These functions didn't exist for all archs prior to 2.6.24. This
patch addes an autoconf test to detect this and add them when needed.
The autoconf check is needed instead of just an #ifndef because in
the most modern kernels atomic64_{cmp}xchg are implemented as in
inline function and not a #define.
Previously Solaris style atomic primitives were implemented simply by
wrapping the desired operation in a global spinlock. This was easy to
implement at the time when I wasn't 100% sure I could safely layer the
Solaris atomic primatives on the Linux counterparts. It however was
likely not good for performance.
After more investigation however it does appear the Solaris primitives
can be layered on Linux's fairly safely. The Linux atomic_t type really
just wraps a long so we can simply cast the Solaris unsigned value to
either a atomic_t or atomic64_t. The only lingering problem for both
implementations is that Solaris provides no atomic read function. This
means reading a 64-bit value on a 32-bit arch can (and will) result in
word breaking. I was very concerned about this initially, but upon
further reflection it is a limitation of the Solaris API. So really
we are just being bug-for-bug compatible here.
With this change the default implementation is layered on top of Linux
atomic types. However, because we're assuming a lot about the internal
implementation of those types I've made it easy to fall-back to the
generic approach. Simply build with --enable-atomic_spinlocks if
issues are encountered with the new implementation.
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.
- Prior to 2.6.17 there were no *_pgdat helper functions in mm/mmzone.c.
Instead for_each_zone() operated directly on pgdat_list which may or
may not have been exported depending on how your kernel was compiled.
Now new configure checks determine if you have the helpers or not, and
if the needed symbols are exported. If they are not exported then they
are dynamically aquired at runtime by kallsyms_lookup_name().
- Configure check for SLES specific API change to vfs_unlink()
and vfs_rename() which added a 'struct vfsmount *' argument.
This was for something called the linux-security-module, but
it appears that it was never adopted upstream.
- Configure check for mutex_lock_nested(). This function was introduced
as part of the mutex validator in 2.6.18, but if it's unavailable then
it's safe to fallback to a plain mutex_lock().
- 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.
As of 2.6.27 kernels the device_create() API changed to include
a private data argument. This check detects which version of
device_create() function the kernel has and properly defines
spl_device_create() to use the correct prototype.
Remove all instances of functions being reimplemented in the SPL.
When the prototypes are available in the linux headers but the
function address itself is not exported use kallsyms_lookup_name()
to find the address. The function name itself can them become a
define which calls a function pointer. This is preferable to
reimplementing the function in the SPL because it ensures we get
the correct version of the function for the running kernel. This
is actually pretty safe because the prototype is defined in the
headers so we know we are calling the function properly.
This patch also includes a rhel5 kernel patch we exports the needed
symbols so we don't need to use kallsyms_lookup_name(). There are
autoconf checks to detect if the symbol is exported and if so to
use it directly. We should add patches for stock upstream kernels
as needed if for no other reason than so we can easily track which
additional symbols we needed exported. Those patches can also be
used by anyone willing to rebuild their kernel, but this should
not be a requirement. The rhel5 version of the export-symbols
patch has been applied to the chaos kernel.
Additional fixes:
1) Implement vmem_size() function using get_vmalloc_info()
2) SPL_CHECK_SYMBOL_EXPORT macro updated to use $LINUX_OBJ instead
of $LINUX because Module.symvers is a build product. When
$LINUX_OBJ != $LINUX we will not properly detect exported symbols.
3) SPL_LINUX_COMPILE_IFELSE macro updated to add include2 and
$LINUX/include search paths to allow proper compilation when
the kernel target build directory is not the source directory.
Added support for Solaris swapfs_minfree, and swapfs_reserve tunables.
In additional availrmem is now available and return a reasonable value
which is reasonably analogous to the Solaris meaning. On linux we
return the sun of free and inactive pages since these are all easily
reclaimable.
All tunables are available in /proc/sys/kernel/spl/vm/* and they may
need a little adjusting once we observe the real behavior. Some of
the defaults are mapped to similar linux counterparts, others are
straight from the OpenSolaris defaults.
Support added to provide reasonable values for the global Solaris
VM variables: minfree, desfree, lotsfree, needfree. These values
are set to the sum of their per-zone linux counterparts which
should be close enough for Solaris consumers.
When a non-GPL app links against the SPL we cannot use the udev
interfaces, which means non of the device special files are created.
Because of this I had added a poor mans udev which cause the SPL
to invoke an upcall and create the basic devices when a minor
is registered. When a minor is unregistered we use the vnode
interface to unlink the special file.
- 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
* configure.ac : Use AC_CONFIG_AUX_DIR to put autoconf products
in ./auotconf.
* autogen.sh : Use --copy to avoid symlinks, remove error
redirection, run aclocal before libtoolize.
git-svn-id: https://outreach.scidac.gov/svn/spl/trunk@180 7e1ea52c-4ff2-0310-8f11-9dd32ca42a1c
