Re: [PATCH 03/24] nvme: let set_capacity_revalidate_and_notify update the bdev size

On 11/9/20 9:53 AM, Christoph Hellwig wrote:

On Mon, Nov 09, 2020 at 08:53:58AM +0100, Hannes Reinecke wrote:

quoted

quoted

index 376096bfc54a83..4e86c9aafd88a7 100644

--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c

@@ -2053,7 +2053,7 @@ static void nvme_update_disk_info(struct gendisk *disk,
   			capacity = 0;

[ .. ]

quoted

Originally nvme multipath would update/change the size of the multipath
device according to the underlying path devices.
With this patch the size of the multipath device will _not_ change if there
is a change on the underlying devices.

Yes, it will.  Take a close look at nvme_update_disk_info and how it is
called.

Okay, then: What would be the correct way of handling a size update for NVMe multipath?
Assuming we're getting an AEN for each path signalling the size change
(or a controller reset leading to a size change).
So if we're updating the size of the multipath device together with the path device at the first AEN/reset we'll end up with the other paths having a different size than the multipath device (and the path we've just been updating).
- Do we care, or cross fingers and hope for the best?
- Shouldn't we detect the case where we won't get a size update for the other paths, or, indeed, we have a genuine device size mismatch due to a misconfiguration on the target?

IE shouldn't we have a flag 'size update pending' for the other paths,, to take them out ouf use temporarily until the other AENs/resets have been processed?

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
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