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SubjectRe: [PATCH v9 10/10] fsdax: set a CoW flag when associate reflink mappings
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在 2022/1/20 16:59, Christoph Hellwig 写道:
> 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.

OK.

>
> But different question, how does this not conflict with:
>
> #define PAGE_MAPPING_ANON 0x1
>
> in page-flags.h?

Now we are treating dax pages, so I think its flags should be different
from normal page. In another word, PAGE_MAPPING_ANON is a flag of rmap
mechanism for normal page, it doesn't work for dax page. And now, we
have dax rmap for dax page. So, I think this two kinds of flags are
supposed to be used in different mechanisms and won't conflect.

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

And that's why I keep them in this dax.c file.


--
Thanks,
Ruan.


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