diff mbox series

[v2] mm: fix unexpected changes to {failslab|fail_page_alloc}.attr

Message ID 20221108035232.87180-1-zhengqi.arch@bytedance.com
State New
Headers
Series [v2] mm: fix unexpected changes to {failslab|fail_page_alloc}.attr |

Commit Message

Qi Zheng Nov. 8, 2022, 3:52 a.m. UTC 
  When we specify __GFP_NOWARN, we only expect that no warnings
will be issued for current caller. But in the __should_failslab()
and __should_fail_alloc_page(), the local GFP flags alter the
global {failslab|fail_page_alloc}.attr, which is persistent and
shared by all tasks. This is not what we expected, let's fix it.

Cc: stable@vger.kernel.org
Fixes: 3f913fc5f974 ("mm: fix missing handler for __GFP_NOWARN")
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
---
 v1: https://lore.kernel.org/lkml/20221107033109.59709-1-zhengqi.arch@bytedance.com/

 Changelog in v1 -> v2:
  - add comment for __should_failslab() and __should_fail_alloc_page()
    (suggested by Jason)

 include/linux/fault-inject.h |  7 +++++--
 lib/fault-inject.c           | 14 +++++++++-----
 mm/failslab.c                | 12 ++++++++++--
 mm/page_alloc.c              |  7 +++++--
 4 files changed, 29 insertions(+), 11 deletions(-)

Comments

Qi Zheng Nov. 8, 2022, 8:58 a.m. UTC | #1 
On 2022/11/8 16:44, Wei Yongjun wrote:
> Hi Zheng Qi,
> 
> On 2022/11/8 11:52, Qi Zheng wrote:
>> When we specify __GFP_NOWARN, we only expect that no warnings
>> will be issued for current caller. But in the __should_failslab()
>> and __should_fail_alloc_page(), the local GFP flags alter the
>> global {failslab|fail_page_alloc}.attr, which is persistent and
>> shared by all tasks. This is not what we expected, let's fix it.
>>
>> Cc: stable@vger.kernel.org
>> Fixes: 3f913fc5f974 ("mm: fix missing handler for __GFP_NOWARN")
>> Reported-by: Dmitry Vyukov <dvyukov@google.com>
>> Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
>> ---
>>   v1: https://lore.kernel.org/lkml/20221107033109.59709-1-zhengqi.arch@bytedance.com/
>>
>>   Changelog in v1 -> v2:
>>    - add comment for __should_failslab() and __should_fail_alloc_page()
>>      (suggested by Jason)
>>
>>   include/linux/fault-inject.h |  7 +++++--
>>   lib/fault-inject.c           | 14 +++++++++-----
>>   mm/failslab.c                | 12 ++++++++++--
>>   mm/page_alloc.c              |  7 +++++--
>>   4 files changed, 29 insertions(+), 11 deletions(-)
>>
>> diff --git a/include/linux/fault-inject.h b/include/linux/fault-inject.h
>> index 9f6e25467844..444236dadcf0 100644
>> --- a/include/linux/fault-inject.h
>> +++ b/include/linux/fault-inject.h
>> @@ -20,7 +20,6 @@ struct fault_attr {
>>   	atomic_t space;
>>   	unsigned long verbose;
>>   	bool task_filter;
>> -	bool no_warn;
>>   	unsigned long stacktrace_depth;
>>   	unsigned long require_start;
>>   	unsigned long require_end;
>> @@ -32,6 +31,10 @@ struct fault_attr {
>>   	struct dentry *dname;
>>   };
>>   
>> +enum fault_flags {
>> +	FAULT_NOWARN =	1 << 0,
>> +};
>> +
>>   #define FAULT_ATTR_INITIALIZER {					\
>>   		.interval = 1,						\
>>   		.times = ATOMIC_INIT(1),				\
>> @@ -40,11 +43,11 @@ struct fault_attr {
>>   		.ratelimit_state = RATELIMIT_STATE_INIT_DISABLED,	\
>>   		.verbose = 2,						\
>>   		.dname = NULL,						\
>> -		.no_warn = false,					\
> 
> How about keep no_warn attr as it be, and export it to user?
> 
> When testing with fault injection, and each fault will print an backtrace.
> but not all of the testsuit can tell us which one is fault injection
> message or other is a real warning/crash like syzkaller do.
> 
> In my case, to make things simple, we usually used a regex to detect whether
> wanring/error happend. So we disabled the slab/page fault warning message by
> default, and only enable it when debug real issue.

