[PATCH 06/12] block: lift setting the readahead size into the block layer

Christoph Hellwig
2020-09-10T20:58:35Z

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.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
block/blk-settings.c | 5 ++---
block/blk-sysfs.c | 10 +++++++++-
block/genhd.c | 5 +++--
drivers/block/aoe/aoeblk.c | 2 --
drivers/block/drbd/drbd_nl.c | 12 +-----------
drivers/md/bcache/super.c | 4 ----
drivers/md/dm-table.c | 3 ---
drivers/md/raid0.c | 16 ----------------
drivers/md/raid10.c | 24 +-----------------------
drivers/md/raid5.c | 13 +------------
10 files changed, 17 insertions(+), 77 deletions(-)

diff --git a/block/blk-settings.c b/block/blk-settings.c
index 76a7e03bcd6cac..01049e9b998f1d 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -452,6 +452,8 @@ 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);

@@ -628,9 +630,6 @@ void disk_stack_limits(struct gendisk *disk, struct block_device *bdev,
printk(KERN_NOTICE "%s: Warning: Device %s is misaligned\n",
top, bottom);
}
-
- t->backing_dev_info->io_pages =
- t->limits.max_sectors >> (PAGE_SHIFT - 9);
}
EXPORT_SYMBOL(disk_stack_limits);

diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 81722cdcf0cb21..95eb35324e1a61 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -245,7 +245,6 @@ queue_max_sectors_store(struct request_queue *q, const char *page, size_t count)

spin_lock_irq(&q->queue_lock);
q->limits.max_sectors = max_sectors_kb << 1;
- q->backing_dev_info->io_pages = max_sectors_kb >> (PAGE_SHIFT - 10);
spin_unlock_irq(&q->queue_lock);

return ret;
@@ -854,6 +853,15 @@ int blk_register_queue(struct gendisk *disk)
percpu_ref_switch_to_percpu(&q->q_usage_counter);
}

+ /*
+ * 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);
+
ret = blk_trace_init_sysfs(dev);
if (ret)
return ret;
diff --git a/block/genhd.c b/block/genhd.c
index 081f1039d9367f..db311a14ddc71a 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -772,6 +772,7 @@ static void __device_add_disk(struct device *parent, struct gendisk *disk,
const struct attribute_group **groups,
bool register_queue)
{
+ struct request_queue *q = disk->queue;
dev_t devt;
int retval;

@@ -782,7 +783,7 @@ static void __device_add_disk(struct device *parent, struct gendisk *disk,
* registration.
*/
if (register_queue)
- elevator_init_mq(disk->queue);
+ elevator_init_mq(q);

/* minors == 0 indicates to use ext devt from part0 and should
* be accompanied with EXT_DEVT flag. Make sure all
@@ -812,7 +813,7 @@ static void __device_add_disk(struct device *parent, struct gendisk *disk,
disk->flags |= GENHD_FL_SUPPRESS_PARTITION_INFO;
disk->flags |= GENHD_FL_NO_PART_SCAN;
} else {
- struct backing_dev_info *bdi = disk->queue->backing_dev_info;
+ struct backing_dev_info *bdi = q->backing_dev_info;
struct device *dev = disk_to_dev(disk);
int ret;

diff --git a/drivers/block/aoe/aoeblk.c b/drivers/block/aoe/aoeblk.c
index 5ca7216e9e01f3..89b33b402b4e52 100644
--- a/drivers/block/aoe/aoeblk.c
+++ b/drivers/block/aoe/aoeblk.c
@@ -347,7 +347,6 @@ aoeblk_gdalloc(void *vp)
mempool_t *mp;
struct request_queue *q;
struct blk_mq_tag_set *set;
- enum { KB = 1024, MB = KB * KB, READ_AHEAD = 2 * MB, };
ulong flags;
int late = 0;
int err;
@@ -407,7 +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 = READ_AHEAD / PAGE_SIZE;
d->bufpool = mp;
d->blkq = gd->queue = q;
q->queuedata = d;
diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
index aaff5bde391506..f8fb1c9b1bb6c1 100644
--- a/drivers/block/drbd/drbd_nl.c
+++ b/drivers/block/drbd/drbd_nl.c
@@ -1360,18 +1360,8 @@ static void drbd_setup_queue_param(struct drbd_device *device, struct drbd_backi
decide_on_discard_support(device, q, b, discard_zeroes_if_aligned);
decide_on_write_same_support(device, q, b, o, disable_write_same);

- if (b) {
+ 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;
- }
- }
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 1bbdc410ee3c51..ff2101d56cd7f1 100644
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -1427,10 +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);
-
atomic_set(&dc->io_errors, 0);
dc->io_disable = false;
dc->error_limit = DEFAULT_CACHED_DEV_ERROR_LIMIT;
diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index 5edc3079e7c199..e1be7697214bd7 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -1924,9 +1924,6 @@ void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,
q->nr_zones = blkdev_nr_zones(t->md->disk);
}
#endif
-
- /* Allow reads to exceed readahead limits */
- q->backing_dev_info->io_pages = limits->max_sectors >> (PAGE_SHIFT - 9);
}

unsigned int dm_table_get_num_targets(struct dm_table *t)
diff --git a/drivers/md/raid0.c b/drivers/md/raid0.c
index f54a449f97aa79..aa2d7279176880 100644
--- 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 9956a04ac13bd6..5d1bdee313ec33 100644
--- 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 9a7d1250894ef1..7ace1f76b14736 100644
--- 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);
- }
}
}

--
2.28.0