vlrureclaim() in vfs_subr.c 1.636 because waiting for the vnode
lock aggravates an existing race condition. It is also undesirable
according to the commit log for 1.631.
Fix the tiny race condition that remains by rechecking the vnode
state after grabbing the vnode lock and grabbing the vnode interlock.
Fix the problem of other threads being starved (which 1.636 attempted
to fix by removing LK_NOWAIT) by calling uio_yield() periodically
in vlrureclaim(). This should be more deterministic than hoping
that VOP_LOCK() without LK_NOWAIT will block, which may not happen
in this loop.
Reviewed by: kan
MFC after: 5 days
is a workaround for non-symetric teardown of the file systems at
shutdown with respect to the mount order at boot. The proper long term
fix is to properly detach devfs from the root mount before unmounting
each, and should be implemented, but since the problem is non-harmful,
this temporary band-aid will prevent false positive bug reports and
unnecessary error output for 6.0-RELEASE.
MFC after: 3 days
Tested by: pav, pjd
vnode is inactivated), possibly leading to a NULL dereference when
checking if the mount wants knotes to be activated in the VOP hooks.
So, we add a new vnode flag VV_NOKNOTE that is only set in getnewvnode(),
if necessary, and check it when activating knotes.
Since the flags are not erased when a vnode is being held, we can safely
read them.
Reviewed by: kris@
MFC after: 3 days
vnlru proc is extremely inefficient, potentially iteration over tens of
thousands of vnodes without blocking. Droping Giant allows other threads
to preempt us although we should revisit the algorithm to fix the runtime
problems especially since this may hold up all vnode allocations.
- Remove the LK_NOWAIT from the VOP_LOCK in vlrureclaim. This provides
a natural blocking point to help alleviate the situation described above
although it may not technically be desirable.
- yield after we make a pass on all mount points to prevent us from
blocking other threads which require Giant.
MFC after: 2 weeks
- Introducing the possibility of using locks different than mutexes
for the knlist locking. In order to do this, we add three arguments to
knlist_init() to specify the functions to use to lock, unlock and
check if the lock is owned. If these arguments are NULL, we assume
mtx_lock, mtx_unlock and mtx_owned, respectively.
- Using the vnode lock for the knlist locking, when doing kqueue operations
on a vnode. This way, we don't have to lock the vnode while holding a
mutex, in filt_vfsread.
Reviewed by: jmg
Approved by: re (scottl), scottl (mentor override)
Pointyhat to: ssouhlal
Will be happy: everyone
are actually caused by a buf with both VNCLEAN and VNDIRTY set. In
the traces it is clear that the buf is removed from the dirty queue while
it is actually on the clean queue which leaves the tail pointer set.
Assert that both flags are not set in buf_vlist_add and buf_vlist_remove.
Sponsored by: Isilon Systems, Inc.
Approved by: re (blanket vfs)
ref while we're calling vgone(). This prevents transient refs from
re-adding us to the free list. Previously, a vfree() triggered via
vinvalbuf() getting rid of all of a vnode's pages could place a partially
destructed vnode on the free list where vtryrecycle() could find it. The
first call to vtryrecycle would hang up on the vnode lock, but when it
failed it would place a now dead vnode onto the free list, and another
call to vtryrecycle() would free an already free vnode. There were many
complications of having a zero ref count while freeing which can now go
away.
- Change vdropl() to release the interlock before returning. All callers
now respect this, so vdropl() directly frees VI_DOOMED vnodes once the
last ref is dropped. This means that we'll never have VI_DOOMED vnodes
on the free list.
- Seperate v_incr_usecount() into v_incr_usecount(), v_decr_usecount() and
v_decr_useonly(). The incr/decr split is so that incr usecount can
return with the interlock still held while decr drops the interlock so
it can call vdropl() which will potentially free the vnode. The calling
function can't drop the lock of an already free'd node. v_decr_useonly()
drops a usecount without droping the hold count. This is done so the
usecount reaches zero in vput() before we recycle, however the holdcount
is still 1 which prevents any new references from placing the vnode
back on the free list.
