On 02/03/2020 13.41, Paul Menzel wrote:
Dear Konstantin,
Thank you for the patch.
On 2020-02-28 15:51, Konstantin Khlebnikov wrote:
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 setup
The verb is spelled with a space *set up*.
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.
Add a Fixes: tag?
Fixes: 9491ae4aade6 ("mm: don't cap request size based on read-ahead setting")
Maybe, but this isn't fatal bug. Just incomplete fix.
Same problem exists for non-disk BDIs. I.e. network filesystem must
set io_pages manually if doesn't want split read requests.
Signed-off-by: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx>
---
block/blk-settings.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/block/blk-settings.c b/block/blk-settings.c
index c8eda2e7b91e..66c45fd79545 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -664,6 +664,8 @@ 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);
Reviewed-by: Paul Menzel <pmenzel@xxxxxxxxxxxxx>
Kind regards,
Paul
