Re: [PATCH 1/1] fuse: fix direct io folio offset and length calculation

[Jingbo Xu <jefflexu@linux.alibaba.com>]

On 12/12/24 4:55 AM, Joanne Koong wrote:
> For the direct io case, the pages from userspace may be part of a huge
> folio, even if all folios in the page cache for fuse are small.
> 
> Fix the logic for calculating the offset and length of the folio for
> the direct io case, which currently incorrectly assumes that all folios
> encountered are one page size.
> 
> Fixes: 3b97c3652d91 ("fuse: convert direct io to use folios")
> Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
> ---
>  fs/fuse/file.c | 28 ++++++++++++++++------------
>  1 file changed, 16 insertions(+), 12 deletions(-)
> 
> diff --git a/fs/fuse/file.c b/fs/fuse/file.c
> index 88d0946b5bc9..15b08d6a5739 100644
> --- a/fs/fuse/file.c
> +++ b/fs/fuse/file.c
> @@ -1557,18 +1557,22 @@ static int fuse_get_user_pages(struct fuse_args_pages *ap, struct iov_iter *ii,
>  
>  		nbytes += ret;
>  
> -		ret += start;
> -		/* Currently, all folios in FUSE are one page */
> -		nfolios = DIV_ROUND_UP(ret, PAGE_SIZE);
> -
> -		ap->descs[ap->num_folios].offset = start;
> -		fuse_folio_descs_length_init(ap->descs, ap->num_folios, nfolios);
> -		for (i = 0; i < nfolios; i++)
> -			ap->folios[i + ap->num_folios] = page_folio(pages[i]);
> -
> -		ap->num_folios += nfolios;
> -		ap->descs[ap->num_folios - 1].length -=
> -			(PAGE_SIZE - ret) & (PAGE_SIZE - 1);
> +		nfolios = DIV_ROUND_UP(ret + start, PAGE_SIZE);
> +
> +		for (i = 0; i < nfolios; i++) {
> +			struct folio *folio = page_folio(pages[i]);
> +			unsigned int offset = start +
> +				(folio_page_idx(folio, pages[i]) << PAGE_SHIFT);
> +			unsigned int len = min_t(unsigned int, ret, PAGE_SIZE - start);
> +
> +			ap->descs[ap->num_folios].offset = offset;
> +			ap->descs[ap->num_folios].length = len;
> +			ap->folios[ap->num_folios] = folio;
> +			start = 0;
> +			ret -= len;
> +			ap->num_folios++;
> +		}
> +
>  		nr_pages += nfolios;
>  	}
>  	kfree(pages);

LGTM.

Reviewed-by: Jingbo Xu <jefflexu@linux.alibaba.com>

-- 
Thanks,
Jingbo