On Fri, Apr 15, 2022 at 08:36:13PM +0800, Jeffle Xu wrote:
> Implement 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 | 86 ++++++++++++++++++++++++++++++++++++++++++++++
> fs/erofs/super.c | 4 +++
> 2 files changed, 90 insertions(+)
>
> diff --git a/fs/erofs/fscache.c b/fs/erofs/fscache.c
> index 08849c15500f..eaa50692ddba 100644
> --- a/fs/erofs/fscache.c
> +++ b/fs/erofs/fscache.c
> @@ -163,12 +163,98 @@ static int erofs_fscache_readpage(struct file *file,
> struct page *page)
> return ret;
> }
>
> +static void erofs_fscache_unlock_folios(struct readahead_control *rac,
> + size_t len)
> +{
> + while (len) {
> + struct folio *folio = readahead_folio(rac);
> +
> + len -= folio_size(folio);
> + folio_mark_uptodate(folio);
> + folio_unlock(folio);
> + }
> +}
> +
> +static void erofs_fscache_readahead(struct readahead_control *rac)
> +{
> + struct inode *inode = rac->mapping->host;
> + struct super_block *sb = inode->i_sb;
> + size_t len, count, done = 0;
> + erofs_off_t pos;
> + loff_t start, offset;
> + int ret;
> +
> + if (!readahead_count(rac))
> + return;
> +
> + start = readahead_pos(rac);
> + len = readahead_length(rac);
> +
> + do {
> + struct erofs_map_blocks map;
> + struct erofs_map_dev mdev;
> +
> + pos = start + done;
> + map.m_la = pos;
> +
> + ret = erofs_map_blocks(inode, &map, EROFS_GET_BLOCKS_RAW);
> + if (ret)
> + return;
> +
> + offset = start + done;
> + count = min_t(size_t, map.m_llen - (pos - map.m_la),
> + len - done);
> +
> + if (!(map.m_flags & EROFS_MAP_MAPPED)) {
> + struct iov_iter iter;
> +
> + iov_iter_xarray(&iter, READ, &rac->mapping->i_pages,
> + offset, count);
> + iov_iter_zero(count, &iter);
> +
> + erofs_fscache_unlock_folios(rac, count);
> + ret = count;
> + continue;
> + }
> +
> + if (map.m_flags & EROFS_MAP_META) {
> + struct folio *folio = readahead_folio(rac);
> +
> + ret = erofs_fscache_readpage_inline(folio, &map);
> + if (!ret) {
> + folio_mark_uptodate(folio);
> + ret = folio_size(folio);
> + }
> +
> + folio_unlock(folio);
> + continue;
> + }
> +
> + mdev = (struct erofs_map_dev) {
> + .m_deviceid = map.m_deviceid,
> + .m_pa = map.m_pa,
> + };
> + ret = erofs_map_dev(sb, &mdev);
> + if (ret)
> + return;
> +
> + ret = erofs_fscache_read_folios(mdev.m_fscache->cookie,
> + rac->mapping, offset, count,
> + mdev.m_pa + (pos - map.m_la));
> + if (!ret) {
> + erofs_fscache_unlock_folios(rac, count);
> + ret = count;
> + }
I think this really needs a comment why we don't need to unlock folios
for the error cases.
Thanks,
Gao Xiang
> + } while (ret > 0 && ((done += ret) < len));
> +}
> +
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