On Fri, Sep 24, 2021 at 09:09:59PM +0800, Shiyang Ruan wrote:
> For reflinked files, one dax page may be associated more than once with
> different fime mapping and index. It will report warning. Now, since
> we have introduced dax-RMAP for this case and also have to keep its
> functionality for other filesystems who are not support rmap, I add this
> exception here.
>
> Signed-off-by: Shiyang Ruan <ruansy.fnst@xxxxxxxxxxx>
> ---
> fs/dax.c | 14 ++++++++------
> 1 file changed, 8 insertions(+), 6 deletions(-)
>
> diff --git a/fs/dax.c b/fs/dax.c
> index 2536c105ec7f..1a57211b1bc9 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
> @@ -352,9 +352,10 @@ static void dax_associate_entry(void *entry, struct address_space *mapping,
> for_each_mapped_pfn(entry, pfn) {
> struct page *page = pfn_to_page(pfn);
>
> - WARN_ON_ONCE(page->mapping);
> - page->mapping = mapping;
> - page->index = index + i++;
> + if (!page->mapping) {
> + page->mapping = mapping;
> + page->index = index + i++;
It feels a little dangerous to have page->mapping for shared storage
point to an actual address_space when there are really multiple
potential address_spaces out there. If the mm or dax folks are ok with
doing this this way then I'll live with it, but it seems like you'd want
to leave /some/ kind of marker once you know that the page has multiple
owners and therefore regular mm rmap via page->mapping won't work.
--D
> + }
> }
> }
>
> @@ -370,9 +371,10 @@ static void dax_disassociate_entry(void *entry, struct address_space *mapping,
> struct page *page = pfn_to_page(pfn);
>
> WARN_ON_ONCE(trunc && page_ref_count(page) > 1);
> - WARN_ON_ONCE(page->mapping && page->mapping != mapping);
> - page->mapping = NULL;
> - page->index = 0;
> + if (page->mapping == mapping) {
> + page->mapping = NULL;
> + page->index = 0;
> + }
> }
> }
>
> --
> 2.33.0
>
>
>
