Re: [PATCH] erofs: enable large folio in device-based mode

[JeffleXu <jefflexu@linux.alibaba.com>]

On 11/10/22 3:40 PM, Jingbo Xu wrote:
> Enable large folio in device-based mode. Then the radahead routine will
> pass down large folio containing multiple pages.
> 
> Enable this feature for non-compressed format for now, until the
> compression part supports large folio later.
> 
> Signed-off-by: Jingbo Xu <jefflexu@linux.alibaba.com>
> ---
> I have tested it under workload of Linux compiling. I know it's not a
> perfect workload testing this feature, because large folio is less
> likely hit in this case since source files are generally small. But I
> indeed observed large folios (e.g. 16 pages) by peeking
> readahead_count(rac) in erofs_readahead().

Sorry, readahead_count(rac) returns the whole number of pages inside the
rac, which can not prove large folio passed in.

I retired later and observed large folio (e.g. with order 2) by peeking
folio_order(ctx->cur_folio) inside iomap_readahead_iter()

> ---
>  fs/erofs/inode.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/fs/erofs/inode.c b/fs/erofs/inode.c
> index ad2a82f2eb4c..e457b8a59ee7 100644
> --- a/fs/erofs/inode.c
> +++ b/fs/erofs/inode.c
> @@ -295,6 +295,8 @@ static int erofs_fill_inode(struct inode *inode)
>  		goto out_unlock;
>  	}
>  	inode->i_mapping->a_ops = &erofs_raw_access_aops;
> +	if (!erofs_is_fscache_mode(inode->i_sb))
> +		mapping_set_large_folios(inode->i_mapping);
>  #ifdef CONFIG_EROFS_FS_ONDEMAND
>  	if (erofs_is_fscache_mode(inode->i_sb))
>  		inode->i_mapping->a_ops = &erofs_fscache_access_aops;

-- 
Thanks,
Jingbo