When HAVE_MUTEX_OWNER is defined and we are directly accessing
mutex->owner treat is as volative with the ACCESS_ONCE() helper.
Without this you may get a stale cached value when accessing it
from different cpus. This can result in incorrect behavior from
mutex_owned() and mutex_owner(). This is not a problem for the
!HAVE_MUTEX_OWNER case because in this case all the accesses
are covered by a spin lock which similarly gaurentees we will
not be accessing stale data.
Secondly, check CONFIG_SMP before allowing access to mutex->owner.
I see that for non-SMP setups the kernel does not track the owner
so we cannot rely on it.
Thirdly, check CONFIG_MUTEX_DEBUG when this is defined and the
HAVE_MUTEX_OWNER is defined surprisingly the mutex->owner will
not be cleared on mutex_exit(). When this is the case the SPL
needs to make sure to do it to ensure MUTEX_HELD() behaves as
expected or you will certainly assert in mutex_destroy().
Finally, improve the mutex regression tests. For mutex_owned() we
now minimally check that it behaves correctly when checked from the
owner thread or the non-owner thread. This subtle behaviour has bit
me before and I'd like to catch it early next time if it reappears.
As for mutex_owned() regression test additonally verify that
mutex->owner is always cleared on mutex_exit().
The call to wake_up() must be moved under the spin lock because
once we drop the lock 'tp' may no longer be valid because the
creating thread has exited. This basic thread implementation
was correct, this was simply a flaw in the test case.
Remove RW_COUNT() from the rwlock implementation. The idea was that it
could be used as a generic wrapper for getting at the internal state
of a rwlock. While a good idea it's proven problematic to keep it
correct for multiple archs and internal implementation changes. In
short it hasn't been worth the trouble.
With that and simplicity in mind things have been updated to use the
rwsem_is_locked() function instead of RW_COUNT for the RW_*_HELD()
functions. As for rw_upgrade() it remains only implemented for
the generic rwsem implemenation. It remains to be determined if its
worth the effort of adding a custom implementation for each arch.
Remove the kmem_set_warning() hack used by the kmem-splat regression
tests with a per-allocation flag called __GFP_NOWARN. This matches
the lower level linux flag of similar by slightly different function.
The idea is you can then explicitly set this flag on requests where
you know your breaking the max 8k rule but you need/want to do it
anyway.
This is currently used by the regression tests where we intentionally
push things to the limit but don't want the log noise. Additionally,
we are forced to use it in spl_kmem_cache_create() because by default
NR_CPUS is very large and theres no easy way to handle that.
Finally, I've added a stack_dump() call to the warning when it is
trigger to make to clear exactly where the allocation is taking place.
Updated AUTHORS, COPYING, DISCLAIMER, and INSTALL files. Added
standardized headers to all source file to clearly indicate the
copyright, license, and to give credit where credit is due.
This test case verifies the correct behavior of taskq_wait_id().
In particular it ensure the the following two cases are handled
properly:
1) Task ids larger than the waited for task id can run and
complete as long as there is an available worker thread.
2) All task ids lower than the waited one must complete before
unblocking even if the waited task id itself has completed.
This regression test could crash in splat_kmem_cache_test_reclaim()
due to a race between the slab relclaim and the normal exiting of
the thread. Specifically, the kct structure could be free'd by
the thread performing the allocations while the reclaim function
was also working on that's threads kct structure. The simplest
fix is to extend the kcp->kcp_lock over the reclaim to prevent
the kct from being freed. A better fix would be to ref count
these structures, but since is just a regression this locking
change is enough. Surprisingly this was only observed commonly
under RHEL5.4 but all platform could have hit this.
I must have been in a hurry when I wrote the vnode regression tests
because the error code handling is not correct. The Solaris vnode
API returns positive errno's, these need to be converted to negative
errno's for Linux before being passed back to user space. Otherwise
the test hardness with report the failure but errno will not be set
with the correct error code.
Additionally tests 3, 4, 6, and 7 may fail in the test file already
exists. To avoid false positives a user mode helper has added to
remove the test files in /tmp/ before running the actual test.
