commit c7cb0ed8215c172aada9664ed34c8dbab606d30d
author Mark Salyzyn <salyzyn@google.com> Tue Jan 22 14:05:32 2019 -0800
committer Mark Salyzyn <salyzyn@google.com> Tue Jan 22 15:28:11 2019 -0800
tree da9a9c486647455a1a3821fd102207b5bb387688
parent 9ccf68f6a36e7dc05d6825095d9846f1823056ed

fs_mgr: overlayfs: validate that kernel supports scratch filesystem

Check for /sys/fs/<fs_type> existence to confirm kernel has
the file system type available.

Test: adb-remount-test.sh
Bug: 109821005
Bug: 123079041
Change-Id: Ic4388e2044bccea8b8edc7762d4ac9b3047206ac

fs_mgr/fs_mgr_overlayfs.cpp

diff --git a/fs_mgr/fs_mgr_overlayfs.cpp b/fs_mgr/fs_mgr_overlayfs.cpp
index 3908683..89d1d82 100644
--- a/fs_mgr/fs_mgr_overlayfs.cpp
+++ b/fs_mgr/fs_mgr_overlayfs.cpp
@@ -626,8 +626,8 @@
 
 // Only a suggestion for _first_ try during mounting
 std::string fs_mgr_overlayfs_scratch_mount_type() {
-    if (!access(kMkF2fs.c_str(), X_OK)) return "f2fs";
-    if (!access(kMkExt4.c_str(), X_OK)) return "ext4";
+    if (!access(kMkF2fs.c_str(), X_OK) && fs_mgr_access("/sys/fs/f2fs")) return "f2fs";
+    if (!access(kMkExt4.c_str(), X_OK) && fs_mgr_access("/sys/fs/ext4")) return "ext4";
     return "auto";
 }
 
@@ -829,8 +829,9 @@
                                                    true /* readonly */)) {
                     auto has_overlayfs_dir = fs_mgr_access(kScratchMountPoint + kOverlayTopDir);
                     fs_mgr_overlayfs_umount_scratch();
-                    if (has_overlayfs_dir)
+                    if (has_overlayfs_dir) {
                         fs_mgr_overlayfs_mount_scratch(scratch_device, mount_type);
+                    }
                 }
             }
         }