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

[Shiyang Ruan]

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.