- Fix vnlrureclaim() to vhold the vnode since it doesn't do a vget(). We
wouldn't want vnlrureclaim() to bump the usecount since this has
different semantics. Also change vnlrureclaim() to do a NOWAIT on the
vn_lock. When this function runs we're usually in a desperate situation
and we wouldn't want to wait for any specific vnode to be released.
- Fix a bunch of misc comments to reflect the new behavior.
- Add vhold() and vdrop() to vflush() for the same reasons that we do in
vlrureclaim(). Previously we held no reference and a vnode could have
been freed while we were waiting on the lock.
- Get rid of vlruvp() and vfreehead(). Neither are used. vlruvp() should
really be rethought before it's reintroduced.
- vgonel() always returns with the vnode locked now and never puts the
vnode back on a free list. The vnode will be freed as soon as the last
reference is released.
Sponsored by: Isilon Systems, Inc.
Debugging help from: Kris Kennaway, Peter Holm
Approved by: re (blanket vfs)
of the clean and dirty lists. This is in an attempt to catch the wrong
bufobj problem sooner.
- In vgonel() don't acquire an extra reference in the active case, the
vnode lock and VI_DOOMED protect us from recursively cleaning.
- Also in vgonel() clean up some stale comments.
Sponsored by: Isilon Systems, Inc.
Approved by: re (blanket vfs)
anyway and it's not used outside of vfs_subr.c.
- Change vgonel() to accept a parameter which determines whether or not
we'll put the vnode on the free list when we're done.
- Use the new vgonel() parameter rather than VI_DOOMED to signal our
intentions in vtryrecycle().
- In vgonel() return if VI_DOOMED is already set, this vnode has already
been reclaimed.
Sponsored by: Isilon Systems, Inc.
events could be added to cover other interesting details.
- Add some VNASSERTs to discover places where we access vnodes after
they have been uma_zfree'd before we try to free them again.
- Add a few more VNASSERTs to vdestroy() to be certain that the vnode is
really unused.
Sponsored by: Isilon Systems, Inc.
UFS by:
- Making the pre and post hooks for the VOP functions work even when
DEBUG_VFS_LOCKS is not defined.
- Moving the KNOTE activations into the corresponding VOP hooks.
- Creating a MNTK_NOKNOTE flag for the mnt_kern_flag field of struct
mount that permits filesystems to disable the new behavior.
- Creating a default VOP_KQFILTER function: vfs_kqfilter()
My benchmarks have not revealed any performance degradation.
Reviewed by: jeff, bde
Approved by: rwatson, jmg (kqueue changes), grehan (mentor)
1. Copy a NULL-terminated string into a fixed-length buffer, and
2. copyout that buffer to userland,
we really ought to
0. Zero the entire buffer
first.
Security: FreeBSD-SA-05:08.kmem
drop the check+initialization for a straight initialization. Also
assert that curthread will never be NULL just to be sure.
Discussed with: rwatson, peter
MFC after: 1 week
are set when we attempt to remove a buffer from a queue we should panic.
Hopefully this will catch the source of the wrong bufobj panics.
Sponsored by: Isilon Systems, Inc.
vtryrecycle(). We could sometimes get into situations where two threads
could try to recycle the same vnode before this.
- vtryrecycle() is now responsible for returning the vnode to the free list
if it fails and someone else hasn't done it.
- Make a new function vfreehead() which moves a vnode to the head of the
free list and use it in vgone() to clean up that code a bit.
Sponsored by: Isilon Systems, Inc.
Reported by: pho, kkenn
do not correctly deal with failures. This presently risks deadlock
problems if dependency processing is held up by failures to allocate
a vnode, however, this is better than the situation with the failures.
Sponsored by: Isilon Systems, Inc.
potential lock order reversal. Also, don't unlock the vnode if this
fails, lockmgr has already unlocked it for us.
