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Date: Sat, 16 May 2020 10:32:19 +0800
From: Xiaoming Ni <nixiaoming@...wei.com>
To: Kees Cook <keescook@...omium.org>
CC: <mcgrof@...nel.org>, <yzaikin@...gle.com>, <adobriyan@...il.com>,
<mingo@...nel.org>, <peterz@...radead.org>,
<akpm@...ux-foundation.org>, <yamada.masahiro@...ionext.com>,
<bauerman@...ux.ibm.com>, <gregkh@...uxfoundation.org>,
<skhan@...uxfoundation.org>, <dvyukov@...gle.com>,
<svens@...ckframe.org>, <joel@...lfernandes.org>,
<tglx@...utronix.de>, <Jisheng.Zhang@...aptics.com>,
<pmladek@...e.com>, <bigeasy@...utronix.de>,
<linux-kernel@...r.kernel.org>, <linux-fsdevel@...r.kernel.org>,
<wangle6@...wei.com>
Subject: Re: [PATCH 2/4] proc/sysctl: add shared variables -1
On 2020/5/16 0:05, Kees Cook wrote:
> On Fri, May 15, 2020 at 05:06:28PM +0800, Xiaoming Ni wrote:
>> On 2020/5/15 16:06, Kees Cook wrote:
>>> On Fri, May 15, 2020 at 12:33:42PM +0800, Xiaoming Ni wrote:
>>>> Add the shared variable SYSCTL_NEG_ONE to replace the variable neg_one
>>>> used in both sysctl_writes_strict and hung_task_warnings.
>>>>
>>>> Signed-off-by: Xiaoming Ni <nixiaoming@...wei.com>
>>>> ---
>>>> fs/proc/proc_sysctl.c | 2 +-
>>>> include/linux/sysctl.h | 1 +
>>>> kernel/hung_task_sysctl.c | 3 +--
>>>> kernel/sysctl.c | 3 +--
>>>
>>> How about doing this refactoring in advance of the extraction patch?
>> Before advance of the extraction patch, neg_one is only used in one file,
>> does it seem to have no value for refactoring?
>
> I guess it doesn't matter much, but I think it's easier to review in the
> sense that neg_one is first extracted and then later everything else is
> moved.
>
Later, when more features sysctl interface is moved to the code file,
there will be more variables that need to be extracted.
So should I only extract the neg_one variable here, or should I extract
all the variables used by multiple features?
fs/proc/proc_sysctl.c | 2 +-
include/linux/sysctl.h | 11 ++++++++---
kernel/sysctl.c | 37 ++++++++++++++++---------------------
3 files changed, 25 insertions(+), 25 deletions(-)
diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
index b6f5d45..3f77e64 100644
--- a/fs/proc/proc_sysctl.c
+++ b/fs/proc/proc_sysctl.c
@@ -23,7 +23,7 @@
static const struct inode_operations proc_sys_dir_operations;
/* shared constants to be used in various sysctls */
-const int sysctl_vals[] = { 0, 1, INT_MAX };
+const int sysctl_vals[] = { -1, 0, 1, 2, 4, 100, 1000, INT_MAX };
EXPORT_SYMBOL(sysctl_vals);
/* Support for permanently empty directories */
diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index 43f8ef9..bf97c30 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -38,9 +38,14 @@
struct ctl_dir;
/* Keep the same order as in fs/proc/proc_sysctl.c */
-#define SYSCTL_ZERO ((void *)&sysctl_vals[0])
-#define SYSCTL_ONE ((void *)&sysctl_vals[1])
-#define SYSCTL_INT_MAX ((void *)&sysctl_vals[2])
+#define SYSCTL_NEG_ONE ((void *)&sysctl_vals[0])
+#define SYSCTL_ZERO ((void *)&sysctl_vals[1])
+#define SYSCTL_ONE ((void *)&sysctl_vals[2])
+#define SYSCTL_TWO ((void *)&sysctl_vals[3])
+#define SYSCTL_FOUR ((void *)&sysctl_vals[4])
+#define SYSCTL_ONE_HUNDRED ((void *)&sysctl_vals[5])
+#define SYSCTL_ONE_THOUSAND ((void *)&sysctl_vals[6])
+#define SYSCTL_INT_MAX ((void *)&sysctl_vals[7])
extern const int sysctl_vals[];
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 5dd6d01..efe6172 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -118,14 +118,9 @@
/* Constants used for minimum and maximum */
-static int __maybe_unused neg_one = -1;
-static int __maybe_unused two = 2;
-static int __maybe_unused four = 4;
static unsigned long zero_ul;
static unsigned long one_ul = 1;
static unsigned long long_max = LONG_MAX;
-static int one_hundred = 100;
-static int one_thousand = 1000;
#ifdef CONFIG_PRINTK
static int ten_thousand = 10000;
#endif
@@ -534,7 +529,7 @@ static int sysrq_sysctl_handler(struct ctl_table
*table, int write,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_dointvec_minmax,
