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(-)