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SubjectRe: [RFC PATCH] block/genhd: Notify udev about capacity change
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On Thu, 2019-12-12 at 10:54 +0100, Christoph Hellwig wrote:
> 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.

Will do!

>
> > +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.
Makes sense, will do

Thanks for the feedback
Balbir Singh.
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