# 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/korg/gcc-11.3.0-nolibc/mips-linux/bin/mips-linux-gcc --version # < /opt/cross/kisskb/korg/gcc-11.3.0-nolibc/mips-linux/bin/mips-linux-ld --version # < git log --format=%s --max-count=1 981ee95cc1f5905ae4936b0dd501085909cdc14f # < make -s -j 160 ARCH=mips O=/kisskb/build/linus_mips-allmodconfig_mips-gcc11 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-11.3.0-nolibc/mips-linux/bin/mips-linux- allmodconfig # Added to kconfig CONFIG_BUILD_DOCSRC=n # Added to kconfig CONFIG_MODULE_SIG=n # Added to kconfig CONFIG_SAMPLES=n # Added to kconfig CONFIG_MIPS_CPS_NS16550_BASE=0x1b0003f8 # Added to kconfig CONFIG_MIPS_CPS_NS16550_SHIFT=0 # Added to kconfig CONFIG_GCC_PLUGINS=n # Added to kconfig # < make -s -j 160 ARCH=mips O=/kisskb/build/linus_mips-allmodconfig_mips-gcc11 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-11.3.0-nolibc/mips-linux/bin/mips-linux- help # make -s -j 160 ARCH=mips O=/kisskb/build/linus_mips-allmodconfig_mips-gcc11 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-11.3.0-nolibc/mips-linux/bin/mips-linux- olddefconfig .config:14307:warning: override: reassigning to symbol MIPS_CPS_NS16550_SHIFT # make -s -j 160 ARCH=mips O=/kisskb/build/linus_mips-allmodconfig_mips-gcc11 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-11.3.0-nolibc/mips-linux/bin/mips-linux- In file included from /kisskb/src/arch/mips/include/asm/div64.h:89, from /kisskb/src/include/linux/math.h:6, from /kisskb/src/include/linux/math64.h:6, from /kisskb/src/include/linux/time64.h:5, from /kisskb/src/include/linux/restart_block.h:10, from /kisskb/src/include/linux/thread_info.h:14, from /kisskb/src/include/asm-generic/current.h:5, from ./arch/mips/include/generated/asm/current.h:1, from /kisskb/src/include/linux/sched.h:12, from /kisskb/src/include/linux/ratelimit.h:6, from /kisskb/src/include/linux/dev_printk.h:16, from /kisskb/src/include/linux/device.h:15, from /kisskb/src/include/linux/auxiliary_bus.h:11, from /kisskb/src/drivers/power/supply/qcom_battmgr.c:6: /kisskb/src/drivers/power/supply/qcom_battmgr.c: In function 'qcom_battmgr_sm8350_callback': /kisskb/src/include/asm-generic/div64.h:222:35: error: comparison of distinct pointer types lacks a cast [-Werror] 222 | (void)(((typeof((n)) *)0) == ((uint64_t *)0)); \ | ^~ /kisskb/src/drivers/power/supply/qcom_battmgr.c:1130:25: note: in expansion of macro 'do_div' 1130 | do_div(battmgr->status.percent, 100); | ^~~~~~ In file included from /kisskb/src/include/linux/dev_printk.h:14, from /kisskb/src/include/linux/device.h:15, from /kisskb/src/include/linux/auxiliary_bus.h:11, from /kisskb/src/drivers/power/supply/qcom_battmgr.c:6: /kisskb/src/include/asm-generic/div64.h:234:32: error: right shift count >= width of type [-Werror=shift-count-overflow] 234 | } else if (likely(((n) >> 32) == 0)) { \ | ^~ /kisskb/src/include/linux/compiler.h:77:45: note: in definition of macro 'likely' 77 | # define likely(x) __builtin_expect(!!(x), 1) | ^ /kisskb/src/drivers/power/supply/qcom_battmgr.c:1130:25: note: in expansion of macro 'do_div' 1130 | do_div(battmgr->status.percent, 100); | ^~~~~~ cc1: all warnings being treated as errors make[5]: *** [/kisskb/src/scripts/Makefile.build:252: drivers/power/supply/qcom_battmgr.o] Error 1 make[4]: *** [/kisskb/src/scripts/Makefile.build:494: drivers/power/supply] Error 2 make[3]: *** [/kisskb/src/scripts/Makefile.build:494: drivers/power] Error 2 make[3]: *** Waiting for unfinished jobs.... make[2]: *** [/kisskb/src/scripts/Makefile.build:494: drivers] Error 2 make[2]: *** Waiting for unfinished jobs.... make[1]: *** [/kisskb/src/Makefile:2028: .] Error 2 make: *** [Makefile:226: __sub-make] Error 2 Command 'make -s -j 160 ARCH=mips O=/kisskb/build/linus_mips-allmodconfig_mips-gcc11 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-11.3.0-nolibc/mips-linux/bin/mips-linux- ' returned non-zero exit status 2 # rm -rf /kisskb/build/linus_mips-allmodconfig_mips-gcc11 # Build took: 0:06:33.632053