- .extra1 = &neg_one,
+ .extra1 = SYSCTL_NEG_ONE,
.extra2 = SYSCTL_ONE,
},
#endif
@@ -865,7 +860,7 @@ static int sysrq_sysctl_handler(struct ctl_table
*table, int write,
.mode = 0644,
.proc_handler = proc_dointvec_minmax_sysadmin,
.extra1 = SYSCTL_ZERO,
- .extra2 = &two,
+ .extra2 = SYSCTL_TWO,
},
#endif
{
@@ -1043,7 +1038,7 @@ static int sysrq_sysctl_handler(struct ctl_table
*table, int write,
.mode = 0644,
.proc_handler = perf_cpu_time_max_percent_handler,
.extra1 = SYSCTL_ZERO,
- .extra2 = &one_hundred,
+ .extra2 = SYSCTL_ONE_HUNDRED,
},
{
.procname = "perf_event_max_stack",
@@ -1061,7 +1056,7 @@ static int sysrq_sysctl_handler(struct ctl_table
*table, int write,
.mode = 0644,
.proc_handler = perf_event_max_stack_handler,
.extra1 = SYSCTL_ZERO,
- .extra2 = &one_thousand,
+ .extra2 = SYSCTL_ONE_THOUSAND,
},
#endif
{
@@ -1136,7 +1131,7 @@ static int sysrq_sysctl_handler(struct ctl_table
*table, int write,
.mode = 0644,
.proc_handler = proc_dointvec_minmax,
.extra1 = SYSCTL_ZERO,
- .extra2 = &two,
+ .extra2 = SYSCTL_TWO,
},
{
.procname = "panic_on_oom",
@@ -1145,7 +1140,7 @@ static int sysrq_sysctl_handler(struct ctl_table
*table, int write,
.mode = 0644,
.proc_handler = proc_dointvec_minmax,
.extra1 = SYSCTL_ZERO,
- .extra2 = &two,
+ .extra2 = SYSCTL_TWO,
},
{
.procname = "oom_kill_allocating_task",
@@ -1190,7 +1185,7 @@ static int sysrq_sysctl_handler(struct ctl_table
*table, int write,
.mode = 0644,
.proc_handler = dirty_background_ratio_handler,
.extra1 = SYSCTL_ZERO,
- .extra2 = &one_hundred,
+ .extra2 = SYSCTL_ONE_HUNDRED,
},
{
.procname = "dirty_background_bytes",
@@ -1207,7 +1202,7 @@ static int sysrq_sysctl_handler(struct ctl_table
*table, int write,
.mode = 0644,
.proc_handler = dirty_ratio_handler,
.extra1 = SYSCTL_ZERO,
- .extra2 = &one_hundred,
+ .extra2 = SYSCTL_ONE_HUNDRED,
},
{
.procname = "dirty_bytes",
@@ -1247,7 +1242,7 @@ static int sysrq_sysctl_handler(struct ctl_table
*table, int write,
.mode = 0644,
.proc_handler = proc_dointvec_minmax,
.extra1 = SYSCTL_ZERO,
- .extra2 = &one_hundred,
+ .extra2 = SYSCTL_ONE_HUNDRED,
},
#ifdef CONFIG_HUGETLB_PAGE
{
@@ -1304,7 +1299,7 @@ static int sysrq_sysctl_handler(struct ctl_table
*table, int write,
.mode = 0200,
.proc_handler = drop_caches_sysctl_handler,
.extra1 = SYSCTL_ONE,
- .extra2 = &four,
+ .extra2 = SYSCTL_FOUR,
},
#ifdef CONFIG_COMPACTION
{
@@ -1357,7 +1352,7 @@ static int sysrq_sysctl_handler(struct ctl_table
*table, int write,
.mode = 0644,
.proc_handler = watermark_scale_factor_sysctl_handler,
.extra1 = SYSCTL_ONE,
- .extra2 = &one_thousand,
+ .extra2 = SYSCTL_ONE_THOUSAND,
},
{
.procname = "percpu_pagelist_fraction",
@@ -1436,7 +1431,7 @@ static int sysrq_sysctl_handler(struct ctl_table
*table, int write,
.mode = 0644,
.proc_handler = sysctl_min_unmapped_ratio_sysctl_handler,
.extra1 = SYSCTL_ZERO,
- .extra2 = &one_hundred,
+ .extra2 = SYSCTL_ONE_HUNDRED,
},
{
.procname = "min_slab_ratio",
@@ -1445,7 +1440,7 @@ static int sysrq_sysctl_handler(struct ctl_table
*table, int write,
.mode = 0644,
.proc_handler = sysctl_min_slab_ratio_sysctl_handler,
.extra1 = SYSCTL_ZERO,
- .extra2 = &one_hundred,
+ .extra2 = SYSCTL_ONE_HUNDRED,
},
#endif
#ifdef CONFIG_SMP
@@ -1728,7 +1723,7 @@ static int sysrq_sysctl_handler(struct ctl_table
*table, int write,
.mode = 0600,
.proc_handler = proc_dointvec_minmax,
.extra1 = SYSCTL_ZERO,
- .extra2 = &two,
+ .extra2 = SYSCTL_TWO,
},
{
.procname = "protected_regular",
@@ -1737,7 +1732,7 @@ static int sysrq_sysctl_handler(struct ctl_table
*table, int write,
.mode = 0600,
.proc_handler = proc_dointvec_minmax,
.extra1 = SYSCTL_ZERO,
- .extra2 = &two,
+ .extra2 = SYSCTL_TWO,
},
{
.procname = "suid_dumpable",
@@ -1746,7 +1741,7 @@ static int sysrq_sysctl_handler(struct ctl_table
*table, int write,
.mode = 0644,
.proc_handler = proc_dointvec_minmax_coredump,
.extra1 = SYSCTL_ZERO,
- .extra2 = &two,
+ .extra2 = SYSCTL_TWO,
},
#if defined(CONFIG_BINFMT_MISC) || defined(CONFIG_BINFMT_MISC_MODULE)
{
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