# git rev-parse -q --verify b8d5109f50969ead9d49c3e8bd78ec1f82e548e3^{commit}
b8d5109f50969ead9d49c3e8bd78ec1f82e548e3
already have revision, skipping fetch
# git checkout -q -f -B kisskb b8d5109f50969ead9d49c3e8bd78ec1f82e548e3
# git clean -qxdf
# < git log -1
# commit b8d5109f50969ead9d49c3e8bd78ec1f82e548e3
# Author: Linus Torvalds <torvalds@linux-foundation.org>
# Date:   Sun Jul 3 14:40:28 2022 -0700
# 
#     lockref: remove unused 'lockref_get_or_lock()' function
#     
#     Looking at the conditional lock acquire functions in the kernel due to
#     the new sparse support (see commit 4a557a5d1a61 "sparse: introduce
#     conditional lock acquire function attribute"), it became obvious that
#     the lockref code has a couple of them, but they don't match the usual
#     naming convention for the other ones, and their return value logic is
#     also reversed.
#     
#     In the other very similar places, the naming pattern is '*_and_lock()'
#     (eg 'atomic_put_and_lock()' and 'refcount_dec_and_lock()'), and the
#     function returns true when the lock is taken.
#     
#     The lockref code is superficially very similar to the refcount code,
#     only with the special "atomic wrt the embedded lock" semantics.  But
#     instead of the '*_and_lock()' naming it uses '*_or_lock()'.
#     
#     And instead of returning true in case it took the lock, it returns true
#     if it *didn't* take the lock.
#     
#     Now, arguably the reflock code is quite logical: it really is a "either
#     decrement _or_ lock" kind of situation - and the return value is about
#     whether the operation succeeded without any special care needed.
#     
#     So despite the similarities, the differences do make some sense, and
#     maybe it's not worth trying to unify the different conditional locking
#     primitives in this area.
#     
#     But while looking at this all, it did become obvious that the
#     'lockref_get_or_lock()' function hasn't actually had any users for
#     almost a decade.
#     
#     The only user it ever had was the shortlived 'd_rcu_to_refcount()'
#     function, and it got removed and replaced with 'lockref_get_not_dead()'
#     back in 2013 in commits 0d98439ea3c6 ("vfs: use lockred 'dead' flag to
#     mark unrecoverably dead dentries") and e5c832d55588 ("vfs: fix dentry
#     RCU to refcounting possibly sleeping dput()")
#     
#     In fact, that single use was removed less than a week after the whole
#     function was introduced in commit b3abd80250c1 ("lockref: add
#     'lockref_get_or_lock() helper") so this function has been around for a
#     decade, but only had a user for six days.
#     
#     Let's just put this mis-designed and unused function out of its misery.
#     
#     We can think about the naming and semantic oddities of the remaining
#     'lockref_put_or_lock()' later, but at least that function has users.
#     
#     And while the naming is different and the return value doesn't match,
#     that function matches the whole '{atomic,refcount}_dec_and_test()'
#     pattern much better (ie the magic happens when the count goes down to
#     zero, not when it is incremented from zero).
#     
#     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 b8d5109f50969ead9d49c3e8bd78ec1f82e548e3
# < make -s -j 40 ARCH=powerpc O=/kisskb/build/linus_44x_fsp2_defconfig_powerpc-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-  44x/fsp2_defconfig
# < make -s -j 40 ARCH=powerpc O=/kisskb/build/linus_44x_fsp2_defconfig_powerpc-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-  help
# make -s -j 40 ARCH=powerpc O=/kisskb/build/linus_44x_fsp2_defconfig_powerpc-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-  olddefconfig
# make -s -j 40 ARCH=powerpc O=/kisskb/build/linus_44x_fsp2_defconfig_powerpc-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-  
Completed OK
# rm -rf /kisskb/build/linus_44x_fsp2_defconfig_powerpc-gcc5
# Build took: 0:00:39.111408