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Date:   Thu, 20 Jan 2022 00:59:12 -0800
From:   Christoph Hellwig <hch@infradead.org>
To:     Shiyang Ruan <ruansy.fnst@fujitsu.com>
Cc:     linux-kernel@vger.kernel.org, linux-xfs@vger.kernel.org,
        nvdimm@lists.linux.dev, linux-mm@kvack.org,
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        dan.j.williams@intel.com, david@fromorbit.com, hch@infradead.org,
        jane.chu@oracle.com
Subject: Re: [PATCH v9 10/10] fsdax: set a CoW flag when associate reflink
 mappings
Message-ID: <YekkYAJ+QegoDKCJ@infradead.org>
References: <20211226143439.3985960-1-ruansy.fnst@fujitsu.com>
 <20211226143439.3985960-11-ruansy.fnst@fujitsu.com>
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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.