The kernel is implementing a '/sys/bus/dax' ABI to allow for alternate device-DAX drivers to be bound to device instances. While the kernel conversion to '/sys/bus/dax' does not effect the primary ndctl use case of putting namespaces into 'devdax' mode since that uses libnvdimm namespace device relative paths, it does break current implementations of 'ndctl list -X' and 'daxctl list'. It is also known to break fio and some pmdk versions that explicitly reference "/sys/class/dax".
In order to avoid userspace regressions the kernel can be configured to maintain '/sys/class/dax' as the default ABI. However, once all '/sys/class/dax' users have been converted, or removed from the installation, an administrator can opt-in to the new '/sys/bus/dax' ABI. The 'dax migrate-device-model' command installs a modprobe rule to blacklist the dax_pmem_compat module and arrange for the dax_pmem module to auto-load in response to the detection of device-DAX instances emitted from the libnvdimm subsystem. Reported-by: Jeff Moyer <[email protected]> Signed-off-by: Dan Williams <[email protected]> --- .gitignore | 1 Documentation/daxctl/Makefile.am | 3 + .../daxctl/daxctl-migrate-device-model.txt | 47 ++++++++++++++++++++ configure.ac | 5 ++ daxctl/Makefile.am | 10 ++++ daxctl/builtin.h | 1 daxctl/daxctl.c | 1 daxctl/lib/Makefile.am | 2 + daxctl/lib/daxctl.conf | 2 + daxctl/migrate.c | 41 +++++++++++++++++ ndctl.spec.in | 1 11 files changed, 113 insertions(+), 1 deletion(-) create mode 100644 Documentation/daxctl/daxctl-migrate-device-model.txt create mode 100644 daxctl/lib/daxctl.conf create mode 100644 daxctl/migrate.c diff --git a/.gitignore b/.gitignore index 5a3d8e4507e5..3ef9ff7a9a2f 100644 --- a/.gitignore +++ b/.gitignore @@ -18,6 +18,7 @@ Documentation/ndctl/asciidoc.conf Documentation/daxctl/asciidoctor-extensions.rb Documentation/ndctl/asciidoctor-extensions.rb .dirstamp +daxctl/config.h daxctl/daxctl daxctl/lib/libdaxctl.la daxctl/lib/libdaxctl.lo diff --git a/Documentation/daxctl/Makefile.am b/Documentation/daxctl/Makefile.am index fc0fbe138d93..6aba035ff543 100644 --- a/Documentation/daxctl/Makefile.am +++ b/Documentation/daxctl/Makefile.am @@ -27,7 +27,8 @@ endif man1_MANS = \ daxctl.1 \ - daxctl-list.1 + daxctl-list.1 \ + daxctl-migrate-device-model.1 CLEANFILES = $(man1_MANS) diff --git a/Documentation/daxctl/daxctl-migrate-device-model.txt b/Documentation/daxctl/daxctl-migrate-device-model.txt new file mode 100644 index 000000000000..23e89f1afafc --- /dev/null +++ b/Documentation/daxctl/daxctl-migrate-device-model.txt @@ -0,0 +1,47 @@ +// SPDX-License-Identifier: GPL-2.0 + +daxctl-migrate-device-model(1) +============================== + +NAME +---- +daxctl-migrate-device-model - Opt-in to the /sys/bus/dax device-model, +allow for alternative Device-DAX instance drivers. + +SYNOPSIS +-------- +[verse] +'daxctl migrate-device-model' + +Arrange for modprobe to disable the dax_pmem_compat, if present, and +instead deploy the dax_pmem module to convert to the /sys/bus/dax model. +Kernel versions prior to v5.1 may not support /sys/bus/dax in which case +the result of this command is a nop until the kernel is updated. The +motivation for changing from /sys/class/dax to /sys/bus/dax is to allow +for alternative drivers for Device-DAX instances, in particular the +dax_kmem driver. + +By default device-dax publishes a /dev/daxX.Y character device for +userspace to directly map performance differentiated memory. This is +fine if the memory is to be exclusively consumed / managed by userspace. +Alternatively an administrator may want the kernel to manage the memory, +make it available via malloc(), allow for over-provisioning, and / or +apply kernel-based resource control schemes to the memory. In that case +the memory fronted by a given Device-DAX instance can be assigned to the +dax_kmem driver which arranges for the core-kernel memory-management +sub-system to assume management of the memory range. + +This behavior is opt-in for consideration of existing applications / +scripts that may be hard coded to use /sys/class/dax. Fixes have been +submitted to applications known to have these direct dependencies +http://git.kernel.dk/cgit/fio/commit/?id=b08e7d6b18b4[FIO] +https://github.com/pmem/pmdk/commit/91bc8620884e[PMDK], however, there may +be others and a system-owner should be aware of