1 files changed, 54 insertions, 0 deletions
diff --git a/fs/erofs/fscache.c b/fs/erofs/fscache.c
index 26f038d9c4e1..ac02af8cce3e 100644
--- a/fs/erofs/fscache.c
+++ b/fs/erofs/fscache.c
@@ -5,6 +5,60 @@
 #include <linux/fscache.h>
 #include "internal.h"
 
+/*
+ * Read data from fscache and fill the read data into page cache described by
+ * @start/len, which shall be both aligned with PAGE_SIZE. @pstart describes
+ * the start physical address in the cache file.
+ */
+static int erofs_fscache_read_folios(struct fscache_cookie *cookie,
+				     struct address_space *mapping,
+				     loff_t start, size_t len,
+				     loff_t pstart)
+{
+	enum netfs_io_source source;
+	struct netfs_io_request rreq = {};
+	struct netfs_io_subrequest subreq = { .rreq = &rreq, };
+	struct netfs_cache_resources *cres = &rreq.cache_resources;
+	struct super_block *sb = mapping->host->i_sb;
+	struct iov_iter iter;
+	size_t done = 0;
+	int ret;
+
+	ret = fscache_begin_read_operation(cres, cookie);
+	if (ret)
+		return ret;
+
+	while (done < len) {
+		subreq.start = pstart + done;
+		subreq.len = len - done;
+		subreq.flags = 1 << NETFS_SREQ_ONDEMAND;
+
+		source = cres->ops->prepare_read(&subreq, LLONG_MAX);
+		if (WARN_ON(subreq.len == 0))
+			source = NETFS_INVALID_READ;
+		if (source != NETFS_READ_FROM_CACHE) {
+			erofs_err(sb, "failed to fscache prepare_read (source %d)",
+				  source);
+			ret = -EIO;
+			goto out;
+		}
+
+		iov_iter_xarray(&iter, READ, &mapping->i_pages,
+				start + done, subreq.len);
+		ret = fscache_read(cres, subreq.start, &iter,
+				   NETFS_READ_HOLE_FAIL, NULL, NULL);
+		if (ret) {
+			erofs_err(sb, "failed to fscache_read (ret %d)", ret);
+			goto out;
+		}
+
+		done += subreq.len;
+	}
+out:
+	fscache_end_operation(cres);
+	return ret;
+}
+
 static const struct address_space_operations erofs_fscache_meta_aops = {
 };