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

[Gao Xiang]

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,
Gao Xiang

> ---
>   fs/erofs/fileio.c | 2 ++
>   fs/erofs/zdata.c  | 6 +++++-
>   2 files changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/erofs/fileio.c b/fs/erofs/fileio.c
> index 3af96b1e2c2a..aa4cb438ea95 100644
> --- a/fs/erofs/fileio.c
> +++ b/fs/erofs/fileio.c
> @@ -88,6 +88,7 @@ static int erofs_fileio_scan_folio(struct erofs_fileio *io, struct folio *folio)
>   	struct erofs_map_blocks *map = &io->map;
>   	unsigned int cur = 0, end = folio_size(folio), len, attached = 0;
>   	loff_t pos = folio_pos(folio), ofs;
> +	bool fully_mapped = true;
>   	struct iov_iter iter;
>   	struct bio_vec bv;
>   	int err = 0;
> @@ -124,6 +125,7 @@ static int erofs_fileio_scan_folio(struct erofs_fileio *io, struct folio *folio)
>   			erofs_put_metabuf(&buf);
>   		} else if (!(map->m_flags & EROFS_MAP_MAPPED)) {
>   			folio_zero_segment(folio, cur, cur + len);
> +			fully_mapped = false;
>   			attached = 0;
>   		} else {
>   			if (io->rq && (map->m_pa + ofs != io->dev.m_pa ||
> diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
> index 8936790618c6..0158de4f3d95 100644
> --- a/fs/erofs/zdata.c
> +++ b/fs/erofs/zdata.c
> @@ -926,7 +926,7 @@ static int z_erofs_scan_folio(struct z_erofs_decompress_frontend *f,
>   	const loff_t offset = folio_pos(folio);
>   	const unsigned int bs = i_blocksize(inode);
>   	unsigned int end = folio_size(folio), split = 0, cur, pgs;
> -	bool tight, excl;
> +	bool tight, excl, fully_mapped = true;
>   	int err = 0;
>   
>   	tight = (bs == PAGE_SIZE);
> @@ -949,6 +949,7 @@ static int z_erofs_scan_folio(struct z_erofs_decompress_frontend *f,
>   
>   		if (!(map->m_flags & EROFS_MAP_MAPPED)) {
>   			folio_zero_segment(folio, cur, end);
> +			fully_mapped = false;
>   			tight = false;
>   		} else if (map->m_flags & EROFS_MAP_FRAGMENT) {
>   			erofs_off_t fpos = offset + cur - map->m_la;
> @@ -1009,6 +1010,9 @@ static int z_erofs_scan_folio(struct z_erofs_decompress_frontend *f,
>   			tight = (bs == PAGE_SIZE);
>   		}
>   	} while ((end = cur) > 0);
> +
> +	if (fully_mapped)
> +		folio_set_mappedtodisk(folio);
>   	erofs_onlinefolio_end(folio, err);
>   	return err;
>   }