The `zfs program` subcommand invokes a LUA interpreter to run ZFS
"channel programs". This interpreter runs in a constrained environment,
with defined memory limits. The LUA stack (used for LUA functions that
call each other) is allocated in the kernel's heap, and is limited by
the `-m MEMORY-LIMIT` flag and the `zfs_lua_max_memlimit` module
parameter. The C stack is used by certain LUA features that are
implemented in C. The C stack is limited by `LUAI_MAXCCALLS=20`, which
limits call depth.
Some LUA C calls use more stack space than others, and `gsub()` uses an
unusually large amount. With a programming trick, it can be invoked
recursively using the C stack (rather than the LUA stack). This
overflows the 16KB Linux kernel stack after about 11 iterations, less
than the limit of 20.
One solution would be to decrease `LUAI_MAXCCALLS`. This could be made
to work, but it has a few drawbacks:
1. The existing test suite does not pass with `LUAI_MAXCCALLS=10`.
2. There may be other LUA functions that use a lot of stack space, and
the stack space may change depending on compiler version and options.
This commit addresses the problem by adding a new limit on the amount of
free space (in bytes) remaining on the C stack while running the LUA
interpreter: `LUAI_MINCSTACK=4096`. If there is less than this amount
of stack space remaining, a LUA runtime error is generated.
Reviewed-by: George Wilson <gwilson@delphix.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Ryan Moeller <ryan@ixsystems.com>
Reviewed-by: Allan Jude <allanjude@freebsd.org>
Reviewed-by: Serapheim Dimitropoulos <serapheim@delphix.com>
Signed-off-by: Matthew Ahrens <mahrens@delphix.com>
Closes#10611Closes#10613
Reviewed-by: Ryan Moeller <ryan@ixsystems.com>
Reviewed-by: Richard Laager <rlaager@wiktel.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Andrea Gelmini <andrea.gelmini@gelma.net>
Closes#9241
The use of void __attribute__((noreturn)) in kernel builds
was causing lots of warnings if CONFIG_STACK_VALIDATION
is active. For now we just remove this attribute to achieve
clean builds for the Lua module. There was no significant
increase in the time to run the full channel_program ZTS tests.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: George Melikov <mail@gmelikov.ru>
Signed-off-by: Don Brady <don.brady@delphix.com>
Closes#7173
Authored by: Chris Williamson <chris.williamson@delphix.com>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: John Kennedy <john.kennedy@delphix.com>
Reviewed by: Dan Kimmel <dan.kimmel@delphix.com>
Approved by: Garrett D'Amore <garrett@damore.org>
Ported-by: Don Brady <don.brady@delphix.com>
Ported-by: John Kennedy <john.kennedy@delphix.com>
OpenZFS-issue: https://www.illumos.org/issues/7431
OpenZFS-commit: https://github.com/openzfs/openzfs/commit/dfc11533
Porting Notes:
* The CLI long option arguments for '-t' and '-m' don't parse on linux
* Switched from kmem_alloc to vmem_alloc in zcp_lua_alloc
* Lua implementation is built as its own module (zlua.ko)
* Lua headers consumed directly by zfs code moved to 'include/sys/lua/'
* There is no native setjmp/longjump available in stock Linux kernel.
Brought over implementations from illumos and FreeBSD
* The get_temporary_prop() was adapted due to VFS platform differences
* Use of inline functions in lua parser to reduce stack usage per C call
* Skip some ZFS Test Suite ZCP tests on sparc64 to avoid stack overflow
Matthew Ahrens
Arvind Sankar
Andrea Gelmini
Don Brady
Chris Williamson