The cv_timedwait() function by definition must wait unconditionally
for cv_signal()/cv_broadcast() before waking. This causes processes
to go in the D state which increases the load average. The load
average is the summation of processes in D state and run queue.
To avoid this it can be desirable to sleep interruptibly. These
processes do not count against the load average but may be woken by
a signal. It is up to the caller to determine why the process
was woken it may be for one of three reasons.
1) cv_signal()/cv_broadcast()
2) the timeout expired
3) a signal was received
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Create spl_inode_lock/spl_inode_unlock compability macros to simply
access to the inode mutex/sem. This avoids the need to have to ugly
up the code with the required #define's at every call site. At the
moment the SPL only uses this in one place but higher layers can
benefit from the macro.
Thread specific data has implemented using a hash table, this avoids
the need to add a member to the task structure and allows maximum
portability between kernels. This implementation has been optimized
to keep the tsd_set() and tsd_get() times as small as possible.
The majority of the entries in the hash table are for specific tsd
entries. These entries are hashed by the product of their key and
pid because by design the key and pid are guaranteed to be unique.
Their product also has the desirable properly that it will be uniformly
distributed over the hash bins providing neither the pid nor key is zero.
Under linux the zero pid is always the init process and thus won't be
used, and this implementation is careful to never to assign a zero key.
By default the hash table is sized to 512 bins which is expected to
be sufficient for light to moderate usage of thread specific data.
The hash table contains two additional type of entries. They first
type is entry is called a 'key' entry and it is added to the hash during
tsd_create(). It is used to store the address of the destructor function
and it is used as an anchor point. All tsd entries which use the same
key will be linked to this entry. This is used during tsd_destory() to
quickly call the destructor function for all tsd associated with the key.
The 'key' entry may be looked up with tsd_hash_search() by passing the
key you wish to lookup and DTOR_PID constant as the pid.
The second type of entry is called a 'pid' entry and it is added to the
hash the first time a process set a key. The 'pid' entry is also used
as an anchor and all tsd for the process will be linked to it. This
list is using during tsd_exit() to ensure all registered destructors
are run for the process. The 'pid' entry may be looked up with
tsd_hash_search() by passing the PID_KEY constant as the key, and
the process pid. Note that tsd_exit() is called by thread_exit()
so if your using the Solaris thread API you should not need to call
tsd_exit() directly.
When HAVE_MUTEX_OWNER and CONFIG_SMP are defined, kmutex_t is just
a typedef for struct mutex.
This is generally OK but has the downside that it can make mistakes
such as mutex_lock(&kmutex_var) to pass by unnoticed until someone
compiles the code without HAVE_MUTEX_OWNER or CONFIG_SMP (in which
case kmutex_t is a real struct). Note that the correct API to call
should have been mutex_enter() rather than mutex_lock().
We prevent these kind of mistakes by making kmutex_t a real structure
with only one field. This makes kmutex_t typesafe and it shouldn't
have any impact on the generated assembly code.
Signed-off-by: Ricardo M. Correia <ricardo.correia@oracle.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
For debugging purposes the condition varaibles keep track of the
mutex used during a wait. The idea is to validate that all callers
always use the same mutex. Unfortunately, we have seen cases where
the caller reuses the condition variable with a different mutex but
in a way which is known to be safe. My reading of the man pages
suggests you should not do this and always cv_destroy()/cv_init()
a new mutex. However, there is overhead in doing this and it does
appear to be allowed under Solaris.
To accomidate this behavior cv_wait_common() and __cv_timedwait()
have been modified to clear the associated mutex when the last
waiter is dropped. This ensures that while the condition variable
is in use the incorrect mutex case is detected. It also allows the
condition variable to be safely recycled without requiring the
overhead of a cv_destroy()/cv_init() as long as it isn't currently
in use.
Finally, spin lock cv->cv_lock was removed because it is not required.
When the condition variable is used properly the caller will always
be holding the mutex so the spin lock is redundant. The lock was
originally added because I expected to need to protect more than
just the cv->cv_mutex. It turns out that was not the case.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
The ZFS module returns ENOTSUP for several error conditions where an operation
is not (yet) supported. The SPL defined ENOTSUP in terms of ENOTSUPP, but that
is an internal Linux kernel error code that should not be seen by user
programs. As a result the zfs utilities print a confusing error message if an
unsupported operation is attempted:
internal error: Unknown error 524
Aborted
This change defines ENOTSUP in terms of EOPNOTSUPP which is consistent with
user space.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
As of linux-2.6.36 RLIM64_INFINITY is defined in linux/resource.h.
