[PATCH 1/2] erofs: pass accurate blob size to prepare_ondemand_read()

[Jingbo Xu]

To make fscache mode support PAGE_SIZE larger than 4KB, the blob image
size may be small than the multiples of PAGE_SIZE (as erofs block size
is no larger than 4KB), while the file range of the blob requested to
read is multiples of PAGE_SIZE and may be larger than the blob image
size.

Therefore we need the accurate blob size, so that the EOF part could be
distinguished and zero-filled then.

Signed-off-by: Jingbo Xu <jefflexu at linux.alibaba.com>
---
 fs/erofs/fscache.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/fs/erofs/fscache.c b/fs/erofs/fscache.c
index 87ff35bff8d5..f7a1e147d0f4 100644
--- a/fs/erofs/fscache.c
+++ b/fs/erofs/fscache.c
@@ -125,7 +125,7 @@ static int erofs_fscache_read_folios_async(struct fscache_cookie *cookie,
 
 	DBG_BUGON(len > req->len - req->submitted);
 
-	ret = fscache_begin_read_operation(cres, cookie);
+	ret = fscache_begin_wait_operation(cres, cookie, FSCACHE_WANT_READ);
 	if (ret)
 		return ret;
 
@@ -134,8 +134,17 @@ static int erofs_fscache_read_folios_async(struct fscache_cookie *cookie,
 		size_t slen = len - done;
 		unsigned long flags = 1 << NETFS_SREQ_ONDEMAND;
 
+		if (sstart >= cookie->object_size) {
+			iov_iter_xarray(&iter, ITER_DEST, &req->mapping->i_pages,
+					lstart + done, slen);
+			iov_iter_zero(slen, &iter);
+			done += slen;
+			continue;
+		}
+
+		slen = min_t(size_t, slen, cookie->object_size - sstart);
 		source = cres->ops->prepare_ondemand_read(cres,
-				sstart, &slen, LLONG_MAX, &flags, 0);
+				sstart, &slen, cookie->object_size, &flags, 0);
 		if (WARN_ON(slen == 0))
 			source = NETFS_INVALID_READ;
 		if (source != NETFS_READ_FROM_CACHE) {
-- 
2.19.1.6.gb485710b