[PATCH v8 17/20] 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>
---
 fs/erofs/fscache.c  | 52 +++++++++++++++++++++++++++++++++++++++++++++
 fs/erofs/inode.c    |  5 +++++
 fs/erofs/internal.h |  2 ++
 3 files changed, 59 insertions(+)

diff --git a/fs/erofs/fscache.c b/fs/erofs/fscache.c
index 158cc273f8fb..65de1c754e80 100644
--- a/fs/erofs/fscache.c
+++ b/fs/erofs/fscache.c
@@ -60,10 +60,62 @@ 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_file_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;
+	}
+
+	/* no-inline readpage */
+	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_file_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,
+};
+
 /*
  * Get the page cache of data blob at the index offset.
  * Return: up to date page on success, ERR_PTR() on failure.
diff --git a/fs/erofs/inode.c b/fs/erofs/inode.c
index e8b37ba5e9ad..88b51b5fb53f 100644
--- a/fs/erofs/inode.c
+++ b/fs/erofs/inode.c
@@ -296,7 +296,12 @@ static int erofs_fill_inode(struct inode *inode, int isdir)
 		err = z_erofs_fill_inode(inode);
 		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 e186051f0640..336d19647c96 100644
--- a/fs/erofs/internal.h
+++ b/fs/erofs/internal.h
@@ -642,6 +642,8 @@ int erofs_fscache_register_cookie(struct super_block *sb,
 void erofs_fscache_unregister_cookie(struct erofs_fscache **fscache);
 
 struct folio *erofs_fscache_get_folio(struct super_block *sb, pgoff_t index);
+
+extern const struct address_space_operations erofs_fscache_access_aops;
 #else
 static inline int erofs_fscache_register_fs(struct super_block *sb) { return 0; }
 static inline void erofs_fscache_unregister_fs(struct super_block *sb) {}
-- 
2.27.0