- Restructure vget() now that vn_lock() does all of VI_DOOMED checking
for us and also handles the case where there is no real lock type.
- If VI_OWEINACT is set, we need to upgrade the lock request to EXCLUSIVE
so that we can call inactive. It's not legal to vget a vnode that hasn't
had INACTIVE called yet.
Sponsored by: Isilon Systems, Inc.
to root cause on exactly how this happens.
- If the assert is disabled, we presently try to handle this case, but the
BUF_UNLOCK was missing. Thus, if this condition ever hit we would leak
a buf lock.
Many thanks to Peter Holm for all his help in finding this bug. He really
put more effort into it than I did.
one to become available for one second and then return ENFILE. We
can run out of vnodes, and there must be a hard limit because without
one we can quickly run out of KVA on x86. Presently the system can
deadlock if there are maxvnodes directories in the namecache. The
original 4.x BSD behavior was to return ENFILE if we reached the max,
but 4.x BSD did not have the vnlru proc so it was less profitable to
wait.
on filesystems which safely support them. It appears that many
network filesystems specifically are not shared lock safe.
Sponsored by: Isilon Systems, Inc.
vnodes whose names it caches, so we no longer need a `generation
number' to tell us if a referenced vnode is invalid. Replace the use
of the parent's v_id in the hash function with the address of the
parent vnode.
Tested by: Peter Holm
Glanced at by: jeff, phk
vhold()s us.
- Avoid an extra mutex acquire and release in the common case of vgonel()
by checking for OWEINACT at the start of the function.
- Fix the case where we set OWEINACT in vput(). LK_EXCLUPGRADE drops our
shared lock if it fails.
Sponsored by: Isilon Systems, Inc.
now always allocates a new vnode.
- Define a new function, vnlru_free, which frees vnodes from the free list.
It takes as a parameter the number of vnodes to free, which is
wantfreevnodes - freevnodes when called from vnlru_proc or 1 when
called from getnewvnode(). For now, getnewvnode() still tries to reclaim
a free vnode before creating a new one when we are near the limit.
- Define a function, vdestroy, which handles the actual release of memory
and teardown of locks, etc. This could become a uma_dtor() routine.
- Get rid of minvnodes. Now wantfreevnodes is 1/4th the max vnodes. This
keeps more unreferenced vnodes around so that files which have only
been stat'd are less likely to be kicked out of the system before we
have a chance to read them, etc. These vnodes may still be freed via
the normal vnlru_proc() routines which may some day become a real lru.
before it can call VOP_INACTIVE(). This must use the EXCLUPGRADE path
because we may violate some lock order with another locked vnode if
we drop and reacquire the lock. If EXCLUPGRADE fails, we mark the
vnode with VI_OWEINACT. This case should be very rare.
- Clear VI_OWEINACT in vinactive() and vbusy().
- If VI_OWEINACT is set in vgone() do the VOP_INACTIVE call here as well.
Sponsored by: Isilon Systems, Inc.
- Move VSHOULDBUSY, VSHOULDFREE, and VTRYRECYCLE into vfs_subr.c so
no one else attempts to grow a dependency on them.
- Now that objects with pages hold the vnode we don't have to do unlocked
checks for the page count in the vm object in VSHOULDFREE. These three
macros could simply check for holdcnt state transitions to determine
whether the vnode is on the free list already, but the extra safety
the flag affords us is probably worth the minimal cost.
- The leafonly sysctl and code have been dead for several years now,
remove the sysctl and the code that employed it from vtryrecycle().
- vtryrecycle() also no longer has to check the object's page count as
the object holds the vnode until it reaches 0.
Sponsored by: Isilon Systems, Inc.
to use only the holdcnt to determine whether a vnode may be recycled,
simplifying the V* macros as well as vtryrecycle(), etc.
Sponsored by: Isilon Systems, Inc.
vtryrecycle(). All obj refs also ref the vnode.
