Skip the log entry as there is nothing good to write out. Don't fail
the syscall though since it already succeeded. There's no reason
filemon's tracing failure should fail the already-succeeded syscall.
Record the error for later to return from close(2) on the filemon devfs
file descriptor.
Discussed with: markj, sjg, kib (briefly with kib)
Reported by: mjg
MFC after: 2 weeks
Sponsored by: EMC / Isilon Storage Division
None of lstat(2), fstat(2), fstatat(2) were tracked either.
The other filemon implementations also do not track stat(2), nor
does bmake utilize it. The act of opening a file for read should
be enough to decide that a file is a dependency. There could be
rare cases where just having a file would cause a dependency but it
is unlikely.
MFC after: 2 weeks
Also noted by: sjg
Sponsored by: EMC / Isilon Storage Division
- proc.p_filemon is added which is protected by PROC_LOCK. This improves
performance and avoids double-fork issues, taking allproc_lock
while in syscalls, and walking the process tree in syscalls. A
particular proc.p_filemon can only be changed to NULL or another
filemon, or the filemon inherited, while the filemon->lock is held.
- Filemon are reference counted. On the last reference the log will be closed.
- When closing the devfs file handle, the filemon will be detached from all
processes and inheritance prevented.
- Disallow attaching to a process already being traced since filemon is
typically intended to be used on children only. This is allowed for
curproc as bmake relies on this behavior for rare cases when combining
.MAKE with .META.
- Detach any previously tracked process on ioctl(FILEMON_SET_PID).
- Handle error from devfs_set_cdevpriv() in filemon_open().
- The global filemon lock and lists are removed.
- A free list is no longer kept. Previously this list was
forever-expanding and never garbage cleaned.
- No longer loses track of double-forks. If the process holding the filemon
handle closes it will close the log rather than wait on a daemonized process,
but it will log all activity until it closes its handle. The filemon
will be removed from the process and not inherited.
- A separate process count is kept only as an optimization for
forced detachment to avoid taking allproc_lock and walking the entire
process tree.
- struct filemon access is protected by sx(9) filemon->lock as it was before.
- Add more comments and KASSERTS.
MFC after: 2 weeks
Reviewed by: kib, mjg, markj (all on previous versions)
Sponsored by: EMC / Isilon Storage Division
Differential Revision: https://reviews.freebsd.org/D5520
Code may still be executing from the wrappers at unload time and thus is
not generally safe to unload. Converting the wrappers to use
EVENTHANDLER(9) will allow this to safely drain on active threads in
hooks. More work on EVENTHANDLER(9) is needed first.
MFC after: 1 week
Sponsored by: EMC / Isilon Storage Division
- remove return statements from void function [1]
- include missing header
- use O_CLOEXEC instead of separate fcntl() calls
PR: docs/179459 [1]
MFC after: 1 week
