->previous_raid_disks - conf->max_degraded;
                int stripe = data_disks *
                        ((mddev->chunk_sectors << 9) / PAGE_SIZE);
-               if (mddev->queue->backing_dev_info->ra_pages < 2 * stripe)
-                       mddev->queue->backing_dev_info->ra_pages = 2 * stripe;
 
                chunk_size = mddev->chunk_sectors << 9;
                blk_queue_io_min(mddev->queue, chunk_size);
@@ -8111,17 +8109,8 @@ static void end_reshape(struct r5conf *conf)
                spin_unlock_irq(&conf->device_lock);
                wake_up(&conf->wait_for_overlap);
 
-               /* read-ahead size must cover two whole stripes, which is
-                * 2 * (datadisks) * chunksize where 'n' is the number of raid devices
-                */
-               if (conf->mddev->queue) {
-                       int data_disks = conf->raid_disks - conf->max_degraded;
-                       int stripe = data_disks * ((conf->chunk_sectors << 9)
-                                                  / PAGE_SIZE);
-                       if (conf->mddev->queue->backing_dev_info->ra_pages < 2 * stripe)
-                               conf->mddev->queue->backing_dev_info->ra_pages = 2 * stripe;
+               if (conf->mddev->queue)
                        raid5_set_io_opt(conf);
-               }
        }
 }
 

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index ea1fa41..741c9bf 100644 (file)
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -2147,6 +2147,7 @@ static int __nvme_revalidate_disk(struct gendisk *disk, struct nvme_id_ns *id)
                nvme_update_disk_info(ns->head->disk, ns, id);
                blk_stack_limits(&ns->head->disk->queue->limits,
                                 &ns->queue->limits, 0);
+               blk_queue_update_readahead(ns->head->disk->queue);
                nvme_update_bdev_size(ns->head->disk);
        }
 #endif

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index be5ef6f..282f5ca 100644 (file)
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1140,6 +1140,7 @@ extern void blk_queue_max_zone_append_sectors(struct request_queue *q,
 extern void blk_queue_physical_block_size(struct request_queue *, unsigned int);
 extern void blk_queue_alignment_offset(struct request_queue *q,
                                       unsigned int alignment);
+void blk_queue_update_readahead(struct request_queue *q);
 extern void blk_limits_io_min(struct queue_limits *limits, unsigned int min);
 extern void blk_queue_io_min(struct request_queue *q, unsigned int min);
 extern void blk_limits_io_opt(struct queue_limits *limits, unsigned int opt);