Re: [PATCH 01/12] fuse: support copying large folios

[Josef Bacik <josef@toxicpanda.com>]

On Fri, Nov 08, 2024 at 04:12:47PM -0800, Joanne Koong wrote:
> Currently, all folios associated with fuse are one page size. As part of
> the work to enable large folios, this commit adds support for copying
> to/from folios larger than one page size.
> 
> Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
> ---
>  fs/fuse/dev.c | 89 +++++++++++++++++++++++----------------------------
>  1 file changed, 40 insertions(+), 49 deletions(-)
> 
> diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
> index 29fc61a072ba..9914cc1243f4 100644
> --- a/fs/fuse/dev.c
> +++ b/fs/fuse/dev.c
> @@ -703,7 +703,7 @@ struct fuse_copy_state {
>  	struct page *pg;
>  	unsigned len;
>  	unsigned offset;
> -	unsigned move_pages:1;
> +	unsigned move_folios:1;
>  };
>  
>  static void fuse_copy_init(struct fuse_copy_state *cs, int write,
> @@ -836,10 +836,10 @@ static int fuse_check_folio(struct folio *folio)
>  	return 0;
>  }
>  
> -static int fuse_try_move_page(struct fuse_copy_state *cs, struct page **pagep)
> +static int fuse_try_move_folio(struct fuse_copy_state *cs, struct folio **foliop)
>  {
>  	int err;
> -	struct folio *oldfolio = page_folio(*pagep);
> +	struct folio *oldfolio = *foliop;
>  	struct folio *newfolio;
>  	struct pipe_buffer *buf = cs->pipebufs;
>  
> @@ -860,7 +860,7 @@ static int fuse_try_move_page(struct fuse_copy_state *cs, struct page **pagep)
>  	cs->pipebufs++;
>  	cs->nr_segs--;
>  
> -	if (cs->len != PAGE_SIZE)
> +	if (cs->len != folio_size(oldfolio))
>  		goto out_fallback;
>  
>  	if (!pipe_buf_try_steal(cs->pipe, buf))
> @@ -906,7 +906,7 @@ static int fuse_try_move_page(struct fuse_copy_state *cs, struct page **pagep)
>  	if (test_bit(FR_ABORTED, &cs->req->flags))
>  		err = -ENOENT;
>  	else
> -		*pagep = &newfolio->page;
> +		*foliop = newfolio;
>  	spin_unlock(&cs->req->waitq.lock);
>  
>  	if (err) {
> @@ -939,8 +939,8 @@ static int fuse_try_move_page(struct fuse_copy_state *cs, struct page **pagep)
>  	goto out_put_old;
>  }
>  
> -static int fuse_ref_page(struct fuse_copy_state *cs, struct page *page,
> -			 unsigned offset, unsigned count)
> +static int fuse_ref_folio(struct fuse_copy_state *cs, struct folio *folio,
> +			  unsigned offset, unsigned count)
>  {
>  	struct pipe_buffer *buf;
>  	int err;
> @@ -948,17 +948,17 @@ static int fuse_ref_page(struct fuse_copy_state *cs, struct page *page,
>  	if (cs->nr_segs >= cs->pipe->max_usage)
>  		return -EIO;
>  
> -	get_page(page);
> +	folio_get(folio);
>  	err = unlock_request(cs->req);
>  	if (err) {
> -		put_page(page);
> +		folio_put(folio);
>  		return err;
>  	}
>  
>  	fuse_copy_finish(cs);
>  
>  	buf = cs->pipebufs;
> -	buf->page = page;
> +	buf->page = &folio->page;
>  	buf->offset = offset;
>  	buf->len = count;
>  
> @@ -970,20 +970,24 @@ static int fuse_ref_page(struct fuse_copy_state *cs, struct page *page,
>  }
>  
>  /*
> - * Copy a page in the request to/from the userspace buffer.  Must be
> + * Copy a folio in the request to/from the userspace buffer.  Must be
>   * done atomically
>   */
> -static int fuse_copy_page(struct fuse_copy_state *cs, struct page **pagep,
> -			  unsigned offset, unsigned count, int zeroing)
> +static int fuse_copy_folio(struct fuse_copy_state *cs, struct folio **foliop,
> +			   unsigned offset, unsigned count, int zeroing)
>  {
>  	int err;
> -	struct page *page = *pagep;
> +	struct folio *folio = *foliop;
> +	size_t size = folio_size(folio);
>  
> -	if (page && zeroing && count < PAGE_SIZE)
> -		clear_highpage(page);
> +	if (folio && zeroing && count < size) {
> +		void *kaddr = kmap_local_folio(folio, 0);
> +		memset(kaddr, 0, size);
> +		kunmap_local(kaddr);

There's a folio_zero_range() that can be used here instead of this, but be sure
you get it right, I definitely did it wrong recently and I think Jan had to fix
my mistake.  Thanks,

Josef