Johannes Weiner 204cb79ad4 kernel: sysctl: make drop_caches write-only ... Currently, the drop_caches proc file and sysctl read back the last value written, suggesting this is somehow a stateful setting instead of a one-time command. Make it write-only, like e.g. compact_memory. While mitigating a VM problem at scale in our fleet, there was confusion about whether writing to this file will permanently switch the kernel into a non-caching mode. This influences the decision making in a tense situation, where tens of people are trying to fix tens of thousands of affected machines: Do we need a rollback strategy? What are the performance implications of operating in a non-caching state for several days? It also caused confusion when the kernel team said we may need to write the file several times to make sure it's effective ("But it already reads back 3?"). Link: http://lkml.kernel.org/r/20191031221602.9375-1-hannes@cmpxchg.org Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Chris Down <chris@chrisdown.name> Acked-by: Vlastimil Babka <vbabka@suse.cz> Acked-by: David Hildenbrand <david@redhat.com> Acked-by: Michal Hocko <mhocko@suse.com> Acked-by: Alexey Dobriyan <adobriyan@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>		2019-12-01 12:59:07 -08:00
..
bpf	Merge branch 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2019-11-26 16:02:40 -08:00
cgroup	Merge branch 'for-5.5' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup	2019-11-25 19:23:46 -08:00
configs	…
debug	kgdb: don't use a notifier to enter kgdb at panic; call directly	2019-09-25 17:51:40 -07:00
dma	dma-mapping updates for 5.5-rc1	2019-11-28 11:16:43 -08:00
events	mm/mmap.c: use IS_ERR_VALUE to check return value of get_unmapped_area	2019-12-01 06:29:19 -08:00
gcov	um: Enable CONFIG_CONSTRUCTORS	2019-09-15 21:37:13 +02:00
irq	irq/irqdomain: Update __irq_domain_alloc_fwnode() function documentation	2019-11-05 00:48:26 +01:00
livepatch	New tracing features:	2019-11-27 11:42:01 -08:00
locking	Merge branch 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2019-11-26 16:02:40 -08:00
power	Merge branches 'pm-sleep', 'pm-domains', 'pm-opp' and 'powercap'	2019-11-26 10:27:49 +01:00
printk	locking/lockdep: Remove unused @nested argument from lock_release()	2019-10-09 12:46:10 +02:00
rcu	Merge branches 'doc.2019.10.29a', 'fixes.2019.10.30a', 'nohz.2019.10.28a', 'replace.2019.10.30a', 'torture.2019.10.05a' and 'lkmm.2019.10.05a' into HEAD	2019-10-30 08:47:13 -07:00
sched	Power management updates for 5.5-rc1	2019-11-26 19:06:44 -08:00
time	Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2019-11-26 15:42:43 -08:00
trace	New tracing features:	2019-11-27 11:42:01 -08:00
.gitignore	…
Kconfig.freezer	…
Kconfig.hz	…
Kconfig.locks	…
Kconfig.preempt	sched/Kconfig: Fix spelling mistake in user-visible help text	2019-11-12 11:35:32 +01:00
Makefile	kernel/sysctl-test: Add null pointer test for sysctl.c:proc_dointvec()	2019-09-30 17:35:01 -06:00
acct.c	…
async.c	…
audit.c	…
audit.h	…
audit_fsnotify.c	…
audit_tree.c	…
audit_watch.c	audit_get_nd(): don't unlock parent too early	2019-11-10 11:56:55 -05:00
auditfilter.c	…
auditsc.c	Revert "bpf: Emit audit messages upon successful prog load and unload"	2019-11-23 09:56:02 -08:00
backtracetest.c	…
bounds.c	…
capability.c	…
compat.c	…
configs.c	kernel/configs: Replace GPL boilerplate code with SPDX identifier	2019-07-30 18:34:15 +02:00
context_tracking.c	context_tracking: Rename context_tracking_is_enabled() => context_tracking_enabled()	2019-10-29 10:01:12 +01:00
cpu.c	Merge branch 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2019-11-26 16:02:40 -08:00
cpu_pm.c	…
crash_core.c	…
crash_dump.c	…
cred.c	Merge branch 'access-creds'	2019-07-25 08:36:29 -07:00
