This commit prevents creation of entry points for jumps within the same
page. In interpreted mode, execution is continued on these kinds of
jumps.
Since this prevents the old hotness detection from working efficiently,
hotness detection has also been changed to work based on instruction
counters, and is such more precise (longer basic blocks are compiled
earlier).
This also breaks the old detection loop safety mechanism and causes
Linux to sometimes loop forever on "calibrating delay loop", so
JIT_ALWAYS_USE_LOOP_SAFETY has been set to 1.
Although hardlinks across filesystems worked quite well in the current
implementation, we will run into problems when we try to implement
different backends for each sub-filesystem.
Note: EPERM is used instead of EXDEV since the mv command will silently
try to use copy-and-unlink when rename(2) fails with EXDEV.
The rules for linking has been reverted back:
- Before commit: Any inode, including forwarders, could be linked as
long as the parent is not a forwarder and is a directory.
- After commit: Only non-forwarders and root-forwarders are allowed to
be linked, and must be linked under a directory and not a forwarder.
- Test both file and directory.
- Test combinations of forwarder/non-forwarder source/destinations
- Test different destination filenames
- Test empty file
Can't test early failure behaviour when destination can't be unlinked,
since right now only non-empty directories and root directories can't be
unlinked and busybox's mv program does not support mv
--no-target-directory.
If mountpoint already exists, then we're silently making its children
inaccessible which may not be what we expected/intended.
Create a new forwarder inode upon mounting.