So you want to set/clear this no_warn attr through the procfs or sysfs
interface, so that you can easily disable/enable the slab/page fault
warning message from the user mode. Right?

Seems reasonable to me. Anyone else has an opinion on this? If it is
really needed, I can do it later.

Thanks,
Qi

> 
> Regards,
> 
> 
>>   	}
>>   
>>   #define DECLARE_FAULT_ATTR(name) struct fault_attr name = FAULT_ATTR_INITIALIZER
>>   int setup_fault_attr(struct fault_attr *attr, char *str);
>> +bool should_fail_ex(struct fault_attr *attr, ssize_t size, int flags);
>>   bool should_fail(struct fault_attr *attr, ssize_t size);
>>   
>>   #ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
>> diff --git a/lib/fault-inject.c b/lib/fault-inject.c
>> index 4b8fafce415c..5971f7c3e49e 100644
>> --- a/lib/fault-inject.c
>> +++ b/lib/fault-inject.c
>> @@ -41,9 +41,6 @@ EXPORT_SYMBOL_GPL(setup_fault_attr);
>>   
>>   static void fail_dump(struct fault_attr *attr)
>>   {
>> -	if (attr->no_warn)
>> -		return;
>> -
>>   	if (attr->verbose > 0 && __ratelimit(&attr->ratelimit_state)) {
>>   		printk(KERN_NOTICE "FAULT_INJECTION: forcing a failure.\n"
>>   		       "name %pd, interval %lu, probability %lu, "
>> @@ -103,7 +100,7 @@ static inline bool fail_stacktrace(struct fault_attr *attr)
>>    * http://www.nongnu.org/failmalloc/
>>    */
>>   
>> -bool should_fail(struct fault_attr *attr, ssize_t size)
>> +bool should_fail_ex(struct fault_attr *attr, ssize_t size, int flags)
>>   {
>>   	bool stack_checked = false;
>>   
>> @@ -152,13 +149,20 @@ bool should_fail(struct fault_attr *attr, ssize_t size)
>>   		return false;
>>   
>>   fail:
>> -	fail_dump(attr);
>> +	if (!(flags & FAULT_NOWARN))
>> +		fail_dump(attr);
>>   
>>   	if (atomic_read(&attr->times) != -1)
>>   		atomic_dec_not_zero(&attr->times);
>>   
>>   	return true;
>>   }
>> +EXPORT_SYMBOL_GPL(should_fail_ex);
>> +
>> +bool should_fail(struct fault_attr *attr, ssize_t size)
>> +{
>> +	return should_fail_ex(attr, size, 0);
>> +}
>>   EXPORT_SYMBOL_GPL(should_fail);
>>   
>>   #ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
>> diff --git a/mm/failslab.c b/mm/failslab.c
>> index 58df9789f1d2..ffc420c0e767 100644
>> --- a/mm/failslab.c
>> +++ b/mm/failslab.c
>> @@ -16,6 +16,8 @@ static struct {
>>   
>>   bool __should_failslab(struct kmem_cache *s, gfp_t gfpflags)
>>   {
>> +	int flags = 0;
>> +
>>   	/* No fault-injection for bootstrap cache */
>>   	if (unlikely(s == kmem_cache))
>>   		return false;
>> @@ -30,10 +32,16 @@ bool __should_failslab(struct kmem_cache *s, gfp_t gfpflags)
>>   	if (failslab.cache_filter && !(s->flags & SLAB_FAILSLAB))
>>   		return false;
>>   
>> +	/*
>> +	 * In some cases, it expects to specify __GFP_NOWARN
>> +	 * to avoid printing any information(not just a warning),
>> +	 * thus avoiding deadlocks. See commit 6b9dbedbe349 for
>> +	 * details.
>> +	 */
>>   	if (gfpflags & __GFP_NOWARN)
>> -		failslab.attr.no_warn = true;
>> +		flags |= FAULT_NOWARN;
>>   
>> -	return should_fail(&failslab.attr, s->object_size);
>> +	return should_fail_ex(&failslab.attr, s->object_size, flags);
>>   }
>>   
>>   static int __init setup_failslab(char *str)
>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>> index 7192ded44ad0..cb6fe715d983 100644
>> --- a/mm/page_alloc.c
>> +++ b/mm/page_alloc.c
>> @@ -3902,6 +3902,8 @@ __setup("fail_page_alloc=", setup_fail_page_alloc);
>>   
>>   static bool __should_fail_alloc_page(gfp_t gfp_mask, unsigned int order)
>>   {
>> +	int flags = 0;
>> +
>>   	if (order < fail_page_alloc.min_order)
>>   		return false;
>>   	if (gfp_mask & __GFP_NOFAIL)
>> @@ -3912,10 +3914,11 @@ static bool __should_fail_alloc_page(gfp_t gfp_mask, unsigned int order)
