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List:       dm-devel
Subject:    Re: [dm-devel] [PATCH v2] dm writecache: reject asynchronous pmem.
From:       Mikulas Patocka <mpatocka () redhat ! com>
Date:       2020-06-30 15:02:19
Message-ID: alpine.LRH.2.02.2006301101210.24028 () file01 ! intranet ! prod ! int ! rdu2 ! redhat ! com
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On Tue, 30 Jun 2020, Michal Suchanek wrote:

> The writecache driver does not handle asynchronous pmem. Reject it when
> supplied as cache.
> 
> Link: https://lore.kernel.org/linux-nvdimm/87lfk5hahc.fsf@linux.ibm.com/
> Fixes: 6e84200c0a29 ("virtio-pmem: Add virtio pmem driver")
> 
> Signed-off-by: Michal Suchanek <msuchanek@suse.de>

OK. I suggest to move this test before persistent_memory_claim (so that 
you don't try to map the whole device).

Mikulas

> ---
>  drivers/md/dm-writecache.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/md/dm-writecache.c b/drivers/md/dm-writecache.c
> index 30505d70f423..1e4f37249e28 100644
> --- a/drivers/md/dm-writecache.c
> +++ b/drivers/md/dm-writecache.c
> @@ -2271,6 +2271,12 @@ static int writecache_ctr(struct dm_target *ti, unsigned argc, char **argv)
>  			ti->error = "Unable to map persistent memory for cache";
>  			goto bad;
>  		}
> +
> +		if (!dax_synchronous(wc->ssd_dev->dax_dev)) {
> +			r = -EOPNOTSUPP;
> +			ti->error = "Asynchronous persistent memory not supported as pmem cache";
> +			goto bad;
> +		}
>  	} else {
>  		size_t n_blocks, n_metadata_blocks;
>  		uint64_t n_bitmap_bits;
> -- 
> 2.26.2
> 

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