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: [email protected]
Fixes: 3f913fc5f974 ("mm: fix missing handler for __GFP_NOWARN")
Reported-by: Dmitry Vyukov <[email protected]>
Signed-off-by: Qi Zheng <[email protected]>
---
include/linux/fault-inject.h | 7 +++++--
lib/fault-inject.c | 14 +++++++++-----
mm/failslab.c | 6 ++++--
mm/page_alloc.c | 6 ++++--
4 files changed, 22 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, \
}
#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..fc046f26606c 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;
@@ -31,9 +33,9 @@ bool __should_failslab(struct kmem_cache *s, gfp_t gfpflags)
return false;
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..e537d3a950a4 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)
@@ -3913,9 +3915,9 @@ static bool __should_fail_alloc_page(gfp_t gfp_mask, unsigned int order)
return false;
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
--
2.20.1
On Mon, Nov 07, 2022 at 11:31:09AM +0800, Qi Zheng wrote:
> @@ -31,9 +33,9 @@ bool __should_failslab(struct kmem_cache *s, gfp_t gfpflags)
> return false;
>
> if (gfpflags & __GFP_NOWARN)
> - failslab.attr.no_warn = true;
> + flags |= FAULT_NOWARN;
You should add a comment here about why this is required, to avoid
deadlocking printk
Jason
On 2022/11/7 20:42, Jason Gunthorpe wrote:
> On Mon, Nov 07, 2022 at 11:31:09AM +0800, Qi Zheng wrote:
>
>> @@ -31,9 +33,9 @@ bool __should_failslab(struct kmem_cache *s, gfp_t gfpflags)
>> return false;
>>
>> if (gfpflags & __GFP_NOWARN)
>> - failslab.attr.no_warn = true;
>> + flags |= FAULT_NOWARN;
>
> You should add a comment here about why this is required, to avoid
> deadlocking printk
I think this comment should be placed where __GFP_NOWARN is specified
instead of here. What do you think? :)
Thanks,
Qi
>
> Jason
--
Thanks,
Qi
On Mon, Nov 07, 2022 at 11:05:42PM +0800, Qi Zheng wrote:
>
>
> On 2022/11/7 20:42, Jason Gunthorpe wrote:
> > On Mon, Nov 07, 2022 at 11:31:09AM +0800, Qi Zheng wrote:
> >
> > > @@ -31,9 +33,9 @@ bool __should_failslab(struct kmem_cache *s, gfp_t gfpflags)
> > > return false;
> > > if (gfpflags & __GFP_NOWARN)
> > > - failslab.attr.no_warn = true;
> > > + flags |= FAULT_NOWARN;
> >
> > You should add a comment here about why this is required, to avoid
> > deadlocking printk
>
> I think this comment should be placed where __GFP_NOWARN is specified
> instead of here. What do you think? :)
NOWARN is clear what it does, it is this specifically that is very
subtle about avoiding deadlock aginst allocations triggered by
printk/etc code.
Jason
On 2022/11/8 00:26, Jason Gunthorpe wrote:
> On Mon, Nov 07, 2022 at 11:05:42PM +0800, Qi Zheng wrote:
>>
>>
>> On 2022/11/7 20:42, Jason Gunthorpe wrote:
>>> On Mon, Nov 07, 2022 at 11:31:09AM +0800, Qi Zheng wrote:
>>>
>>>> @@ -31,9 +33,9 @@ bool __should_failslab(struct kmem_cache *s, gfp_t gfpflags)
>>>> return false;
>>>> if (gfpflags & __GFP_NOWARN)
>>>> - failslab.attr.no_warn = true;
>>>> + flags |= FAULT_NOWARN;
>>>
>>> You should add a comment here about why this is required, to avoid
>>> deadlocking printk
>>
>> I think this comment should be placed where __GFP_NOWARN is specified
>> instead of here. What do you think? :)
>
> NOWARN is clear what it does, it is this specifically that is very
> subtle about avoiding deadlock aginst allocations triggered by
> printk/etc code.
Oh, maybe I understand your concern. Some people may think that this
is just a print of fault injection information, not a warning. I'll
add a comment explaining why in some cases there must be no printing.
Thanks,
Qi
>
> Jason
--
Thanks,
Qi
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: [email protected]
Fixes: 3f913fc5f974 ("mm: fix missing handler for __GFP_NOWARN")
Reported-by: Dmitry Vyukov <[email protected]>
Signed-off-by: Qi Zheng <[email protected]>
---
v1: https://lore.kernel.org/lkml/[email protected]/
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, \
}
#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
--
2.20.1
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: [email protected]
>> Fixes: 3f913fc5f974 ("mm: fix missing handler for __GFP_NOWARN")
>> Reported-by: Dmitry Vyukov <[email protected]>
>> Signed-off-by: Qi Zheng <[email protected]>
>> ---
>> v1: https://lore.kernel.org/lkml/[email protected]/
>>
>> 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
--
Thanks,
Qi
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: [email protected]
>>>> Fixes: 3f913fc5f974 ("mm: fix missing handler for __GFP_NOWARN")
>>>> Reported-by: Dmitry Vyukov <[email protected]>
>>>> Signed-off-by: Qi Zheng <[email protected]>
>>>> ---
>>>> v1: https://lore.kernel.org/lkml/[email protected]/
>>>>
>>>> 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
>>
--
Thanks,
Qi
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
2022年11月8日(火) 12:52 Qi Zheng <[email protected]>:
>
> 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: [email protected]
> Fixes: 3f913fc5f974 ("mm: fix missing handler for __GFP_NOWARN")
> Reported-by: Dmitry Vyukov <[email protected]>
> Signed-off-by: Qi Zheng <[email protected]>
> ---
> v1: https://lore.kernel.org/lkml/[email protected]/
>
> Changelog in v1 -> v2:
> - add comment for __should_failslab() and __should_fail_alloc_page()
> (suggested by Jason)
Looks good.
Reviewed-by: Akinobu Mita <[email protected]>
On 2022/11/9 01:36, Akinobu Mita wrote:
> 2022年11月8日(火) 12:52 Qi Zheng <[email protected]>:
>>
>> 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: [email protected]
>> Fixes: 3f913fc5f974 ("mm: fix missing handler for __GFP_NOWARN")
>> Reported-by: Dmitry Vyukov <[email protected]>
>> Signed-off-by: Qi Zheng <[email protected]>
>> ---
>> v1: https://lore.kernel.org/lkml/[email protected]/
>>
>> Changelog in v1 -> v2:
>> - add comment for __should_failslab() and __should_fail_alloc_page()
>> (suggested by Jason)
>
> Looks good.
>
> Reviewed-by: Akinobu Mita <[email protected]>
Thanks. And hi Andrew, seems no action left for me, can this patch
be applied to mm-unstable tree for testing? :)
--
Thanks,
Qi