This is handled by conditionally defining RLIM64_INFINITY in the
SPL only when the kernel does not provide it.
It's important to clear mp->owner after calling mutex_unlock()
because when CONFIG_DEBUG_MUTEXES is defined the mutex owner
is verified in mutex_unlock(). If we set it to NULL this check
fails and the lockdep support is immediately disabled.
A local variable must be used for the return value to avoid a
potential race once the spin lock is dropped.
Signed-off-by: Ricardo M. Correia <ricardo.correia@oracle.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
One of the neat tricks an autoconf style project is capable of
is allow configurion/building in a directory other than the
source directory. The major advantage to this is that you can
build the project various different ways while making changes
in a single source tree.
For example, this project is designed to work on various different
Linux distributions each of which work slightly differently. This
means that changes need to verified on each of those supported
distributions perferably before the change is committed to the
public git repo.
Using nfs and custom build directories makes this much easier.
I now have a single source tree in nfs mounted on several different
systems each running a supported distribution. When I make a
change to the source base I suspect may break things I can
concurrently build from the same source on all the systems each
in their own subdirectory.
wget -c http://github.com/downloads/behlendorf/spl/spl-x.y.z.tar.gz
tar -xzf spl-x.y.z.tar.gz
cd spl-x-y-z
------------------------- run concurrently ----------------------
<ubuntu system> <fedora system> <debian system> <rhel6 system>
mkdir ubuntu mkdir fedora mkdir debian mkdir rhel6
cd ubuntu cd fedora cd debian cd rhel6
../configure ../configure ../configure ../configure
make make make make
make check make check make check make check
This is something the project has almost supported for a long time
but finishing this support should save me lots of time.
This check was previously done with a hack in config.guess.
However, since a new config.guess is copied in to place when
forcing a full autoreconf this change was easily lost and
never a good idea. This commit also updates all of the
autoconf style support scripts in config.
The list_link_replace() function with swap a new item it to the place
of an old item in a list. It is the callers responsibility to ensure
all lists involved are locked properly.
At some point we are going to need to implement the kmem cache
move callbacks to allow for kmem cache defragmentation. This
commit simply lays a small part of the API ground work, it does
not actually implement any of this feature. This is safe for
now because the move callbacks are just an optimization. Even
if they are registered we don't ever really have to call them.
These functions were not previous needed so they were not added.
Now they are so add the full set.
atomic_inc_32_nv()
atomic_dec_32_nv()
atomic_inc_64_nv()
atomic_dec_64_nv()
Unless __GFP_IO and __GFP_FS are removed from the file mapping gfp
mask we may enter memory reclaim during IO. In this case shrink_slab()
entered another file system which is notoriously hungry for stack.
This additional stack usage may cause a stack overflow. This patch
removes __GFP_IO and __GFP_FS from the mapping gfp mask of each file
during vn_open() to avoid any reclaim in the vn_rdwr() IO path. The
original mask is then restored at vn_close() time. Hats off to the
loop driver which does something similiar for the same reason.
[...]
shrink_slab+0xdc/0x153
try_to_free_pages+0x1da/0x2d7
__alloc_pages+0x1d7/0x2da
do_generic_mapping_read+0x2c9/0x36f
file_read_actor+0x0/0x145
__generic_file_aio_read+0x14f/0x19b
generic_file_aio_read+0x34/0x39
do_sync_read+0xc7/0x104
vfs_read+0xcb/0x171
:spl:vn_rdwr+0x2b8/0x402
:zfs:vdev_file_io_start+0xad/0xe1
[...]
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
A race condition in rwsem_is_locked() was fixed in Linux 2.6.33 and the fix was
backported to RHEL5 as of kernel 2.6.18-190.el5. Details can be found here:
https://bugzilla.redhat.com/show_bug.cgi?id=526092
The race condition was fixed in the kernel by acquiring the semaphore's
wait_lock inside rwsem_is_locked(). The SPL worked around the race condition
by acquiring the wait_lock before calling that function, but with the fix in
place it must not do that.
