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Matthew Ahrens
43186f94f4
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 #10611 Closes #10613
ZFS on Linux is an advanced file system and volume manager which was originally developed for Solaris and is now maintained by the OpenZFS community.
Official Resources
Installation
Full documentation for installing ZoL on your favorite Linux distribution can be found at our site.
Contribute & Develop
We have a separate document with contribution guidelines.
Release
ZFS on Linux is released under a CDDL license.
For more details see the NOTICE, LICENSE and COPYRIGHT files; UCRL-CODE-235197
Supported Kernels
- The
METAfile contains the officially recognized supported kernel versions.