block: keep bdi->io_pages in sync with max_sectors_kb for stacked devices

[ Upstream commit e74d93e96d721c4297f2a900ad0191890d2fc2b0 ]

Field bdi->io_pages added in commit 9491ae4aade6 ("mm: don't cap request
size based on read-ahead setting") removes unneeded split of read requests.

Stacked drivers do not call blk_queue_max_hw_sectors(). Instead they set
limits of their devices by blk_set_stacking_limits() + disk_stack_limits().
Field bio->io_pages stays zero until user set max_sectors_kb via sysfs.

This patch updates io_pages after merging limits in disk_stack_limits().

Commit c6d6e9b0f6b4 ("dm: do not allow readahead to limit IO size") fixed
the same problem for device-mapper devices, this one fixes MD RAIDs.

Fixes: 9491ae4aade6 ("mm: don't cap request size based on read-ahead setting")
Reviewed-by: Paul Menzel <pmenzel@molgen.mpg.de>
Reviewed-by: Bob Liu <bob.liu@oracle.com>
Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Signed-off-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/block/blk-settings.c b/block/blk-settings.c
index 6c2faaa38cc1e47f41cb81f2e223df82f6db4c4b..e0a744921ed3d349a5a43711364781b2f4d702e6 100644 (file)
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -717,6 +717,9 @@ 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);