linux-kernel - Re: [PATCH v2] mtd: mtd_blkdevs: Initialize rq.limits.discard

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Date:   Fri, 18 Jun 2021 09:52:07 +0200
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Zhihao Cheng <chengzhihao1@...wei.com>
Cc:     <richard@....at>, <vigneshr@...com>,
        <linux-mtd@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
        <yukuai3@...wei.com>, Christoph Hellwig <hch@....de>
Subject: Re: [PATCH v2] mtd: mtd_blkdevs: Initialize
 rq.limits.discard_granularity

Hi Zhihao,

Zhihao Cheng <chengzhihao1@...wei.com> wrote on Tue, 15 Jun 2021
17:39:05 +0800:

> Since commit b35fd7422c2f8("block: check queue's limits.discard_granularity
> in __blkdev_issue_discard()") checks rq.limits.discard_granularity in
> __blkdev_issue_discard(), we may get following warnings on formatted ftl:
> 
>   WARNING: CPU: 2 PID: 7313 at block/blk-lib.c:51
>   __blkdev_issue_discard+0x2a7/0x390
> 
> Reproducer:
>   1. ftl_format /dev/mtd0
>   2. modprobe ftl
>   3. mkfs.vfat /dev/ftla
>   4. mount -odiscard /dev/ftla temp
>   5. dd if=/dev/zero of=temp/tst bs=1M count=10 oflag=direct
>   6. dd if=/dev/zero of=temp/tst bs=1M count=10 oflag=direct
> 
> Fix it by initializing rq.limits.discard_granularity if device supports
> discard operation.

Can you please verify that this is still needed after Christoph's
additional fix:
https://patchwork.kernel.org/project/xen-devel/patch/20210602065345.355274-10-hch@lst.de/

> 
> Signed-off-by: Zhihao Cheng <chengzhihao1@...wei.com>
> ---
>  drivers/mtd/mtd_blkdevs.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/mtd/mtd_blkdevs.c b/drivers/mtd/mtd_blkdevs.c
> index 01bf234e7f3a..6eac1c9c164d 100644
> --- a/drivers/mtd/mtd_blkdevs.c
> +++ b/drivers/mtd/mtd_blkdevs.c
> @@ -413,6 +413,7 @@ int add_mtd_blktrans_dev(struct mtd_blktrans_dev *new)
>  	if (tr->discard) {
>  		blk_queue_flag_set(QUEUE_FLAG_DISCARD, new->rq);
>  		blk_queue_max_discard_sectors(new->rq, UINT_MAX);
> +		new->rq->limits.discard_granularity = tr->blksize;
>  	}
>  
>  	gd->queue = new->rq;




Thanks,
Miquèl