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SubjectRe: [RFC PATCH] block/genhd: Notify udev about capacity change
On Tue, Dec 10, 2019 at 03:01:31AM +0000, Balbir Singh wrote:
> Allow block/genhd to notify user space (via udev) 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 via udev if
> the current capacity or the target capacity is not zero.
>
> disk_set_capacity() is not enabled for all devices, just virtio block,
> xen-blockfront, nvme and sd. Owners of other block disk devices can
> easily move over by changing set_capacity() to disk_set_capacity()
>
> 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.
>
> Testing:
> 1. I did some basic testing with an NVME device, by resizing it in
> the backend and ensured that udevd received the event.
>
> Suggested-by: Christoph Hellwig <hch@lst.de>
> Signed-off-by: Balbir Singh <sblbir@amazon.com>
> Signed-off-by: Someswarudu Sangaraju <ssomesh@amazon.com>
> ---
> 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(-)
>
> diff --git a/block/genhd.c b/block/genhd.c
> index ff6268970ddc..94faec98607b 100644
> --- a/block/genhd.c
> +++ b/block/genhd.c
> @@ -46,6 +46,25 @@ static void disk_add_events(struct gendisk *disk);
> static void disk_del_events(struct gendisk *disk);
> static void disk_release_events(struct gendisk *disk);
>
> +/*
> + * Set disk capacity and notify if the size is not currently
> + * zero and will not be set to zero

Nit: Use up all the 80 chars per line. Also maybe turn this into a
kerneldoc comment. I think you also want to mention the notification
as well.

> +EXPORT_SYMBOL_GPL(disk_set_capacity);
> +
> +
> void part_inc_in_flight(struct request_queue *q, struct hd_struct *part, int rw)

No need for the double empty line.

> {
> if (queue_is_mq(q))
> diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
> index 7ffd719d89de..869cd3c31529 100644
> --- a/drivers/block/virtio_blk.c
> +++ b/drivers/block/virtio_blk.c

And you probably want to turn this into a series with patch 1 adding
the infrastructure, and then one patch per driver switched over.
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