Re: [REGRESSION] RLIMIT_DATA crashes named

[Konstantin Khlebnikov <koct9i@gmail.com>]

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On Sat, Sep 17, 2016 at 7:08 AM, Joe Perches <joe@perches.com> wrote:
> On Fri, 2016-09-16 at 17:040700, Linus Torvalds wrote:
>> On Fri, Sep 16, 2016 at 4:58 PM, Linus Torvalds <torvalds@linux-foundation.org> wrote:
>> > Here's a totally untested patch. What do people say?
>> Heh. It looks like "pr_xyz_once()" is used in places that haven't
>> included "ratelimit.h", so this doesn't actually build for everything.
>> But I guess as a concept patch it's not hard to understand, even if
>> the implementation needs a bit of tweaking.
>
> do_just_once just isn't a good name for a global
> rate limited mechanism that does something very
> different than the name.
>
> Maybe allow_once_per_ratelimit or the like
>
> There could be an equivalent do_once
>
> https://lkml.org/lkml/2009/5/22/3
>

What about this printk_reriodic() and pr_warn_once_per_minute()?

It simply remembers next jiffies to print rather than using that
complicated ratelimiting engine.

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printk: add pr_warn_once_per_minute

From: Konstantin Khlebnikov <koct9i@gmail.com>

Signed-off-by: Konstantin Khlebnikov <koct9i@gmail.com>
---
 include/linux/printk.h |   16 ++++++++++++++++
 mm/mmap.c              |    2 +-
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/include/linux/printk.h b/include/linux/printk.h
index 696a56be7d3e..af1646483dbb 100644
--- a/include/linux/printk.h
+++ b/include/linux/printk.h
@@ -341,11 +341,24 @@ extern asmlinkage void dump_stack(void) __cold;
 	}							\
 	unlikely(__ret_print_once);				\
 })
+#define printk_periodic(period, fmt, ...)			\
+({								\
+	static unsigned long __print_next __read_mostly = INITIAL_JIFFIES; \
+	bool __do_print = time_after_eq(jiffies, __print_next); \
+								\
+	if (__do_print) {					\
+		__print_next = jiffies + (period);		\
+		printk(fmt, ##__VA_ARGS__);			\
+	}							\
+	unlikely(__do_print);					\
+})
 #else
 #define printk_once(fmt, ...)					\
 	no_printk(fmt, ##__VA_ARGS__)
 #define printk_deferred_once(fmt, ...)				\
 	no_printk(fmt, ##__VA_ARGS__)
+#define printk_periodic(period, fmt, ...)			\
+	no_printk(fmt, ##__VA_ARGS__)
 #endif
 
 #define pr_emerg_once(fmt, ...)					\
@@ -365,6 +378,9 @@ extern asmlinkage void dump_stack(void) __cold;
 #define pr_cont_once(fmt, ...)					\
 	printk_once(KERN_CONT pr_fmt(fmt), ##__VA_ARGS__)
 
+#define pr_warn_once_per_minute(fmt, ...)			\
+	printk_periodic(HZ * 60, KERN_WARNING pr_fmt(fmt), ##__VA_ARGS__)
+
 #if defined(DEBUG)
 #define pr_devel_once(fmt, ...)					\
 	printk_once(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__)
diff --git a/mm/mmap.c b/mm/mmap.c
index ca9d91bca0d6..34f9fb2adcab 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2935,7 +2935,7 @@ bool may_expand_vm(struct mm_struct *mm, vm_flags_t flags, unsigned long npages)
 		    mm->data_vm + npages <= rlimit_max(RLIMIT_DATA) >> PAGE_SHIFT)
 			return true;
 		if (!ignore_rlimit_data) {
-			pr_warn_once("%s (%d): VmData %lu exceed data ulimit %lu. Update limits or use boot option ignore_rlimit_data.\n",
+			pr_warn_once_per_minute("%s (%d): VmData %lu exceed data ulimit %lu. Update limits or use boot option ignore_rlimit_data.\n",
 				     current->comm, current->pid,
 				     (mm->data_vm + npages) << PAGE_SHIFT,
 				     rlimit(RLIMIT_DATA));