>>   			(gfp_mask & __GFP_DIRECT_RECLAIM))
>>   		return false;
>>   
>> +	/* See comment in __should_failslab() */
>>   	if (gfp_mask & __GFP_NOWARN)
>> -		fail_page_alloc.attr.no_warn = true;
>> +		flags |= FAULT_NOWARN;
>>   
>> -	return should_fail(&fail_page_alloc.attr, 1 << order);
>> +	return should_fail_ex(&fail_page_alloc.attr, 1 << order, flags);
>>   }
>>   
>>   #ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
Qi Zheng Nov. 8, 2022, 9:45 a.m. UTC | #2 
On 2022/11/8 17:32, Wei Yongjun wrote:
> 
> 
> On 2022/11/8 16:58, Qi Zheng wrote:
>>
>>
>> On 2022/11/8 16:44, Wei Yongjun wrote:
>>> Hi Zheng Qi,
>>>
>>> On 2022/11/8 11:52, Qi Zheng wrote:
>>>> When we specify __GFP_NOWARN, we only expect that no warnings
>>>> will be issued for current caller. But in the __should_failslab()
>>>> and __should_fail_alloc_page(), the local GFP flags alter the
>>>> global {failslab|fail_page_alloc}.attr, which is persistent and
>>>> shared by all tasks. This is not what we expected, let's fix it.
>>>>
>>>> Cc: stable@vger.kernel.org
>>>> Fixes: 3f913fc5f974 ("mm: fix missing handler for __GFP_NOWARN")
>>>> Reported-by: Dmitry Vyukov <dvyukov@google.com>
>>>> Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
>>>> ---
>>>>    v1: https://lore.kernel.org/lkml/20221107033109.59709-1-zhengqi.arch@bytedance.com/
>>>>
>>>>    Changelog in v1 -> v2:
>>>>     - add comment for __should_failslab() and __should_fail_alloc_page()
>>>>       (suggested by Jason)
>>>>
>>>>    include/linux/fault-inject.h |  7 +++++--
>>>>    lib/fault-inject.c           | 14 +++++++++-----
>>>>    mm/failslab.c                | 12 ++++++++++--
>>>>    mm/page_alloc.c              |  7 +++++--
>>>>    4 files changed, 29 insertions(+), 11 deletions(-)
>>>>
>>>> diff --git a/include/linux/fault-inject.h b/include/linux/fault-inject.h
>>>> index 9f6e25467844..444236dadcf0 100644
>>>> --- a/include/linux/fault-inject.h
>>>> +++ b/include/linux/fault-inject.h
>>>> @@ -20,7 +20,6 @@ struct fault_attr {
>>>>        atomic_t space;
>>>>        unsigned long verbose;
>>>>        bool task_filter;
>>>> -    bool no_warn;
>>>>        unsigned long stacktrace_depth;
>>>>        unsigned long require_start;
>>>>        unsigned long require_end;
>>>> @@ -32,6 +31,10 @@ struct fault_attr {
>>>>        struct dentry *dname;
>>>>    };
>>>>    +enum fault_flags {
>>>> +    FAULT_NOWARN =    1 << 0,
>>>> +};
>>>> +
>>>>    #define FAULT_ATTR_INITIALIZER {                    \
>>>>            .interval = 1,                        \
>>>>            .times = ATOMIC_INIT(1),                \
>>>> @@ -40,11 +43,11 @@ struct fault_attr {
>>>>            .ratelimit_state = RATELIMIT_STATE_INIT_DISABLED,    \
>>>>            .verbose = 2,                        \
>>>>            .dname = NULL,                        \
>>>> -        .no_warn = false,                    \
>>>
>>> How about keep no_warn attr as it be, and export it to user?
>>>
>>> When testing with fault injection, and each fault will print an backtrace.
>>> but not all of the testsuit can tell us which one is fault injection
>>> message or other is a real warning/crash like syzkaller do.
>>>
>>> In my case, to make things simple, we usually used a regex to detect whether
>>> wanring/error happend. So we disabled the slab/page fault warning message by
>>> default, and only enable it when debug real issue.
>>
>> So you want to set/clear this no_warn attr through the procfs or sysfs
>> interface, so that you can easily disable/enable the slab/page fault
>> warning message from the user mode. Right?
> 
> Yes, just like:
> 
> echo 1 > /sys/kernel/debug/failslab/no_warn  #disable message
> echo 0 > /sys/kernel/debug/failslab/no_warn  #enable message

