On Sat 19-08-17 15:49:31, Abdul Haleem wrote:
> Hi Michal,
>
> 'sysctl -a' command never completes on my PowerPC machine with latest
> next kernel (As of next-20170811)
>
> Machine Type : Power8 bare-metal
> Kernel version : 4.13.0-rc4-next-20170817
> gcc version : 4.8.5
>
>
> command output
> --------------
> $ sysctl -a
> [...
> vm.hugetlb_shm_group = 0
> vm.laptop_mode = 0
> vm.legacy_va_layout = 0
> vm.lowmem_reserve_ratio = 256 256 32
> vm.max_map_count = 65530
> vm.min_free_kbytes = 6637
> vm.min_slab_ratio = 5
> vm.min_unmapped_ratio = 1
> vm.mmap_min_addr = 4096
> vm.mmap_rnd_bits = 14
> vm.mmap_rnd_compat_bits = 7
> vm.nr_hugepages = 0
> vm.nr_hugepages_mempolicy = 0
> vm.nr_overcommit_hugepages = 0
> vm.nr_pdflush_threads = 0
> vm.numa_zonelist_order = Node
> vm.numa_zonelist_order = e
> vm.numa_zonelist_order = ode
> vm.numa_zonelist_order =
> vm.numa_zonelist_order = de
> vm.numa_zonelist_order = Node
> vm.numa_zonelist_order = e
> vm.numa_zonelist_order = ode
> vm.numa_zonelist_order =
> vm.numa_zonelist_order = de
> vm.numa_zonelist_order = Node
> vm.numa_zonelist_order = e
> vm.numa_zonelist_order = ode
> vm.numa_zonelist_order =
> vm.numa_zonelist_order = de
> vm.numa_zonelist_order = Node
> vm.numa_zonelist_order = e
> vm.numa_zonelist_order = ode
> ....]
>
> The last string 'vm.numa_zonelist_order = ' keeps flooding the stdout
> and command never exit.
>
> A bisection resulted commit c64e09ce mm, page_alloc: rip out
> ZONELIST_ORDER_ZONE
Yeah, my read implementation is broken. I do not update the ppos and so
the reader doesn't know it should exit. Mel was suggesting to keep the
proc_dostring but I thought I was more clever. Sigh...
This should do the trick. Andrew, could you fold it into
mm-page_alloc-rip-out-zonelist_order_zone.patch please?
Thanks for the report Abdul!
---
commit 69885605ee3ba681deb54021e3df645f46589ba1
Author: Michal Hocko <mhocko@xxxxxxxx>
Date: Mon Aug 21 09:46:04 2017 +0200
mmotm: mm-page_alloc-rip-out-zonelist_order_zone-fix
Abdul has noticed that reading sysctl vm.numa_zonelist_order
read will never terminate. This is because of
http://lkml.kernel.org/r/20170714080006.7250-2-mhocko@xxxxxxxxxx
where the reading side doesn't update ppos and so the reader will
never get 0. Return back to proc_dostring which does all the necessary
stuff.
Reported-by: Abdul Haleem <abdhalee@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index fda9afbd14d9..e7e92c8f4883 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -894,6 +894,8 @@ int sysctl_min_slab_ratio_sysctl_handler(struct ctl_table *, int,
extern int numa_zonelist_order_handler(struct ctl_table *, int,
void __user *, size_t *, loff_t *);
+extern char numa_zonelist_order[];
+#define NUMA_ZONELIST_ORDER_LEN 16
#ifndef CONFIG_NEED_MULTIPLE_NODES
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 0cbce40f5426..655686d546cb 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1553,6 +1553,8 @@ static struct ctl_table vm_table[] = {
#ifdef CONFIG_NUMA
{
.procname = "numa_zonelist_order",
+ .data = &numa_zonelist_order,
+ .maxlen = NUMA_ZONELIST_ORDER_LEN,
.mode = 0644,
.proc_handler = numa_zonelist_order_handler,
},
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 5cba36337893..b55e97decac4 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -4859,6 +4859,8 @@ static __init int setup_numa_zonelist_order(char *s)
}
early_param("numa_zonelist_order", setup_numa_zonelist_order);
+char numa_zonelist_order[] = "Node";
+
/*
* sysctl handler for numa_zonelist_order
*/
@@ -4869,12 +4871,8 @@ int numa_zonelist_order_handler(struct ctl_table *table, int write,
char *str;
int ret;
- if (!write) {
- int len = sizeof("Node");
- if (copy_to_user(buffer, "Node", len))
- return -EFAULT;
- return len;
- }
+ if (!write)
+ return proc_dostring(table, write, buffer, length, ppos);
str = memdup_user_nul(buffer, 16);
if (IS_ERR(str))
return PTR_ERR(str);
--
Michal Hocko
SUSE Labs
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