linux-kernel - Re: [PATCH v9 10/10] fsdax: set a CoW flag when associate reflink mappings

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Date:   Thu, 20 Jan 2022 00:59:12 -0800
From:   Christoph Hellwig <hch@...radead.org>
To:     Shiyang Ruan <ruansy.fnst@...itsu.com>
Cc:     linux-kernel@...r.kernel.org, linux-xfs@...r.kernel.org,
        nvdimm@...ts.linux.dev, linux-mm@...ck.org,
        linux-fsdevel@...r.kernel.org, djwong@...nel.org,
        dan.j.williams@...el.com, david@...morbit.com, hch@...radead.org,
        jane.chu@...cle.com
Subject: Re: [PATCH v9 10/10] fsdax: set a CoW flag when associate reflink
 mappings

On Sun, Dec 26, 2021 at 10:34:39PM +0800, Shiyang Ruan wrote:
> +#define FS_DAX_MAPPING_COW	1UL
> +
> +#define MAPPING_SET_COW(m)	(m = (struct address_space *)FS_DAX_MAPPING_COW)
> +#define MAPPING_TEST_COW(m)	(((unsigned long)m & FS_DAX_MAPPING_COW) == \
> +					FS_DAX_MAPPING_COW)

These really should be inline functions and probably use lower case
names.

But different question, how does this not conflict with:

#define PAGE_MAPPING_ANON       0x1

in page-flags.h?

Either way I think this flag should move to page-flags.h and be
integrated with the PAGE_MAPPING_FLAGS infrastucture.