Got it. Let's wait for the other people's comments and suggestions. :)

> 
> Regards
> Wei Yongjun
> 
>>
>> Seems reasonable to me. Anyone else has an opinion on this? If it is
>> really needed, I can do it later.
>>
>> Thanks,
>> Qi
>>
>>>
>>> Regards,
>>>
>>>
>>>>        }
>>>>      #define DECLARE_FAULT_ATTR(name) struct fault_attr name = FAULT_ATTR_INITIALIZER
>>>>    int setup_fault_attr(struct fault_attr *attr, char *str);
>>>> +bool should_fail_ex(struct fault_attr *attr, ssize_t size, int flags);
>>>>    bool should_fail(struct fault_attr *attr, ssize_t size);
>>>>      #ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
>>>> diff --git a/lib/fault-inject.c b/lib/fault-inject.c
>>>> index 4b8fafce415c..5971f7c3e49e 100644
>>>> --- a/lib/fault-inject.c
>>>> +++ b/lib/fault-inject.c
>>>> @@ -41,9 +41,6 @@ EXPORT_SYMBOL_GPL(setup_fault_attr);
>>>>      static void fail_dump(struct fault_attr *attr)
>>>>    {
>>>> -    if (attr->no_warn)
>>>> -        return;
>>>> -
>>>>        if (attr->verbose > 0 && __ratelimit(&attr->ratelimit_state)) {
>>>>            printk(KERN_NOTICE "FAULT_INJECTION: forcing a failure.\n"
>>>>                   "name %pd, interval %lu, probability %lu, "
>>>> @@ -103,7 +100,7 @@ static inline bool fail_stacktrace(struct fault_attr *attr)
>>>>     * http://www.nongnu.org/failmalloc/
>>>>     */
>>>>    -bool should_fail(struct fault_attr *attr, ssize_t size)
>>>> +bool should_fail_ex(struct fault_attr *attr, ssize_t size, int flags)
>>>>    {
>>>>        bool stack_checked = false;
>>>>    @@ -152,13 +149,20 @@ bool should_fail(struct fault_attr *attr, ssize_t size)
>>>>            return false;
>>>>      fail:
>>>> -    fail_dump(attr);
>>>> +    if (!(flags & FAULT_NOWARN))
>>>> +        fail_dump(attr);
>>>>          if (atomic_read(&attr->times) != -1)
>>>>            atomic_dec_not_zero(&attr->times);
>>>>          return true;
>>>>    }
>>>> +EXPORT_SYMBOL_GPL(should_fail_ex);
>>>> +
>>>> +bool should_fail(struct fault_attr *attr, ssize_t size)
>>>> +{
>>>> +    return should_fail_ex(attr, size, 0);
>>>> +}
>>>>    EXPORT_SYMBOL_GPL(should_fail);
>>>>      #ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
>>>> diff --git a/mm/failslab.c b/mm/failslab.c
>>>> index 58df9789f1d2..ffc420c0e767 100644
>>>> --- a/mm/failslab.c
>>>> +++ b/mm/failslab.c
>>>> @@ -16,6 +16,8 @@ static struct {
>>>>      bool __should_failslab(struct kmem_cache *s, gfp_t gfpflags)
>>>>    {
