a file system, but need to obtain a vnode. We may not be able to do it, because
all vnodes could be already in use and other processes cannot release them,
because they are waiting in "suspfs" state.
In such situation, we allow to allocate a vnode anyway.
This is a temporary fix - there is no backpressure to free vnodes allocated in
those circumstances.
MFC after: 1 week
Reviewed by: tegge
in 1999, and there are changes to the sysctl names compared to PR,
according to that discussion. The description is in sys/conf/NOTES.
Lines in the GENERIC files are added in commented-out form.
I'll attach the test script I've used to PR.
PR: kern/14584
Submitted by: babkin
If B_NOCACHE is set the pages of vm backed buffers will be invalidated.
However clean buffers can be backed by dirty VM pages so invalidating them
can lead to data loss.
Add support for flush dirty page in the data invalidation function
of some network file systems.
This fixes data losses during vnode recycling (and other code paths
using invalbuf(*,V_SAVE,*,*)) for data written using an mmaped file.
Collaborative effort by: jhb@,mohans@,peter@,ps@,ups@
Reviewed by: tegge@
MFC after: 7 days
vn_start_write() is always called earlier in the code path and calling
the function recursively may lead to a deadlock.
Confirmed by: tegge
MFC after: 2 weeks
buffers to go on the buf daemon's DIRTYGIANT queue.
- Set BO_NEEDSGIANT on ffs's devvp since the ffs_copyonwrite handler
runs in the context of the buf daemon and may require Giant.
recycling for an unrelated filesystem. I really don't like potentially
acquiring giant in the context of a giantless filesystem but there
are reasonable objections to removing the recycling from this path.
Sponsored by: Isilon Systems, Inc.
called.
- vfs_getvfs has to return a reference to prevent the returned mountpoint
from changing identities.
- Release references acquired via vfs_getvfs.
Discussed with: tegge
Tested by: kris
Sponsored by: Isilon Systems, Inc.
requires Giant. It is set in bgetvp and cleared in brelvp.
- Create QUEUE_DIRTY_GIANT for dirty buffers that require giant.
- In the buf daemon, only grab giant when processing QUEUE_DIRTY_GIANT and
only if we think there are buffers in that queue.
Sponsored by: Isilon Systems, Inc.
the target directory or file. This case should fail in the filesystem
anyway and perhaps kern_rename() should catch it.
Sponsored by: Isilon Systems, Inc.
replacement for vn_write_suspend_wait() to better account for secondary write
processing.
Close race where secondary writes could be started after ffs_sync() returned
but before the file system was marked as suspended.
Detect if secondary writes or softdep processing occurred during vnode sync
loop in ffs_sync() and retry the loop if needed.
be called without any vnode locks held. Remove calls to vn_start_write() and
vn_finished_write() in vnode_pager_putpages() and add these calls before the
vnode lock is obtained to most of the callers that don't already have them.
has many positive effects including improved smp locking, reducing
interdependencies between mounts that can lead to deadlocks, etc.
- Add the softdep worklist and various counters to the ufsmnt structure.
- Add a mount pointer to the workitem and remove mount pointers from the
various structures derived from the workitem as they are now redundant.
- Remove the poor-man's semaphore protecting softdep_process_worklist and
softdep_flushworklist. Several threads may now process the list
simultaneously.
- Add softdep_waitidle() to block the thread until all pending
dependencies being operated on by other threads have been flushed.
- Use softdep_waitidle() in unmount and snapshots to block either
operation until the fs is stable.
- Remove softdep worklist processing from the syncer and move it into the
softdep_flush() thread. This thread processes all softdep mounts
once each second and when it is called via the new softdep_speedup()
when there is a resource shortage. This removes the softdep hook
from the kernel and various hacks in header files to support it.
Reviewed by/Discussed with: tegge, truckman, mckusick
Tested by: kris
the last reference is dropped. I forgot that vnodes can stick around
for a very long time until processes discover that they are dead. This
means that a vnode reference is not sufficient to keep the mount
referenced and even more code will be required to ref mount points.
Discovered by: kris
prevent the mount point from going away while we're waiting on the lock.