- Consistently use v_incr_usecount() to increment the usecount. This will
be more important later.
Sponsored by: Isilon Systems, Inc.
- Add a vn_start_write/vn_finished_write around vlrureclaim so we don't do
writing ops without suspending. This could suspend the vlruproc which
should not be a problem under normal circumstances.
- Manually implement VMIGHTFREE in vlrureclaim as this was the only instance
where it was used.
- Acquire a lock before calling vgone() as it now requires it.
- Move the acquisition of the vnode interlock from vtryrecycle() to
getnewvnode() so that if it fails we don't drop and reacquire the
vnode_free_list_mtx.
- Check for a usecount or holdcount at the end of vtryrecycle() in case
someone grabbed a ref while we were recycling. Abort the recycle, and
on the final ref drop this vnode will be placed on the head of the free
list.
- Move the redundant VOP_INACTIVE protection code into the local
vinactive() routine to avoid code bloat.
- Keep the vnode lock held across calls to vgone() in several places.
- vgonel() no longer uses XLOCK, instead callers must hold an exclusive
vnode lock. The VI_DOOMED flag is set to allow other threads to detect
a vnode which is no longer valid. This flag is set until the last
reference is gone, and there are no chances for a new ref. vgonel()
holds this lock across the entire function, which greatly simplifies
logic.
_ Only vfree() in one place in vgone() not three.
- Adjust vget() to check the VI_DOOMED flag prior to waiting on the lock
in the LK_NOWAIT case. In other cases, check after we have slept and
acquired an exlusive lock. This will simulate the old vx_wait()
behavior.
Sponsored by: Isilon Systems, Inc.
has been set. Assert that this is the case so that we catch filesystems
who are using naked VOP_LOCKs in illegal cases.
Sponsored by: Isilon Systems, Inc.
considered to be as good as an exclusive lock, although there is still a
possibility of someone acquiring a VOP LOCK while xlock is held.
Sponsored by: Isilon Systems, Inc.
List devfs_dirents rather than vnodes off their shared struct cdev, this
saves a pointer field in the vnode at the expense of a field in the
devfs_dirent. There are often 100 times more vnodes so this is bargain.
In addition it makes it harder for people to try to do stypid things like
"finding the vnode from cdev".
Since DEVFS handles all VCHR nodes now, we can do the vnode related
cleanup in devfs_reclaim() instead of in dev_rel() and vgonel().
Similarly, we can do the struct cdev related cleanup in dev_rel()
instead of devfs_reclaim().
rename idestroy_dev() to destroy_devl() for consistency.
Add LIST_ENTRY de_alias to struct devfs_dirent.
Remove v_specnext from struct vnode.
Change si_hlist to si_alist in struct cdev.
String new devfs vnodes' devfs_dirent on si_alist when
we create them and take them off in devfs_reclaim().
Fix devfs_revoke() accordingly. Also don't clear fields
devfs_reclaim() will clear when called from vgone();
Let devfs_reclaim() call dev_rel() instead of vgonel().
Move the usecount tracking from dev_rel() to devfs_reclaim(),
and let dev_rel() take a struct cdev argument instead of vnode.
Destroy SI_CHEAPCLONE devices in dev_rel() (instead of
devfs_reclaim()) when they are no longer used. (This
should maybe happen in devfs_close() instead.)
patch from kan@).
Pull bufobj_invalbuf() out of vinvalbuf() and make g_vfs call it on
close. This is not yet a generally safe function, but for this very
specific use it is safe. This solves the problem with buffers not
being flushed by unmount or after failed mount attempts.
to off.
- Protect access to mnt_kern_flag with the mointpoint mutex.
- Remove some KASSERTs which are not legal checks without the appropriate
locks held.
- Use VCANRECYCLE() rather than rolling several slightly different
checks together.
- Return from vtryrecycle() with a recycled vnode rather than a locked
vnode. This simplifies some locking.
