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

[Gao Xiang]

On Fri, Nov 11, 2022 at 02:36:25PM +0800, Gao Xiang wrote:
> Hi,
> 
> On Thu, Nov 10, 2022 at 03:59:14PM +0800, JeffleXu wrote:
> > 
> > 
> > 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 at 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()
> 
> I will test it as well after I send out all bug fixes for this cycle.

I've updated the subject and commit message as:
"
erofs: enable large folios for iomap mode
Enable large folios for iomap mode.  Then the readahead routine will
pass down large folios containing multiple pages.

Let's enable this for non-compressed format for now, until the
compression part supports large folios later.
"

Thanks,
Gao Xiang