[PATCH RFC] fs: erofs: support PG_mappedtodisk flag for folios with zero-filled

[Barry Song]

On Thu, Oct 17, 2024 at 9:00 PM Gao Xiang <hsiangkao at linux.alibaba.com> wrote:
>
>
>
> On 2024/10/17 15:58, Gao Xiang wrote:
> > Hi Barry,
> >
> > On 2024/10/17 15:43, Barry Song wrote:
> >> From: Barry Song <v-songbaohua at oppo.com>
> >>
> >> When a folio has never been zero-filled, mark it as mappedtodisk
> >> to allow other software components to recognize and utilize the
> >> flag.
> >>
> >> Signed-off-by: Barry Song <v-songbaohua at oppo.com>
> >
> > Thanks for this!
> >
> > It looks good to me as an improvement as long as PG_mappedtodisk
> > is long-term lived and useful to users.
> >
> > Reviewed-by: Gao Xiang <hsiangkao at linux.alibaba.com>
>

thanks!

> BTW, I wonder if iomap supports this since uncompressed EROFS
> relies on iomap paths...

In the core layer, I only see fs/buffer.c's block_read_full_folio()
and fs/mpage.c's mpage_readahead() and mpage_readahead()
supporting this. I haven't found any code in iomap that sets the
flag.

I guess erofs doesn't call the above functions for non-compressed
files?

>
> Thanks,
> Gao Xiang

Barry