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	Sun, 28 Apr 2024 23:23:49 +0000
Date: Mon, 29 Apr 2024 00:23:49 +0100
From: Al Viro <viro@zeniv.linux.org.uk>
To: Stefan Haberland <sth@linux.ibm.com>
Cc: linux-s390@vger.kernel.org, jack@suse.cz, hch@lst.de,
	brauner@kernel.org, axboe@kernel.dk, linux-fsdevel@vger.kernel.org,
	linux-block@vger.kernel.org, yi.zhang@huawei.com,
	yangerkun@huawei.com, yukuai3@huawei.com,
	Yu Kuai <yukuai1@huaweicloud.com>,
	Eduard Shishkin <edward6@linux.ibm.com>,
	Alexander Gordeev <agordeev@linux.ibm.com>,
	Jan Hoeppner <hoeppner@linux.ibm.com>
Subject: Re: [PATCH vfs.all 15/26] s390/dasd: use bdev api in dasd_format()
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Sender: Al Viro <viro@ftp.linux.org.uk>

On Sun, Apr 28, 2024 at 07:58:23PM +0100, Al Viro wrote:
> On Wed, Apr 17, 2024 at 02:47:14PM +0200, Stefan Haberland wrote:
> 
> > set_blocksize() does basically also set i_blkbits like it was before.
> > The dasd_format ioctl does only work on a disabled device. To achieve this
> > all partitions need to be unmounted.
> > The tooling also refuses to work on disks actually in use.
> > 
> > So there should be no page cache to evict.
> 
> You mean this?
>         if (base->state != DASD_STATE_BASIC) {
>                 pr_warn("%s: The DASD cannot be formatted while it is enabled\n",
>                         dev_name(&base->cdev->dev));
>                 return -EBUSY;
>         }  
> 
> OK, but what would prevent dasd_ioctl_disable() from working while
> disk is in use?  And I don't see anything that would evict the
> page cache in dasd_ioctl_disable() either, actually...
> 
> What am I missing here?

BTW, you are updating block size according to new device size, before
        rc = base->discipline->format_device(base, fdata, 1);
	if (rc == -EAGAIN)
		rc = base->discipline->format_device(base, fdata, 0);
Unless something very unidiomatic is going on, this attempt to
format might fail...