>>>> +    int flags = 0;
>>>> +
>>>>        /* No fault-injection for bootstrap cache */
>>>>        if (unlikely(s == kmem_cache))
>>>>            return false;
>>>> @@ -30,10 +32,16 @@ bool __should_failslab(struct kmem_cache *s, gfp_t gfpflags)
>>>>        if (failslab.cache_filter && !(s->flags & SLAB_FAILSLAB))
>>>>            return false;
>>>>    +    /*
>>>> +     * In some cases, it expects to specify __GFP_NOWARN
>>>> +     * to avoid printing any information(not just a warning),
>>>> +     * thus avoiding deadlocks. See commit 6b9dbedbe349 for
>>>> +     * details.
>>>> +     */
>>>>        if (gfpflags & __GFP_NOWARN)
>>>> -        failslab.attr.no_warn = true;
>>>> +        flags |= FAULT_NOWARN;
>>>>    -    return should_fail(&failslab.attr, s->object_size);
>>>> +    return should_fail_ex(&failslab.attr, s->object_size, flags);
>>>>    }
>>>>      static int __init setup_failslab(char *str)
>>>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>>>> index 7192ded44ad0..cb6fe715d983 100644
>>>> --- a/mm/page_alloc.c
>>>> +++ b/mm/page_alloc.c
>>>> @@ -3902,6 +3902,8 @@ __setup("fail_page_alloc=", setup_fail_page_alloc);
>>>>      static bool __should_fail_alloc_page(gfp_t gfp_mask, unsigned int order)
>>>>    {
>>>> +    int flags = 0;
>>>> +
>>>>        if (order < fail_page_alloc.min_order)
>>>>            return false;
>>>>        if (gfp_mask & __GFP_NOFAIL)
>>>> @@ -3912,10 +3914,11 @@ static bool __should_fail_alloc_page(gfp_t gfp_mask, unsigned int order)
>>>>                (gfp_mask & __GFP_DIRECT_RECLAIM))
>>>>            return false;
>>>>    +    /* See comment in __should_failslab() */
>>>>        if (gfp_mask & __GFP_NOWARN)
>>>> -        fail_page_alloc.attr.no_warn = true;
>>>> +        flags |= FAULT_NOWARN;
>>>>    -    return should_fail(&fail_page_alloc.attr, 1 << order);
>>>> +    return should_fail_ex(&fail_page_alloc.attr, 1 << order, flags);
>>>>    }
>>>>      #ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
>>
Jason Gunthorpe Nov. 8, 2022, 12:04 p.m. UTC | #3 
On Tue, Nov 08, 2022 at 05:32:52PM +0800, Wei Yongjun wrote:
> > So you want to set/clear this no_warn attr through the procfs or sysfs
> > interface, so that you can easily disable/enable the slab/page fault
> > warning message from the user mode. Right?
> 
> Yes, just like:
> 
> echo 1 > /sys/kernel/debug/failslab/no_warn  #disable message
> echo 0 > /sys/kernel/debug/failslab/no_warn  #enable message

