Re: [PATCH v10 24/25] fuse: Convert from readpages to readahead

Miklos Szeredi
2020-03-25T09:43:09Z

On Mon, Mar 23, 2020 at 9:23 PM Matthew Wilcox <willy@infradead.org> wrote:
>
> From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
>
> Use the new readahead operation in fuse. Switching away from the
> read_cache_pages() helper gets rid of an implicit call to put_page(),
> so we can get rid of the get_page() call in fuse_readpages_fill().
>
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> Reviewed-by: Dave Chinner <dchinner@redhat.com>
> Reviewed-by: William Kucharski <william.kucharski@oracle.com>
> ---
> fs/fuse/file.c | 46 +++++++++++++++++++---------------------------
> 1 file changed, 19 insertions(+), 27 deletions(-)
>
> diff --git a/fs/fuse/file.c b/fs/fuse/file.c
> index 9d67b830fb7a..5749505bcff6 100644
> --- a/fs/fuse/file.c
> +++ b/fs/fuse/file.c
> @@ -923,9 +923,8 @@ struct fuse_fill_data {
> unsigned int max_pages;
> };
>
> -static int fuse_readpages_fill(void *_data, struct page *page)
> +static int fuse_readpages_fill(struct fuse_fill_data *data, struct page *page)
> {
> - struct fuse_fill_data *data = _data;
> struct fuse_io_args *ia = data->ia;
> struct fuse_args_pages *ap = &ia->ap;
> struct inode *inode = data->inode;
> @@ -941,10 +940,8 @@ static int fuse_readpages_fill(void *_data, struct page *page)
> fc->max_pages);
> fuse_send_readpages(ia, data->file);
> data->ia = ia = fuse_io_alloc(NULL, data->max_pages);
> - if (!ia) {
> - unlock_page(page);
> + if (!ia)
> return -ENOMEM;
> - }
> ap = &ia->ap;
> }
>
> @@ -954,7 +951,6 @@ static int fuse_readpages_fill(void *_data, struct page *page)
> return -EIO;
> }
>
> - get_page(page);
> ap->pages[ap->num_pages] = page;
> ap->descs[ap->num_pages].length = PAGE_SIZE;
> ap->num_pages++;
> @@ -962,37 +958,33 @@ static int fuse_readpages_fill(void *_data, struct page *page)
> return 0;
> }
>
> -static int fuse_readpages(struct file *file, struct address_space *mapping,
> - struct list_head *pages, unsigned nr_pages)
> +static void fuse_readahead(struct readahead_control *rac)
> {
> - struct inode *inode = mapping->host;
> + struct inode *inode = rac->mapping->host;
> struct fuse_conn *fc = get_fuse_conn(inode);
> struct fuse_fill_data data;
> - int err;
> + struct page *page;
>
> - err = -EIO;
> if (is_bad_inode(inode))
> - goto out;
> + return;
>
> - data.file = file;
> + data.file = rac->file;
> data.inode = inode;
> - data.nr_pages = nr_pages;
> - data.max_pages = min_t(unsigned int, nr_pages, fc->max_pages);
> -;
> + data.nr_pages = readahead_count(rac);
> + data.max_pages = min_t(unsigned int, data.nr_pages, fc->max_pages);
> data.ia = fuse_io_alloc(NULL, data.max_pages);
> - err = -ENOMEM;
> if (!data.ia)
> - goto out;
> + return;
>
> - err = read_cache_pages(mapping, pages, fuse_readpages_fill, &data);
> - if (!err) {
> - if (data.ia->ap.num_pages)
> - fuse_send_readpages(data.ia, file);
> - else
> - fuse_io_free(data.ia);
> + while ((page = readahead_page(rac))) {
> + if (fuse_readpages_fill(&data, page) != 0)

Shouldn't this unlock + put page on error?

Otherwise looks good.

Thanks,
Miklos