# git rev-parse -q --verify 981ee95cc1f5905ae4936b0dd501085909cdc14f^{commit} 981ee95cc1f5905ae4936b0dd501085909cdc14f already have revision, skipping fetch # git checkout -q -f -B kisskb 981ee95cc1f5905ae4936b0dd501085909cdc14f # git clean -qxdf # < git log -1 # commit 981ee95cc1f5905ae4936b0dd501085909cdc14f # Author: Mateusz Guzik # Date: Wed Jan 25 16:55:57 2023 +0100 # # vfs: avoid duplicating creds in faccessat if possible # # access(2) remains commonly used, for example on exec: # access("/etc/ld.so.preload", R_OK) # # or when running gcc: strace -c gcc empty.c # # % time seconds usecs/call calls errors syscall # ------ ----------- ----------- --------- --------- ---------------- # 0.00 0.000000 0 42 26 access # # It falls down to do_faccessat without the AT_EACCESS flag, which in turn # results in allocation of new creds in order to modify fsuid/fsgid and # caps. This is a very expensive process single-threaded and most notably # multi-threaded, with numerous structures getting refed and unrefed on # imminent new cred destruction. # # Turns out for typical consumers the resulting creds would be identical # and this can be checked upfront, avoiding the hard work. # # An access benchmark plugged into will-it-scale running on Cascade Lake # shows: # # test proc before after # access1 1 1310582 2908735 (+121%) # distinct files # access1 24 4716491 63822173 (+1353%) # distinct files # access2 24 2378041 5370335 (+125%) # same file # # The above benchmarks are not integrated into will-it-scale, but can be # found in a pull request: # # https://github.com/antonblanchard/will-it-scale/pull/36/files # # Signed-off-by: Mateusz Guzik # Cc: Al Viro # Signed-off-by: Linus Torvalds # < /opt/cross/kisskb/x86-64--glibc--bleeding-edge-2022.08-1/bin/x86_64-linux-gcc --version # < /opt/cross/kisskb/x86-64--glibc--bleeding-edge-2022.08-1/bin/x86_64-linux-ld --version # < git log --format=%s --max-count=1 981ee95cc1f5905ae4936b0dd501085909cdc14f # < make -s -j 32 ARCH=um O=/kisskb/build/linus_um-allmodconfig_um-x86_64-gcc12 CROSS_COMPILE=/opt/cross/kisskb/x86-64--glibc--bleeding-edge-2022.08-1/bin/x86_64-linux- SUBARCH=x86_64 allmodconfig # Added to kconfig CONFIG_STANDALONE=y # Added to kconfig CONFIG_KCOV=n # Added to kconfig CONFIG_GCC_PLUGINS=n # Added to kconfig CONFIG_GCC_PLUGIN_CYC_COMPLEXITY=n # Added to kconfig CONFIG_GCC_PLUGIN_SANCOV=n # Added to kconfig CONFIG_GCC_PLUGIN_LATENT_ENTROPY=n # Added to kconfig CONFIG_GCC_PLUGIN_STRUCTLEAK=n # Added to kconfig CONFIG_GCC_PLUGIN_RANDSTRUCT=n # Added to kconfig CONFIG_UML_NET=n # Added to kconfig CONFIG_UML_NET_ETHERTAP=n # Added to kconfig CONFIG_UML_NET_TUNTAP=n # Added to kconfig CONFIG_UML_NET_SLIP=n # Added to kconfig CONFIG_UML_NET_DAEMON=n # Added to kconfig CONFIG_UML_NET_VDE=n # Added to kconfig CONFIG_UML_NET_MCAST=n # Added to kconfig CONFIG_UML_NET_PCAP=n # Added to kconfig CONFIG_UML_NET_SLIRP=n # Added to kconfig CONFIG_GCOV_KERNEL=n # Added to kconfig CONFIG_DEBUG_INFO_BTF=n # Added to kconfig CONFIG_BPF_PRELOAD=n # < make -s -j 32 ARCH=um O=/kisskb/build/linus_um-allmodconfig_um-x86_64-gcc12 CROSS_COMPILE=/opt/cross/kisskb/x86-64--glibc--bleeding-edge-2022.08-1/bin/x86_64-linux- SUBARCH=x86_64 help # make -s -j 32 ARCH=um O=/kisskb/build/linus_um-allmodconfig_um-x86_64-gcc12 CROSS_COMPILE=/opt/cross/kisskb/x86-64--glibc--bleeding-edge-2022.08-1/bin/x86_64-linux- SUBARCH=x86_64 