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Subject: Re: [resend v1 0/5] Add support for block disk resize notification
To:     Balbir Singh <sblbir@amazon.com>, linux-kernel@vger.kernel.org,
        linux-block@vger.kernel.org, linux-nvme@lists.infradead.org
Cc:     axboe@kernel.dk, ssomesh@amazon.com, jejb@linux.ibm.com,
        hch@lst.de, mst@redhat.com, Chaitanya.Kulkarni@wdc.com
References: <20200102075315.22652-1-sblbir@amazon.com>
From:   Bob Liu <bob.liu@oracle.com>
Message-ID: <62ef2cd2-42a2-6117-155d-ed052a136c5c@oracle.com>
Date:   Mon, 6 Jan 2020 13:59:17 +0800
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On 1/2/20 3:53 PM, Balbir Singh wrote:
> Allow block/genhd to notify user space about disk size changes
> using a new helper disk_set_capacity(), which is a wrapper on top
> of set_capacity(). disk_set_capacity() will only notify if
> the current capacity or the target capacity is not zero.
> 

set_capacity_and_notify() may be a more straightforward name.

> Background:
> 
> As a part of a patch to allow sending the RESIZE event on disk capacity
> change, Christoph (hch@lst.de) requested that the patch be made generic
> and the hacks for virtio block and xen block devices be removed and
> merged via a generic helper.
> 
> This series consists of 5 changes. The first one adds the basic
> support for changing the size and notifying. The follow up patches
> are per block subsystem changes. Other block drivers can add their
> changes as necessary on top of this series.
> 
> Testing:
> 1. I did some basic testing with an NVME device, by resizing it in
> the backend and ensured that udevd received the event.
> 
> NOTE: After these changes, the notification might happen before
> revalidate disk, where as it occured later before.
> 

It's better not to change original behavior.
How about something like:

+void set_capacity_and_notify(struct gendisk *disk, sector_t size, bool revalidate)
{
	sector_t capacity = get_capacity(disk);

	set_capacity(disk, size);

+        if (revalidate)
+		revalidate_disk(disk);
	if (capacity != 0 && size != 0) {
		char *envp[] = { "RESIZE=1", NULL };

		kobject_uevent_env(&disk_to_dev(disk)->kobj, KOBJ_CHANGE, envp);
	}
}

> Balbir Singh (5):
>   block/genhd: Notify udev about capacity change
>   drivers/block/virtio_blk.c: Convert to use disk_set_capacity
>   drivers/block/xen-blkfront.c: Convert to use disk_set_capacity
>   drivers/nvme/host/core.c: Convert to use disk_set_capacity
>   drivers/scsi/sd.c: Convert to use disk_set_capacity
> 
>  block/genhd.c                | 19 +++++++++++++++++++
>  drivers/block/virtio_blk.c   |  4 +---
>  drivers/block/xen-blkfront.c |  5 +----
>  drivers/nvme/host/core.c     |  2 +-
>  drivers/scsi/sd.c            |  2 +-
>  include/linux/genhd.h        |  1 +
>  6 files changed, 24 insertions(+), 9 deletions(-)
>