# 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 <mjguzik@gmail.com>
# 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 <mjguzik@gmail.com>
#     Cc: Al Viro <viro@zeniv.linux.org.uk>
#     Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
# < /opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-gcc --version
# < /opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-ld --version
# < git log --format=%s --max-count=1 981ee95cc1f5905ae4936b0dd501085909cdc14f
# < make -s -j 160 ARCH=powerpc O=/kisskb/build/linus_skiroot_defconfig_powerpc-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-  skiroot_defconfig
# < make -s -j 160 ARCH=powerpc O=/kisskb/build/linus_skiroot_defconfig_powerpc-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-  help
# make -s -j 160 ARCH=powerpc O=/kisskb/build/linus_skiroot_defconfig_powerpc-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-  olddefconfig
# make -s -j 160 ARCH=powerpc O=/kisskb/build/linus_skiroot_defconfig_powerpc-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-  
/kisskb/src/fs/btrfs/extent_io.c: In function 'extent_fiemap':
/kisskb/src/fs/btrfs/extent_io.c:3542:19: warning: 'last_extent_end' may be used uninitialized in this function [-Wmaybe-uninitialized]
  if (cache.cached && cache.offset + cache.len >= last_extent_end) {
                   ^
/kisskb/src/fs/btrfs/extent_io.c: At top level:
cc1: warning: unrecognized command line option '-Wno-shift-negative-value'
/kisskb/src/fs/btrfs/send.c: In function 'get_cur_inode_state':
/kisskb/src/fs/btrfs/send.c:1902:23: warning: 'right_gen' may be used uninitialized in this function [-Wmaybe-uninitialized]
   if (left_gen == gen && right_gen == gen) {
                       ^
/kisskb/src/fs/btrfs/volumes.c: In function 'btrfs_init_new_device':
/kisskb/src/fs/btrfs/volumes.c:2515:2: warning: 'seed_devices' may be used uninitialized in this function [-Wmaybe-uninitialized]
  list_add(&seed_devices->seed_list, &fs_devices->seed_list);
  ^
/kisskb/src/fs/btrfs/volumes.c:2612:27: note: 'seed_devices' was declared here
  struct btrfs_fs_devices *seed_devices;
                           ^
/kisskb/src/fs/btrfs/volumes.c: At top level:
cc1: warning: unrecognized command line option '-Wno-shift-negative-value'
/kisskb/src/fs/btrfs/send.c: At top level:
cc1: warning: unrecognized command line option '-Wno-shift-negative-value'
Completed OK
# rm -rf /kisskb/build/linus_skiroot_defconfig_powerpc-gcc5
# Build took: 0:02:28.885434