Add erofs_fscache_read_folios() helper reading from fscache. It supports
on-demand read semantics. That is, it will make the backend prepare for
the data when cache miss. Once data ready, it will reinitiate a read
from the cache.
This helper can then be used to implement .readpage()/.readahead() of
on-demand read semantics.
Signed-off-by: Jeffle Xu <jefflexu@xxxxxxxxxxxxxxxxx>
---
fs/erofs/fscache.c | 29 +++++++++++++++++++++++++++++
1 file changed, 29 insertions(+)
diff --git a/fs/erofs/fscache.c b/fs/erofs/fscache.c
index 1c88614203d2..d38a6efc8e50 100644
--- a/fs/erofs/fscache.c
+++ b/fs/erofs/fscache.c
@@ -5,6 +5,35 @@
#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)
+{
+ struct netfs_cache_resources cres;
+ struct iov_iter iter;
+ int ret;
+
+ memset(&cres, 0, sizeof(cres));
+
+ ret = fscache_begin_read_operation(&cres, cookie);
+ if (ret)
+ return ret;
+
+ iov_iter_xarray(&iter, READ, &mapping->i_pages, start, len);
+
+ ret = fscache_read(&cres, pstart, &iter,
+ NETFS_READ_HOLE_ONDEMAND, NULL, NULL);
+
+ fscache_end_operation(&cres);
+ return ret;
+}
+
static const struct address_space_operations erofs_fscache_meta_aops = {
};
--
2.27.0