olddefconfig .config:12719:warning: override: reassigning to symbol GCC_PLUGIN_LATENT_ENTROPY .config:12723:warning: override: reassigning to symbol UML_NET_ETHERTAP .config:12725:warning: override: reassigning to symbol UML_NET_SLIP .config:12728:warning: override: reassigning to symbol UML_NET_MCAST .config:12730:warning: override: reassigning to symbol UML_NET_SLIRP # make -s -j 32 ARCH=um O=/kisskb/build/linus_um-allmodconfig_um-x86_64-gcc12 CROSS_COMPILE=/opt/cross/kisskb/x86-64--glibc--bleeding-edge-2022.08-1/bin/x86_64-linux- SUBARCH=x86_64 /kisskb/src/drivers/spi/spi-stm32-qspi.c: In function 'stm32_qspi_dirmap_read': /kisskb/src/drivers/spi/spi-stm32-qspi.c:523:27: error: 'op' is used uninitialized [-Werror=uninitialized] 523 | struct spi_mem_op op; | ^~ /kisskb/src/drivers/spi/spi-stm32-qspi.c:523:27: note: 'op' declared here 523 | struct spi_mem_op op; | ^~ /kisskb/src/drivers/spi/spi-stm32-qspi.c: In function 'stm32_qspi_transfer_one_message': /kisskb/src/drivers/spi/spi-stm32-qspi.c:564:27: error: 'op' is used uninitialized [-Werror=uninitialized] 564 | struct spi_mem_op op; | ^~ /kisskb/src/drivers/spi/spi-stm32-qspi.c:564:27: note: 'op' declared here 564 | struct spi_mem_op op; | ^~ cc1: all warnings being treated as errors make[4]: *** [/kisskb/src/scripts/Makefile.build:252: drivers/spi/spi-stm32-qspi.o] Error 1 make[4]: *** Waiting for unfinished jobs.... make[3]: *** [/kisskb/src/scripts/Makefile.build:494: drivers/spi] Error 2 make[3]: *** Waiting for unfinished jobs.... In file included from /kisskb/src/arch/x86/um/asm/processor.h:41, from /kisskb/src/include/linux/mutex.h:19, from /kisskb/src/include/linux/kernfs.h:11, from /kisskb/src/include/linux/sysfs.h:16, from /kisskb/src/include/linux/kobject.h:20, from /kisskb/src/include/linux/pci.h:35, from /kisskb/src/drivers/gpu/drm/amd/amdgpu/../amdkfd/kfd_topology.c:26: /kisskb/src/drivers/gpu/drm/amd/amdgpu/../amdkfd/kfd_topology.c: In function 'kfd_cpumask_to_apic_id': /kisskb/src/arch/um/include/asm/processor-generic.h:94:19: error: called object is not a function or function pointer 94 | #define cpu_data (&boot_cpu_data) | ~^~~~~~~~~~~~~~~ /kisskb/src/drivers/gpu/drm/amd/amdgpu/../amdkfd/kfd_topology.c:2157:16: note: in expansion of macro 'cpu_data' 2157 | return cpu_data(first_cpu_of_numa_node).apicid; | ^~~~~~~~ /kisskb/src/drivers/gpu/drm/amd/amdgpu/../amdkfd/kfd_topology.c:2161:1: error: control reaches end of non-void function [-Werror=return-type] 2161 | } | ^ cc1: all warnings being treated as errors make[6]: *** [/kisskb/src/scripts/Makefile.build:252: drivers/gpu/drm/amd/amdgpu/../amdkfd/kfd_topology.o] Error 1 make[5]: *** [/kisskb/src/scripts/Makefile.build:494: drivers/gpu/drm/amd/amdgpu] Error 2 make[5]: *** Waiting for unfinished jobs.... make[4]: *** [/kisskb/src/scripts/Makefile.build:494: drivers/gpu/drm] Error 2 make[3]: *** [/kisskb/src/scripts/Makefile.build:494: drivers/gpu] Error 2 make[2]: *** [/kisskb/src/scripts/Makefile.build:494: drivers] Error 2 make[1]: *** [/kisskb/src/Makefile:2028: .] Error 2 make: *** [Makefile:226: __sub-make] Error 2 Command 'make -s -j 32 ARCH=um O=/kisskb/build/linus_um-allmodconfig_um-x86_64-gcc12 CROSS_COMPILE=/opt/cross/kisskb/x86-64--glibc--bleeding-edge-2022.08-1/bin/x86_64-linux- SUBARCH=x86_64 ' returned non-zero exit status 2 # rm -rf /kisskb/build/linus_um-allmodconfig_um-x86_64-gcc12 # Build took: 0:11:13.332373