The big fix here is the removal of kmalloc() in kv_alloc(). It used
to be true in previous kernels that kmallocs over PAGE_SIZE would
always be pages aligned. This is no longer true atleast in 2.6.31
there are no longer any alignment expectations. Since kv_alloc()
requires the resulting address to be page align we no only either
directly allocate pages in the KMC_KMEM case, or directly call
__vmalloc() both of which will always return a page aligned address.
Additionally, to avoid wasting memory size is always a power of two.
As for cleanup several helper functions were introduced to calculate
the aligned sizes of various data structures. This helps ensure no
case is accidentally missed where the alignment needs to be taken in
to account. The helpers now use P2ROUNDUP_TYPE instead of P2ROUNDUP
which is safer since the type will be explict and we no longer count
on the compiler to auto promote types hopefully as we expected.
Always wnforce minimum (SPL_KMEM_CACHE_ALIGN) and maximum (PAGE_SIZE)
alignment restrictions at cache creation time.
Use SPL_KMEM_CACHE_ALIGN in splat alignment test.
As of 2.6.25 kobj->k_name was replaced with kobj->name. Some distros
such as RHEL5 (2.6.18) add a patch to prevent this from being a problem
but other older distros such as SLES10 (2.6.16) have not. To avoid
the whole issue I'm updating the code to use kobject_set_name() which
does what I want and has existed all the way back to 2.6.11.
Ricardo has pointed out that under Solaris the cwd is set to '/'
during module load, while under Linux it is set to the callers cwd.
To handle this cleanly I've reworked the module *_init()/_exit()
macros so they call a *_setup()/_cleanup() function when any SPL
dependent module is loaded or unloaded. This gives us a chance to
perform any needed modification of the process, in this case changing
the cwd. It also handily provides a way to avoid creating wrapper
init()/exit() functions because the Solaris and Linux prototypes
differ slightly. All dependent modules should now call the spl
helper macros spl_module_{init,exit}() instead of the native linux
versions.
Unfortunately, it appears that under Linux there has been no consistent
API in the kernel to set the cwd in a module. Because of this I have
had to add more autoconf magic than I'd like. However, what I have
done is correct and has been tested on RHEL5, SLES11, FC11, and CHAOS
kernels.
In addition, I have change the rootdir type from a 'void *' to the
correct 'vnode_t *' type. And I've set rootdir to a non-NULL value.
For a generic explanation of why mutexs needed to be reimplemented
to work with the kernel lock profiling see commits:
e811949a57 and
d28db80fd0
The specific changes made to the mutex implemetation are as follows.
The Linux mutex structure is now directly embedded in the kmutex_t.
This allows a kmutex_t to be directly case to a mutex struct and
passed directly to the Linux primative.
Just like with the rwlocks it is critical that these functions be
implemented as '#defines to ensure the location information is
preserved. The preprocessor can then do a direct replacement of
the Solaris primative with the linux primative.
Just as with the rwlocks we need to track the lock owner. Here
things get a little more interesting because depending on your
kernel version, and how you've built your kernel Linux may already
do this for you. If your running a 2.6.29 or newer kernel on a
SMP system the lock owner will be tracked. This was added to Linux
to support adaptive mutexs, more on that shortly. Alternately, your
kernel might track the lock owner if you've set CONFIG_DEBUG_MUTEXES
in the kernel build. If neither of the above things is true for
your kernel the kmutex_t type will include and track the lock owner
to ensure correct behavior. This is all handled by a new autoconf
check called SPL_AC_MUTEX_OWNER.
Concerning adaptive mutexs these are a very recent development and
they did not make it in to either the latest FC11 of SLES11 kernels.
Ideally, I'd love to see this kernel change appear in one of these
distros because it does help performance. From Linux kernel commit:
0d66bf6d3514b35eb6897629059443132992dbd7
"Testing with Ingo's test-mutex application...
gave a 345% boost for VFS scalability on my testbox"
However, if you don't want to backport this change yourself you
can still simply export the task_curr() symbol. The kmutex_t
implementation will use this symbol when it's available to
provide it's own adaptive mutexs.
Finally, DEBUG_MUTEX support was removed including the proc handlers.
This was done because now that we are cleanly integrated with the
kernel profiling all this information and much much more is available
in debug kernel builds. This code was now redundant.