This commit implements an autoconf test to detect whether the fixed version of
rwsem_is_locked() is present. The previous version of rwsem_is_locked() was an
inline static function while the new version is exported as a symbol which we
can check for in module.symvers. Depending on the result we correctly
implement the needed compatibility macros for proper spinlock handling.
Finally, we do the right thing with spin locks in RW_*_HELD() by using the
new compatibility macros. We only only acquire the semaphore's wait_lock if
it is calling a rwsem_is_locked() that does not itself try to acquire the lock.
Some new overhead and a small harmless race is introduced by this change.
This is because RW_READ_HELD() and RW_WRITE_HELD() now acquire and release
the wait_lock twice: once for the call to rwsem_is_locked() and once for
the call to rw_owner(). This can't be avoided if calling a rwsem_is_locked()
that takes the wait_lock, as it will in more recent kernels.
The other case which only occurs in legacy kernels could be optimized by
taking the lock only once, as was done prior to this commit. However, I
decided that the performance gain probably wasn't significant enough to
justify the messy special cases required.
The function spl_rw_get_owner() was only used to enable the afore-mentioned
optimization. Since it is no longer used, I removed it.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Extend the Makefiles with an uninstall target to cleanly
remove a package which was installed with 'make install'.
Additionally, ensure a 'depmod -a' is run as part of the
install to update the module dependency information.
The long term fix for Debian and Slackware style packaging is
to add native support for building these packages. Unfortunately,
that is a large chunk of work I don't have time for right now.
That said it would be nice to have at least basic packages for
these distributions.
As a quick short/medium term solution I've settled on using alien
to convert the RPM packages to DEB or TGZ style packages. The
build system has been updated with the following build targets
which will first build RPM packages and then convert them as
needed to the target package type:
make rpm: Create .rpm packages
make deb: Create .deb packages
make tgz: Create .tgz packages
make pkg: Create the right package type for your distribution
The solution comes with lot of caveats and your mileage may vary.
But basically the big limitations are that the resulting packages:
1) Will not have the correct dependency information.
2) Will not not include the kernel version in the release.
3) Will not handle all differences between distributions.
But the resulting packages should be easy to install and remove
from your system and take care of running 'depmod -a' and such.
As I said at the top this is not the right long term solution.
If any of the upstream distribution maintainers want to jump in
and help do this right for their distribution I'd love the help.
The Solaris semantics for kmem_alloc() and vmem_alloc() are that they
must never fail when called with KM_SLEEP. They may only fail if
called with KM_NOSLEEP otherwise they must block until memory is
available. This is quite different from how the Linux memory
allocators work, under Linux a memory allocation failure is always
possible and must be dealt with.
At one point in the past the kmem code did properly implement this
behavior, however as the code evolved this behavior was overlooked
in places. This patch goes through all three implementations of
the kmem/vmem allocation functions and ensures that they will all
block in the KM_SLEEP case when memory is not available. They
may still fail in the KM_NOSLEEP case in which case the caller
is responsible for handling the failure.
Special care is taken in vmalloc_nofail() to avoid thrashing the
system on the virtual address space spin lock. The down side of
course is if you do see a failure here, which is unlikely for
64-bit systems, your allocation will delay for an entire second.
Still this is preferable to locking up your system and it is the
best we can do given the constraints.
Additionally, the code was cleaned up to be much more readable
and comments were added to describe the various kmem-debug-*
configure options. The default configure options remain:
"--enable-debug-kmem --disable-debug-kmem-tracking"
It was being defined as the constant 64 and at first I changed it to be
NR_CPUS instead.
However, NR_CPUS can be a large value on recent kernels (4096), and this
may cause too large kmem allocations to happen.
Therefore, now we use num_possible_cpus(), which should return a (typically)
small value which represents the maximum number of CPUs than can be brought
online in the running hardware (this value is determined at boot time by
arch-specific kernel code).
Signed-off-by: Ricardo M. Correia <ricardo.correia@oracle.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Under Solaris bcopy() allows overlapping memory areas so we
must use memmove() instead of memcpy().