You can already do that:

 echo 0 > /sys/kernel/debug/failslab/verbose  #disable message

Jason
Akinobu Mita Nov. 8, 2022, 5:36 p.m. UTC | #4 
2022年11月8日(火) 12:52 Qi Zheng <zhengqi.arch@bytedance.com>:
>
> When we specify __GFP_NOWARN, we only expect that no warnings
> will be issued for current caller. But in the __should_failslab()
> and __should_fail_alloc_page(), the local GFP flags alter the
> global {failslab|fail_page_alloc}.attr, which is persistent and
> shared by all tasks. This is not what we expected, let's fix it.
>
> Cc: stable@vger.kernel.org
> Fixes: 3f913fc5f974 ("mm: fix missing handler for __GFP_NOWARN")
> Reported-by: Dmitry Vyukov <dvyukov@google.com>
> Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
> ---
>  v1: https://lore.kernel.org/lkml/20221107033109.59709-1-zhengqi.arch@bytedance.com/
>
>  Changelog in v1 -> v2:
>   - add comment for __should_failslab() and __should_fail_alloc_page()
>     (suggested by Jason)

Looks good.

Reviewed-by: Akinobu Mita <akinobu.mita@gmail.com>
Qi Zheng Nov. 14, 2022, 3:59 a.m. UTC | #5 
On 2022/11/9 01:36, Akinobu Mita wrote:
> 2022年11月8日(火) 12:52 Qi Zheng <zhengqi.arch@bytedance.com>:
>>
>> When we specify __GFP_NOWARN, we only expect that no warnings
>> will be issued for current caller. But in the __should_failslab()
>> and __should_fail_alloc_page(), the local GFP flags alter the
>> global {failslab|fail_page_alloc}.attr, which is persistent and
>> shared by all tasks. This is not what we expected, let's fix it.
>>
>> Cc: stable@vger.kernel.org
>> Fixes: 3f913fc5f974 ("mm: fix missing handler for __GFP_NOWARN")
>> Reported-by: Dmitry Vyukov <dvyukov@google.com>
>> Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
>> ---
>>   v1: https://lore.kernel.org/lkml/20221107033109.59709-1-zhengqi.arch@bytedance.com/
>>
>>   Changelog in v1 -> v2:
>>    - add comment for __should_failslab() and __should_fail_alloc_page()
>>      (suggested by Jason)
> 
> Looks good.
> 
> Reviewed-by: Akinobu Mita <akinobu.mita@gmail.com>

Thanks. And hi Andrew, seems no action left for me, can this patch
be applied to mm-unstable tree for testing? :)
diff mbox series

Patch

diff --git a/include/linux/fault-inject.h b/include/linux/fault-inject.h
index 9f6e25467844..444236dadcf0 100644
--- a/include/linux/fault-inject.h
+++ b/include/linux/fault-inject.h
@@ -20,7 +20,6 @@  struct fault_attr {
 	atomic_t space;
 	unsigned long verbose;
 	bool task_filter;
-	bool no_warn;
 	unsigned long stacktrace_depth;
 	unsigned long require_start;
 	unsigned long require_end;
@@ -32,6 +31,10 @@  struct fault_attr {
 	struct dentry *dname;
 };
 
+enum fault_flags {
+	FAULT_NOWARN =	1 << 0,
+};
+
 #define FAULT_ATTR_INITIALIZER {					\
 		.interval = 1,						\
 		.times = ATOMIC_INIT(1),				\
@@ -40,11 +43,11 @@  struct fault_attr {
 		.ratelimit_state = RATELIMIT_STATE_INIT_DISABLED,	\
 		.verbose = 2,						\
 		.dname = NULL,						\
-		.no_warn = false,					\
 	}
 
 #define DECLARE_FAULT_ATTR(name) struct fault_attr name = FAULT_ATTR_INITIALIZER
 int setup_fault_attr(struct fault_attr *attr, char *str);
+bool should_fail_ex(struct fault_attr *attr, ssize_t size, int flags);
 bool should_fail(struct fault_attr *attr, ssize_t size);
 