Update mutexs validated on:
- SLES10 (ppc64)
- SLES11 (x86_64)
- CHAOS4.2 (x86_64)
- RHEL5.3 (x86_64)
- RHEL6 (x86_64)
- FC11 (x86_64)
It turns out that the previous rwlock implementation worked well but
did not integrate properly with the upstream kernel lock profiling/
analysis tools. This is a major problem since it would be awfully
nice to be able to use the automatic lock checker and profiler.
The problem is that the upstream lock tools use the pre-processor
to create a lock class for each uniquely named locked. Since the
rwsem was embedded in a wrapper structure the name was always the
same. The effect was that we only ended up with one lock class for
the entire SPL which caused the lock dependency checker to flag
nearly everything as a possible deadlock.
The solution was to directly map a krwlock to a Linux rwsem using
a typedef there by eliminating the wrapper structure. This was not
done initially because the rwsem implementation is specific to the arch.
To fully implement the Solaris krwlock API using only the provided rwsem
API is not possible. It can only be done by directly accessing some of
the internal data member of the rwsem structure.
For example, the Linux API provides a different function for dropping
a reader vs writer lock. Whereas the Solaris API uses the same function
and the caller does not pass in what type of lock it is. This means to
properly drop the lock we need to determine if the lock is currently a
reader or writer lock. Then we need to call the proper Linux API function.
Unfortunately, there is no provided API for this so we must extracted this
information directly from arch specific lock implementation. This is
all do able, and what I did, but it does complicate things considerably.
The good news is that in addition to the profiling benefits of this
change. We may see performance improvements due to slightly reduced
overhead when creating rwlocks and manipulating them.
The only function I was forced to sacrafice was rw_owner() because this
information is simply not stored anywhere in the rwsem. Luckily this
appears not to be a commonly used function on Solaris, and it is my
understanding it is mainly used for debugging anyway.
In addition to the core rwlock changes, extensive updates were made to
the rwlock regression tests. Each class of test was extended to provide
more API coverage and to be more rigerous in checking for misbehavior.
This is a pretty significant change and with that in mind I have been
careful to validate it on several platforms before committing. The full
SPLAT regression test suite was run numberous times on all of the following
platforms. This includes various kernels ranging from 2.6.16 to 2.6.29.
- SLES10 (ppc64)
- SLES11 (x86_64)
- CHAOS4.2 (x86_64)
- RHEL5.3 (x86_64)
- RHEL6 (x86_64)
- FC11 (x86_64)
Basically everything we need to monitor the global memory state of
the system is now cleanly available via global_page_state(). The
problem is that this interface is still fairly recent, and there
has been one change in the page state enum which we need to handle.
These changes basically boil down to the following:
- If global_page_state() is available we should use it. Several
autoconf checks have been added to detect the correct enum names.
- If global_page_state() is not available check to see if
get_zone_counts() symbol is available and use that.
- If the get_zone_counts() symbol is not exported we have no choice
be to dynamically aquire it at load time. This is an absolute
last resort for old kernel which we don't want to patch to
cleanly export the symbol.
The previous credential implementation simply provided the needed types and
a couple of dummy functions needed. This update correctly ties the basic
Solaris credential API in to one of two Linux kernel APIs.
Prior to 2.6.29 the linux kernel embeded all credentials in the task
structure. For these kernels, we pass around the entire task struct as if
it were the credential, then we use the helper functions to extract the
credential related bits.
As of 2.6.29 a new credential type was added which we can and do fairly
cleanly layer on top of. Once again the helper functions nicely hide
the implementation details from all callers.
Three tests were added to the splat test framework to verify basic
correctness. They should be extended as needed when need credential
functions are added.
The slab_overcommit test case could hang on a system with fragmented
memory because it was creating a kmem based slab with 256K objects.
To avoid this I've removed the KMC_KMEM flag which allows the slab
to decide if it should be kmem or vmem backed based on the object
side. The slab_lock test shares this code and will also be effected.
But the point of these two tests is to stress cache locking and
memory overcommit, the type of slab is not critical. In fact, allowing
the slab to do the default smart thing is preferable.