delayacct.c	…
dma.c	…
elfcore.c	kernel/elfcore.c: include proper prototypes	2019-09-25 17:51:39 -07:00
exec_domain.c	…
exit.c	Merge branch 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2019-11-26 16:02:40 -08:00
extable.c	bpf: Add support for BTF pointers to x86 JIT	2019-10-17 16:44:36 +02:00
fail_function.c	…
fork.c	fork: support VMAP_STACK with KASAN_VMALLOC	2019-12-01 12:59:05 -08:00
freezer.c	Revert "libata, freezer: avoid block device removal while system is frozen"	2019-10-06 09:11:37 -06:00
futex.c	futex: Prevent exit livelock	2019-11-20 09:40:38 +01:00
gen_kheaders.sh	kheaders: substituting --sort in archive creation	2019-10-17 09:08:19 +09:00
groups.c	…
hung_task.c	…
iomem.c	…
irq_work.c	…
jump_label.c	jump_label: Don't warn on __exit jump entries	2019-08-29 15:10:10 +01:00
kallsyms.c	kallsyms: Don't let kallsyms_lookup_size_offset() fail on retrieving the first symbol	2019-08-27 16:19:56 +01:00
kcmp.c	…
kcov.c	…
kexec.c	kexec_load: Disable at runtime if the kernel is locked down	2019-08-19 21:54:15 -07:00
kexec_core.c	kexec: bail out upon SIGKILL when allocating memory.	2019-09-25 17:51:40 -07:00
kexec_elf.c	kexec_elf: support 32 bit ELF files	2019-09-06 23:58:44 +02:00
kexec_file.c	Merge branch 'next-lockdown' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security	2019-09-28 08:14:15 -07:00
kexec_internal.h	…
kheaders.c	…
kmod.c	…
kprobes.c	Tracing updates:	2019-09-20 11:19:48 -07:00
ksysfs.c	…
kthread.c	kthread: make __kthread_queue_delayed_work static	2019-10-16 09:20:58 -07:00
latencytop.c	…
module-internal.h	…
module.c	New tracing features:	2019-11-27 11:42:01 -08:00
module_signature.c	MODSIGN: Export module signature definitions	2019-08-05 18:39:56 -04:00
module_signing.c	MODSIGN: Export module signature definitions	2019-08-05 18:39:56 -04:00
notifier.c	…
nsproxy.c	…
padata.c	padata: remove cpu_index from the parallel_queue	2019-09-13 21:15:41 +10:00
panic.c	locking/refcount: Remove unused 'refcount_error_report()' function	2019-11-25 09:15:42 +01:00
params.c	lockdown: Lock down module params that specify hardware parameters (eg. ioport)	2019-08-19 21:54:16 -07:00
pid.c	fork: extend clone3() to support setting a PID	2019-11-15 23:49:22 +01:00
pid_namespace.c	fork: extend clone3() to support setting a PID	2019-11-15 23:49:22 +01:00
profile.c	…
ptrace.c	…
range.c	…
reboot.c	…
relay.c	…
resource.c	mm/memory_hotplug.c: use PFN_UP / PFN_DOWN in walk_system_ram_range()	2019-09-24 15:54:09 -07:00
rseq.c	…
seccomp.c	…
signal.c	cgroup: freezer: call cgroup_enter_frozen() with preemption disabled in ptrace_stop()	2019-10-11 08:39:57 -07:00
smp.c	…
smpboot.c	…
smpboot.h	…
softirq.c	…
stackleak.c	…
stacktrace.c	stacktrace: Get rid of unneeded '!!' pattern	2019-11-11 10:30:59 +01:00
stop_machine.c	Merge branch 'for-mingo' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into core/rcu	2019-10-31 09:33:19 +01:00
sys.c	Merge branch 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2019-09-17 12:35:15 -07:00
sys_ni.c	…
sysctl-test.c	kernel/sysctl-test: Add null pointer test for sysctl.c:proc_dointvec()	2019-09-30 17:35:01 -06:00
sysctl.c	kernel: sysctl: make drop_caches write-only	2019-12-01 12:59:07 -08:00
sysctl_binary.c	…
task_work.c	…
taskstats.c	…
test_kprobes.c	…
torture.c	torture: Remove exporting of internal functions	2019-08-01 14:30:22 -07:00
tracepoint.c	…
tsacct.c	…
ucount.c	…
uid16.c	…
uid16.h	…
umh.c	…
up.c	…
user-return-notifier.c	…
user.c	…
user_namespace.c	…
utsname.c	…
utsname_sysctl.c	…
watchdog.c	watchdog: Mark watchdog_hrtimer to expire in hard interrupt context	2019-08-01 20:51:20 +02:00
watchdog_hld.c	…
workqueue.c	Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2019-11-26 15:42:43 -08:00
workqueue_internal.h	…