Our vput calls vm_object_deallocate() --> vm_object_terminate(). The
vm_object_terminate() calls vn_lock(), since UN_LOCKED has been
already cleared in union_unlock(). Then, union_lock locks upper vnode
when UN_ULOCK is not set. The upper vnode is not unlocked when
UN_KLOCK is set in union_unlock(), thus, union_lock tries to lock
locked vnode and we get panic.
UN_ULOCK flag. This shows a locking violation but I couldn't find the
reason UN_ULOCK is not set or upper vnode is not unlocked. I added
the code that detect this case and adjust un_flags. DIAGNOSTIC kernel
doesn't adjust un_flags, but just panic here to help debug by kernel
hackers.
# mount -t union (or null) dir1 dir2
# mount -t union (or null) dir2 dir1
The function namei in union_mount calls union_root. The upper vnode
has been already locked and vn_lock in union_root causes above panic.
Add printf's included in `#ifdef DIAGNOSTIC' for EDEADLK cases.
is NULLVP, union node will have neither uppervp nor lowervp. This
causes page fault trap.
The union_removed_upper just remove union node from cache and it
doesn't set uppervp to NULLVP. Since union node is removed from
cache, it will not be referenced.
The code that remove union node from cache was copied from
union_inactive.
VOP_LINK(). The reason of strange behavior was wrong order of the
argument, that is, the operation
# ln foo bar
in a union fs tried to do
# ln bar foo
in ufs layer.
Now we can make a link in a union fs.
fix!
The ufs_link() assumes that vnode is not unlocked and tries to lock it
in certain case. Because union_link calls VOP_LINK after locking vnode,
vn_lock in ufs_link causes above panic.
Currently, I don't know the real fix for a locking violation in
union_link, but I think it is important to avoid panic.
A vnode is unlocked before calling VOP_LINK and is locked after it if
the vnode is not union fs. Even though panic went away, the process
that access the union fs in which link was made will hang-up.
Hang-up can be easily reproduced by following operation:
mount -t union a b
cd b
ln foo bar
ls
same directory pair.
If we do:
mount -t union a b
mount -t union a b
then, (1) namei tries to lock fs which has been already locked by
first union mount and (2) union_root() tries to lock locked fs. To
avoid first deadlock condition, unlock vnode if lowerrootvp is union
node, and to avoid second case, union_mount returns EDEADLK when multi
union mount is detected.
dolock is not set (that is, targetvp == overlaying vnode object).
Current code use FIXUP macro to do this, and never unlocks overlaying
vnode object in union_fsync. So, the vnode object will be locked
twice and never unlocked.
PR: 3271
Submitted by: kato
relookup() in union_relookup() is succeeded. However, if relookup()
returns non-zero value, that is relookup fails, VOP_MKDIR is never
called (c.f. union_mkshadow). Thus, pathname buffer is never FREEed.
Reviewed by: phk
Submitted by: kato
PR: 3262
by Alan Cox <alc@cs.rice.edu>, and his description of the problem.
The bug was primarily in procfs_mem, but the mistake likely happened
due to the lack of vm system support for the operation. I added
better support for selective marking of page dirty flags so that
vm_map_pageable(wiring) will not cause this problem again.
The code in procfs_mem is now less bogus (but maybe still a little
so.)
in procfs_allocvp(). This fixes at least stat() of /proc/*/mem.
stat() of /proc/*/file already worked. I think procfs_allocvp() isn't
actually called for type Pfile.
partly because the #define's for them were moved to a different
file. At least the null VOP_LOCK() no longer works, since vclean()
expects VOP_LOCK( ..., LK_DRAIN | LK_INTERLOCK, ...) to clear the
interlock. This probably only matters when simple_lock() is not
null, i.e., when there are multiple CPUs or SIMPLELOCK_DEBUG is
defined.
Call vget/VOP_UNLOCK with the correct number of
arguments. Call vn_lock where appropriate.
vfs_goneall is now replaced by VOP_REVOKE.
Submitted by: bde
changes, so don't expect to be able to run the kernel as-is (very well)
without the appropriate Lite/2 userland changes.
The system boots and can mount UFS filesystems.
Untested: ext2fs, msdosfs, NFS
Known problems: Incorrect Berkeley ID strings in some files.
Mount_std mounts will not work until the getfsent
library routine is changed.
Reviewed by: various people
Submitted by: Jeffery Hsu <hsu@freebsd.org>
This will make a number of things easier in the future, as well as (finally!)
avoiding the Id-smashing problem which has plagued developers for so long.
Boy, I'm glad we're not using sup anymore. This update would have been
insane otherwise.
Broke locking on named pipes in the same way as locking on non-vnodes
(wrong errno). This will be fixed later.
The fix involves negative logic. Named pipes are now distinguished from
other types of files with vnodes, and there is additional code to handle
vnodes and named pipes in the same way only where that makes sense (not
for lseek, locking or TIOCSCTTY).
fcntl() and EOPNOTSUPP for flock(). POSIX specifies the weaker EINVAL
errno and the man page agrees.
Not fixed:
deadfs: always returns wrong EBADF
devfs, msdosfs: always return sometimes-wrong EINVAL
cd9660, fdesc, kernfs, portal: always return sometimes-wrong EOPNOTSUPP
procfs: always returns wrong EIO
mfs: panic?!
nfs: fudged
NetBSD uses a generic file system genfs to do return the sometimes-wrong
EOPNOTSUPP more consistently :-)(.
Found by: NIST-PCTS
also fixes a bug I've been chasing for a LONG TIME,
due to the fact that spec_bwrite is a NOP and I didn't realise it..
old symptom:
mount -t devfs devfs /mnt
mount /mnt/wd0e /mnt/mnt2
umount /mnt2 <process hangs>
there are some pretty large structural differences internal to devfs
but outwards it should look the same.
I have not yet tested extensively but will do so and fix 3 warnings tomorrow.