Signed-off-by: Ricardo M. Correia <ricardo.correia@oracle.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
When CONFIG_DEBUG_MUTEXES is turned on in RHEL5's kernel config, the mutexes
store the owner for debugging purposes, therefore the SPL will enable
HAVE_MUTEX_OWNER. However, the SPL code uses ACCESS_ONCE() to access the
owner, and this macro is not defined in the RHEL5 kernel, therefore we define it
ourselves in include/linux/compiler_compat.h.
Signed-off-by: Ricardo M. Correia <ricardo.correia@oracle.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
To avoid conflicts with symbols defined by dependent packages
all debugging symbols have been prefixed with a 'S' for SPL.
Any dependent package needing to integrate with the SPL debug
should include the spl-debug.h header and use the 'S' prefixed
macros. They must also build with DEBUG defined.
To avoid symbol conflicts with dependent packages the debug
header must be split in to several parts. The <sys/debug.h>
header now only contains the Solaris macro's such as ASSERT
and VERIFY. The spl-debug.h header contain the spl specific
debugging infrastructure and should be included by any package
which needs to use the spl logging. Finally the spl-trace.h
header contains internal data structures only used for the log
facility and should not be included by anythign by spl-debug.c.
This way dependent packages can include the standard Solaris
headers without picking up any SPL debug macros. However, if
the dependant package want to integrate with the SPL debugging
subsystem they can then explicitly include spl-debug.h.
Along with this change I have dropped the CHECK_STACK macros
because the upstream Linux kernel now has much better stack
depth checking built in and we don't need this complexity.
Additionally SBUG has been replaced with PANIC and provided as
part of the Solaris macro set. While the Solaris version is
really panic() that conflicts with the Linux kernel so we'll
just have to make due to PANIC. It should rarely be called
directly, the prefered usage would be an ASSERT or VERIFY.
There's lots of change here but this cleanup was overdue.
The prototype for filp_fsync() drop the unused argument 'stuct dentry *'.
I've fixed this by adding the needed autoconf check and moving all of
those filp related functions to file_compat.h. This will simplify
handling any further API changes in the future.
Deadlocks in the zvol were observed when one of the ZFS threads
performing IO trys to allocate memory while the system is low
on memory. The low memory condition causes dirty pages to be
synced to the zvol but this can't progress because the original
thread is blocked waiting on a memory allocation. Thus we end
up deadlocking.
A proper solution proposed by Wizeman is to change KM_SLEEP from
GFP_KERNEL top GFP_NOFS. This will prevent the memory allocation
which is trying to allocate memory from forcing a sync to the
zvol in shrink_page_list()->pageout().
The down side to all of this is that we are using a pretty big
hammer by changing KM_SLEEP. This change means ALL of the zfs
memory allocations will be until to trigger dirty data to be
synced. The caller still should be able to reclaim memory from
the various slab caches. We will be totally dependent of other
kernel processes which happen to be running and a small number
of asynchronous reclaim threads to trigger the reclaim of dirty
data pages. This should be OK but I think we may see some
slightly longer allocation times when under memory pressure.
We shall see.
Up until now no SPL consumer attempted to perform signed 64-bit
division so there was no need to support this. That has now
changed so I adding 64-bit division support for 32-bit platforms.
The signed implementation is based on the unsigned version.
Since the have been several bug reports in the past concerning
correct 64-bit division on 32-bit platforms I added some long
over due regression tests. Much to my surprise the unsigned
64-bit division regression tests failed.
This was surprising because __udivdi3() was implemented by simply
calling div64_u64() which is provided by the kernel. This meant
that the linux kernels 64-bit division algorithm on 32-bit platforms
was flawed. After some investigation this turned out to be exactly
the case.
Because of this I was forced to abandon the kernel helper and
instead to fully implement 64-bit division in the spl. There are
several published implementation out there on how to do this
properly and I settled on one proposed in the book Hacker's Delight.
Their proposed algoritm is freely available without restriction
and I have just modified it to be linux kernel friendly.
The update implementation now passed all the unsigned and signed
regression tests. This should be functional, but not fast, which is
good enough for out purposes. If you want fast too I'd strongly
suggest you upgrade to a 64-bit platform. I have also reported the
kernel bug and we'll see if we can't get it fixed up stream.