- Remove several GIANT_REQUIRED lines.
- Add a few KASSERTs to help with INACT debugging.
Sponsored By: Isilon Systems, Inc.
unhappiness lately.
As far as I can tell, no files that have made it safely to disk
have been endangered, but stuff in transit has been in peril.
Pointy hat: phk
TAILQ_FOREACH_SAFE().
Loose the error pointer argument and return any errors the normal way.
Return EAGAIN for the case where more work needs to be done.
I'm not sure why a credential was added to these in the first place, it is
not used anywhere and it doesn't make much sense:
The credentials for syncing a file (ability to write to the
file) should be checked at the system call level.
Credentials for syncing one or more filesystems ("none")
should be checked at the system call level as well.
If the filesystem implementation needs a particular credential
to carry out the syncing it would logically have to the
cached mount credential, or a credential cached along with
any delayed write data.
Discussed with: rwatson
split the conversion of the remaining three filesystems out from the root
mounting changes, so in one go:
cd9660:
Convert to nmount.
Add omount compat shims.
Remove dedicated rootfs mounting code.
Use vfs_mountedfrom()
Rely on vfs_mount.c calling VFS_STATFS()
nfs(client):
Convert to nmount (the simple way, mount_nfs(8) is still necessary).
Add omount compat shims.
Drop COMPAT_PRELITE2 mount arg compatibility.
ffs:
Convert to nmount.
Add omount compat shims.
Remove dedicated rootfs mounting code.
Use vfs_mountedfrom()
Rely on vfs_mount.c calling VFS_STATFS()
Remove vfs_omount() method, all filesystems are now converted.
Remove MNTK_WANTRDWR, handling RO/RW conversions is a filesystem
task, and they all do it now.
Change rootmounting to use DEVFS trampoline:
vfs_mount.c:
Mount devfs on /. Devfs needs no 'from' so this is clean.
symlink /dev to /. This makes it possible to lookup /dev/foo.
Mount "real" root filesystem on /.
Surgically move the devfs mountpoint from under the real root
filesystem onto /dev in the real root filesystem.
Remove now unnecessary getdiskbyname().
kern_init.c:
Don't do devfs mounting and rootvnode assignment here, it was
already handled by vfs_mount.c.
Remove now unused bdevvp(), addaliasu() and addalias(). Put the
few necessary lines in devfs where they belong. This eliminates the
second-last source of bogo vnodes, leaving only the lemming-syncer.
Remove rootdev variable, it doesn't give meaning in a global context and
was not trustworth anyway. Correct information is provided by
statfs(/).
initializations but we did have lofty goals and big ideals.
Adjust to more contemporary circumstances and gain type checking.
Replace the entire vop_t frobbing thing with properly typed
structures. The only casualty is that we can not add a new
VOP_ method with a loadable module. History has not given
us reason to belive this would ever be feasible in the the
first place.
Eliminate in toto VOCALL(), vop_t, VNODEOP_SET() etc.
Give coda correct prototypes and function definitions for
all vop_()s.
Generate a bit more data from the vnode_if.src file: a
struct vop_vector and protype typedefs for all vop methods.
Add a new vop_bypass() and make vop_default be a pointer
to another struct vop_vector.
Remove a lot of vfs_init since vop_vector is ready to use
from the compiler.
Cast various vop_mumble() to void * with uppercase name,
for instance VOP_PANIC, VOP_NULL etc.
Implement VCALL() by making vdesc_offset the offsetof() the
relevant function pointer in vop_vector. This is disgusting
but since the code is generated by a script comparatively
safe. The alternative for nullfs etc. would be much worse.
Fix up all vnode method vectors to remove casts so they
become typesafe. (The bulk of this is generated by scripts)
At some point later the syncer will unlearn about vnodes and the filesystems
method called by the syncer will know enough about what's in bo_private to
do the right thing.
[1] Ok, I know, but I couldn't resist the pun.
