linux-kernel - Re: [PATCH RESEND v6 9/9] fsdax: add exception for reflinked files

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Date:   Thu, 5 Aug 2021 17:46:52 -0700
From:   Jane Chu <jane.chu@...cle.com>
To:     Shiyang Ruan <ruansy.fnst@...itsu.com>,
        linux-kernel@...r.kernel.org, linux-xfs@...r.kernel.org,
        nvdimm@...ts.linux.dev, linux-mm@...ck.org,
        linux-fsdevel@...r.kernel.org, dm-devel@...hat.com
Cc:     djwong@...nel.org, dan.j.williams@...el.com, david@...morbit.com,
        hch@....de, agk@...hat.com, snitzer@...hat.com
Subject: Re: [PATCH RESEND v6 9/9] fsdax: add exception for reflinked files


On 7/30/2021 3:01 AM, 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             ^^^typo here?

> 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@...itsu.com>
> ---
>   fs/dax.c | 14 ++++++++------
>   1 file changed, 8 insertions(+), 6 deletions(-)
> 
> diff --git a/fs/dax.c b/fs/dax.c
> index dce6307a12eb..f5910d178695 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++;
> +		}
>   	}
>   }
>   
> @@ -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;
> +		}
>   	}
>   }
>   
>