On Fri, Feb 12, 2021 at 10:45:32AM -0500, Mike Snitzer wrote:

On Mon, Nov 16, 2020 at 10:05 AM Christoph Hellwig [off-list ref] wrote:

quoted

Use set_capacity_and_notify to set the size of both the disk and block
device.  This also gets the uevent notifications for the resize for free.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
---
 drivers/md/dm.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index c18fc25485186d..62ad44925e73ec 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c

@@ -1971,8 +1971,7 @@ static struct dm_table *__bind(struct mapped_device *md, struct dm_table *t,
        if (size != dm_get_size(md))
                memset(&md->geometry, 0, sizeof(md->geometry));

-       set_capacity(md->disk, size);
-       bd_set_nr_sectors(md->bdev, size);
+       set_capacity_and_notify(md->disk, size);

        dm_table_event_callback(t, event_callback, md);

Not yet pinned down _why_ DM is calling set_capacity_and_notify() with
a size of 0 but, when running various DM regression tests, I'm seeing
a lot of noise like:

[  689.240037] dm-2: detected capacity change from 2097152 to 0

Is this pr_info really useful?  Should it be moved to below: if
(!capacity || !size) so that it only prints if a uevent is sent?

In general I suspect such a size change might be interesting to users
if it e.g. comes from a remote event.  So I'd be curious why this happens
with DM, and if we can detect some higher level gendisk state to supress
it if it is indeed spurious.