From: Konstantin Khlebnikov <khlebnikov@yandex-team.ru> [ 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> --- block/blk-settings.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/block/blk-settings.c b/block/blk-settings.c index 96376ea..1bfb377 100644 --- a/block/blk-settings.c +++ b/block/blk-settings.c @@ -723,6 +723,9 @@ 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); -- 1.8.3