linux-kernel - Re: [RFC PATCH V3 1/1] block: reject I/O for same fd if block size changed

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Date:   Tue, 5 Jan 2021 10:04:56 +0900
From:   Minwoo Im <minwoo.im.dev@...il.com>
To:     Christoph Hellwig <hch@....de>
Cc:     linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, Jens Axboe <axboe@...nel.dk>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Chaitanya Kulkarni <Chaitanya.Kulkarni@....com>
Subject: Re: [RFC PATCH V3 1/1] block: reject I/O for same fd if block size
 changed

Hello Christoph,

Thanks for your review.

On 21-01-04 18:11:41, Christoph Hellwig wrote:
> On Mon, Jan 04, 2021 at 06:11:08PM +0100, Christoph Hellwig wrote:
> > On Mon, Jan 04, 2021 at 10:06:59PM +0900, Minwoo Im wrote:
> > > +	if (q->backing_dev_info && q->backing_dev_info->owner &&
> > > +			limits->logical_block_size != size) {
> > > +		bdev = blkdev_get_no_open(q->backing_dev_info->owner->devt);
> > > +		bdev->bd_disk->flags |= GENHD_FL_BLOCK_SIZE_CHANGED;
> > > +		blkdev_put_no_open(bdev);
> > > +	}
> > 
> > We really need the backpointer from the queue to the gendisk I've wanted
> > to add for a while.  Can we at least restrict this to a live gendisk?

It was a point that I really would like to ask by RFC whether we can
have backpointer to the gendisk from the request_queue.  And I'd like to
have it to simplify this routine and for future usages also.

I will restrict this one by checking GENHD_FL_UP flag from the gendisk
for the next patch.

> 
> Alternatively we could make this request_queue QUEUE* flag for now.

As this patch rejects I/O from the block layer partition code, can we
have this flag in gendisk rather than request_queue ?

Thanks,