Re: [PATCH 09/12] fuse: support large folios for readahead

[Josef Bacik <josef@toxicpanda.com>]

On Fri, Nov 08, 2024 at 04:12:55PM -0800, Joanne Koong wrote:
> Add support for folios larger than one page size for readahead.
> 
> Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
> ---
>  fs/fuse/file.c | 28 +++++++++++++++++++---------
>  1 file changed, 19 insertions(+), 9 deletions(-)
> 
> diff --git a/fs/fuse/file.c b/fs/fuse/file.c
> index 44a65bdfe8fb..255c7f2f2ed4 100644
> --- a/fs/fuse/file.c
> +++ b/fs/fuse/file.c
> @@ -885,14 +885,13 @@ static void fuse_readpages_end(struct fuse_mount *fm, struct fuse_args *args,
>  	fuse_io_free(ia);
>  }
>  
> -static void fuse_send_readpages(struct fuse_io_args *ia, struct file *file)
> +static void fuse_send_readpages(struct fuse_io_args *ia, struct file *file,
> +				unsigned int count)
>  {
>  	struct fuse_file *ff = file->private_data;
>  	struct fuse_mount *fm = ff->fm;
>  	struct fuse_args_pages *ap = &ia->ap;
>  	loff_t pos = folio_pos(ap->folios[0]);
> -	/* Currently, all folios in FUSE are one page */
> -	size_t count = ap->num_folios << PAGE_SHIFT;
>  	ssize_t res;
>  	int err;
>  
> @@ -929,6 +928,7 @@ static void fuse_readahead(struct readahead_control *rac)
>  	unsigned int max_pages, nr_pages;
>  	loff_t first = readahead_pos(rac);
>  	loff_t last = first + readahead_length(rac) - 1;
> +	struct folio *folio = NULL;
>  
>  	if (fuse_is_bad(inode))
>  		return;
> @@ -952,8 +952,8 @@ static void fuse_readahead(struct readahead_control *rac)
>  	while (nr_pages) {
>  		struct fuse_io_args *ia;
>  		struct fuse_args_pages *ap;
> -		struct folio *folio;
>  		unsigned cur_pages = min(max_pages, nr_pages);
> +		unsigned int pages = 0;
>  
>  		if (fc->num_background >= fc->congestion_threshold &&
>  		    rac->ra->async_size >= readahead_count(rac))
> @@ -968,14 +968,24 @@ static void fuse_readahead(struct readahead_control *rac)
>  			return;
>  		ap = &ia->ap;
>  
> -		while (ap->num_folios < cur_pages) {
> -			folio = readahead_folio(rac);
> +		while (pages < cur_pages) {
> +			unsigned int folio_pages;
> +
> +			if (!folio)
> +				folio = readahead_folio(rac);
> +
> +			folio_pages = folio_nr_pages(folio);
> +			if (folio_pages > cur_pages - pages)
> +				break;
> +
>  			ap->folios[ap->num_folios] = folio;
> -			ap->descs[ap->num_folios].length = folio_size(folio);
> +			ap->descs[ap->num_folios].length = folio_pages << PAGE_SHIFT;

Why change this?  Aren't these equivalent?  Thanks,

Josef