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Subject: Re: [PATCH] block: keep bdi->io_pages in sync with max_sectors_kb for
 stacked devices
To:     Konstantin Khlebnikov <khlebnikov@yandex-team.ru>,
        linux-block@vger.kernel.org, Jens Axboe <axboe@kernel.dk>,
        linux-kernel@vger.kernel.org
Cc:     linux-raid@vger.kernel.org, Song Liu <song@kernel.org>,
        Dmitry Monakhov <dmtrmonakhov@yandex-team.ru>
References: <158290150891.4423.13566449569964563258.stgit@buzz>
From:   Paul Menzel <pmenzel@molgen.mpg.de>
Message-ID: <35ef813c-d5a4-8eb8-073d-9c5814266299@molgen.mpg.de>
Date:   Mon, 2 Mar 2020 11:41:28 +0100
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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 reques=
t
> size based on read-ahead setting") removes unneeded split of read reque=
sts.
>=20
> Stacked drivers do not call blk_queue_max_hw_sectors(). Instead they se=
tup

The verb is spelled with a space *set up*.

> limits of their devices by blk_set_stacking_limits() + disk_stack_limit=
s().
> Field bio->io_pages stays zero until user set max_sectors_kb via sysfs.=

>=20
> This patch updates io_pages after merging limits in disk_stack_limits()=
=2E
>=20
> Commit c6d6e9b0f6b4 ("dm: do not allow readahead to limit IO size") fix=
ed
> 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 sett=
ing")

> Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
> ---
>  block/blk-settings.c |    2 ++
>  1 file changed, 2 insertions(+)
>=20
> 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 =3D t->limits.max_sectors >> (PAGE_SHIF=
T-9);
>  }
>  EXPORT_SYMBOL(disk_stack_limits);

Reviewed-by: Paul Menzel <pmenzel@molgen.mpg.de>


Kind regards,

Paul


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