- Proper ioctl() 32/64-bit binary compatibility. We need to ensure the
ioctl data itself is always packed the same for 32/64-bit binaries.
Additionally, the correct thing to do is encode this size in bytes
as part of the command using _IOC_SIZE().
- Minor formatting changes to respect the 80 character limit.
- Move all SPLAT_SUBSYSTEM_* defines in to splat-ctl.h.
- Increase SPLAT_SUBSYSTEM_UNKNOWN because we were getting close
to accidentally using it for a real registered subsystem.
- Add compat_ioctl() handler, by default 64-bit SLES systems build 32-bit
ELF binaries. For the 32-bit binaries to pass ioctl information to a
64-bit kernel a compatibility handler needs to be registered. In our
case no additional conversions are needed to convert 32-bit ioctl()
commands to 64-bit commands so we can just call the default handler.
- Enable builds for powerpc ISA type.
- Add DIV_ROUND_UP and roundup macros if unavailable.
- Cast 64-bit values for %lld format string to (long long) to
quiet compile warning.
- Configure check, the div64_64() function was renamed to
div64_u64() as of 2.6.26.
- Configure check, the global_page_state() fuction was introduced
in 2.6.18 kernels. The earlier 2.6.16 based SLES10 must not try
and use it, thankfully get_zone_counts() is still available.
- To simplify debugging poison all symbols aquired dynamically
using spl_kallsyms_lookup_name() with SYMBOL_POISON.
- Add console messages when the user mode helpers fail.
- spl_kmem_init_globals() use bit shifts instead of division.
- When the monotonic clock is unavailable __gethrtime() must perform
the HZ division as an 'unsigned long long' because the SPL only
implements __udivdi3(), and not __divdi3() for 'long long' division
on 32-bit arches.
We need dependent packages to be able to include spl_config.h so they
can leverage the configure checks the SPL has done. This is important
because several of the spl headers need the results of these checks to
work properly. Unfortunately, the autoheader build product is always
private to a particular build and defined certain common things.
(PACKAGE, VERSION, etc). This prevents other packages which also use
autoheader from being include because the definitions conflict. To
avoid this problem the SPL build system leverage AH_BOTTOM to include
a spl_unconfig.h at the botton of the autoheader build product. This
custom include undefs all known shared symbols to prevent the confict.
This does however mean that those definition are also not availble
to the SPL package either. The SPL package therefore uses the
equivilant SPL_META_* definitions.
In the interests of portability I have added a FC10/i686 box to
my list of development platforms. The hope is this will allow me
to keep current with upstream kernel API changes, and at the same
time ensure I don't accidentally break x86 support. This patch
resolves all remaining issues observed under that environment.
1) SPL_AC_ZONE_STAT_ITEM_FIA autoconf check added. As of 2.6.21
the kernel added a clean API for modules to get the global count
for free, inactive, and active pages. The SPL attempts to detect
if this API is available and directly map spl_global_page_state()
to global_page_state(). If the full API is not available then
spl_global_page_state() is implemented as a thin layer to get
these values via get_zone_counts() if that symbol is available.
2) New kmem:vmem_size regression test added to validate correct
vmem_size() functionality. The test case acquires the current
global vmem state, allocates from the vmem region, then verifies
the allocation is correctly reflected in the vmem_size() stats.
3) Change splat_kmem_cache_thread_test() to always use KMC_KMEM
based memory. On x86 systems with limited virtual address space
failures resulted due to exhaustig the address space. The tests
really need to problem exhausting all memory on the system thus
we need to use the physical address space.
4) Change kmem:slab_lock to cap it's memory usage at availrmem
instead of using the native linux nr_free_pages(). This provides
additional test coverage of the SPL Linux VM integration.
5) Change kmem:slab_overcommit to perform allocation of 256K
instead of 1M. On x86 based systems it is not possible to create
a kmem backed slab with entires of that size. To compensate for
this the number of allocations performed in increased by 4x.
6) Additional autoconf documentation for proposed upstream API
changes to make additional symbols available to modules.
7) Console error messages added when spl_kallsyms_lookup_name()
fails to locate an expected symbol. This causes the module to fail
to load and we need to know exactly which symbol was not available.
