fuse: fix writepages on 32bit

BugLink: https://bugs.launchpad.net/bugs/1832661

commit 9de5be06 upstream.

Writepage requests were cropped to i_size & 0xffffffff, which meant that
mmaped writes to any file larger than 4G might be silently discarded.

Fix by storing the file size in a properly sized variable (loff_t instead
of size_t).
Reported-by: Antonio SJ Musumeci <trapexit@spawn.link>
Fixes: 6eaf4782 ("fuse: writepages: crop secondary requests")
Cc: <stable@vger.kernel.org> # v3.13
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

fs/fuse/file.c

@@ -1533,7 +1533,7 @@ __acquires(fc->lock)
 {
 	struct fuse_conn *fc = get_fuse_conn(inode);
 	struct fuse_inode *fi = get_fuse_inode(inode);
-	size_t crop = i_size_read(inode);
+	loff_t crop = i_size_read(inode);
 	struct fuse_req *req;
 
 	while (fi->writectr >= 0 && !list_empty(&fi->queued_writes)) {