[PATCH] nvme: fix discard support without oncs

[Laurence Oberman]

On Mon, 2023-04-03 at 13:09 -0700, Keith Busch wrote:
> From: Keith Busch <kbusch at kernel.org>
> 
> The device can report discard support without setting the ONCS DSM
> bit.
> When not set, the driver clears max_discard_size expecting it to be
> set
> later. We don't know the size until we have the namespace format,
> though, so setting it is deferred until configuring one, but the
> driver
> was abandoning the discard settings due to that initial clearing.
> 
> Move the max_discard_size calculation above the check for a '0'
> discard
> size.
> 
> Fixes: 1a86924e4f46475 ("nvme: fix interpretation of DMRSL")
> Cc: Tom Yan <tom.ty89 at gmail.com>
> Reported-by: Laurence Oberman <loberman at redhat.com>
> Signed-off-by: Keith Busch <kbusch at kernel.org>
> ---
>  drivers/nvme/host/core.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
> index 53ef028596c61..d6a9bac91a4cd 100644
> --- a/drivers/nvme/host/core.c
> +++ b/drivers/nvme/host/core.c
> @@ -1674,6 +1674,9 @@ static void nvme_config_discard(struct gendisk
> *disk, struct nvme_ns *ns)
>         struct request_queue *queue = disk->queue;
>         u32 size = queue_logical_block_size(queue);
>  
> +       if (ctrl->dmrsl && ctrl->dmrsl <= nvme_sect_to_lba(ns,
> UINT_MAX))
> +               ctrl->max_discard_sectors = nvme_lba_to_sect(ns,
> ctrl->dmrsl);
> +
>         if (ctrl->max_discard_sectors == 0) {
>                 blk_queue_max_discard_sectors(queue, 0);
>                 return;
> @@ -1688,9 +1691,6 @@ static void nvme_config_discard(struct gendisk
> *disk, struct nvme_ns *ns)
>         if (queue->limits.max_discard_sectors)
>                 return;
>  
> -       if (ctrl->dmrsl && ctrl->dmrsl <= nvme_sect_to_lba(ns,
> UINT_MAX))
> -               ctrl->max_discard_sectors = nvme_lba_to_sect(ns,
> ctrl->dmrsl);
> -
>         blk_queue_max_discard_sectors(queue, ctrl-
> >max_discard_sectors);
>         blk_queue_max_discard_segments(queue, ctrl-
> >max_discard_segments);
>  

Many Thanks Keith for the quick ressponse

I can confirm this patch fixes the issue and I have discard support
again on the Infinidat device.

[   33.240602] nvme nvme1: creating 8 I/O queues.
[   33.330643] nvme nvme1: mapped 8/0/0 default/read/poll queues.
[   33.348589] nvme nvme1: new ctrl: NQN "nqn.2020-
01.com.infinidat:36000-subsystem-696", addr 192.168.1.2:4420
[   37.590766] XFS (nvme1n1): Mounting V5 Filesystem 6763a33f-18cc-
4a26-894b-8b0f8d79a98a
[   40.762363] XFS (nvme1n1): Ending clean mount

Tested-by: Laurence Oberman <loberman at redhat.com>