erofs: implement fscache-based data read for non-inline layout

Implement the data plane of reading data from data blobs over fscache
for non-inline layout.

Signed-off-by: Jeffle Xu <jefflexu@linux.alibaba.com>
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20220425122143.56815-19-jefflexu@linux.alibaba.com
Acked-by: Chao Yu <chao@kernel.org>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

1 files changed, 51 insertions, 0 deletions

diff --git a/fs/erofs/fscache.c b/fs/erofs/fscache.c
index 23d7e862eed8..b3af72af7c88 100644
--- a/fs/erofs/fscache.c
+++ b/fs/erofs/fscache.c
@@ -83,10 +83,61 @@ out:
 	return ret;
 }
 
+static int erofs_fscache_readpage(struct file *file, struct page *page)
+{
+	struct folio *folio = page_folio(page);
+	struct inode *inode = folio_mapping(folio)->host;
+	struct super_block *sb = inode->i_sb;
+	struct erofs_map_blocks map;
+	struct erofs_map_dev mdev;
+	erofs_off_t pos;
+	loff_t pstart;
+	int ret;
+
+	DBG_BUGON(folio_size(folio) != EROFS_BLKSIZ);
+
+	pos = folio_pos(folio);
+	map.m_la = pos;
+
+	ret = erofs_map_blocks(inode, &map, EROFS_GET_BLOCKS_RAW);
+	if (ret)
+		goto out_unlock;
+
+	if (!(map.m_flags & EROFS_MAP_MAPPED)) {
+		folio_zero_range(folio, 0, folio_size(folio));
+		goto out_uptodate;
+	}
+
+	mdev = (struct erofs_map_dev) {
+		.m_deviceid = map.m_deviceid,
+		.m_pa = map.m_pa,
+	};
+
+	ret = erofs_map_dev(sb, &mdev);
+	if (ret)
+		goto out_unlock;
+
+	pstart = mdev.m_pa + (pos - map.m_la);
+	ret = erofs_fscache_read_folios(mdev.m_fscache->cookie,
+			folio_mapping(folio), folio_pos(folio),
+			folio_size(folio), pstart);
+
+out_uptodate:
+	if (!ret)
+		folio_mark_uptodate(folio);
+out_unlock:
+	folio_unlock(folio);
+	return ret;
+}
+
 static const struct address_space_operations erofs_fscache_meta_aops = {
 	.readpage = erofs_fscache_meta_readpage,
 };
 
+const struct address_space_operations erofs_fscache_access_aops = {
+	.readpage = erofs_fscache_readpage,
+};
+
 int erofs_fscache_register_cookie(struct super_block *sb,
 				  struct erofs_fscache **fscache,
 				  char *name, bool need_inode)