the potential for +regression of Device-DAX consuming scripts, applications, or older +daxctl binaries. + +The modprobe policy established by this utility becomes effective after +the next reboot, or after all DAX related modules have been removed and +re-loaded with "udevadm trigger" + +include::../copyright.txt[] diff --git a/configure.ac b/configure.ac index a02a2d80e1d5..5b4f1fc8d346 100644 --- a/configure.ac +++ b/configure.ac @@ -159,6 +159,11 @@ ndctl_monitorconf=monitor.conf AC_SUBST([ndctl_monitorconfdir]) AC_SUBST([ndctl_monitorconf]) +daxctl_modprobe_datadir=${datadir}/daxctl +daxctl_modprobe_data=daxctl.conf +AC_SUBST([daxctl_modprobe_datadir]) +AC_SUBST([daxctl_modprobe_data]) + my_CFLAGS="\ -Wall \ -Wchar-subscripts \ diff --git a/daxctl/Makefile.am b/daxctl/Makefile.am index fe467d030c38..e424d435c22b 100644 --- a/daxctl/Makefile.am +++ b/daxctl/Makefile.am @@ -2,9 +2,19 @@ include $(top_srcdir)/Makefile.am.in bin_PROGRAMS = daxctl +DISTCLEANFILES = config.h +BUILT_SOURCES = config.h +config.h: Makefile + $(AM_V_GEN) echo "/* Autogenerated by daxctl/Makefile.am */" >$@ + $(AM_V_GEN) echo '#define DAXCTL_MODPROBE_DATA \ + "$(daxctl_modprobe_datadir)/$(daxctl_modprobe_data)"' >>$@ + $(AM_V_GEN) echo '#define DAXCTL_MODPROBE_INSTALL \ + "$(sysconfdir)/modprobe.d/$(daxctl_modprobe_data)"' >>$@ + daxctl_SOURCES =\ daxctl.c \ list.c \ + migrate.c \ ../util/json.c daxctl_LDADD =\ diff --git a/daxctl/builtin.h b/daxctl/builtin.h index dae2615b7ddb..00ef5e930417 100644 --- a/daxctl/builtin.h +++ b/daxctl/builtin.h @@ -5,4 +5,5 @@ struct daxctl_ctx; int cmd_list(int argc, const char **argv, struct daxctl_ctx *ctx); +int cmd_migrate(int argc, const char **argv, struct daxctl_ctx *ctx); #endif /* _DAXCTL_BUILTIN_H_ */ diff --git a/daxctl/daxctl.c b/daxctl/daxctl.c index cb6f50e39170..2e41747b5ea9 100644 --- a/daxctl/daxctl.c +++ b/daxctl/daxctl.c @@ -70,6 +70,7 @@ static struct cmd_struct commands[] = { { "version", .d_fn = cmd_version }, { "list", .d_fn = cmd_list }, { "help", .d_fn = cmd_help }, + { "migrate-device-model", .d_fn = cmd_migrate }, }; int main(int argc, const char **argv) diff --git a/daxctl/lib/Makefile.am b/daxctl/lib/Makefile.am index 0167e3995b00..d3d4852916ca 100644 --- a/daxctl/lib/Makefile.am +++ b/daxctl/lib/Makefile.am @@ -18,6 +18,8 @@ libdaxctl_la_SOURCES =\ libdaxctl_la_LIBADD =\ $(UUID_LIBS) +daxctl_modprobe_data_DATA = daxctl.conf + EXTRA_DIST += libdaxctl.sym libdaxctl_la_LDFLAGS = $(AM_LDFLAGS) \ diff --git a/daxctl/lib/daxctl.conf b/daxctl/lib/daxctl.conf new file mode 100644 index 000000000000..c64a088cbc0b --- /dev/null +++ b/daxctl/lib/daxctl.conf @@ -0,0 +1,2 @@ +blacklist dax_pmem_compat +alias nd:t7* dax_pmem diff --git a/daxctl/migrate.c b/daxctl/migrate.c new file mode 100644 index 000000000000..f7bf8347c4ea --- /dev/null +++ b/daxctl/migrate.c @@ -0,0 +1,41 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* Copyright(c) 2015-2018 Intel Corporation. All rights reserved. */ +#include <sys/types.h> +#include <sys/stat.h> +#include <stdio.h> +#include <errno.h> +#include <fcntl.h> +#include <daxctl/config.h> +#include <daxctl/libdaxctl.h> +#include <util/parse-options.h> +#include <ccan/array_size/array_size.h> + +int cmd_migrate(int argc, const char **argv, struct daxctl_ctx *ctx) +{ + int i; + static const struct option options[] = { + OPT_END(), + }; + const char * const u[] = { + "daxctl migrate-device-model", + NULL + }; + + argc = parse_options(argc, argv, options, u, 0); + for (i = 0; i < argc; i++) + error("unknown parameter \"%s\"\n", argv[i]); + + if (argc) + usage_with_options(u, options); + + if (symlink(DAXCTL_MODPROBE_DATA, DAXCTL_MODPROBE_INSTALL) == 0) { + fprintf(stderr, " Success: installed %s\n", + DAXCTL_MODPROBE_INSTALL); + return EXIT_SUCCESS; + } + + error("failed to install %s: %s\n", DAXCTL_MODPROBE_INSTALL, + strerror(errno)); + + return EXIT_FAILURE; +} diff --git a/ndctl.spec.in b/ndctl.spec.in index bc4d65c1f988..bc65a471a6d2 100644 --- a/ndctl.spec.in +++ b/ndctl.spec.in @@ -126,6 +126,7 @@ make check %license util/COPYING licenses/BSD-MIT licenses/CC0 %{_bindir}/daxctl %{_mandir}/man1/daxctl* +%{_datadir}/daxctl/daxctl.conf %files -n LNAME %defattr(-,root,root) _______________________________________________ Linux-nvdimm mailing list [email protected] https://lists.01.org/mailman/listinfo/linux-nvdimm