I'm very surprised this has not surfaced until now. But the taskq_wait()
implementation work only wait successfully the first time it was called.
Subsequent usage of taskq_wait() on the taskq would not wait.
The issue was caused by tq->tq_lowest_id being set to MAX_INT after the
first wait completed. This caused subsequent waits which check that the
waiting id is less than the lowest taskq id to always succeed. The fix
is to ensure that tq->tq_lowest_id is never set larger than tq->tq_next.id.
Additional fixes which were added to this patch include:
1) Fix a race by placing the taskq_wait_check() in the tq->tq_lock spinlock.
2) taskq_wait() should wait for the largest outstanding id.
3) Multiple spelling corrections.
4) Added taskq wait regression test to validate correct behavior.
Mainly for portability reasons I have rebased the mutex tests on Solaris
taskqs instead of linux work queues. The linux workqueue API changed post
2.6.18 kernels and using task queues avoids having to conditionally detect
which workqueue API to use.
Additionally, this is basically free additional testing for the task queues.
Much to my surprise after updating these test cases they did expose a long
standing bug in the taskq_wait() implementation. This patch does not
address that issue but the followup patch does.
An update to the build system to properly support all commonly
used Makefile targets these include:
make all # Build everything
make install # Install everything
make clean # Clean up build products
make distclean # Clean up everything
make dist # Create package tarball
make srpm # Create package source RPM
make rpm # Create package binary RPMs
make tags # Create ctags and etags for everything
Extra care was taken to ensure that the source RPMs are fully
rebuildable against Fedora/RHEL/Chaos kernels. To build binary
RPMs from the source RPM for your system simply run:
rpmbuild --rebuild spl-x.y.z-1.src.rpm
This will produce two binary RPMs with correct 'requires'
dependencies for your kernel. One will contain all spl modules
and support utilities, the other is a devel package for compiling
additional kernel modules which are dependant on the spl.
spl-x.y.z-1_<kernel version>.x86_64.rpm
spl-devel-x.y.2-1_<kernel version>.x86_64.rpm
Accidentally leaked list item li in error path. The fix is to
adjust this error path to ensure the allocated list item which
has not yet been added to the list gets freed. To do this we
simply add a new goto label slightly earlier to use the existing
cleanup logic and minimize the number of unique return points.
This was a false positive the callpath being walked is impossible
because the splat_kmem_cache_test_kcp_alloc() function will ensure
kcp->kcp_kcd[0] is initialized to NULL. However, there is no harm
is making this explicit for the test case so I'm adding a line to
clearly set it to correct the analysis.
- Added SPL_AC_3ARGS_ON_EACH_CPU configure check to determine
if the older 4 argument version of on_each_cpu() should be
used or the new 3 argument version. The retry argument was
dropped in the new API which was never used anyway.
- Updated work queue compatibility wrappers. The old way this
worked was to pass a data point when initialized the workqueue.
The new API assumed the work item is embedding in a structure
and we us container_of() to find that data pointer.
- Updated skc->skc_flags to be an unsigned long which is now
type checked in the bit operations. This silences the warnings.
- Updated autogen products and splat tests accordingly
- Added slab work queue task which gradually ages and free's slabs
from the cache which have not been used recently.
- Optimized slab packing algorithm to ensure each slab contains the
maximum number of objects without create to large a slab.
- Fix deadlock, we can never call kv_free() under the skc_lock. We
now unlink the objects and slabs from the cache itself and attach
them to a private work list. The contents of the list are then
subsequently freed outside the spin lock.
- Move magazine create/destroy operation on to local cpu.
- Further performace optimizations by minimize the usage of the large
per-cache skc_lock. This includes the addition of KMC_BIT_REAPING
bit mask which is used to prevent concurrent reaping, and to defer
new slab creation when reaping is occuring.
- Add KMC_BIT_DESTROYING bit mask which is set when the cache is being
destroyed, this is used to catch any task accessing the cache while
it is being destroyed.
- Add comments to all the functions and additional comments to try
and make everything as clear as possible.
- Major cleanup and additions to the SPLAT kmem tests to more
rigerously stress the cache implementation and look for any problems.
This includes correctness and performance tests.
- Updated portable work queue interfaces
