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>
The RHEL5 2.6.18-194.7.1.el5 kernel added atomic64_cmpxchg to
asm-x86_64/atomic.h. That macro is defined in terms of cmpxchg which
is provided by asm/system.h. However, asm/system.h is not #included by
atomic.h in this kernel nor by the autoconf test for atomic64_cmpxchg, so
the test failed with "implicit declaration of function 'cmpxchg'". This
leads the build system to erroneously conclude that the kernel does not
define atomic64_cmpxchg and enable the built-in definition. This in
turn produces a '"atomic64_cmpxchg" redefined' build warning which is fatal
when building with --enable-debug. This commit fixes this by including
asm/system.h in the autoconf test.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
When TQ_SLEEP is used, taskq_dispatch() should always succeed even if the
number of pending tasks is above tq->tq_maxalloc. This semantic is similar
to KM_SLEEP in kmem allocations, which also always succeed.
However, we cannot block forever otherwise there is a risk of deadlock.
Therefore, we still allow the number of pending tasks to go above
tq->tq_maxalloc with TQ_SLEEP, but we may sleep up to 1 second per task
dispatch, thereby throttling the task dispatch rate.
One of the existing splat tests was also augmented to test for this scenario.
The test would fail with the previous implementation but now it succeeds.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Using kmem_free() results in deducting X bytes from the memory
accounting when --enable-debug is set. Unfortunately, currently
the counterpart kmem_asprintf() and friends do not properly
account for memory allocated, so we must do the same on free.
If we don't then we end up with a negative number of lost bytes
reported when the module is unloaded.
A better long term fix would be to add the accounting in to the
allocation side but that's a project for another day.
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"
In cmd/splat.c there was a comparison between an __u32 and an int. To
resolve the issue simply use a __u32 and strtoul() when converting the
provided user string.
In module/spl/spl-vnode.c we should explicitly cast nd->last.name to
a const char * which is what is expected by the prototype.
Commit 55abb0929e removed the never
used format1 argument of spl_debug_msg(). That in turn resulted
in some deadcode which should be removed since it's now useless.
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>
When the kvasprintf() call fails they should reset the arguments
by calling va_start()/va_copy() and va_end() inside the loop,
otherwise they'll try to read more arguments rather than starting
over and reading them from the beginning.
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 threads in the splat atomic:64-bit test share the data structure
atomic_priv_t ap, which lives on the kernel stack of the splat user-space
utility. If splat terminates before the threads, accesses to that memory
location by the other threads become invalid. Splat synchronizes with
the threads with the call:
wait_event_interruptible(ap.ap_waitq, splat_atomic_test1_cond(&ap, i));
Apparently, the SIGINT wakes and terminates splat prematurely, so that
GPFs or other bad things happen when the threads subsequently access ap.
This commit prevents this by using the uninterruptible form:
wait_event(ap.ap_waitq, splat_atomic_test1_cond(&ap, i));
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.
As of autoconf-2.65 the AC_LANG_SOURCE source macro no longer
includes the confdef.h results when expanded. To handle this
simply explicitly include confdef.h in conftest.c. This will
cause two copies to of confdef.h to be added to the test for
earlier autoconf versions but this is not harmful.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
For some reason when awk invoked by the usermode helper the command
always fails. Interestingly gawk does not suffer from this problem
which is why I never observed this failure since the distro I tested
with all had gawk installed instead of awk. Anyway, the simplest
thing to do here is to just make gawk mandatory. I've added a
configure check for gawk specifically and have updated the command
to call gawk not awk.
I didn't notice at the time but user_path_dir() was not introduced
at the same time as set_fs_pwd() change. I had lumped the two
together but in fact user_path_dir() was introduced in 2.6.27 and
set_fs_pwd() taking 2 args was introduced in 2.6.25. This means
builds against 2.6.25-2.6.26 kernels were broken.
To fix this I've added a check for user_path_dir() and no longer
assume that if set_fs_pwd() takes 2 args then user_path_dir() is
also available.
Use 3 threads and 8 tasks. Dispatch the final 3 tasks with TQ_FRONT.
The first three tasks keep the worker threads busy while we stuff the
queues. Use msleep() to force a known execution order, assuming
TQ_FRONT is properly honored. Verify that the expected completion
order occurs.
The splat_taskq_test5_order() function may be useful in more than
one test. This commit generalizes it by renaming the function to
splat_taskq_test_order() and adding a name argument instead of
assuming SPLAT_TASKQ_TEST5_NAME as the test name.
The documentation for splat taskq regression test #5 swaps the two required
completion orders in the diagram. This commit corrects the error.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
On open() and initialize the buffer with the SPL version string. The
user space splat utility expects to find the SPL version string when
it opens and reads from /dev/splatctl.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
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>
Whoops, I momentarilly forgot I had explicitly set these as CC
options so dependent packages which need to include spl_config.h
would not end up having these defined which can result in
accidentally hanging debug enabled at best, or a build failure
at worst.
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.
It seems the upstream community moved the definition of UTS_RELEASE
yet again as of linux-2.6.33. Update the build system to check in
all three possible locations where your kernel version may be defined.
$kernelbuild/include/linux/version.h
$kernelbuild/include/linux/utsrelease.h
$kernelbuild/include/generated/utsrelease.h
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.
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().
This fix was long overdue. Most of the ground work was laid long
ago to include the exact function and line number in the error message
which there was an issue with a memory allocation call. However,
probably due to lack of time at the moment that informatin never
made it in to the error message. This patch fixes that and trys
to standardize the kmem debug messages as well.
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.
