erofs: remove unused device mapping in meta routine

Currently metadata is always on bootstrap, and thus device mapping is
not needed so far.  Remove the redundant device mapping in the meta
routine.
Signed-off-by: Jingbo Xu <jefflexu@linux.alibaba.com>
Reviewed-by: Jia Zhu <zhujia.zj@bytedance.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Link: https://lore.kernel.org/r/20230209063913.46341-2-jefflexu@linux.alibaba.comSigned-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

fs/erofs/fscache.c

@@ -164,18 +164,8 @@ static int erofs_fscache_read_folios_async(struct fscache_cookie *cookie,
 static int erofs_fscache_meta_read_folio(struct file *data, struct folio *folio)
 {
 	int ret;
-	struct super_block *sb = folio_mapping(folio)->host->i_sb;
+	struct erofs_fscache *ctx = folio_mapping(folio)->host->i_private;
 	struct erofs_fscache_request *req;
-	struct erofs_map_dev mdev = {
-		.m_deviceid = 0,
-		.m_pa = folio_pos(folio),
-	};
-
-	ret = erofs_map_dev(sb, &mdev);
-	if (ret) {
-		folio_unlock(folio);
-		return ret;
-	}
 
 	req = erofs_fscache_req_alloc(folio_mapping(folio),
 				folio_pos(folio), folio_size(folio));
@@ -184,8 +174,8 @@ static int erofs_fscache_meta_read_folio(struct file *data, struct folio *folio)
 		return PTR_ERR(req);
 	}
 
-	ret = erofs_fscache_read_folios_async(mdev.m_fscache->cookie,
-				req, mdev.m_pa, folio_size(folio));
+	ret = erofs_fscache_read_folios_async(ctx->cookie, req,
+				folio_pos(folio), folio_size(folio));
 	if (ret)
 		req->error = ret;
 
@@ -469,6 +459,7 @@ struct erofs_fscache *erofs_fscache_acquire_cookie(struct super_block *sb,
 		inode->i_size = OFFSET_MAX;
 		inode->i_mapping->a_ops = &erofs_fscache_meta_aops;
 		mapping_set_gfp_mask(inode->i_mapping, GFP_NOFS);
+		inode->i_private = ctx;
 
 		ctx->inode = inode;
 	}