new file mode 100644
@@ -0,0 +1,16 @@
+--- a/mount_root.c
++++ b/mount_root.c
+@@ -75,6 +75,13 @@ start(int argc, char *argv[1])
+ case FS_F2FS:
+ case FS_JFFS2:
+ case FS_UBIFS:
++ /*
++ * Filesystem is in a valid state so we can go ahead and mount
++ * the target overlay, or this is the first boot after an upgrade
++ * that preserved files, so we hang preinit_main while we format
++ * the partition (oops... this is undesired) and then launch the
++ * target overlay (skip the intermediate tmpfs step).
++ */
+ mount_overlay(data);
+ break;
+
Sysupgrades that preserve volatile files ('sysupgrade -c ...') replace the 0xDEADCODE marker at the rootfs/rootfs_data boundary with the tar bundle of preserved files. The 0xDEADCODE marker is moved to the start of the next erase block. Upon the subsequent first boot, the mount_root utility reads a valid jffs2 file in the first block of rootfs_data, concludes that the partition has already been formatted, and summons the jffs2 driver. The jffs2 driver finds the 0xDEADCODE marker after the tar file and assumes that now is a safe time to format the rootfs_data partition and launch the jffs2 overlay. This is a bug, since preinit_main hangs while the jffs2 driver formats the partition, which can cause fatal soft lockups on systems with weak cpu and large rootfs_data partitions. The intended behavior for a first boot is to have mount_root kick off an intermediate tmpfs overlay, deferring the jffs2 switch until the /etc/init.d/done call. Patching this bug would lead to the preserved files being lost during upgrades or downgrades to or from the fixed build, so it is probably best to leave it as is. Fortunately, the preinit_main hang is survivable on most current systems. This bug should be described in comments for the sake of maintaining accurate descriptions of the system. Signed-off-by: Sean Miller <seanmmiller.business@gmail.com> --- .../patches/010-mount_root-overlay-bug.patch | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) create mode 100644 package/system/fstools/patches/010-mount_root-overlay-bug.patch