On Sat, Feb 22, 2025 at 04:45:13PM +0800, Ruiwu Chen wrote: > When 'echo 4 > /proc/sys/vm/drop_caches' the message is disabled, > but there is no interface to enable the message, only by restarting > the way, so add the 'echo 0 > /proc/sys/vm/drop_caches' way to > enabled the message again. > > Signed-off-by: Ruiwu Chen <rwchen404@xxxxxxxxx> You are overcomplicating things, if you just want to re-enable messages you can just use: - stfu |= sysctl_drop_caches & 4; + stfu = sysctl_drop_caches & 4; The bool is there as 4 is intended as a bit flag, you can can figure out what values you want and just append 4 to it to get the expected result. Luis > --- > v2: - updated Documentation/ to note this new API. > - renamed the variable. > - rebase this on top of sysctl-next [1]. > [1] https://git.kernel.org/pub/scm/linux/kernel/git/sysctl/sysctl.git/log/?h=sysctl-next > > Documentation/admin-guide/sysctl/vm.rst | 11 ++++++++++- > fs/drop_caches.c | 11 +++++++---- > 2 files changed, 17 insertions(+), 5 deletions(-) > > diff --git a/Documentation/admin-guide/sysctl/vm.rst b/Documentation/admin-guide/sysctl/vm.rst > index f48eaa98d22d..ef73d36e8b84 100644 > --- a/Documentation/admin-guide/sysctl/vm.rst > +++ b/Documentation/admin-guide/sysctl/vm.rst > @@ -266,7 +266,16 @@ used:: > cat (1234): drop_caches: 3 > > These are informational only. They do not mean that anything is wrong > -with your system. To disable them, echo 4 (bit 2) into drop_caches. > +with your system. > + > +To disable informational:: > + > + echo 4 > /proc/sys/vm/drop_caches > + > +To enable informational:: > + > + echo 0 > /proc/sys/vm/drop_caches > + > > enable_soft_offline > =================== > diff --git a/fs/drop_caches.c b/fs/drop_caches.c > index 019a8b4eaaf9..a49af7023886 100644 > --- a/fs/drop_caches.c > +++ b/fs/drop_caches.c > @@ -57,7 +57,7 @@ static int drop_caches_sysctl_handler(const struct ctl_table *table, int write, > if (ret) > return ret; > if (write) { > - static int stfu; > + static bool silent; > > if (sysctl_drop_caches & 1) { > lru_add_drain_all(); > @@ -68,12 +68,15 @@ static int drop_caches_sysctl_handler(const struct ctl_table *table, int write, > drop_slab(); > count_vm_event(DROP_SLAB); > } > - if (!stfu) { > + if (!silent) { > pr_info("%s (%d): drop_caches: %d\n", > current->comm, task_pid_nr(current), > sysctl_drop_caches); > } > - stfu |= sysctl_drop_caches & 4; > + if (sysctl_drop_caches == 0) > + silent = true; > + else if (sysctl_drop_caches == 4) > + silent = false; > } > return 0; > } > @@ -85,7 +88,7 @@ static const struct ctl_table drop_caches_table[] = { > .maxlen = sizeof(int), > .mode = 0200, > .proc_handler = drop_caches_sysctl_handler, > - .extra1 = SYSCTL_ONE, > + .extra1 = SYSCTL_ZERO, > .extra2 = SYSCTL_FOUR, > }, > }; > -- > 2.27.0 >