Adds a task queue to receive tasks dispatched with TQ_FRONT. Worker
threads pull tasks from this high priority queue before the default
pending queue.
Executing tasks out of FIFO order potentially breaks taskq_lowest_id()
if we do not preserve the ordering of the work list by taskqid.
Therefore, instead of always appending to the work list, we search for
the appropriate place to insert a task. The common case is to append
to the list, so we make this operation efficient by searching the work
list in reverse order.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
While in theory I like the idea of compiler warnings always being
fatal. In practice this causes problems when small harmless errors
cause build failures for end users. To handle this I've updated
the build system such that -Werror is only used when --enable-debug
is passed to configure. This is how I always build when developing
so I'll catch all build warnings and end users will not get stuck
by minor issues.
Prior to linux-2.6.33 only O_DSYNC semantics were implemented and
they used the O_SYNC flag. As of linux-2.6.33 this behavior was
properly split in to O_SYNC and O_DSYNC respectively.
As of linux-2.6.33 the ctl_name member of the ctl_table struct
has been entirely removed. The upstream code has been updated
to depend entirely on the the procname member. To handle this
all references to ctl_name are wrapped in a CTL_NAME macro which
simply expands to nothing for newer kernels. Older kernels are
supported by having it expand to .ctl_name = X just as before.
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().
For the moment the SPL accepts the TASKQ_DC_BATCH and TQ_FRONT
flags however they get silently ignored. This is harmless for
the moment but it does need to be implemented at some point.
We might as well have both asprintf() variants. This allows us
to safely pass a va_list through several levels of the stack
using va_copy() instead of va_start().
It turns out Solaris incidentally includes kstat.h from kmem.h. As
a side effect of this certain higher level .c files which should
explicitly include kstat.h don't because they happen to get it
via kmem.h. To make like easier for everyone I do the same.
This patch adds three missing Solaris functions: kmem_asprintf(), strfree(),
and strdup(). They are all implemented as a thin layer which just calls
their Linux counterparts. As part of this an autoconf check for kvasprintf
was added because it does not appear in older kernels. If the kernel does
not provide it then spl-generic implements it.
Additionally the dead DEBUG_KMEM_UNIMPLEMENTED code was removed to clean
things up and make the kmem.h a little more readable.
Add the basic xuio structure and typedefs for Solaris style zero copy.
There's a decent chance this will not be the way I handle this on Linux
but providing the basic types simplifies things for now.
Under linux the proc.h header is for the /proc filesystem, and under
Solaris the proc/h header if for processes. This patch correctly
moves the Linux proc functionality in a linux/proc_compat.h header
and leaves the sys/proc.h for use by Solaris. Minor updates were
required to all the call sites where it was included of course.
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.
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 is a minor extension to the condition variable API to allow
for reasonable signal handling on Linux. The cv_wait() function by
definition must wait unconditionally for cv_signal()/cv_broadcast()
before waking it. This makes it impossible to woken by a signal
such as SIGTERM. The cv_wait_interruptible() function was added
to handle this case. It behaves identically to cv_wait() with the
exception that it waits interruptibly allowing a signal to wake it
up. This means you do need to be careful and check issig() after
waking.
For kernels using the CONFIG_RWSEM_GENERIC_SPINLOCK implementation
nothing has changed. But if your kernel is building with arch
specific rwsems rw_tryupgrade() has been disabled until it can
be implemented correctly. In particular, the x86 implementation
now leverages atomic primatives for serialization rather than
spinlocks. So to get this working again it will need to be
implemented as a cmpxchg for x86 and likely something similiar
for other arches we are interested in. For now it's safest
to simply disable it.
The cleanest way to do this is to set AM_LIBTOOLFLAGS = --silent. However,
AM_LIBTOOLFLAGS is not honored by automake-1.9.6-2.1 which is what I have
been using. To cleanly handle this I am updating to automake-1.11-3 which
is why it looks like there is a lot of churn in the Makefiles.
We need dependent packages to be able to include spl_config.h to
build properly. This was partially solved in commit 0cbaeb1 by using
AH_BOTTOM to #undef common #defines (PACKAGE, VERSION, etc) which
autoconf always adds and cannot be easily removed. This solution
works as long as the spl_config.h is included before your projects
config.h. That turns out to be easier said than done. In particular,
this is a problem when your package includes its config.h using the
-include gcc option which ensures the first thing included is your
config.h.
