Due to limited stack space recursive functions are frowned upon in
the Linux kernel. However, they often are the most elegant solution
to a problem. The following code preserves the recursive function
traverse_visitbp() but moves the local variables AND function
arguments to the heap to minimize the stack frame size. Enough
space is initially allocated on the stack for 20 levels of recursion.
This change does ugly-up-the-code but it reduces the worst case
usage from roughly 4160 bytes to 960 bytes on x86_64 archs.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Implement zio_execute() as a wrapper around the static function
__zio_execute() so that we can force __zio_execute() to be inlined.
This reduces stack overhead which is important because __zio_execute()
is called recursively in several zio code paths. zio_execute() itself
cannot be inlined because it is externally visible.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Eliminated local variables pointing to members of the zio struct.
Just refer to the struct members directly. This saved about 32 bytes per
call, but this function can be called recurisvely up to 19 levels deep,
so we potentially save up to 608 bytes.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
We should not put a 4k maxpathlen buffer on the stack, instead
locate it to the heap. Even in user space we run ztest with 8K
stacks to verify correctness
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Certain function must never be automatically inlined by gcc because
they are stack heavy or called recursively. This patch flags all
such functions I've found as 'noinline' to prevent gcc from making
the optimization.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reduce kernel stack usage by lzjb_compress() by moving uint16 array
off the stack and on to the heap. The exact performance implications
of this I have not measured but we absolutely need to keep stack
usage to a minimum. If/when this becomes and issue we optimize.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Decrease stack usage for various call paths by forcing certain
functions to be inlined. By inlining the functions the overhead
of a new stack frame is removed at the cost of increased code size.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
To reduce stack overhead this topic branch moves the 128 byte
blkptr_t data strucutre in dsl_scan_visitbp() to the heap.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reduce stack usage in dsl_deleg_get, gcc flagged it as consuming a
whopping 1040 bytes or potentially 1/4 of a 4K stack. This patch
moves all the large structures and buffer off the stack and on to
the heap. This includes 2 zap_cursor_t structs each 52 bytes in
size, 2 zap_attribute_t structs each 280 bytes in size, and 1
256 byte char array. The total saves on the stack is 880 bytes
after you account for the 5 new pointers added.
Also the source buffer length has been increased from MAXNAMELEN
to MAXNAMELEN+strlen(MOS_DIR_NAME)+1 as described by the comment in
dsl_dir_name(). A buffer overrun may have been possible with the
slightly smaller buffer.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Move dsl_dataset_t local variable from the stack to the heap.
This reduces the stack usage of this function from 2048 bytes
to 176 bytes for x84_64 arches.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reduce stack usage by 276 bytes by moving the snaparg struct from the
stack to the heap. We have limited stack space we must not waste.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
This commit preserves the recursive function dbuf_hold_impl() but moves
the local variables and function arguments to the heap to minimize
the stack frame size. Enough space is initially allocated on the
stack for 20 levels of recursion. This technique was based on commit
34229a2f2a which reduced stack usage of
traverse_visitbp().
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
The dnode_move() functionality is only used in the kernel build.
As such we should be careful to wrap all of the related code
with '#ifdef _KERNEL' to avoid gcc warnings about unused code.
This is a portability change which removes the dependence of the Solaris
thread library. All locations where Solaris thread API was used before
have been replaced with equivilant Solaris kernel style thread calls.
In user space the kernel style threading API is implemented in term of
the portable pthreads library. This includes all threads, mutexs,
condition variables, reader/writer locks, and taskqs.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Interestingly this looks like an upstream bug as well. If for some
reason we are unable to get a zvols statistics, because perhaps the
zpool is hopelessly corrupt, we would trigger the VERIFY. This
commit adds the proper error handling just to propagate the error
back to user space. Now the user space tools still must handle this
properly but in the worst case the tool will crash or perhaps have
some missing output. That's far far better than crashing the host.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
The zio_taskq_dispatch() function may be called at interrupt time
and it is critical that we never sleep.
Additionally, wrap taskq_dispatch() in a while loop because it may
fail. This is non optimal but is OK for now.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
This look like a typo. The intention was to use strlcat() however
strncat() was used instead accidentally this may lead to a buffer
overflow. This was caught by gcc -D_FORTIFY_SOURCE=2.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Do not use zmod.h in userspace.
This has also been filed with the ZFS team. It makes the userspace
libzpool code use the zlib API, instead of the Solaris-only and
non-standard zmod.h. The zlib API is almost identical and is a de
facto standard, so this is a no-brainer.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
If your only going to allow one allocator to be used and it is defined
at compile time there is no point including the others in the build.
This patch could/should be refined for Linux to make the metaslab
configurable at run time. That might be a bit tricky however since
you would need to quiese all IO. Short of that making it configurable
as a module load option would be a reasonable compromise.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Remove all instances of list handling where the API is not used
and instead list data members are directly accessed. Doing this
sort of thing is bad for portability.
Additionally, ensure that list_link_init() is called on newly
created list nodes. This ensures the node is properly initialized
and does not rely on the assumption that zero'ing the list_node_t
via kmem_zalloc() is the same as proper initialization.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Move xiou stat structures from a header to the dmu.c source as is
done with all the other kstat interfaces. This information is local
to dmu.c registered the xuio kstat and should stay that way.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Replace non-fatal assertion with warning. This was being observed
during testing and it should not be fatal.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
1) In vn_open(), if fstat64() returned an error, the real errno
was being obscured by calling close().
2) Add error handling for both pwrite64() calls in vn_rdwr().
Signed-off-by: Ricardo M. Correia <Ricardo.M.Correia@Sun.COM>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Remove deadcode. It's possible the code should be in use
somewhere, but as the source code is laid out it currently
is not.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
In the linux kernel 'current' is defined to mean the current process
and can never be used as a local variable in a function. Simply
replace all usage of 'current' with 'curr' in this function.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
The upstream commit cb code had a few bugs:
1) The arguments of the list_move_tail() call in txg_dispatch_callbacks()
were reversed by mistake. This caused the commit callbacks to not be
called at all.
2) ztest had a bug in ztest_dmu_commit_callbacks() where "error" was not
initialized correctly. This seems to have caused the test to always take
the simulated error code path, which made ztest unable to detect whether
commit cbs were being called for transactions that successfuly complete.
3) ztest had another bug in ztest_dmu_commit_callbacks() where the commit
cb threshold was not being compared correctly.
4) The commit cb taskq was using 'max_ncpus * 2' as the maxalloc argument
of taskq_create(), which could have caused unnecessary delays in the txg
sync thread.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Use constructor attribute on non-Solaris platforms.
The #pragma init/fini ->__attribute__((constructor/destructor))
conversions, these should go upstream.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Resolve issues uncovered by -D_FORTIFY_SOURCE=2, the default redhat
macro's file adds this option to the cflags. This causes warnings
of the following type designed to keep the developer honest:
warning: ignoring return value of 'foo', declared
with attribute warn_unused_result
The short term fix is to wrap these calls in VERIFY() to check the
return code. The code was already assusing these would never fail.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Fix non-c90 compliant code, for the most part these changes
simply deal with where a particular variable is declared.
Under c90 it must alway be done at the very start of a block.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
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()
Brian Behlendorf
Ned Bass
Ricardo M. Correia
Ricardo M. Correia