On Wed, Mar 16, 2022 at 09:17:22PM +0800, Jeffle Xu wrote:
> This patch implements fscache-based data readahead. Also registers an
> individual bdi for each erofs instance to enable readahead.
> 
> Signed-off-by: Jeffle Xu <jeffl...@linux.alibaba.com>
> ---
>  fs/erofs/fscache.c | 153 +++++++++++++++++++++++++++++++++++++++++++++
>  fs/erofs/super.c   |   4 ++
>  2 files changed, 157 insertions(+)
> 
> diff --git a/fs/erofs/fscache.c b/fs/erofs/fscache.c
> index 82c52b6e077e..913ca891deb9 100644
> --- a/fs/erofs/fscache.c
> +++ b/fs/erofs/fscache.c
> @@ -10,6 +10,13 @@ struct erofs_fscache_map {
>       u64 m_llen;
>  };
>  
> +struct erofs_fscahce_ra_ctx {

typo,  should be `erofs_fscache_ra_ctx'

> +     struct readahead_control *rac;
> +     struct address_space *mapping;
> +     loff_t start;
> +     size_t len, done;
> +};
> +
>  static struct fscache_volume *volume;
>  
>  /*
> @@ -199,12 +206,158 @@ static int erofs_fscache_readpage(struct file *file, 
> struct page *page)
>       return ret;
>  }
>  
> +static inline size_t erofs_fscache_calc_len(struct erofs_fscahce_ra_ctx 
> *ractx,
> +                                         struct erofs_fscache_map *fsmap)
> +{
> +     /*
> +      * 1) For CHUNK_BASED layout, the output m_la is rounded down to the
> +      * nearest chunk boundary, and the output m_llen actually starts from
> +      * the start of the containing chunk.
> +      * 2) For other cases, the output m_la is equal to o_la.
> +      */
> +     size_t len = fsmap->m_llen - (fsmap->o_la - fsmap->m_la);
> +
> +     return min_t(size_t, len, ractx->len - ractx->done);
> +}
> +
> +static inline void erofs_fscache_unlock_pages(struct readahead_control *rac,
> +                                           size_t len)

Can we convert them into folios in advance? it seems much
straight-forward to convert these...

Or I have to convert them later, and it seems unnecessary...


> +{
> +     while (len) {
> +             struct page *page = readahead_page(rac);
> +
> +             SetPageUptodate(page);
> +             unlock_page(page);
> +             put_page(page);
> +
> +             len -= PAGE_SIZE;
> +     }
> +}
> +
> +static int erofs_fscache_ra_hole(struct erofs_fscahce_ra_ctx *ractx,
> +                              struct erofs_fscache_map *fsmap)
> +{
> +     struct iov_iter iter;
> +     loff_t start = ractx->start + ractx->done;
> +     size_t length = erofs_fscache_calc_len(ractx, fsmap);
> +
> +     iov_iter_xarray(&iter, READ, &ractx->mapping->i_pages, start, length);
> +     iov_iter_zero(length, &iter);
> +
> +     erofs_fscache_unlock_pages(ractx->rac, length);
> +     return length;
> +}
> +
> +static int erofs_fscache_ra_noinline(struct erofs_fscahce_ra_ctx *ractx,
> +                                  struct erofs_fscache_map *fsmap)
> +{
> +     struct fscache_cookie *cookie = fsmap->m_ctx->cookie;
> +     loff_t start = ractx->start + ractx->done;
> +     size_t length = erofs_fscache_calc_len(ractx, fsmap);
> +     loff_t pstart = fsmap->m_pa + (fsmap->o_la - fsmap->m_la);
> +     int ret;
> +
> +     ret = erofs_fscache_read_pages(cookie, ractx->mapping,
> +                                    start, length, pstart);
> +     if (!ret) {
> +             erofs_fscache_unlock_pages(ractx->rac, length);
> +             ret = length;
> +     }
> +
> +     return ret;
> +}
> +
> +static int erofs_fscache_ra_inline(struct erofs_fscahce_ra_ctx *ractx,
> +                                struct erofs_fscache_map *fsmap)
> +{

We could fold in this, since it has the only user.

Thanks,
Gao Xiang

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