The ref does not need to persist once we have the lock because the
lock prevents the mount point from being unmounted.
MFC After: 1 week
vfs_mount_destroy waiting for this ref to hit 0. We don't print an
error if we are rebooting as the root mount always retains some refernces
by init proc.
- Acquire a mnt ref for every vnode allocated to a mount point. Drop this
ref only once vdestroy() has been called and the mount has been freed.
- No longer NULL the v_mount pointer in delmntque() so that we may release
the ref after vgone() has been called. This allows us to guarantee
that the mount point structure will be valid until the last vnode has
lost its last ref.
- Fix a few places that rely on checking v_mount to detect recycling.
Sponsored by: Isilon Systems, Inc.
MFC After: 1 week
on a lock held the last usecount ref on a vnode and the lock failed we
would not call INACTIVE. Solve this by only holding a holdcnt to prevent
the vnode from disappearing while we wait on vn_lock. Other callers
may now VOP_INACTIVE while we are waiting on the lock, however this race
is acceptable, while losing INACTIVE is not.
Discussed with: kan, pjd
Tested by: kkenn
Sponsored by: Isilon Systems, Inc.
MFC After: 1 week
prototypes, as the majority of new functions added have been in this
style. Changing prototype style now results in gcc noticing that the
implementation of vn_pollrecord() has a 'short' argument instead of
'int' as prototyped in vnode.h, so correct that definition. In practice
this didn't matter as only poll flags in the lower 16 bits are used.
MFC after: 1 week
The race is very real, but conditions needed for triggering it are rather
hard to meet now.
When gjournal will be committed (where it is quite easy to trigger) we need
to fix it.
For now, verify if it is really hard to trigger.
Discussed with: kan
The PR and patch have the details. The ultimate fix requires architectural
changes and clarifications to the VFS API, but this will prevent the system
from panicking when someone does "ls /dev" while running in a shell under the
linuxulator.
This issue affects HEAD and RELENG_6 only.
PR: 88249
Submitted by: "Devon H. O'Dell" <dodell@ixsystems.com>
MFC after: 3 days
- Prefer '_' to ' ', as it results in more easily parsed results in
memory monitoring tools such as vmstat.
- Remove punctuation that is incompatible with using memory type names
as file names, such as '/' characters.
- Disambiguate some collisions by adding subsystem prefixes to some
memory types.
- Generally prefer lower case to upper case.
- If the same type is defined in multiple architecture directories,
attempt to use the same name in additional cases.
Not all instances were caught in this change, so more work is required to
finish this conversion. Similar changes are required for UMA zone names.
so we are ready for mpsafevfs=1 by default on sparc64 too. I have been
running this on all my sparc64 machines for over 6 months, and have not
encountered MD problems.
MFC after: 1 week
Add a new private thread flag to indicate that the thread should
not sleep if runningbufspace is too large.
Set this flag on the bufdaemon and syncer threads so that they skip
the waitrunningbufspace() call in bufwrite() rather than than
checking the proc pointer vs. the known proc pointers for these two
threads. A way of preventing these threads from being starved for
I/O but still placing limits on their outstanding I/O would be
desirable.
Set this flag in ffs_copyonwrite() to prevent bufwrite() calls from
blocking on the runningbufspace check while holding snaplk. This
prevents snaplk from being held for an arbitrarily long period of
time if runningbufspace is high and greatly reduces the contention
for snaplk. The disadvantage is that ffs_copyonwrite() can start
a large amount of I/O if there are a large number of snapshots,
which could cause a deadlock in other parts of the code.
Call runningbufwakeup() in ffs_copyonwrite() to decrement runningbufspace
before attempting to grab snaplk so that I/O requests waiting on
snaplk are not counted in runningbufspace as being in-progress.
Increment runningbufspace again before actually launching the
original I/O request.
Prior to the above two changes, the system could deadlock if enough
I/O requests were blocked by snaplk to prevent runningbufspace from
falling below lorunningspace and one of the bawrite() calls in
ffs_copyonwrite() blocked in waitrunningbufspace() while holding
snaplk.
See <http://www.holm.cc/stress/log/cons143.html>
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)
