[PATCH v9 18/21] erofs: implement fscache-based data read for non-inline layout

[Jeffle Xu <jefflexu@xxxxxxxxxxxxxxxxx>]

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

Signed-off-by: Jeffle Xu <jefflexu@xxxxxxxxxxxxxxxxx>
Reviewed-by: Gao Xiang <hsiangkao@xxxxxxxxxxxxxxxxx>
---
 fs/erofs/fscache.c  | 51 +++++++++++++++++++++++++++++++++++++++++++++
 fs/erofs/inode.c    |  4 ++++
 fs/erofs/internal.h |  2 ++
 3 files changed, 57 insertions(+)

diff --git a/fs/erofs/fscache.c b/fs/erofs/fscache.c
index 3f00eb34ac35..b799b0fe1b67 100644
--- a/fs/erofs/fscache.c
+++ b/fs/erofs/fscache.c
@@ -84,10 +84,61 @@ static int erofs_fscache_meta_readpage(struct file *data, struct page *page)
 	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 = 0;
+
+	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,
+};
+
 /*
  * Create an fscache context for data blob.
  * Return: 0 on success and allocated fscache context is assigned to @fscache,
diff --git a/fs/erofs/inode.c b/fs/erofs/inode.c
index e8b37ba5e9ad..8d3f56c6469b 100644
--- a/fs/erofs/inode.c
+++ b/fs/erofs/inode.c
@@ -297,6 +297,10 @@ static int erofs_fill_inode(struct inode *inode, int isdir)
 		goto out_unlock;
 	}
 	inode->i_mapping->a_ops = &erofs_raw_access_aops;
+#ifdef CONFIG_EROFS_FS_ONDEMAND
+	if (erofs_is_fscache_mode(inode->i_sb))
+		inode->i_mapping->a_ops = &erofs_fscache_access_aops;
+#endif
 
 out_unlock:
 	erofs_put_metabuf(&buf);
diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
index fa488af8dfcf..c8f6ac910976 100644
--- a/fs/erofs/internal.h
+++ b/fs/erofs/internal.h
@@ -639,6 +639,8 @@ int erofs_fscache_register_cookie(struct super_block *sb,
 				  struct erofs_fscache **fscache,
 				  char *name, bool need_inode);
 void erofs_fscache_unregister_cookie(struct erofs_fscache **fscache);
+
+extern const struct address_space_operations erofs_fscache_access_aops;
 #else
 static inline int erofs_fscache_register_fs(struct super_block *sb)
 {
-- 
2.27.0