To handle all cases cleanly I have removed the AH_BOTTOM hack and
replaced it with an AC_CONFIG_HEADERS command. This command runs
immediately after spl_config.h is written and with a little awk-foo
it strips the offending #defines from the file. This eliminates
the problem entirely and makes header safe for inclusion.
Also in this change I have removed the few places in the code where
spl_config.h is included. It is now added to the gcc compile line
to ensure the config results are always available.
Finally, I have also disabled the verbose kernel builds. If you
want them back you can always build with 'make V=1'. Since things
are working now they don't need to be on by default.
As of linux-2.6.32 the 'struct file *filp' argument was dropped from
the proc_handle() prototype. It was apparently unused _almost_
everywhere in the kernel and this was simply cleanup.
I've added a new SPL_AC_5ARGS_PROC_HANDLER autoconf check for this and
the proper compat macros to correctly define the prototypes and some
helper functions. It's not pretty but API compat changes rarely are.
As part of the 2.6.28 cleanup which moved all the linux/include/asm/
headers in to linux/arch, the guard headers for many header files
changed. The i386 rwsem implementation keys off this header to
ensure the internal members of the rwsem structure are interpreted
correctly. This change checks for the new guard macro in addition
to the only one, the implementation of the rwsem has not changed
for i386 so this is safe and correct.
This patch is another step towards updating the code to handle the
32-bit kernels which I have not been regularly testing. This changes
do not really impact the common case I'm expected which is the latest
kernel running on an x86_64 arch.
Until the linux-2.6.31 kernel the x86 arch did not have support for
64-bit atomic operations. Additionally, the new atomic_compat.h support
for this case was wrong because it embedded a spinlock in the atomic
variable which must always and only be 64-bits total. To handle these
32-bit issues we now simply fall back to the --enable-atomic-spinlock
implementation if the kernel does not provide the 64-bit atomic funcs.
The second issue this patch addresses is the DEBUG_KMEM assumption that
there will always be atomic64 funcs available. On 32-bit archs this may
not be true, and actually that's just fine. In that case the kernel will
will never be able to allocate more the 32-bits worth anyway. So just
check if atomic64 funcs are available, if they are not it means this
is a 32-bit machine and we can safely use atomic_t's instead.
The use of these functions was added with the recent atomic work
and not tested on 32-bit systems. Add the missing compat functions:
atomic64_inc, atomic64_dec, atomic64_add_return, atomic64_sub_return,
atomic64_inc_return, atomic64_dec_return.
This symbol can be used by GPL modules which use the SPL to handle
cases where a call path takes a two different locks by the same
name. This is needed to avoid a false positive in the lock checker.
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 2.6.31 it's clear __GFP_NOFAIL should no longer be used and it
may disappear from the kernel at any time. To handle this I have simply
added *_nofail wrappers in the kmem implementation which perform the
retry for non-atomic allocations.
From linux-2.6.31 mm/page_alloc.c:1166
/*
* __GFP_NOFAIL is not to be used in new code.
*
* All __GFP_NOFAIL callers should be fixed so that they
* properly detect and handle allocation failures.
*
* We most definitely don't want callers attempting to
* allocate greater than order-1 page units with
* __GFP_NOFAIL.
*/
WARN_ON_ONCE(order > 1);
SPL_AC_2ARGS_SET_FS_PWD macro updated to explicitly include
linux/fs_struct.h which was dropped from linux/sched.h.
min_wmark_pages, low_wmark_pages, high_wmark_pages macros
introduced in newer kernels. For older kernels mm_compat.h
was introduced to define them as needed as direct mappings
to per zone min_pages, low_pages, max_pages.
Cleanup the --enable-debug-* configure options, this has been pending
for quite some time and I am glad I finally got to it. To summerize:
1) All SPL_AC_DEBUG_* macros were updated to be a more autoconf
friendly. This mainly involved shift to the GNU approved usage of
AC_ARG_ENABLE and ensuring AS_IF is used rather than directly using
an if [ test ] construct.
