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

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Message-ID: <65c549aa701cb_afa42943d@dwillia2-xfh.jf.intel.com.notmuch>
Date: Thu, 8 Feb 2024 13:37:46 -0800
From: Dan Williams <dan.j.williams@...el.com>
To: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, Dan Williams
	<dan.j.williams@...el.com>, Arnd Bergmann <arnd@...db.de>, Dave Chinner
	<david@...morbit.com>
CC: <linux-kernel@...r.kernel.org>, Mathieu Desnoyers
	<mathieu.desnoyers@...icios.com>, Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>, Vishal Verma
	<vishal.l.verma@...el.com>, Dave Jiang <dave.jiang@...el.com>, Matthew Wilcox
	<willy@...radead.org>, Russell King <linux@...linux.org.uk>,
	<linux-arch@...r.kernel.org>, <linux-cxl@...r.kernel.org>,
	<linux-fsdevel@...r.kernel.org>, <linux-mm@...ck.org>,
	<linux-xfs@...r.kernel.org>, <dm-devel@...ts.linux.dev>,
	<nvdimm@...ts.linux.dev>, <linux-s390@...r.kernel.org>, Alasdair Kergon
	<agk@...hat.com>, Mike Snitzer <snitzer@...nel.org>, Mikulas Patocka
	<mpatocka@...hat.com>
Subject: RE: [PATCH v4 05/12] virtio: Treat alloc_dax() -EOPNOTSUPP failure
 as non-fatal

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@...el.com>
> Signed-off-by: Dan Williams <dan.j.williams@...el.com>
> Fixes: d92576f1167c ("dax: does not work correctly with virtual aliasing caches")
> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
> Cc: Alasdair Kergon <agk@...hat.com>
> Cc: Mike Snitzer <snitzer@...nel.org>
> Cc: Mikulas Patocka <mpatocka@...hat.com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Linus Torvalds <torvalds@...ux-foundation.org>
> Cc: Dan Williams <dan.j.williams@...el.com>
> Cc: Vishal Verma <vishal.l.verma@...el.com>
> Cc: Dave Jiang <dave.jiang@...el.com>
> Cc: Matthew Wilcox <willy@...radead.org>
> Cc: Arnd Bergmann <arnd@...db.de>
> Cc: Russell King <linux@...linux.org.uk>
> Cc: linux-arch@...r.kernel.org
> Cc: linux-cxl@...r.kernel.org
> Cc: linux-fsdevel@...r.kernel.org
> Cc: linux-mm@...ck.org
> Cc: linux-xfs@...r.kernel.org
> Cc: dm-devel@...ts.linux.dev
> Cc: nvdimm@...ts.linux.dev
> ---
>  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)?