 #ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
diff --git a/lib/fault-inject.c b/lib/fault-inject.c
index 4b8fafce415c..5971f7c3e49e 100644
--- a/lib/fault-inject.c
+++ b/lib/fault-inject.c
@@ -41,9 +41,6 @@  EXPORT_SYMBOL_GPL(setup_fault_attr);
 
 static void fail_dump(struct fault_attr *attr)
 {
-	if (attr->no_warn)
-		return;
-
 	if (attr->verbose > 0 && __ratelimit(&attr->ratelimit_state)) {
 		printk(KERN_NOTICE "FAULT_INJECTION: forcing a failure.\n"
 		       "name %pd, interval %lu, probability %lu, "
@@ -103,7 +100,7 @@  static inline bool fail_stacktrace(struct fault_attr *attr)
  * http://www.nongnu.org/failmalloc/
  */
 
-bool should_fail(struct fault_attr *attr, ssize_t size)
+bool should_fail_ex(struct fault_attr *attr, ssize_t size, int flags)
 {
 	bool stack_checked = false;
 
@@ -152,13 +149,20 @@  bool should_fail(struct fault_attr *attr, ssize_t size)
 		return false;
 
 fail:
-	fail_dump(attr);
+	if (!(flags & FAULT_NOWARN))
+		fail_dump(attr);
 
 	if (atomic_read(&attr->times) != -1)
 		atomic_dec_not_zero(&attr->times);
 
 	return true;
 }
+EXPORT_SYMBOL_GPL(should_fail_ex);
+
+bool should_fail(struct fault_attr *attr, ssize_t size)
+{
+	return should_fail_ex(attr, size, 0);
+}
 EXPORT_SYMBOL_GPL(should_fail);
 
 #ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
diff --git a/mm/failslab.c b/mm/failslab.c
index 58df9789f1d2..ffc420c0e767 100644
--- a/mm/failslab.c
+++ b/mm/failslab.c
@@ -16,6 +16,8 @@  static struct {
 
 bool __should_failslab(struct kmem_cache *s, gfp_t gfpflags)
 {
+	int flags = 0;
+
 	/* No fault-injection for bootstrap cache */
 	if (unlikely(s == kmem_cache))
 		return false;
@@ -30,10 +32,16 @@  bool __should_failslab(struct kmem_cache *s, gfp_t gfpflags)
 	if (failslab.cache_filter && !(s->flags & SLAB_FAILSLAB))
 		return false;
 
+	/*
+	 * In some cases, it expects to specify __GFP_NOWARN
+	 * to avoid printing any information(not just a warning),
+	 * thus avoiding deadlocks. See commit 6b9dbedbe349 for
+	 * details.
+	 */
 	if (gfpflags & __GFP_NOWARN)
-		failslab.attr.no_warn = true;
+		flags |= FAULT_NOWARN;
 
-	return should_fail(&failslab.attr, s->object_size);
+	return should_fail_ex(&failslab.attr, s->object_size, flags);
 }
 
 static int __init setup_failslab(char *str)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 7192ded44ad0..cb6fe715d983 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3902,6 +3902,8 @@  __setup("fail_page_alloc=", setup_fail_page_alloc);
 
 static bool __should_fail_alloc_page(gfp_t gfp_mask, unsigned int order)
 {
+	int flags = 0;
+
 	if (order < fail_page_alloc.min_order)
 		return false;
 	if (gfp_mask & __GFP_NOFAIL)
@@ -3912,10 +3914,11 @@  static bool __should_fail_alloc_page(gfp_t gfp_mask, unsigned int order)
 			(gfp_mask & __GFP_DIRECT_RECLAIM))
 		return false;
 
+	/* See comment in __should_failslab() */
 	if (gfp_mask & __GFP_NOWARN)
-		fail_page_alloc.attr.no_warn = true;
+		flags |= FAULT_NOWARN;
 
-	return should_fail(&fail_page_alloc.attr, 1 << order);
+	return should_fail_ex(&fail_page_alloc.attr, 1 << order, flags);
 }
 
 #ifdef CONFIG_FAULT_INJECTION_DEBUG_FS