2) --enable-debug-kmem=yes by default. This simply enabled keeping
a running tally of total memory allocated and freed and reporting a
memory leak if there was one at module unload. Additionally, it
ensure /proc/spl/kmem/slab will exist by default which is handy.
The overhead is low for this and it should not impact performance.
3) --enable-debug-kmem-tracking=no by default. This option was added
to provide a configure option to enable to detailed memory allocation
tracking. This support was always there but you had to know where to
turn it on. By default this support is disabled because it is known
to badly hurt performence, however it is invaluable when chasing a
memory leak.
4) --enable-debug-kstat removed. After further reflection I can't see
why you would ever really want to turn this support off. It is now
always on which had the nice side effect of simplifying the proc handling
code in spl-proc.c. We can now always assume the top level directory
will be there.
5) --enable-debug-callb removed. This never really did anything, it was
put in provisionally because it might have been needed. It turns out
it was not so I am just removing it to prevent confusion.
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.
We need to directly call __init_rwsem() or the name gets expanded
to SEM(lock-name). This is safe and correct for the support arches
x86/x86_64/ppc/ppc64.
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)
The behavior of RW_*_HELD was updated because it was not quite right.
It is not sufficient to return non-zero when the lock is help, we must
only do this when the current task in the holder.
This means we need to track the lock owner which is not something
tracked in a Linux semaphore. After some experimentation the
solution I settled on was to embed the Linux semaphore at the start
of a larger krwlock_t structure which includes the owner field.
This maintains good performance and allows us to cleanly intergrate
with the kernel lock analysis tools. My reasons:
1) By placing the Linux semaphore at the start of krwlock_t we can
then simply cast krwlock_t to a rw_semaphore and pass that on to
the linux kernel. This allows us to use '#defines so the preprocessor
can do direct replacement of the Solaris primative with the linux
equivilant. This is important because it then maintains the location
information for each rw_* call point.
2) Additionally, by adding the owner to krwlock_t we can keep this
needed extra information adjacent to the lock itself. This removes
the need for a fancy lookup to get the owner which is optimal for
performance. We can also leverage the existing spin lock in the
semaphore to ensure owner is updated correctly.
3) All helper functions which do not need to strictly be implemented
as a define to preserve location information can be done as a static
inline function.
4) Adding the owner to krwlock_t allows us to remove all memory
allocations done during lock initialization. This is good for all
the obvious reasons, we do give up the ability to specific the lock
name. The Linux profiling tools will stringify the lock name used
in the code via the preprocessor and use that.
Update rwlocks 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)
The run time stack overflow checking is being disabled by default
because it is not safe for use with 2.6.29 and latter kernels. These
kernels do now have their own stack overflow checking so this support
has become redundant anyway. It can be re-enabled for older kernels or
arches without stack overflow checking by redefining CHECK_STACK().
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.
used to scale the number of threads based on the number of online
CPUs. As CPUs are added/removed we should rescale the thread
count appropriately, but currently this is only done at create.
- Allow checking for exported symbols in both Module.symvers
and Module.symvers. My stock SLES kernel ships an objects
directory with Module.symvers, yet produces a Module.symvers
in the local build directory.
- Properly honor --prefix in build system and rpm spec file.
- Add '--define require_kdir' to spec file to support building
rpms against kernel sources installed in non-default locations.
- Add '--define require_kobj' to spec file to support building
rpms against kernel object installed in non-default locations.
- Stop suppressing errors in autogen.sh script.
- Improved logic to detect missing kernel objects when they are
not located with the source. This is the common case for SLES
as well as in-tree chaos kernel builds and is done to simply
support for multiple arches.
- Moved spl-devel build products to /usr/src/spl-<version>, a
spl symlink is created to reference the last installed version.
- 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.
- Initial SLES testing uncovered a long standing bug in the debug
tracing. The tcd_for_each() macro expected a NULL to terminate
the trace_data[i] array but this was only ever true due to luck.
All trace_data[] iterators are now properly capped by TCD_TYPE_MAX.
- SPLAT_MAJOR 229 conflicted with a 'hvc' device on my SLES system.
Since this was always an arbitrary choice I picked something else.
- The HAVE_PGDAT_LIST case should set pgdat_list_addr to the value stored
at the address of the memory location returned by kallsyms_lookup_name().
- 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().
- 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 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().
