RE: [PATCH v4 05/12] virtio: Treat alloc_dax() -EOPNOTSUPP failure as non-fatal

[Dan Williams]

Mathieu Desnoyers wrote:
> In preparation for checking whether the architecture has data cache
> aliasing within alloc_dax(), modify the error handling of virtio
> virtio_fs_setup_dax() to treat alloc_dax() -EOPNOTSUPP failure as
> non-fatal.
> 
> For the transition, consider that alloc_dax() returning NULL is the
> same as returning -EOPNOTSUPP.
> 
> Co-developed-by: Dan Williams <dan.j.williams@xxxxxxxxx>
> Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
> Fixes: d92576f1167c ("dax: does not work correctly with virtual aliasing caches")
> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
> Cc: Alasdair Kergon <agk@xxxxxxxxxx>
> Cc: Mike Snitzer <snitzer@xxxxxxxxxx>
> Cc: Mikulas Patocka <mpatocka@xxxxxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
> Cc: Vishal Verma <vishal.l.verma@xxxxxxxxx>
> Cc: Dave Jiang <dave.jiang@xxxxxxxxx>
> Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
> Cc: Arnd Bergmann <arnd@xxxxxxxx>
> Cc: Russell King <linux@xxxxxxxxxxxxxxx>
> Cc: linux-arch@xxxxxxxxxxxxxxx
> Cc: linux-cxl@xxxxxxxxxxxxxxx
> Cc: linux-fsdevel@xxxxxxxxxxxxxxx
> Cc: linux-mm@xxxxxxxxx
> Cc: linux-xfs@xxxxxxxxxxxxxxx
> Cc: dm-devel@xxxxxxxxxxxxxxx
> Cc: nvdimm@xxxxxxxxxxxxxxx
> ---
>  fs/fuse/virtio_fs.c | 15 +++++++++++----
>  1 file changed, 11 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/fuse/virtio_fs.c b/fs/fuse/virtio_fs.c
> index 5f1be1da92ce..621b1bca2d55 100644
> --- a/fs/fuse/virtio_fs.c
> +++ b/fs/fuse/virtio_fs.c
> @@ -16,6 +16,7 @@
>  #include <linux/fs_context.h>
>  #include <linux/fs_parser.h>
>  #include <linux/highmem.h>
> +#include <linux/cleanup.h>
>  #include <linux/uio.h>
>  #include "fuse_i.h"
>  
> @@ -795,8 +796,11 @@ static void virtio_fs_cleanup_dax(void *data)
>  	put_dax(dax_dev);
>  }
>  
> +DEFINE_FREE(cleanup_dax, struct dax_dev *, if (!IS_ERR_OR_NULL(_T)) virtio_fs_cleanup_dax(_T))

This IS_ERR_OR_NULL is ok because dax_dev is initialized to NULL, but
maybe this could just be IS_ERR() and then initialize @dax_dev to
ERR_PTR(-EOPNOTSUPP)?