Re: [PATCH v6 5/8] fs: xfs: replace BIO_MAX_SECTORS with BIO_MAX_PAGES

[Christoph Hellwig <hch@xxxxxxxxxxxxx>]

On Mon, May 30, 2016 at 09:34:33PM +0800, Ming Lei wrote:
> diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
> index e71cfbd..e5d713b 100644
> --- a/fs/xfs/xfs_buf.c
> +++ b/fs/xfs/xfs_buf.c
> @@ -1157,9 +1157,7 @@ xfs_buf_ioapply_map(
>  
>  next_chunk:
>       atomic_inc(&bp->b_io_remaining);
> -     nr_pages = BIO_MAX_SECTORS >> (PAGE_SHIFT - BBSHIFT);
> -     if (nr_pages > total_nr_pages)
> -             nr_pages = total_nr_pages;
> +     nr_pages = min(total_nr_pages, BIO_MAX_PAGES);
>  
>       bio = bio_alloc(GFP_NOIO, nr_pages);

While I think this is a useful cleanup on it's own I think
you'd make everyones life easier if bio_alloc simply clamped down
the passed nr_pages value to the maximum allowed.