Re: [PATCH 2/4] mpage: mpage_readpages() should submit IO as read-ahead

[Randy Dunlap <rdunlap@infradead.org>]

On 06/20/2018 06:07 PM, Jens Axboe wrote:
> a_ops->readpages() is only ever used for read-ahead, yet we don't
> flag the IO being submitted as such. Fix that up. Any file system
> that uses mpage_readpages() as its ->readpages() implementation
> will now get this right.
> 
> Since we're passing in whether the IO is read-ahead or not, we
> don't need to pass in the 'gfp' separately, as it is dependent
> on the IO being read-ahead. Kill off that member.
> 
> Add some documentation notes on ->readpages() being purely for
> read-ahead.
> 
> Signed-off-by: Jens Axboe <axboe@kernel.dk>
> ---
>  fs/f2fs/data.c     |  5 +++++
>  fs/mpage.c         | 29 +++++++++++++++++++----------
>  include/linux/fs.h |  4 ++++
>  3 files changed, 28 insertions(+), 10 deletions(-)
> 
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index 8f931d699287..b7c9b58acf3e 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -1421,6 +1421,11 @@ int f2fs_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
>  /*
>   * This function was originally taken from fs/mpage.c, and customized for f2fs.
>   * Major change was from block_size == page_size in f2fs by default.
> + *
> + * Note that the aops->readpages() function is ONLY used for read-ahead. If
> + * this function ever deviates from doing just read-ahead, it should either
> + * use ->readpage() or do the necessary surgery to decouple ->readpages()
> + * readom read-ahead.

      eh?

>   */


-- 
~Randy